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The effect of feeding diets matched for rate of degradation of carbohydrate and protein on milk production… Tembo, Wicliff Khuzwayo Adamson 1995

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THE EFFECT OF FEEDING DIETS MATCHED FOR RATE OF DEGRADATION OF CARBOHYDRATE AND PROTEIN ON MILK PRODUCTION CHARACTERISTICS OF DAIRY COWS. By WICLIFF KHUZWAYO ADAMSON TEMBO B. A g r i c . S c i . , The U n i v e r s i t y o f Zambia, 1981 M . S c , (Animal S c i e n c e s ) The U n i v e r s i t y o f M a n i t o b a , 1987 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n THE FACULTY OF GRADUATE STUDIES (THE FACULTY OF AGRICULTURAL SCIENCES) (Department o f A n i m a l S c i e n c e s ) We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA SEPTEMBER 1995 ©Wicliff Tembo, 1995 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of A^I^Al- G>C-i±f/££S* The University of British Columbia Vancouver, Canada Date DE-6 (2/88) ABSTRACT. Adequate knowledge o f t h e r u m i n a l d e g r a d a t i o n c h a r a c t e r i s t i c s o f f e e d s t u f f s f e d t o r u m i n a n t s i s paramount t o s u c c e s s f u l r a t i o n f o r m u l a t i o n u s i n g t h e r e c e n t l y proposed p r o t e i n r a t i o n i n g systems. I n t h e f i r s t o f two t r i a l s , i n s i t u rumen d e g r a d a t i o n c h a r a c t e r i s t i c s o f c e r e a l g r a i n s w i t h o r w i t h o u t steam r o l l i n g , roughages and a g r o - b y p r o d u c t s were e v a l u a t e d . I n v i t r o s t a r c h r e l e a s e o f t h e c e r e a l s by t h e enzyme a m y l o g l u c o s i d a s e was a l s o i n v e s t i g a t e d . Steam r o l l i n g (SR) s i g n i f i c a n t l y r e d u c e d t h e i n s i t u r a t e o f d e g r a d a t i o n o f DM, CP and s t a r c h o f c e r e a l g r a i n s . Compared t o u n p r o c e s s e d c e r e a l s , i n s i t u r a t e o f d e g r a d a t i o n o f t h e s e p a r a m e t e r s was s i g n i f i c a n t l y l o wer f o r c o r n t h a n f o r b a r l e y o r wheat, f o r b o t h t h e steam r o l l e d and t h e u n p r o c e s s e d t r e a t m e n t s . However, SR tend e d t o i n c r e a s e t h e i n v i t r o s t a r c h r e l e a s e by a m y l o g l u c o s i d a s e from c e r e a l g r a i n s . I n s i t u d e g r a d a t i o n c h a r a c t e r i s t i c s v a r i e d s i g n i f i c a n t l y (P<0.01) among roughages and a g r o - b y p r o d u c t s , w i t h a l f a l f a hay and r y e d i s t i l l e r s g r a i n s h a v i n g h i g h e r r a t e s o f d e g r a d a t i o n . Beet p u l p had t h e h i g h e s t n e u t r a l d e t e r g e n t f i b e r (NDF) (P<0.01) e f f e c t i v e d e g r a d a b i l i t y among t h e a g r o - b y p r o d u c t s . I n t h e second t r i a l , t w e l v e l a c t a t i n g d a i r y cows were used t o d e t e r m i n e t h e e f f e c t o f d i e t s matched f o r r a t e o f c a r b o h y d r a t e and p r o t e i n d e g r a d a t i o n on f e e d i n t a k e , d i g e s t i b i l i t y , rumen and b l o o d components, and t h e y i e l d and c o m p o s i t i o n o f m i l k . Four d i e t s ; s t e a m - r o l l e d c o r n - f i s h meal (SRC-FM), s t e a m - r o l l e d c o r n - c a n o l a meal (SRC-CM), s t e a m - r o l l e d b a r l e y - f i s h meal (SRB-FM) and s t e a m - r o l l e d b a r l e y - c a n o l a meal (SRB-CM) were a l l f e d w i t h a l f a l f a hay t o t h e cows f o u r t i m e s p e r day. Feed i n t a k e was n o t i n f l u e n c e d by s o u r c e o f c a r b o h y d r a t e o r p r o t e i n (P>0.10), but t h e d i g e s t i b i l i t y o f most n u t r i e n t s was s i g n i f i c a n t l y i n f l u e n c e d (P<.10) by s o u r c e o f c a r b o h y d r a t e , b e i n g h i g h e r on t h e SRB d i e t s t h a n on t h e SRC d i e t s . T o t a l rumen v o l a t i l e f a t t y a c i d s and rumen ammonia n i t r o g e n were s i g n i f i c a n t l y i n f l u e n c e d by s o u r c e o f p r o t e i n (P<0.10), w i t h most o t h e r p a r a m e t e r s , i n c l u d i n g b l o o d p a r a m e t e r s , showing s i g n i f i c a n t i n t e r a c t i o n s (P<0.01) between s o u r c e o f c a r b o h y d r a t e and s o u r c e o f p r o t e i n . M i l k p r o d u c t i o n , and t h e y i e l d o f p r o t e i n , t o t a l s o l i d s (TS), and s o l i d s - n o t - f a t (SNF) were s i g n i f i c a n t l y i n f l u e n c e d (P<.01) by s o u r c e o f c a r b o h y d r a t e , w i t h t h e cows consuming SRB d i e t s p r o d u c i n g more o f t h e above t h a n t h o s e consuming SRC d i e t s . P e r c e n t f a t and p e r c e n t SNF were h i g h e r and l o w e r r e s p e c t i v e l y on t h e SRC d i e t s t h a n t h e SRB d i e t s . W i t h a l f a l f a hay as roughage, SRB, when f e d i n c o m b i n a t i o n w i t h e i t h e r FM o r CM, r e s u l t e d i n more m i l k p r o d u c t i o n t h a n when SRC was f e d w i t h e i t h e r FM o r CM. D i f f e r e n t s t a r c h and roughage s o u r c e s and a g r o - b y p r o d u c t s degrade a t d i f f e r e n t r a t e s . T h i s v a r i a b i l i t y i n d e g r a d a t i o n c h a r a c t e r i s t i c s can be e x p l o i t e d i n r a t i o n f o r m u l a t i o n i n such a way t h a t t h e p r o v i s i o n o f energy can be matched t o t h e p r o v i s i o n o f n i t r o g e n i n o r d e r t o o p t i m i z e m i c r o b i a l p r o d u c t i o n , maximize performance and m i n i m i z e p r o t e i n wastage. i i i TABLE OP CONTENTS. ABSTRACT i i TABLE OF CONTENTS. i v LIST OF TABLES v i i i ACKNOWLEDGEMENTS X GENERAL INTRODUCTION 1 REFERENCES 7 CHAPTER 1. LITERATURE REVIEW 11 1.1. DEGRADATION OF CARBOHYDRATES AND PROTEINS 11 1.1.1. DEGRADATION OF CARBOHYDRATES 11 1.1.1.1. G e n e r a l 11 1.1.1.2. S t r u c t u r e o f s t a r c h 11 1.1.1.3. I n v i t r o d e g r a d a t i o n o f s t a r c h 14 1.1.1.4. I n s i t u d e g r a d a t i o n o f s t a r c h 15 1.1.2. DEGRADATION OF PROTEINS 16 1.1.2.1. G e n e r a l 16 1.1.2.2.0. C h a r a c t e r i s a t i o n o f d i e t a r y f e e d p r o t e i n s 19 1.1.2.2.1. N i t r o g e n d e t e r m i n a t i o n 19 1.1.2.2.2. P a r t i t i o n i n g o f d i e t a r y p r o t e i n 19 1.1.2.2.3. Methods o f e s t i m a t i n g p o s t - r u m i n a l d i g e s t i o n o f u n d e g r a d a b l e i n t a k e p r o t e i n (UIP) 22 1.1.2.2.4. D e g r a d a t i o n o f p r o t e i n i n t h e rumen 24 1.1.2.2.5. D i g e s t i b i l i t y o f rumen undegraded p r o t e i n i n t h e s m a l l i n t e s t i n e s 28 1.2. PERFORMANCE STUDIES 32 1.2.1. MATCHING OF CARBOHYDRATE AND PROTEIN SOURCES VARYING IN RATE OF STARCH AND PROTEIN DEGRADABILITY. . . 32 1.2.2. MILK PRODUCTION. 38. 1.3. REFERENCES 40 i v CHAPTER 2. THE EFFECT GF STEAM-ROLLING CORN, BARLEY AND WHEAT ON IN VITRO STARCH RELEASE AND IN SITU DEGRADABILITY OF DRY MATTER, CRUDE PROTEIN AND STARCH 49 2.0. ABSTRACT 49 2.1. INTRODUCTION. . 51 2.2.0. MATERIALS AND METHODS. . 54 2.2.1. Source and d e s c r i p t i o n o f f e e d s t u f f s and i n i t i a l h a n d l i n g 54 2.2.2. Cows, d i e t s and n y l o n bags. 55 2.2.3. E x p e r i m e n t a l d e s i g n 58 2.2.4.0. I n c u b a t i o n p r o c e d u r e s 58 2.2.4.1. Rumen i n c u b a t i o n 58 2.2.4.2. A n a l y t i c a l p r o c e d u r e s 60 2.2.4.3. Treatment o f r e s u l t s and s t a t i s t i c a l a n a l y s i s 61 2.2.4.4. Enzyme i n v i t r o s t a r c h r e l e a s e p r o c e d u r e 63 2.3.0. RESULTS AND DISCUSSION 63 2.3.1. G e n e r a l o b s e r v a t i o n s 63 2.3.2.0 Dry M a t t e r d e g r a d a t i o n c h a r a c t e r i s t i c s 66 2.3.2.1. R a p i d l y d e g r a d a b l e f r a c t i o n o f DM. . . . 66 2.3.2.2. S l o w l y d e g r a d a b l e f r a c t i o n o f DM 67 2.3.2.3. Rate o f d e g r a d a t i o n o f DM 68 2.3.2.4. Lag t i m e o f DM d e g r a d a t i o n 69 2.3.2.5. E f f e c t i v e d e g r a d a b i l i t y o f DM 70 2.3.3.0. S t a r c h d e g r a d a t i o n c h a r a c t e r i s t i c s 71 2.3.3.1. R a p i d l y d e g r a d a b l e f r a c t i o n o f s t a r c h . . 71 2.3.3.2. S l o w l y d e g r a d a b l e f r a c t i o n o f s t a r c h . . . 72 2.3.3.3. Rate o f d e g r a d a t i o n o f s t a r c h 73 2.3.3.4. Lag t i m e o f s t a r c h d e g r a d a t i o n 77 2.3.3.5. E f f e c t i v e d e g r a d a b i l i t y o f s t a r c h . . . . 78 2.3.4.0 P r o t e i n d e g r a d a t i o n c h a r a c t e r i s t i c s 79 2.3.4.1. R a p i d l y d e g r a d a b l e f r a c t i o n o f CP. . . . 79 2.3.4.2. S l o w l y d e g r a d a b l e f r a c t i o n o f CP 81 2.3.4.3. Rate o f d e g r a d a t i o n o f CP 82 2.3.4.4. Lag t i m e o f CP d e g r a d a t i o n 83 2.3.4.5. E f f e c t i v e d e g r a d a b i l i t y o f CP 84 2.3.5. I n v i t r o s t a r c h r e l e a s e 85 2.4.0. SUMMARY AND CONCLUSION 87 2.5.0. REFERENCES 89 2.6.0. TABLES. 94 V CHAPTER 3. IN SITU DEGRADABILITY OF DRY MATTER AND NEUTRAL DETERGENT FIBER OF THREE ROUGHAGES AND AGRO-BYPRODUCTS USED AS LIVESTOCK FEEDS. . . . 101 3.0. ABSTRACT 101 3.1. INTRODUCTION. 103 3.2.0. MATERIALS AND METHODS. 106 3.2.1. Source and d e s c r i p t i o n o f f e e d s t u f f s and i n i t i a l h a n d l i n g 106 3.2.2. Cows, d i e t s and n y l o n bags 107 3.2.3. A n a l y t i c a l P r o c e d u r e s 107 3.2.4. Treatment o f r e s u l t s and s t a t i s t i c a l a n a l y s i s 107 3.3.0. RESULTS AND DISCUSSION. 108 3.3.1. Che m i c a l c o m p o s i t i o n 108 3.3.2. DM and NDF d e g r a d a t i o n c h a r a c t e r i s t i c s o f a g r o - b y p r o d u c t s 109 3.3.3. DM and NDF d e g r a d a t i o n c h a r a c t e r i s t i c s o f roughages 116 3.4.0. SUMMARY AND CONCLUSION 122 3.5.0. REFERENCES 124 3.6.0. TABLES 128 CHAPTER 4. THE EFFECT OF DIETS MATCHED FOR RATE OF DEGRADATION OF CARBOHYDRATE AND PROTEIN ON MILK PRODUCTION CHARACTERISTICS OF DAIRY COWS 131 4.0. ABSTRACT 131 4.1. INTRODUCTION 133 4.2 .0. MATERIALS AND METHODS 135 4.2.1. D i e t s 135 4.2.2. Cow management and e x p e r i m e n t a l d e s i g n . . . . 136 4.2.3. N y l o n bag s t u d i e s 137 4.2.4. N u t r i e n t i n t a k e and a p p a r e n t t o t a l t r a c t d i g e s t i b i l i t y 138 4.2.5. A n a l y t i c a l p r o c e d u r e s 141 4.2.6. Rate of passage 142 4.2.7. B l o o d Sampling 144 4.2.8. Rumen s a m p l i n g 144 4.2.9. M i l k p r o d u c t i o n and c o m p o s i t i o n 145 4.2.10. S t a t i s t i c a l a n a l y s i s 146 4.3.0. RESULTS AND DISCUSSION 148 v i 4.3.1. I n s i t u T r i a l 148 4.3.2.0. I n t a k e 153 4.3.2.1. E f f e c t o f c a r b o h y d r a t e s o u r c e 153 4.3.2.2. E f f e c t o f p r o t e i n s o u r c e 155 4.3.3.0. Dry m a t t e r , o r g a n i c m a t t e r and n u t r i e n t d i g e s t i b i l i t y 155 4.3.3.1. E f f e c t o f c a r b o h y d r a t e s o u r c e 155 4.3.3.2. E f f e c t o f s o u r c e o f p r o t e i n 157 4.3.4.0. Ruminal VFAs, NH3-N and pH 158 4.3.5.0 Rate o f passage 167 4.3.6.0. M i l k y i e l d and c o m p o s i t i o n 169 4.4.0. SUMMARY AND CONCLUSIONS 176 4.5.0. REFERENCES 177 4.6.0 TABLES 184 5.0 GENERAL CONCLUSIONS AND RECOMMENDATIONS 193 6.0 APPENDICES 196 APPENDIX 1. SAS program used t o c a l c u l a t e d e g r a d a t i o n c h a r a c t e r i s t i c s f o r f e e d s u s i n g t h e m o d i f i e d e q u a t i o n o f 0 r s k o v and MacDonald, (1979) 196 APPENDIX 2. Schematic r e p r e s e n t a t i o n o f t h e a l l o c a t i o n o f d i e t s f o r a 4 t r e a t m e n t / 3 p e r i o d s w i t c h back d e s i g n used f o r t h e d a i r y cow t r i a l 1 198 v i i LIST OP TABLES TABLE 1. I n g r e d i e n t s o f t h e d i e t consumed by r u m i n a l l y f i s t u l a t e d cows used f o r t h e i n s i t u e x p e r i m e n t s (DM b a s i s ) 94 T a b l e 2. C h e m i c a l c o m p o s i t i o n o f i n g r e d i e n t s used i n t h e d i e t consumed by r u m i n a l l y f i s t u l a t e d cows used f o r i n s i t u s t u d y (DM b a s i s ) 95 T a b l e 3. C h e m i c a l c o m p o s i t i o n o f c e r e a l g r a i n s used i n i n s i t u and i n v i t r o e x p e r i m e n t s (DM b a s i s ) 95 T a b l e 4. S t a r c h c o n t e n t o f t e s t f e e d s t u f f s and v a l i d a t i o n o f s t a r c h a n a l y s i s method (DM b a s i s ) 96 T a b l e 5. The e f f e c t o f t y p e o f c e r e a l and s t e a m - r o l l i n g on i n s i t u d r y m a t t e r d e g r a d a t i o n c h a r a c t e r i s t i c s o f c o r n , b a r l e y and wheat i n c u b a t e d i n t h e rumen o f d a i r y cows. . . 97 T a b l e 6. The e f f e c t o f t y p e o f c e r e a l and s t e a m - r o l l i n g on i n s i t u s t a r c h d e g r a d a t i o n c h a r a c t e r i s t i c s o f c o r n , b a r l e y and wheat i n c u b a t e d i n t h e rumen o f d a i r y cows 98 T a b l e 7. The e f f e c t o f t y p e o f c e r e a l and s t e a m - r o l l i n g on i n s i t u c r u d e p r o t e i n d e g r a d a t i o n c h a r a c t e r i s t i c s o f c o r n , b a r l e y and wheat i n c u b a t e d i n t h e rumen o f d a i r y cows. . . 99 T a b l e 8. T a b l e 9. T a b l e 10. I n v i t r o s t a r c h r e l e a s e (% o f DM) by steam r o l l e d and u n p r o c e s s e d c e r e a l g r a i n s i n c u b a t e d w i t h a m y l o g l u c o s i d a s e enzyme 100 Ch e m i c a l c o m p o s i t i o n o f a g r o - b y p r o d u c t s and roughages used i n i n s i t u e xperiment (DM b a s i s ) 128 I n s i t u d e g r a d a t i o n c h a r a c t e r i s t i c s o f d r y m a t t e r and n e u t r a l d e t e r g e n t f i b e r o f wheat m i l l r u n , r y e d i s t i l l e r s g r a i n and beet p u l p 1 129 T a b l e 11. I n s i t u d e g r a d a t i o n c h a r a c t e r i s t i c s o f d r y m a t t e r and n e u t r a l d e t e r g e n t f i b e r o f c o r n - g r a s s s i l a g e , o r c h a r d g r a s s hay and a l f a l f a hay 1 130 T a b l e 12. I n g r e d i e n t s c o m p o s i t i o n o f c o n c e n t r a t e s f e d t o l a c t a t i n g d a i r y cows as a p e r c e n t a g e o f t h e d r y m a t t e r 1 . . . 184 T a b l e 13. N u t r i e n t a n a l y s i s o f major d i e t a r y i n g r e d i e n t s f e d t o l a c t a t i n g d a i r y cows 1. 185 v i i i T a b l e 14. C h e m i c a l a n a l y s i s o f d i e t s f e d t o l a c t a t i n g d a i r y cows 1 2 186 T a b l e 15a. I n s i t u d i s a p p e a r a n c e o f d r y m a t t e r , s t a r c h and n e u t r a l d e t e r g e n t f i b e r i n cows o f a l f a l f a hay and c e r e a l i n g r e d i e n t s u sed i n r a t i o n s f o r l a c t a t i n g d a i r y cows 1 2 187 T a b l e 15b. I n s i t u d i s a p p e a r a n c e o f d r y m a t t e r and c r u d e p r o t e i n i n cows o f FM and CM i n g r e d i e n t s used i n r a t i o n s f o r l a c t a t i n g d a i r y cows 1 2 188 T a b l e 16. L e a s t square means f o r d r y m a t t e r , o r g a n i c m a t t e r and n u t r i e n t i n t a k e s o f l a c t a t i n g cows r e c e i v i n g SRC o r SRB w i t h e i t h e r FM o r CM d u r i n g t h e i n t a k e s t u d y . . . . 189 T a b l e 17. L e a s t square means o f d r y m a t t e r and o r g a n i c m a t t e r i n t a k e s , t o t a l a p p a r e n t n u t r i e n t d i g e s t i b i l i t i e s and r a t e o f passage f o r l a c t a t i n g cows f e d e i t h e r SRC o r SRB w i t h e i t h e r FM o r CM d u r i n g t h e d i g e s t i b i l i t y t r i a l . . . 190 T a b l e 18. L e a s t s q u a r e s means o f changes i n r u m i n a l v o l a t i l e f a t t y a c i d s , pH, ammonia-N, b l o o d g l u c o s e and b l o o d urea-N c o n c e n t r a t i o n s f o r cows f e d SRC o r SRB w i t h e i t h e r FM o r CM1 191 T a b l e 19. L e a s t square means f o r m i l k p r o d u c t i o n , y i e l d components, m i l k c o m p o s i t i o n , g r o s s e f f i c i e n c i e s and body w e i g h t change f o r cows f e d SRC o r SRB w i t h e i t h e r FM o r CM 192 i x ACKNOWLEDGEMENTS My s i n c e r e a p p r e c i a t i o n t o my t h e s i s s u p e r v i s o r Dr. J.A. S h e l f o r d f o r t h e g u i d a n c e and v a l u a b l e s u g g e s t i o n s i n b o t h course-work as w e l l as r e s e a r c h l e a d i n g t o t h i s r e p o r t . The a d v i c e and s e r v i c e s o f t h e f o l l o w i n g members o f t h e t h e s i s committee i s g r e a t l y a p p r e c i a t e d ; Dr. L . J . F i s h e r and Dr. R.M. T a i t . The p a r t i c i p a t i o n o f Dr. R.M. Beames and Dr. D.D. K i t t s as u n i v e r s i t y examiners i s g r e a t l y a p p r e c i a t e d . Many t h a n k s t o Dr. J.W. H a l l ( A g r i c u l t u r e and A g r i - F o o d Canada) f o r h i s h e l p w i t h t h e s t a t i s t i c a l a n a l y s i s o f t h e d a t a . I would l i k e t o thank l a b o r a t o r y t e c h n i c a l s t a f f , South campus ( D a i r y c a t t l e u n i t ) and a d m i n i s t r a t i v e s t a f f f o r a l l t h e s u p p o r t g i v e n t o me d u r i n g t h e c o u r s e o f my s t u d i e s i n t h e department. I have e n j o y e d t h e v a l u a b l e s u p p o r t o f my f e l l o w g r a d u a t e s t u d e n t s i n t h e department; I j u s t want t o say t h a t a l l o f you were g r e a t . I would l i k e t o thank t h e U n i v e r s i t y o f Zambia (Lusaka) f o r g r a n t i n g me s t u d y l e a v e and f i n a n c i a l s u p p o r t f o r my s t u d i e s . Many t h a n k s t o t h e Canadian I n t e r n a t i o n a l Development Agency f o r t h e f i n a n c i a l s u p p o r t t o r e a l i s e my dreams. To t h e many f r i e n d s t h a t I met a t UBC and t h e community, b o t h Canadians and v a r i o u s o t h e r n a t i o n a l s , I say thank you f o r y o u r h o s p i t a l i t y and s h a r i n g . L a s t l y , I thank my w i f e , Rose f o r t y p i n g most o f t h e l a s t d r a f t o f t h i s t h e s i s a t a d i f f i c u l t t i m e . To my son, Nsalamu, thank you f o r b e i n g n i c e and f o r y o u r company a t South Campus. I would l i k e t o welcome t h e new a d d i t i o n t o my f a m i l y , my d a u g h t e r , Mukonde J e l e s i . D e d i c a t e d t o my f a m i l y and my own f a m i l y My dad and mama used t o say, ' K u l i m b i k i l a zabwino z i l i m t s o g o r o ' ( n y a n j a ) which means, 'Stay s t r o n g , t h e g o o d i e s a r e i n t h e f u t u r e ' x GENERAL INTRODUCTION. The a b i l i t y o f r u m i n a n t a n i m a l s t o u t i l i z e f i b r o u s f e e d s t u f f s has a l l o w e d man t o m a i n t a i n t h e s e a n i m a l s and produce meat and m i l k w h o l l y on roughages. E f f i c i e n t and economic meat and m i l k p r o d u c t i o n r e q u i r e s a s u f f i c i e n t s u p p l y o f n u t r i e n t s from t h e rumen and s m a l l i n t e s t i n e s t o o p t i m i s e p r o d u c t i o n . I n s p i t e o f t h e a b i l i t y t o u t i l i z e f i b r o u s f e e d s and m a i n t a i n body w e i g h t and s u p p o r t moderate p r o d u c t i o n l e v e l s , r u m i n a n t s have l i m i t e d c a p a c i t y t o consume l a r g e amounts t o meet t h e i r n u t r i e n t r e q u i r e m e n t s , p a r t i c u l a r l y cows i n e a r l y l a c t a t i o n and young gr o w i n g a n i m a l s . Good q u a l i t y roughage can s u p p l y energy, p r o t e i n and o t h e r n u t r i e n t s . However imbalance o f t h e s e n u t r i e n t s r e s u l t s i n an i n a d e q u a t e o r o v e r - s u p p l y o f some n u t r i e n t s t o t h e a n i m a l . I n l i g h t o f t h e above f a c t s , s u p p l e m e n t a t i o n o f roughages w i t h c o n c e n t r a t e s becomes i m p o r t a n t t o c o r r e c t t h e i m b a l a n c e s and ensure an adequate s u p p l y o f n u t r i e n t s i n o r d e r t o r e a l i s e t h e f u l l p o t e n t i a l o f t h e a n i m a l . S u p p l e m e n t a t i o n w i t h c o n c e n t r a t e s r e s u l t s i n i n c r e a s e d d r y m a t t e r i n t a k e (DMI) and s u p p l y o f n u t r i e n t s and improved a n i m a l p e r formance (Galloway e t a l . , 1993 and F o s t e r e t a l . , 1993). S p e c i e s , v a r i e t y , s t o r a g e , h a n d l i n g and p r o c e s s i n g o f c o n c e n t r a t e s a r e among t h e f a c t o r s t h a t d e t e r m i n e t h e q u a l i t y and r u m i n a l d e g r a d a t i o n c h a r a c t e r i s t i c s . C e r e a l g r a i n s c o n t a i n l a r g e amounts o f s t a r c h and a r e t h e r e f o r e i n c l u d e d i n d i e t s as energy supplements, w h i l e c o n c e n t r a t e s based on a n i m a l and o i l - s e e d b y p r o d u c t s a r e used as p r o t e i n supplements. C o n c e n t r a t e f e e d s a r e compounded u s u a l l y from h i g h energy and p r o t e i n i n g r e d i e n t s w h i c h commonly i n c l u d e c e r e a l g r a i n s and p l a n t and a n i m a l p r o t e i n s o u r c e s , r e s p e c t i v e l y . When t h e s e m a t e r i a l s a r e consumed t h e y undergo f e r m e n t a t i v e breakdown i n t h e rumen, r e l e a s i n g energy and n i t r o g e n which a r e u t i l i z e d by m i c r o b e s t o b u i l d t h e i r own c e l l s . A p o r t i o n o f t h e f e e d t h a t does n o t g e t d i g e s t e d i n t h e rumen p l u s m i c r o b i a l p r o t e i n , p a s s e s t o t h e s m a l l i n t e s t i n e where i t i s d i g e s t e d by p a n c r e a t i c and i n t e s t i n a l enzymes. M i c r o b i a l p r o t e i n i s a b l e t o meet p r o t e i n r e q u i r e m e n t s f o r most a n i m a l s a t d i f f e r e n t p r o d u c t i o n s t a g e s because o f i t s h i g h q u a l i t y compared t o most f e e d p r o t e i n (Storm and 0 r s k o v , 1983). However, i n c r e a s e d n u t r i e n t demands by h i g h - p r o d u c i n g e a r l y -l a c t a t i o n d a i r y cows and young growing beef a n i m a l s may r e s u l t i n m i c r o b i a l p r o t e i n not b e i n g adequate t o meet t h e a n i m a l ' s r e q u i r e m e n t s f o r amino a c i d s such as m e t h i o n i n e and l y s i n e w h i c h a r e l i m i t i n g i n m i c r o b i a l p r o t e i n (Storm and 0 r s k o v , 1983, 1984). I t has been proposed t h a t p r o v i d i n g some of t h e d i e t a r y p r o t e i n i n an u n d e g r a d a b l e form i n t h e rumen and m a x i m i z i n g m i c r o b i a l p r o t e i n s y n t h e s i s t h r o u g h p r o p e r c a r b o h y d r a t e and p r o t e i n r a t i o n b a l a n c i n g i s t h e s o l u t i o n t o m e e t i n g t h e h i g h e r p r o t e i n r e q u i r e m e n t s f o r h i g h p r o d u c i n g d a i r y cows and f a s t young g r o w i n g beef s t e e r s (Nocek and R u s s e l l , 1988). T h e r e f o r e , knowledge o f t h e b e h a v i o r o f c a r b o h y d r a t e s and p r o t e i n s i n t h e rumen becomes i m p o r t a n t i n o r d e r t o o p t i m i s e u t i l i z a t i o n o f b o t h energy and p r o t e i n supplements. 2 C a r b o h y d r a t e s i n c l u d e p l a n t m a t e r i a l d e r i v e d from t h e c e l l -w a l l , r e f e r r e d t o as s t r u c t u r a l c a r b o h y d r a t e s (SC) and t h a t p o r t i o n d e r i v e d from c e l l - c o n t e n t s r e f e r r e d t o as n o n - s t r u c t u r a l c a r b o h y d r a t e s (NSC) (Van S o e s t , 1982 and Van S o e s t , 1986). N o n - s t r u c t u r a l c a r b o h y d r a t e s w h i c h i n c l u d e s u g a r s and s t a r c h e s a r e more s o l u b l e t h a n SC which i n c l u d e s a l l m a t e r i a l s r e l a t e d t o c e l l - w a l l i n c l u d i n g c e l l u l o s e , h e m i c e l l u l o s e , l i g n i n , s i l i c a , and h e a t damaged p r o t e i n . A l s o d i f f e r e n c e s i n s o l u b i l i t y e x i s t between and w i t h i n c a r b o h y d r a t e groups. Sugars a r e more s o l u b l e t h a n s t a r c h e s w h i c h a r e more s o l u b l e t h a n t h e complex m o l e c u l e s o f c e l l -w a l l s (Van S o e s t , 1982 and Van S o e s t , 1986). E v a l u a t i o n o f f i v e c e r e a l g r a i n s , c o r n , sorghum, wheat, o a t s , and b a r l e y showed g r e a t e r i n v i t r o and i n s i t u d e g r a d a t i o n o f b a r l e y , wheat and o a t s t a r c h t h a n t o s t a r c h from c o r n and sorghum ( H e r r e r a - S a l d a n a e t a l . , 1990b). S i m i l a r r e s u l t s i n v i t r o ( M a l e s t e i n e t a l . , 1988, and Cone e t a l . , 1989) and i n s i t u (Fiems e t a l . , 1990; Tamminga e t a l . , 1990, and M a l c o l m and K i e s l i n g , 1993) have been r e p o r t e d . P r o c e s s i n g such as g r i n d i n g , d r y r o l l i n g , steam f l a k i n g , steam r o l l i n g and p o p p i n g r e s u l t e d i n i n c r e a s e d i n v i t r o ( M a l e s t e i n e t a l . , 1988, and Cone e t a l . , 1989) and i n s i t u s t a r c h d e g r a d a t i o n f o r most g r a i n s (Galyean e t a l . , 1981; T h e u r e r , 1986 and Thomas e t a l . , 1988). However o t h e r w o r k e r s r e p o r t e d d e c r e a s e d i n s i t u s t a r c h d e g r a d a t i o n due t o steam f l a k i n g o f c o r n , wheat and b a r l e y (Fiems e t a l . , 1990), steam r o l l i n g o f b a r l e y (Engstrom e t a l . , 1992) and e x t r u s i o n o r e x p a n s i o n o f wheat, b a r l e y and c o r n ( A r i e l i e t a l . , 1995). However, degree o f g e l a t i n i z a t i o n 3 measured i n v i t r o u s i n g g r a n u l a r a m y l o g l u c o s i d a s e enzyme o r b i r e f r i g e n c e shows t h a t sugar and s t a r c h r e l e a s e i s improved a f t e r s t e a m - f l a k i n g (Fiems e t a l . , 1990 and M a l c o l m and K i e s l i n g , 1993) and steam r o l l i n g ( M a t h i s o n e t a l . , 1991). I n v i v o s t u d i e s a l s o s u p p o r t i n v i t r o and i n s i t u f i n d i n g s . B a r l e y s t a r c h was more d e g r a d a b l e i n t h e rumen t h a n s t a r c h from c o r n ; however t o t a l d i g e s t i b i l i t y was s i m i l a r ( S p i c e r e t a l . , 1986; McCarthy e t a l . , 1989; H e r r e r a - S a l d a n a e t a l . , 1990a and H u n t i n g t o n , 1994). Steam r o l l i n g and f l a k i n g i n c r e a s e d i n v i v o r u m i n a l DM and s t a r c h d i g e s t i b i l i t y o f g r a i n s ( H a l e , 1973; G a l y e a n e t a l . , 1981 and T h e u r e r , 198 6) . S t e a m - r o l l i n g a l s o h e l p s t o r e d u c e f i n e s and t h e r e f o r e d u s t n e s s r e s u l t i n g i n improved i n t a k e s f o r c e r t a i n c e r e a l g r a i n s such as b a r l e y . S i m i l a r l y s t r u c t u r a l c a r b o h y d r a t e s , l i k e n o n - s t r u c t u r a l c a r b o h y d r a t e s , degrade a t d i f f e r e n t r a t e s and t o d i f f e r e n t e x t e n t s . Varga and Hoover, (1983) r e p o r t e d h i g h e r i n saeco d e g r a d a b i l i t y o f NDF f o r a l f a l f a hay and c l o v e r t h a n f o r g r a s s e s such as o r c h a r d g r a s s , w h i l e NDF from c o r n s i l a g e was more r e a d i l y degraded t h a n NDF from legumes and g r a s s hays. Corn cobs, soy h u l l s and a hay c r o p s i l a g e were l o w e s t i n r a t e o f d e g r a d a t i o n w h i l e a g r o -b y p r o d u c t s were s i m i l a r o r s l i g h t l y l o wer t h a n legume and g r a s s hay and a g r o - b y p r o d u c t s such as wheat b r a n , brewers g r a i n , b e e t p u l p . S i m i l a r r e s u l t s have been obse r v e d f o r legumes and g r a s s e s u s i n g i n v i t r o (Darcy and B e y l e a , 1980 and B e y l e a e t a l . , 1983) and i n v i v o (Holden e t a l . , 1994) t e c h n i q u e s and a l s o o t h e r i n s i t u methods (Shaver e t a l . , 1988). Other workers have r e p o r t e d d i f f e r e n c e s i n 4 t h e r a t e o f DM and n e u t r a l - d e t e r g e n t - f i b e r (NDF) d e g r a d a t i o n o f a wide range o f f e e d s t u f s i n c l u d i n g b y p r o d u c t s (Souvant e t a l . 1985; Tamminga e t a l . , 1990 and de Smet e t a l . , 1995). These d i f f e r e n c e s i n c a r b o h y d r a t e breakdown i n t h e rumen can be e x p l o i t e d i n r a t i o n f o r m u l a t i o n so t h a t energy r e l e a s e i s c o n s i s t e n t and adequate t o c a p t u r e t h e n i t r o g e n r e l e a s e d d u r i n g f e r m e n t a t i o n . P r o t e i n s from d i f f e r e n t s o u r c e s , l i k e c a r b o h y d r a t e s , degrade a t d i f f e r e n t r a t e s i n t h e rumen ( H v e l p l u n d , 1985; Tamminga e t a l , 1990; H e r r e r a - S a l d a n a e t a l . , 1990b; Erasmus e t a l . , 1990, 1994 and S t e r n e t a l . , 1994). Some p h y s i c a l (eg, m e c h a n i c a l e x t r a c t i o n o f o i l from soybean) and c h e m i c a l p r o c e s s e s ( e x t r a c t i o n o f o i l from soybean u s i n g hexane) a p p l i e d d u r i n g f e e d o r f o o d p r o c e s s i n g c o n t r i b u t e t o t h e d e c r e a s e i n p r o t e i n d e g r a d a t i o n i n t h e rumen ( H v e l p l u n d , 1985 and S t e r n e t a l . , 1994). I n o r d e r t o u t i l i z e p r o t e i n e f f i c i e n t l y , i t i s i m p o r t a n t t h a t n i t r o g e n r e l e a s e i s c o o r d i n a t e d w i t h p r e s e n c e o f s u f f i c i e n t c a r b o h y d r a t e f o r t h e c a p t u r e o f n i t r o g e n by b a c t e r i a and a l s o t o m i n i m i z e p r o t e i n wastage (Nocek and R u s s e l l , 1988 and H e r r e r a - S a l d a n a e t a l . , 1990a). I n o r d e r t o a c c o m p l i s h t h e above, knowledge o f r u m i n a l and i n t e s t i n a l b e h a v i o r o f c a r b o h y d r a t e s and p r o t e i n s f o r f e e d i n g r e d i e n t s i s i m p o r t a n t f o r p r o p e r b a l a n c i n g o f t h e r a t i o n t o maximize m i c r o b i a l p r o t e i n p r o d u c t i o n i n t h e rumen and a l s o t o p r o v i d e s u f f i c i e n t t o t a l d i e t a r y n u t r i e n t s t o meet t h e a n i m a l ' s n u t r i e n t r e q u i r e m e n t s . 5 The main o b j e c t i v e s o f t h i s s t u d y were; 1. To d e t e r m i n e t h e r a t e and e x t e n t of breakdown o f DM, CP, s t a r c h and NDF o f commonly used c e r e a l s , roughages and a g r o - b y p r o d u c t s u s i n g i n s i t u and i n v i t r o methods, 2. To d e t e r m i n e t h e e f f e c t o f f e e d i n g d i e t s matched f o r r a t e o f c a r b o h y d r a t e and p r o t e i n d e g r a d a t i o n on n u t r i e n t i n t a k e , a p p a r e n t t o t a l t r a c t d i g e s t i b i l i t y , r u m i n a l and b l o o d p a r a m e t e r s and m i l k p r o d u c t i o n c h a r a c t e r i s t i c s o f l a c t a t i n g d a i r y cows. 6 REFERENCES A r i e l i , A., T. B r u c k e n t a l , O. Kedar, and D. S k l a n . 1995. I n sacco d i s a p p p e a r a n c e o f s t a r c h , n i t r o g e n and f a t i n p r o c e s s e d g r a i n s . Anim. Feed S c i . and Tech. 51:287. B e y l e a , R.L., M.B. F o s t e r , and G.M. Z i n n . 1983. E f f e c t o f d e l i g n i f i c a t i o n on i n v i t r o d i g e s t i o n o f a l f a l f a c e l l u l o s e J . D a i r y S c i . 66:1277. Cone, J.W., W. C l i n e - T h e i l , A. M a l e s t e i n and A.Th. v a n ' t K l o o s t e r . 1 9 89.Degradation o f s t a r c h by i n c u b a t i o n w i t h rumen f l u i d . A comparison o f d i f f e r e n t s t a r c h s o u r c e s . J . S c i . Food A g r i c . 49:173. Darcy, B.K., and R.L. B e y l e a . 1980. E f f e c t o f d e l i g n i f i c a t i o n upon i n v i t r o d i g e s t i o n o f f o r a g e c e l l u l o s e . J . Anim. S c i . 51:798. de Smet, A.M., J.L. de Boever, D.L. de brabander, J.M. Vanacker and Ch. V. Boucque. 1995. I n v e s t i g a t i o n o f d r y m a t t e r d e g r a d a t i o n and a c i d o t i c e f f e c t o f some f e e d s t u f f s by means o f i n s a c c o and i n v i t r o i n c u b a t i o n s . Anim. Feed S c i . and Tech. 51:297. Engstrom, D.F. G.W. M a t h i s o n , and L.A. Goonewardene. 1992. E f f e c t o f B - g l u c a n , s t a r c h and f i b e r c o n t e n t and steam v s d r y r o l l i n g o f b a r l e y g r a i n on i t s d e g r a d a b i l i t y and u t i l i z a t i o n by s t e e r s . Anim. Feed S c i . and Tech. 37:33. Erasmus, L . J . , P.M. Botha, P. L e b z i e n , and H.H. M e i s s n e r . 1990. C o m p o s i t i o n and i n t e s t i n a l d i g e s t i b i l i t y o f rumen-fermented f e e d s and duodenal d i g e s t a i n cows u s i n g n y l o n bag t e c h n i q u e s . J . D a i r y S c i . 73:3494. Erasmus, L . J . , P.M., Botha, C.W. Cruywagen, and H.H. M e i s s n e r . 1994. Amino a c i d p r o f i l e and i n t e s t i n a l d i g e s t i b i l i t y i n d a i r y cows o f rumen-undegradable p r o t e i n from v a r i o u s f e e d s t u f f s . J . D a i r y S c i . 77:541. Fiems, L.O., B.G. C o t t y n , Ch. V. Boucque, J.M. Vanacker, and F.X. Buysse. 1990. E f f e c t o f g r a i n p r o c e s s i n g on i n s a c c o d i g e s t i b i l i t y and d e g r a d a b i l i t y i n t h e rumen. A r c h . Anim. N u t r . B e r l i n 40:713. F o s t e r , L.A. , J r . , A.L. Goetsch, D.L. G a l l o w a y , S r . , and Z.B. Johnson. 1993. Feed i n t a k e and d i g e s t i b i l i t y and l i v e w e i g h t g a i n by c a t t l e consuming f o r a g e supplemented w i t h r i c e b r a n and (or) c o r n . J . Anim. S c i . 17:3105. 7 G a l l o w a y , D.L.,Sr., A.L. G o e t s c h , L.A. F o s t e r , J r . , A.R. P a t i l , W. Sun, and Z.B. Johnson. 1993. Feed i n t a k e and d i g e s t i b i l i t y by c a t t l e consuming bermudagrass o r o r c h a r d g r a s s hay supplemented w i t h soybean h u l l s and (or) c o r n . J . Anim. S c i . 71:3087. G a l y e a n , M.L., D.G. Wagner, and F.N. Owens. 1981. Dry m a t t e r and s t a r c h d i s a p p e a r a n c e of c o r n and sorghum as i n f l u e n c e d by p a r t i c l e s i z e and p r o c e s s i n g . J . D a i r y S c i . 64:1804. H a l e , W.H. 1973. I n f l u e n c e o f p r o c e s s i n g on u t i l i z a t i o n o f g r a i n s t a r c h by r u m i n a n t s . J . Anim. S c i . 37:1075. H e r r e r a - S a l d a n a , R., R. Gomez-alarcon, M. T o r a b i , and J . L . Huber. 1990a. I n f l u e n c e o f s y n c h r o n i z i n g p r o t e i n and s t a r c h d e g r a d a t i o n i n t h e rumen on n u t r i e n t u t i l i z a t i o n and m i c r o b i a l p r o t e i n s y n t h e s i s . J . D a i r y S c i . 73:142. H e r r e r a - S a l d a n a , R., J.T. Huber, and M.H. Poore. 1990b. Dry m a t t e r , c r u d e p r o t e i n and s t a r c h d e g r a d a b i l i t y o f f i v e c e r e a l g r a i n s . J . D a i r y S c i . 73:2386. Holden, L.A., B.P. G l e n , R.A. Erdman, and W.E. P o l t s . 1994. E f f e c t s o f a l f a l f a and o r c h a r d g r a s s on d i g e s t i o n by d a i r y cows. J . D a i r y S c i . 77:2580. H u n t i n g t o n , G.B. 1994. Ruminant s t a r c h u t i l i z a t i o n p r o g r e s s has been e x t e n s i v e . F e e d s t u f f s . June 6:16. H v e l p l u n d , T. 1985. D i g e s t i b i l i t y o f rumen m i c r o b i a l p r o t e i n and undegraded d i e t a r y p r o t e i n e s t i m a t e d i n t h e s m a l l i n t e s t i n e o f sheep and by i n s a c c o p r o c e d u r e . A c t a A g r i c . Scand. (Suppl).25:132. M a lcolm, K . J . , and H.E. K i e s l i n g . 1993. Dry m a t t e r d i s a p p e a r a n c e and g e l a t i n i z a t i o n o f g r a i n s as i n f l u e n c e d by p r o c e s s i n g and c o n d i t i o n i n g . Anim. Feed S c i . and Tech. 40:321. M a l e s t e i n , A., A. Th. v a n ' t K l o o s t e r , and J.W. Cone. 1988. D e g r a d a b i l i t y o f v a r i o u s t y p e s of s t a r c h by i n c u b a t i o n w i t h rumen f l u i d s o r b a c t e r i a l a l p h a - a m y l a s e . J . Anim. P h y s i o l .a. Anim. N u t r . 59:225. M a t h i s o n , G.W., R. H i r o n a k a , B.K. K e r r i g a n , I . V l a c h , L.P. M i l l i g a n , and R.D, Weisenberger. 1991. Rate o f s t a r c h d e g r a d a t i o n , a p p a r e n t d i g e s t i b i l i t y , and r a t e and e f f i c i e n c y o f s t e e r g a i n as i n f l u e n c e d by b a r l e y g r a i n volume-weight and p r o c e s s i n g method. Can. J . Anim. S c i . 71:867. McCarthy, R.D., J r . , T.H. Klusmeyer, J.L. V i n c i n i , J.H. C l a r k , and D.R. N e l s o n . 1989. E f f e c t s o f s o u r c e o f p r o t e i n and c a r b o h y d r a t e on r u m i n a l f e r m e n t a t i o n and passage of n u t r i e n t s t o t h e s m a l l i n t e s t i n e o f l a c t a t i n g cows. J . D a i r y S c i . 72:2002. 8 Nocek, J.E., and J.B. R u s s e l l . 1988. P r o t e i n and energy as an i n t e r g r a t e d system. R e l a t i o n s h i p o f r u m i n a n t p r o t e i n and c a r b o h y d r a t e a v a i l a b i l i t y t o m i c r o b i a l p r o t e i n s y n t h e s i s and m i l k p r o d u c t i o n . J . D a i r y S c i . 71:2070. Shaver, R.D., L.D. S a t t e r , and A. J o r g e n s e n . 1988. Impact of f o r a g e c o n t e n t on d i g e s t i o n and d i g e s t i b l e passage i n l a c t a t i n g d a i r y cows. J . D a i r y S c i . 71:1556. Souvant, D., D. B e r t r a n d , and S. G i g e r . 1985. V a r i a t i o n and p r e c i s i o n o f t h e i n s a c c o d r y m a t t e r d i g e s t i o n o f c o n c e n t r a t e s and b y p r o d u c t s . Anim. Feed S c i . Tech. 13:7. S p i c e r , L.A., C.B. T h e u r e r , J . Sowe, and T.H. Noon. 1986. Ruminal and p o s t r u m i n a l u t i l i z a t i o n o f n i t r o g e n and s t a r c h from sorghum g r a i n - , c o r n - , and b a r l e y - b a s e d d i e t s by beef s t e e r s . J . Anim. S c i . 62:521. S t e r n , M.D., G.A. Varga, J.H. C l a r k , J.L. F i r k i n s , J.T. Huber, and D.L. P a l m q u i s t . 1994. Symposium: M e t a b o l i c r e l a t i o n s h i p i n s u p p l y o f n u t r i e n t s f o r m i l k p r o t e i n s y n t h e s i s . E v a l u a t i o n o f c h e m i c a l and p h y s i c a l p r o p e r t i e s o f f e e d s t h a t a f f e c t m e t a b o l i s m i n t h e rumen. J . D a i r y S c i . 77:2762. Storm, E. , and E.R. 0 r s k o v . 1983. The n u t r i t i v e v a l u e o f rumen m i c r o - o r g a n i s m s i n r u m i n a n t s . 1. Large s c a l e i s o l a t i o n and c h e m i c a l c o m p o s i t i o n o f m i c r o - o r g a n i s m a . B r . J . N u t r . 50:463. Storm, E. , and E.R. 0 r s k o v . 1984. The n u t r i t i v e v a l u e o f rumen m i c r o - o r g a n i s m s i n r u m i n a n t s . 4. The l i m i t i n g amino a c i d s o f m i c r o b i a l p r o t e i n i n g r o w i n g sheep d e t e r m i n e d by new approach. B r . J . N u t r . 52:613. Tamminga, S., A.M. Van Vuren, C.J. Van Der K o e l e n , R.S. K e t e l a a r , and P.L. van Der J o g t . 1990. Ruminal b e h a v i o r o f s t r u c t u r a l c a r b o h y d r a t e s , n o n - s t r u c t u r a l c a r b o h y d r a t e s and c r u d e p r o t e i n from c o n c e n t r a t e i n g r e d i e n t s i n d a i r y cows. Neth. J . A g r i c . S c i . 38:513. T h e u r e r , C.B. 1986. G r a i n p r o c e s s i n g e f f e c t s on s t a r c h u t i l i z a t i o n by r u m i n a n t s . J . Anim. S c i . 63:1649. Thomas, E.E., G.W. T u r n b u l l , and R.W. R u s s e l l . 1988. E f f e c t o f p a r t i c l e s i z e and steam t r e a t m e n t o f f e e d s t u f f s on t h e r a t e and e x t e n t o f d i g e s t i o n ( i n v i t r o and i n s i t u ) . J . Anim. S c i . 66:243. Van S o e s t , P . J . 1982. N u t r i t i o n a l E c o l o g y o f t h e Ruminant. 2nd ed. , C o r n e l l U n i v e r s i t y P r e s , I t h a c a , NY. Van S o e s t , P.J. 198 6. S o l u b l e c a r b o h y d r a t e s . C o r n e l l N u t r i t i o n C o n f e r e n c e f o r f e e d M a n u f a c t u r e r s . S y r a c u s e M a r r i o t t , E a s t S y r a c u s e , pp. 73-79. 9 V a r g a , G.A., and W.H. Hoover. 1983. Rate and e x t e n t o f n e u t r a l d e t e r g e n t f i b e r d e g r a d a t i o n o f f e e d s t u f f s i n - s i t u . J . D a i r y S c i . 66:1209. 10 CHAPTER 1. LITERATURE REVIEW. 1.1. DEGRADATION OF CARBOHYDRATES AND PROTEINS. 1.1.1. DEGRADATION OF CARBOHYDRATES. 1.1.1.1. General. D i g e s t i o n o r d e g r a d a t i o n o f c a r b o h y d r a t e s d e c r e a s e s as you move from s i m p l e s u g a r s , o l i g o s a c c h a r i d e s t h r o u g h p e c t i n s and b e t a -g l u c a n s t o s t a r c h (Van S o e s t , 1982, 1986). S t r u c t u r a l c a r b o h y d r a t e s (SC) a r e l e s s degraded i n t h e rumen t h a n n o n - s t r u c t u r a l c a r b o h y d r a t e s (NSC). T h e r e f o r e , n u t r i e n t a v a i l a b i l i t y i n t h e rumen i s dependent on t h e r e l a t i o n s h i p between n o n - s t r u c t u r a l and s t r u c t u r a l c a r b o h y d r a t e s i n t h e f e e d s t u f f . Reasons f o r d i f f e r e n c e s i n d e g r a d a b i l i t y o f c a r b o h y d r a t e s i n c l u d e s i m p l i c i t y / c o m p l e x i t y o f m o l e c u l e s ( s i m p l e s u g a r s v s s t a r c h ) , c h e m i c a l and p h y s i c a l s t r u c t u r e o f t h e m o l e c u l e ( i n t e r and i n t r a c a r b o h y d r a t e d i f f e r e n c e s - s t a r c h v s NDF and amylose v s a m y l o p e c t i n ) , p h y s i c a l and c h e m i c a l a s s o c i a t i o n between DM components ( l i g n i n / h e m i c e l l u l o s e and c e l l u l o s e , s t a r c h / p r o t e i n s and f a t s ) and s o u r c e o f c a r b o h y d r a t e (legume v s g r a s s e s , roughages v s g r a i n s , b a r l e y v s c o r n , e t c . ) ( F r e n c h , 1973; Moran, 1982 and Rooney and P f l u g f e l d e r , 198 6 ) . 1.1.1.2. Structure of starch. S t a r c h i s a heterogeneous p o l y s a c c h a r i d e composed o f t h e two pol y m e r s , amylose and a m y l o p e c t i n . Amylose i s a l i n e a r m o l e c u l e o f 11 900-3000 d - g l u c o p y r a n o s e r e s i d u e s l i n k e d by a-1,4 bonds. A m y l o p e c t i n i s h i g h l y branched polymer, a v e r a g i n g 10 4-10 5 g l u c o s e r e s i d u e s and c o n s i s t i n g o f a - l , 4 - l i n k e d D-glucan c h a i n s j o i n e d a t b r a n c h p o i n t s by a-1,6 bonds ( G u i l b o t and M e r c i e r , 1985; F r e n c h , 1973; Banks and M u i r , 1980 and W i l l i a m s , 1968). These polymers a r e d e p o s i t e d w i t h i n endosperm c e l l s i n t h e s e m i c r y s t a l l i n e g r a n u l e s whose shape ( l e n t i c u l a r , p o l y h e d r i c o r s p h e r i c a l ) , s i z e (1-38/xm) and p e r c e n t c o n t e n t of amylose and a m y l o p e c t i n v a r y w i t h p l a n t s p e c i e s and c u l t i v a r ( G u i l b o t and M e r c i e r , 1985; Banks and M u i r , 1980 and W i l l i a m s , 1968). S t a r c h e s p u r i f i e d from nonwaxy and heterowaxy c u l t i v a r s of v a r i o u s g r a i n s c o n t a i n 14-34% amylose. S t a r c h e s from waxy c u l t i v a r s have l e s s t h a n 1% amylose. The s t a r c h g r a n u l e i s m i n i m a l l y h y d r a t e d and i s s t a b i l i z e d by i n t e r - and i n t r a m o l e c u l a r hydrogen bonding. U n l e s s t h e g r a n u l e s a r e damaged by g r a i n p r o c e s s i n g , t h e y a r e r e s i s t a n t t o w a t e r e n t r y and a r e not h y d r o l y z e d by a l l amylases ( G u i l b o t and M e r c i e r , 1985; W i l l i a m s , 1968, Robyt and Whelan, 1968 and F o g a r t y and K e l l y , 1979). The d i s t r i b u t i o n o f t h e s t a r c h g r a n u l e s w i t h i n t h e k e r n e l v a r i e s w i t h c e r e a l g r a i n t y p e and c u l t i v a r ( F r e n c h , 1973 and Moran, 1982) . I n b r i e f , t h e c e r e a l k e r n e l c o n t a i n s t h r e e components; 1. t h e p r o t e c t i v e o u t e r c o v e r i n g ( p e r i c a r p ) , 2. t h e embryo (germ) and 3. t h e endosperm. The p e r i c a r p and t h e germ r e g u l a t e w a t e r uptake by t h e mature k e r n e l . They c o n t a i n l i t t l e s t a r c h and t o g e t h e r r e p r e s e n t a s m a l l p e r c e n t a g e of t h e k e r n e l . Most o f t h e s t a r c h i s i n t h e endosperm, which can be d i v i d e d i n t o t h e t h e outermost a l e u r o n e l a y e r , t h e p e r i p h e r a l endosperm ( s u b a l e u r o n e l a y e r ) , t h e 12 u n d e r l y i n g corneous endosperm and i n n e r m o s t , f l o u r y endosperm. The a l e u r o n e c e l l s do no c o n t a i n s t a r c h g r a n u l e s bu t do c o n t a i n a u t o l y t i c enzymes, amylases and p r o t e a s e i n h i b i t o r s , w a t e r - s o l u b l e v i t a m i n s , m i n e r a l s and s p h e r i c a l b o d i e s t h a t c o n t a i n p r o t e i n and l i p i d . The s t a r c h g r a n u l e s i n t h e p e r i p h e r a l and corneous endosperm a r e s u r r o u n d e d by p r o t e i n s t o r a g e b o d i e s m a t r i x o f t h e d r i e d endosperm c e l l s . T h i s m a t r i x c o n s i s t s m a i n l y o f p r o t e i n and non-s t a r c h c a r b o h y d r a t e s and i s r e l a t i v e l y i m p e r v i o u s t o w a t e r and h y d r o l y t i c enzymes. I n c o n t r a s t , t h e f l o u r y endosperm has l i t t l e c e l l u l a r s t r u c t u r e and t h e h i g h e s t d e n s i t y o f s t a r c h g r a n u l e s . The s t a r c h g r a n u l e s a r e more a c c e s s i b l e t o e n z y m a t i c h y d r o l y s i s i n t h i s p o r t i o n o f t h e endosperm (Rooney and M i l l e r , 1982; S e c k i n g e r and Wolf, 1973). The p r o p o r t i o n s o f p e r i p h e r a l , corneous and f l o u r y endosperm v a r y among c e r e a l g r a i n s . G r a i n c u l t i v a r s whose k e r n e l s have h i g h p r o p o r t i o n s o f p e r i p h e r a l and corneous endosperm a r e termed v i t r e o u s , corneous o r f l i n t y because o f t h e i r g l a s s y appearance. K e r n e l s c o n t a i n i n g h i g h p r o p o r t i o n s o f f l o u r y endosperm a r e c h a l k y i n appearance and a r e termed f l o u r y , opaque o r s o f t . C e r e a l p r o c e s s i n g i s done t o a i d d i g e s t i o n and t o f a c i l i t a t e t h e m i x i n g of i n g r e d i e n t s i n t h e manufacture o f compound f e e d s . P r o c e s s i n g i s performed t o i n c r e a s e t h e s u r f a c e a r e a exposed t o b a c t e r i a l and/or e n z y m a t i c a c t i v i t y o r t o change p h y s i c a l o r c h e m i c a l p r o p e r t i e s . C e r e a l p r o c e s s i n g methods, such a s , s t e a m - r o l l i n g , steam-f l a k i n g , e x t r u s i o n and e x p a n s i o n , i n v o l v e h y d r o t h e r m a l and m e c h a n i c a l a c t i o n s t o break down t h e endosperm s t r u c t u r e , e x p o s i n g 13 t h e s t a r c h g r a n u l e s and c a u s i n g v a r y i n g degrees o f s t a r c h g r a n u l e s a b s o r b w a t e r , s w e l l and f i n a l l y r e l e a s e amylose and a m y l o p e c t i n i r r e v e r s i b l y from t h e i r s e m i c r y s t a l l i n e arrangement ( G u i l b o t and M e r c i e r , 1985; F r e n c h , 1973 and Banks and M u i r , 1980). Steam r o l l i n g , i n c a s e of b a r l e y , i s sometimes done t o r e d u c e f i n e s , t h e r e b y r e d u c i n g d u s t i n e s s o f t h e ground g r a i n . I f w a t e r i s a p p l i e d , t h e polymers become h y d r a t e d , i n c r e a s i n g t h e i r s u s c e p t i b i l i t y t o e n z y m a t i c h y d r o l y s i s ( G u i l b o t and M e r c i e r , 1985; F r e n c h , 1973; Banks and M u i r , 1980 and W i l l i a m s , 1968). D u r i n g p r o c e s s i n g , t h e p e r i p h e r a l and corneous r e g i o n s o f t h e endosperm r e t a i n t h e i r s t r u c t u r e l o n g e r t h a n t h e f l o u r y endosperm r e t a i n t h e i r s t r u c t u r e l o n g e r t h a n t h e f l o u r y endosperm. Thus, more s t a r c h damage and g e l a t i n i z a t i o n o c c u r i n t h e f l o u r y endosperm t h a n i n t h e corneous o r p e r i p h e r a l endosperm t h a n i n t h e c o r n eous o r p e r i p h e r a l endosperm d u r i n g p r o c e s s i n g (Rooney and M i l l e r , 1982). 1.1.1.3. In v i t r o degradation of starch. S t a r c h i s t h e main component and most abundant o f a l l t h e NSC and i s t h e r e f o r e t h e major energy s o u r c e f o r most a n i m a l s where c e r e a l g r a i n s a r e a v a i l a b l e . I t i s however p e r p l e x i n g t o n o t e t h a t i t seems t o have been p r o t e c t e d t h r o u g h c r y s t a l l i n i t y o r some o t h e r m o d i f i c a t i o n t o p r e v e n t i t from becoming a r e a d i l y a v a i l a b l e energy s o u r c e t o a n i m a l s (Van S o e s t , 1986). D i f f e r e n c e s i n i n v i t r o r a t e s o f s t a r c h d e g r a d a b i l i t y u s i n g rumen f l u i d ( M a l e s t e i n e t a l . , 1988; Cone e t a l . , 1989 and Cone and V l o t , 1990) and/or pure enzyme p r e p a r a t i o n s have been r e p o r t e d 14 ( M a l e s t e i n e t a l . , 1988; H e r r e r a - S a l d a n a and Huber, 1989; Cone e t a l . , 1989 and Cone and V l o t , 1990). M a l e s t e i n e t a l . (1988), Cone e t a l . (1989) and Cone and V l o t , (1990) showed a c o n s t a n t r a n k i n g i n degree o f d e g r a d a b i l i t y o f d i f f e r e n t s t a r c h s o u r c e s upon 6 h i n c u b a t i o n w i t h rumen f l u i d from cows f e d e i t h e r a hay o r hay p l u s c o n c e n t r a t e d i e t . Unprocessed maize was l e s s degraded t h a n wheat and wheat was l e s s degraded t h a n b a r l e y . Steam f l a k i n g and popping s i g n i f i c a n t l y i n c r e a s e d g r a i n d e g r a d a b i l i t y . F o r a l l samples, s t a r c h d e g r a d a t i o n was h i g h e r i n cows f e d a h a y - c o n c e n t r a t e t h a n a hay d i e t a l o n e . T h i s d i f f e r e n c e was a t t r i b u t e d t o d i f f e r e n c e s i n a m y l o l y t i c a c t i v i t y o f t h e m i c r o f l o r a ( M a l e s t e i n e t a l . , 1988 and Cone e t a l . , 1989). These r e s u l t s a r e i n agreement w i t h t h o s e o f H e r r e r a - S a l d a n a and Huber, (1989) and H e r r e r a - S a l d a n a e t a l . , 1990b. 1.1.1.4. In s i t u degradation of starch. There a r e l i m i t e d d a t a r e g a r d i n g i n s i t u r a t e s o f s t a r c h d e g r a d a t i o n , i n s p i t e o f i n c r e a s e d i n t e r e s t i n s t a r c h , and t h i s can be seen from r e c e n t l y p u b l i s h e d r e v i e w s (Nocek and Tamminga, 1991; Hoover and S t o k e s , 1991; H u n t i n g t o n , 1994 and S t e r n e t a l . , 1994). H e r r e r a - S a l d a n a e t a l . (1990b) found t h a t c o r n , m i l o and o a t s had s i g n i f i c a n t l y l o w e r r a t e s o f i n s i t u s t a r c h d e g r a d a t i o n t h a n wheat o r b a r l e y , w h i c h were s i m i l a r . Oats showed had t h e h i g h e s t r a p i d l y d e g r a d a b l e f r a c t i o n o f s t a r c h compared t o t h e r e s t o f t h e c e r e a l s . B a r l e y and wheat had s i m i l a r amounts o f s t a r c h t h a t were degraded b u t were h i g h e r t h a n c o r n and m i l o w h i c h were v e r y low. Tamminga 15 and e t a l . (.1990) and H u s s e i n e t a l . (1991a) have p u b l i s h e d rumen d e g r a d a t i o n c h a r a c t e r i s t i c s o f s t a r c h p l u s s u g a r s o f s e v e r a l c o n c e n t r a t e i n g r e d i e n t s . T h e i r r e s u l t s c o n f i r m t h e f i n d i n g s o f H e r r e r a - S a l d a n a e t a l . , (1990b). 1.1.2. DEGRADATION OF PROTEINS. 1.1.2.1. General. A l l a n i m a l s r e q u i r e n i t r o g e n (N) f o r muscle t i s s u e , hormone and enzyme s y n t h e s i s . N i t r o g e n i n f e e d s t u f f s f o r a n i m a l s i s s u p p l i e d i n t h e form o f t r u e p r o t e i n s and n o n - p r o t e i n n i t r o g e n (NPN) . I n t h e case o f m o n o g a s t r i c a n i m a l s t h e u l t i m a t e end p r o d u c t s o f p r o t e i n d i g e s t i o n a r e p e p t i d e s and a m i n o - a c i d s , w h i c h a r e s u b s e q u e n t l y absorbed t o p r o v i d e nourishment. T h i s means t h a t d i g e s t i o n i n m o n o g a s t r i c s r e s u l t s i n end p r o d u c t s t h a t a r e s i m i l a r i n c o m p o s i t i o n t o t h e f e e d consumed by t h e a n i m a l . I n ru m i n a n t s on t h e o t h e r hand, d i e t a r y p r o t e i n f i r s t undergoes f e r m e n t a t i o n i n t h e rumen r e l e a s i n g ammonia-N, a m i n o - a c i d s and p e p t i d e s . A s m a l l p a r t o f t h e s e end p r o d u c t s i s absorbed i n t o t h e b l o o d system and t h e major p a r t o f i t i s used by rumen m i c r o b e s t o s y n t h e s i s e t h e i r own body p r o t e i n s . These m i c r o b e s a r e washed down t o t h e s m a l l i n t e s t i n e s t o g e t h e r w i t h t h e unfermented f e e d where t h e y a r e d i g e s t e d by p a n c r e a t i c and i n t e s t i n a l enzymes y i e l d i n g a m i n o - a c i d s and p e p t i d e s w h i c h a r e s u b s e q u e n t l y absorbed. T h i s means t h a t t h e c o m p o s i t i o n o f end p r o d u c t s o f d i g e s t i o n i n r u m i n a n t s i s not s i m i l a r t o t h e c o m p o s i t i o n o f d i e t a r y p r o t e i n because o f t h e s u b s t a n t i a l changes t h a t t h e f e e d undergoes i n t h e rumen. I t i s 16 t h e r e f o r e i m p o r t a n t t h a t f e e d i n g o f r u m i n a n t s t a k e s i n t o c o n s i d e r a t i o n b o t h f e e d i n g f o r m i c r o b i a l growth and f e e d i n g o f t h e a n i m a l i t s e l f . Work i n v i v o , i n v i t r o , and w i t h p ure c u l t u r e s has shown t h a t some amino a c i d s were r a p i d l y removed from c u l t u r e o r rumen f l u i d w h i l e o t h e r s accumulated (Lewis and Emery, 1962: C h a l u p a , 1976 and S c h e i f i n g e r e t a l . , 1976), i m p l y i n g t h a t a p r e f e r e n c e f o r c e r t a i n amino a c i d s e x i s t s . S e v e r a l s p e c i e s o f rumen b a c t e r i a r e q u i r e s p e c i f i c amino a c i d s f o r growth ( F o r s b e r g , 1978; Jones and P i c k a r d , 1980 and Gomez-Alarcon e t a l . , 1982). Work i n v i t r o w i t h mixed c u l t u r e s i n d i c a t e d t h a t c e r t a i n amino a c i d s o r groups o f amino a c i d s s t i m u l a t e m i c r o b i a l growth more t h a n o t h e r s (Maeng e t a l . , 1976). Some b a c t e r i a l s t r a i n s r e q u i r e amino a c i d s i n p e p t i d e form (Pitman and B y r a n t , 1964 and Pitman e t a l . , 1967), and work i n v i t r o has shown t h a t p e p t i d e carbon i s more e f f i c i e n t l y u t i l i z e d t h a n amino a c i d c a r b o n (Wright and Hungate, 19 6 7 ) . A r g y l e and B a l d w i n (1989) r e p o r t e d t h a t l i t t l e b a c t e r i a l g rowth o c c u r r e d w i t h ammonia as t h e s o l e N s o u r c e u s i n g i n v i t r o t e c h n i q u e s . W h i l e t h e p r e s e n c e of m i c r o b e s i n t h e g u t has a l l o w e d r u m i n a n t s t o u t i l i z e f i b r o u s f e e d s , t h i s has been a c h a l l e n g e t o r u m i n a n t n u t r i t i o n i s t s . M o n o g a s t r i c n u t r i t i o n i s t s a r e now a b l e t o s e l e c t i v e l y f e e d f o r s p e c i f i c d i e t a r y r e q u i r e m e n t s f o r a m i n o - a c i d s w i t h o u t c o n c e r n t h a t t h e d i e t a r y a m i n o - a c i d s p r o f i l e w i l l be changed. Because of t h e s e d i f f e r e n c e s i n t h e a b i l i t i e s o f m o n o g a s t r i c s and r u m i n a n t s t o u t i l i z e f i b r o u s f e e d s and p r o t e i n s (and o t h e r f e e d components) ruminant n u t r i t i o n i s t s have proposed c a r b o h y d r a t e ( G o e r i n g and S o e s t , 1970; Fox e t a l . , 1992; R u s s e l l e t a l . , 1992; S n i f f e n e t a l . , 1992 and O'Connor e t a l . , 1993) and p r o t e i n r a t i o n i n g systems (ARC, 1984; NRC 1985; NKJ, 1985; V e r i t e and Peyraund, 1989 and AFRC, 1992) f o r f e e d a n a l y s i s , c h a r a c t e r i s a t i o n and f e e d i n g s t a n d a r d s . A l l systems agree t h a t p r o t e i n r a t i o n i n g o f r u m i n a n t s r e q u i r e s p r o v i s i o n o f n i t r o g e n i n t h e form o f rumen d e g r a d a b l e p r o t e i n (RDP) and u n d e g r a d a b l e p r o t e i n (UDP) t o c a t e r f o r t h e n i t r o g e n r e q u i r e m e n t s o f rumen m i c r o b e s and t h e a m i n o - a c i d r e q u i r e m e n t s o f t h e a n i m a l t h r o u g h p o s t - r u m i n a l d i g e s t i o n . I n v i t r o , i n s i t u and i n v i v o methods a r e used t o d e t e r m i n e t h e d e g r a d a b i l i t y and d i g e s t i o n o f p r o t e i n s . I n f o r m a t i o n d e r i v e d from t h e s e methods has been used i n t h e p r o p o s e d p r o t e i n r a t i o n i n g systems (NKJ, 1985; Madsen, 1985; NRC, 1989, V e r i t e and Pyraund, 1989 and ARC 1984) . T h i s i s d i s c u s s e d i n d e t a i l under s e c t i o n 1.1.2.2.2 o f t h i s t h e s i s . I n a d d i t i o n , t h e new p r o t e i n systems a l s o r e c o g n i s e t h a t m i c r o b i a l p r o t e i n s y n t h e s i s r e q u i r e s t h e p r e s e n c e o f a c a r b o n s o u r c e from c a r b o h y d r a t e s i n adequate amounts i n o r d e r t o m i n i m i z e d i e t a r y N wastage, maximize m i c r o b i a l p r o t e i n s y n t h e s i s and t h e r e f o r e p r o d u c t i v i t y . D e g r a d a b i l i t y o f f e e d p r o t e i n i s t h e most i n t e n s i v e l y as w e l l as e x t e n s i v e l y r e s e a r c h e d a r e a o f rum i n a n t n u t r i t i o n when compared t o c a r b o h y d r a t e s . 18 1.1.2.2.0. Characterisation of dietary feed proteins. 1.1.2.2.1. Nitrogen determination. N i t r o g e n (N) d e t e r m i n a t i o n o f f e e d s i s a c c o m p l i s h e d by t h e K j e l d a h l d i g e s t i o n p r o c e d u r e i n v o l v i n g d i g e s t i o n o f t h e m a t e r i a l i n c o n c e n t r a t e d s u l f u r i c a c i d t o r e l e a s e t h e n i t r o g e n . The n i t r o g e n c o n t e n t o f t h e f e e d i s e x p r e s s e d as crud e p r o t e i n by m u l t i p l y i n g feed-N by 6.25. The n i t r o g e n c o n t e n t from d i f f e r e n t n a t u r a l f e e d s v a r i e s a c c o r d i n g t o t h e a m i n o - a c i d p r o f i l e o f t h e p r o t e i n . W h i l e d e t e r m i n a t i o n o f t o t a l N o f t h e f e e d g i v e s some i n d i c a t i o n o f t h e q u a l i t y o f a f e e d , i t does not g i v e an i n d i c a t i o n as t o t h e degree o f u t i l i z a t i o n by t h e a n i m a l . 1.1.2.2.2. P a r t i t i o n i n g of dietary protein. I n o r d e r t o meet t h e p r o t e i n needs o f l a c t a t i n g d a i r y cows, r a t i o n f o r m u l a t i o n systems proposed by NKJ (1985), Madsen (1985), NRC (1989), V e r i t e and Pyraund (1989) and ARC (1984), r e q u i r e p a r t i t i o n i n g d i e t a r y p r o t e i n s i n t o f r a c t i o n s degraded i n t h e rumen ( d e g r a d a b l e i n t a k e p r o t e i n , DIP) and t h o s e f r a c t i o n s t h a t a r e r e s i s t a n t t o rumen d e g r a d a t i o n (undegradable i n t a k e p r o t e i n , U I P ) . A c o m b i n a t i o n o f i n v i t r o , i n s i t u and i n v i v o methods have been used t o p a r t i t i o n d i e t a r y p r o t e i n s i n t o t h e d i f f e r e n t f r a c t i o n s ; where; UIP = duodenal N - m i c r o b i a l N N i n t a k e and 19 DIP = 1-UIP and DIP i s f u r t h e r b r o k e n down t o r a p i d l y d e g r a d a b l e and s l o w l y d e g r a d a b l e - N . R a p i d l y d egradable-N (a) i s assumed t o be e q u a l t o w a t e r s o l u b l e n i t r o g e n and s l o w l y d e g r a d a b l e - N (b) e q u a l DIP minus r a p i d l y d e g r a d a b l e - N . R a p i d l y d e g r a d a b l e - N and DIP a r e e s t i m a t e d from d e g r a d a b i l i t y s t u d i e s w i t h p o l y s t e r bags u s i n g t h e e q u a t i o n o f 0 r s k o v and McDonald (1979); a + b = a + bc/(c+k) ( E q u a t i o n 1.1); where a = w a t e r s o l u b l e n i t r o g e n ( R a p i d l y d e g r a d a b l e - N ) , b = s l o w l y d e g r a d a b l e N, a + b = d e g r a d a t i o n o f d i e t a r y N a t t i m e i n f i n i t y , c = f r a c t i o n a l r a t e o f d e g r a d a t i o n o f b/h, and k = f r a c t i o n a l r a t e o f rumen o u t f l o w / h The model a l s o t a k e s c a r e o f t h e t o t a l l y u n d i g e s t e d u n a v a i l a b l l e f r a c t i o n (u) u s u a l l y g i v e n by; u = 100 - (a + b ) ; I n v i t r o methods o f measuring r a t e o f p r o t e i n d e g r a d a b i l i t y have been m o d i f i c a t i o n s o f t h e T i l l e y and T e r r y , (1963) p r o c e d u r e w h i c h i n v o l v e s i n c u b a t i o n o f a f e e d sample w i t h an i n o c u l u m o f s t r a i n e d rumen f l u i d i n a c e n t r i f u g e t u b e c l o s e d w i t h a bunsen v a l v e . T h i s i s s t i l l a p o p u l a r method. However, t h e p r o c e d u r e 20 r e q u i r e s rumen c a n n u l a t e d a n i m a l s . T h i s prompted v a r i o u s m o d i f i c a t i o n s . M o d i f i c a t i o n s i n c l u d e use o f p ure n o n - b a c t e r i a l enzymes such as p e p s i n , p a n c r e a t i n and p r o n a s e and b a c t e r i a l p r o t e o l y t i c enzymes (Poos e t a l . , 1980a and K r i s h n a m o o r t h y e t a l . , 1983) . M a t h e m a t i c a l t r e a t m e n t o f d a t a f o r i n v i t r o s t u d i e s i s a n a l y s e d t h e same way as i n s i t u d a t a . The development of i n v i t r o c o n t i n u o u s c u l t u r e systems added new advantages o v e r t h e t r a d i t i o n a l b a t c h c u l t u r e systems mentioned above, w h i c h a r e p r o c e d u r e l y s t a t i c . These r e q u i r e t h e use o f rumen c a n n u l a t e d a n i m a l s t o s u p p l y i n o c u l u m . S o l i d f e e d i s i n c u b a t e d w i t h rumen f l u i d i n f e r m e n t a t i o n v e s s e l s f i t t e d w i t h a g i t a t o r s and an i n l e t and o u t l e t t o a l l o w movement, f e e d i n g , sample c o l l e c t i o n and a l s o c o n t r o l o f l i q u i d and s o l i d t u r n o v e r r a t e s . C o n t i n o u s c u l t u r e s have been used s u c c e s s f u l l y t o measure f e e d d e g r a d a b i l i t y and t o e s t i m a t e m i c r o b i a l p r o t e i n s y n t h e s i s (Hoover e t a l . , 1976 and H u s s e i n e t a l , 1991a). C z e r k a w s k i and B r e c k e n r i d g e (1977) came up w i t h t h e rumen s i m u l a t e d t e c h n i q u e (RUSITEC) t o d e t e r m i n e d e g r a d a b i l i t y o f f e e d s and t o e s t i m a t e m i c r o b i a l p r o t e i n p r o d u c t i o n . Measurement of d e g r a d a b i l i t y i n v i v o i n v o l v e s d i r e c t measurement o f t o t a l N f l o w t o t h e duodenum, m i c r o b i a l N f l o w t o t h e duodenum and t o t a l N i n t a k e by use o f exogenous and endogenous f e e d and m i c r o b i a l markers (Mathers and M i l l e r , 1981; M c A l l a n e t a l . , 1988; Owens and Hanson, 1992 and B r o d e r i c k and Merchen, 1992;) . 21 N i t r o g e n d e g r a d a b i l i t y can be c a l c u l a t e d a c c o r d i n g t o t h e f o l l o w i n g e q u a t i o n s ( M c A l l a n e t a l . , 1988); N d e g r a d a b i l i t y = ( T o t a l NAN flow-(MN flow+EN f l o w ) / T o t a l NAN i n t a k e ) ( E q u a t i o n 1.2); where; NAN = Non-ammonia n i t r o g e n MN = M i c r o b i a l n i t r o g e n EN = Endogenous n i t r o g e n 1.1.2.2.3. Methods of estimating post-ruminal digestion of undegradable intake protein (UIP). The p o r t i o n o f d i e t a r y p r o t e i n t h a t escapes d e g r a d a t i o n i n t h e rumen goes t o t h e s m a l l i n t e s t i n e s where some i s d i g e s t e d by p a n c r e a t i c and i n t e s t i n a l enzymes. P a r t o f t h i s p r o t e i n a l s o escapes d i g e s t i o n and a p o r t i o n g e t s f e r m e n t e d i n t h e l a r g e i n t e s t i n e s , t h a t w h i c h i s r e s i s t a n t p a s s e s on t o c o n s t i t u t e t h e u n d i g e s t e d - N ( u n a v a i l a b l e ) f r a c t i o n and i s v o i d e d . The p o r t i o n t h a t g e t s f e r m e n t e d i n t h e l a r g e i n t e s t i n e i s u t i l i z e d by m i c r o b e s . However, because of t h e l i m i t e d c a p a c i t y o f t h e l a r g e i n t e s t i n e t o a b s o r b n u t r i e n t s , t h e b e n e f i t t o t h e a n i m a l from h i n d g u t f e r m e n t a t i o n i s not v e r y s i g n i f i c a n t . From a p r o d u c t i v i t y p o i n t o f v i e w i t i s i m p o r t a n t t h a t t h e UIP i s h i g h l y d i g e s t i b l e i n t h e s m a l l i n t e s t i n e s t o maximize t h e r e l e a s e o f a m i n o - a c i d s , w h i c h a r e t h e u l t i m a t e p r o t e i n forms n u t r i e n t r e q u i r e d by t h e a n i m a l . 22 E s t i m a t i o n o f t h e d i g e s t i o n o f UIP has been a c c o m p l i s h e d by use o f t h e m o b i l e n y l o n bag t e c h n i q u e and r e q u i r e s a n i m a l s w i t h c a n n u l a e a t t h e rumen and duodenum ( H v e l p l u n d , 1985 and de Boer e t a l . , 1987) o r a t t h e rumen o n l y ( V a r v i k k o e t a l . , 1983 and K e n d a l l e t a l . , 1991). I n t h i s method, rumen-incubated f e e d samples i n p o l y e s t e r mesh bags a r e r e c o v e r e d from t h e rumen, washed i n t h e u s u a l way and d r i e d . Some of t h e s e bags a r e a n a l y s e d f o r d e g r a d a b l e - N and a m i n o - a c i d s and t h e r e m a i n i n g bags a r e p u t back i n t h e i n t e s t i n a l t r a c t t h r o u g h t h e duodenal c a n n u l a and can be r e c o v e r e d e i t h e r i n t h e i l e u m o r f e c e s . The bags a r e t h e n washed, d r i e d and a n a l y s e d f o r d i g e s t e d - N and amino a c i d s . The p o r t i o n t h a t has been d i g e s t e d p o s t - r u m i n a l l y i s c a l c u l a t e d by d i f f e r e n c e between what e n t e r e d a t t h e duodenum and what remained i n t h e bags. Other w o r k e r s ( V a r v i k k o e t a l . , 1983 and K e n d a l l e t a l . , 1991) u s i n g cows w i t h rumen c a n n u l a have d i g e s t e d rumen undegraded samples u s i n g t h e p e p s i n d i g e s t i o n p r o c e d u r e t o s i m u l a t e i n t e s t i n a l d i g e s t i o n . Though a l l t h e s e methods have been used s u c c e s s f u l l y w i t h i n t h e i r l i m i t a t i o n s , t h e y a l l have t h e i r own i n h e r e n t problems. T h e o r e t i c a l l y , i n v i v o methods a r e b e s t s i n c e d a t a a r e c o l l e c t e d on t h e a n i m a l i t s e l f . However, t h e i n c r e a s e d p r e s s u r e from a n i m a l w e l f a r e a c t i v i s t s on a n i m a l n u t r i t i o n i s t s n o t t o use a n i m a l s f o r r e s e a r c h , may mean t h i s method may not be p o p u l a r i n f u t u r e . T h i s has a l r e a d y r e s u l t e d i n e f f o r t s t o improve i n v i t r o t e c h n i q u e s t o s i m u l a t e d i g e s t i o n i n t h e g u t . I n v i t r o t e c h n i q u e s a r e a l s o l e s s e x p e n s i v e . 23 P r e s e n t l y t h e amount o f d i e t a r y p r o t e i n t h a t escapes d e g r a d a t i o n i n t h e rumen cannot be measured e a s i l y u s i n g i n v i v o t e c h n i q u e s . T h i s p r e s e n t s some problems i n a s s e s s i n g l a b o r a t o r y methods f o r p r e d i c t i n g d e g r a d a b i l i t y . S t u d i e s w h i c h have a t t e m p t e d t o compare i n v i v o measurements and i n v i t r o e s t i m a t e s o f d e g r a d a b i l i t y w i t h e s t i m a t e s based on t h e r a t e o f d i s a p p e a r a n c e o f f e e d s from p o l y e s t e r bags suspended i n t h e rumen, have c o n c l u d e d t h a t t h e c o r r e l a t i o n between t h e methods was poor (Poos e t a l . , 1980b and K r i s h n a m o o r t h y e t a l . , 1983). I n s p i t e o f poor c o r r e l a t i o n t h e r e i s a l r e a d y a l o t o f work i n p r o g r e s s and more i s needed t o e s t a b l i s h a c c u r a t e measurements o f i n v i v o d e g r a d a b i l i t y so as t o improve t h e measurement and c o r r e l a t i o n w i t h i n s i t u d a t a . 1.1.2.2.4. Degradation of protein i n the rumen. N i t r o g e n i n fe e d s i s found i n t h e form o f t r u e p r o t e i n and n o n - p r o t e i n n i t r o g e n (NPN). True p r o t e i n s a r e complex m o l e c u l e s such as a l b u m i n s , g l o b u l i n s , p r o l a m i n s and g l u t e l i n s composed o f a m i n o - a c i d s . N o n - p r o t e i n n i t r o g e n s o u r c e s i n c l u d e s u r e a , ammonia-N, b i u r e t , n i t r a t e , n u c l e i c a c i d s , p u r i n e d e r i v a t i v e s such as u r i c a c i d and i n d i v i d u a l amino a c i d s . I n g e n e r a l terms d e g r a d a b i l i t y o f n i t r o g e n e o u s compounds, l i k e c a r b o h y d r a t e s , d e c r e a s e s w i t h t h e c o m p l e x i t y o f t h e m o l e c u l e . T h i s means t h a t NPN i s r a p i d l y degraded t o ammonia compared t o complex m o l e c u l e s such as albu m i n s and g l o b u l i n s and t h a t d i f f e r e n c e s i n d e g r a d a b i l i t y a l s o e x i s t w i t h i n d i f f e r e n t groups o f n i t r o g e n s o u r c e s . The t e r m s o l u b i l i t y was once used t o d e s c r i b e d e g r a d a b i l i t y o f p r o t e i n s i n t h e rumen. T h i s i s d e t e r m i n e d by use o f a number o f s o l v e n t s and used t o rank f e e d s , a l t h o u g h t h e r e l a t i v e r a n k i n g o f t h e f e e d s v a r i e s w i t h t h e s o l v e n t ( C r o o k e r e t a l . , 1978 and W i l l i a m s , 1986). The method assumed t h a t a l l t h e s o l u b l e p r o t e i n s were r a p i d l y and c o m p l e t e l y degraded i n t h e rumen w h i l e t h e i n s o l u b l e p r o t e i n s were n o t . I t i s , however, now e s t a b l i s h e d t h a t c h e m i c a l bonds r a t h e r t h a n s o l u b i l i t y a r e r e s p o n s i b l e f o r t h e r e s i s t a n c e t o d e g r a d a t i o n by rumen p r o t e o l y t i c enzymes (Mahadevan e t a l . , 1980). F or t h i s r e a s o n s o l u b i l i t y cannot be equated t o d e g r a d a b i l i t y . However i t has been proposed t h a t w a t e r s o l u b l e - N s h o u l d be assumed t o be r a p i d l y d e g r a d a b l e - N (a) f o r purposes o f p r o t e i n r a t i o n i n g o f r u m i n a n t s ( W i l l i a m s , 1986). D e g r a d a b i l i t y o f d i e t a r y p r o t e i n i n t h e rumen i s an i m p o r t a n t f a c t o r i n f l u e n c i n g i n t e s t i n a l s u p p l y o f a m i n o - a c i d s t o l a c t a t i n g d a i r y cows. The r a t e and e x t e n t o f p r o t e i n d e g r a d a t i o n i n t h e rumen a f f e c t s m i c r o b i a l p r o t e i n s y n t h e s i s and a l s o d e t e r m i n e s t h e q u a n t i t y o f undegraded d i e t a r y p r o t e i n t h a t r e a c h e s t h e duodenum. T h e r e f o r e , as m i l k y i e l d and t h e r e q u i r e m e n t s f o r r u m i n a l l y d e g r a d a b l e p r o t e i n i n c r e a s e , p r o t e i n d e g r a d a t i o n i n t h e rumen becomes an i n c r e a s i n g l y i m p o r t a n t f a c t o r i n f l u e n c i n g t h e amount o f a m i n o - a c i d s absorbed from t h e s m a l l i n t e s t i n e s . The e x t e n t t o w h i c h d i e t a r y p r o t e i n i s degraded depends on m i c r o b i a l p r o t e o l y t i c a c t i v i t y i n t h e rumen, m i c r o b i a l a c c e s s t o t h e p r o t e i n , and r u m i n a l r e t e n t i o n t i m e (Waltz and S t e r n , 1989). Other f a c t o r s i n f l u e n c i n g p r o t e i n d e g r a d a b i l i t y i n c l u d e p r o t e i n 25 s o l u b i l i t y and r u m i n a l pH ( W i l l i a m s , 1986). P r o t e i n s t r u c t u r e i n f l u e n c e s a c c e s s i b i l i t y t o p r o t e o l y t i c enzymes, t h e r e b y a f f e c t i n g d e g r a d a b i l i t y o f p r o t e i n i n t h e rumen (Mahadevan e t a l . , 1980 and O p s t v e d t e t a l . , 1984). Some d i e t a r y f e e d i n g r e d i e n t s a r e n a t u r a l l y r e s i s t a n t t o m i c r o b i a l d e g r a d a t i o n and o t h e r c o n s t i t u e n t s may have g r e a t e r o r l ower r e s i s t a n c e t o m i c r o b i a l d e g r a d a t i o n because of p h y s i c a l and c h e m i c a l p r o c e s s i n g (Madsen and H v e l p l u n d 1985; W a l tz and S t e r n , 1989; K h o r a s a n i e t a l . , 1989 and S t e r n e t a l . , 1994). Compiled n y l o n bag d a t a from d i f f e r e n t s o u r c e s (NRC, 1989 and S t e r n e t a l . , 1994) i n d i c a t e s t h a t a n i m a l p r o t e i n ( f i s h , b l o o d , meat and bone and h y d r o l y s e d f e a t h e r meal) and p r o t e i n s o u r c e s of c e r e a l p r o c e s s i n g o r i g i n a r e more r e s i s t a n t t o r u m i n a l d e g r a d a t i o n t h a n a r e c o n v e n t i o n a l p l a n t p r o t e i n s o u r c e s such, as c a n o l a , soy bean and s u n - f l o w e r meal. D i f f e r e n t s o u r c e s w i t h i n each group a l s o degrade a t d i f f e r e n t r a t e s . Ruminal u n d e g r a d a b i l i t y o f a n i m a l p r o t e i n supplements ranged from 48% f o r f i s h meal t o 82% f o r b l o o d meal (NRC, 1989) . F i s h meal s o u r c e s commonly used i n l a c t a t i n g d a i r y cow r a t i o n s have u n d e g r a d a b i l i t y v a l u e s i n t h e o r d e r o f 70% f o r w e l l p r e s e r v e d f i s h meal and t h a t f o r r a p e s e e d meals a v e r a g i n g around 30% (Madsen and H v e l p l u n d 1985; de Boer e t a l . , 1987 and Erasmus e t a l . , 1994). U n l i k e a n i m a l p r o t e i n s t h e r e i s a d i v e r s e s u p p l y o f p l a n t p r o t e i n s o u r c e s t h a t a r e used as p r o t e i n supplements i n d i e t s o f cows. T h i s d i v e r s i t y i s even g r e a t e r when m a t e r i a l s t h a t have been t r e a t e d t o reduce r u m i n a l d e g r a d a b i l i t y a r e i n c l u d e d a l o n g w i t h p r o t e i n supplements from c e r e a l g r a i n p r o c e s s i n g (brewers and d i s t i l l e r s g r a i n s , and g l u t e n meals) 26 (Madsen and H v e l p l u n d , 1985 and NRC, 1989). F o r most commonly used p l a n t p r o t e i n supplements d e g r a d a b i l i t y f a l l s around 50%, w i t h a m a j o r i t y b e i n g above 50%. C e r e a l b y - p r o d u c t p r o t e i n s a r e l e s s d e g r a d a b l e t h a n t h e c o n v e n t i o n a l p l a n t p r o t e i n s , f a l l i n g between 40-50% d e g r a d a b i l i t y and sometimes l o w e r t h a n some o f t h e p r o t e i n s o f a n i m a l o r i g i n . Soybean meal was l e s s d e g r a d a b l e t h a n c a n o l a meal; f i s h meal was l e s s d e g r a d a b l e t h a n meat and bone meal and c o r n - g l u t e n meal was t h e l e a s t d e g r a d a b l e o f a l l meals (de Boer e t a l . , 1987). Erasmus e t a l . , (1994) were a l s o a b l e t o d i s c r i m i n a t e a group o f f e e d s t u f f s on t h e b a s i s o f t h e i r d e g r a d a b i l i t y i n t h e rumen of cows. A n i m a l p r o t e i n s o u r c e s ( f i s h meal and b l o o d meal) were l e s s d e g r a d a b l e t h a n p l a n t p r o t e i n s o u r c e s (soybean, c o t t o n s e e d , peanut and s u n f l o w e r meals) w i t h c o r n g l u t e n b e i n g t h e l e a s t . A n i m a l and p l a n t p r o t e i n s o u r c e s averaged 2 3.8 and 56.5%, r e s p e c t i v e l y i n n i t r o g e n d e g r a d a b i l i t y , w h i l e t h a t f o r c o r n g l u t e n meal was 18.6%. Among p l a n t p r o t e i n s o u r c e s t h e r e l a t i v e r a n k i n g i n i n c r e a s i n g o r d e r o f d e g r a d a b i l i t y i s ; c o t t o n seed (42.5%) < soybean (46.2%) < peanut (65.0%) < s u n f l o w e r ( 7 2 . 1 % ) . B l o o d meal i s t h e l e a s t i n rumen d e g r a d a b i l i t y when compared t o f i s h meal (18.6 v e r s u s 28.3%) w h i l e meat meal was s i m i l a r t o soybean meal. The r e l a t i v e r a n k i n g i n t e r and i n t r a group of each f e e d s t u f f may sometimes change due t o f u r t h e r t r e a t m e n t s (eg, h e a t a p p l i c a t i o n d u r i n g f o o d p r o c e s s i n g ) t h e r e b y i n c r e a s i n g r e s i s t a n c e t o d e g r a d a t i o n ( H v e l p l u n d 1985; Madsen and H v e l p l u n d 1985; NRC, 1989). Common methods f o r r e d u c i n g d e g r a d a b i l i t y i n t h e rumen i n c l u d e p h y s i c a l and c h e m i c a l 27 t r e a t m e n t s . W a ltz and S t e r n , (1989) s t u d i e d t h e e f f e c t o f p r o t e c t i o n methods on t h e me t a b o l i s m o f p r o t e i n from soybean meal on i n s i t u rumen d e g r a d a t i o n . R e s u l t s showed t h a t e x p e l l e r p r o c e s s i n g and c a l c i u m l i g n o s u l f o n a t e t r e a t m e n t s were most e f f e c t i v e i n r e d u c i n g r u m i n a l p r o t e i n d e g r a d a t i o n . The o r d e r o f e f f e c t i v e n e s s by method was; c o n t r o l < sodium h y d r o x i d e < e t h a n o l < p r o p i o n i c a c i d < c a l c i u m l i g n o s u l f o n a t e < e x p l e l l e r p r o c e s s i n g < formald e h y d e . Formaldehyde and a c e t i c a c i d t r e a t m e n t o f soybean and ra p e s e e d meal s i g n i f i c a n t l y r educed t h e r u m i n a l d e g r a d a t i o n o f p r o t e i n ( V a r v i k k o e t a l . , 1983 and K h o r a s a n i e t a l . , 1989). A l t h o u g h c e r e a l g r a i n s a r e used m a i n l y as energy s o u r c e s i n d i e t s t h e y do s u p p l y a s u b s t a n t i a l amount o f p r o t e i n and i n f l u e n c e m e t a b o l i s m o f n i t r o g e n . H e r r e r a - S a l d a n a e t a l . (1990b) compared i n s i t u p r o t e i n d e g r a d a b i l i t y f o r c o r n , m i l o , wheat, b a r l e y and o a t s . They found s i g n i f i c a n t d i f f e r e n c e s i n t h e r a t e o f d e g r a d a b i l i t y o f p r o t e i n o f c e r e a l s o u r c e s and t h e r a n k i n g was as f o l l o w s i n i n c r e a s i n g o r d e r ; m i l o < c o r n < o a t s < b a r l e y < wheat. However o a t s had t h e h i g h e s t r u m i n a l a v a i l a b i l i t y o f p r o t e i n because o f t h e h i g h e r r a p i d l y d e g r a d a b l e p o r t i o n . S i m i l a r r e s u l t s have been r e p o r t e d f o r wheat, b a r l e y and c o r n (Fiems e t a l . , 1990) and f o r c o r n and sorghum g r a i n (Erasmus e t a l . , 1994). 1.1.2.2.5. D i g e s t i b i l i t y o f rumen undegraded protein i n the small i n t e s t i n e s . W h i l e i t i s i m p o r t a n t t o have p a r t o f t h e d i e t a r y p r o t e i n escape d e g r a d a t i o n i n t h e rumen, i t s v a l u e t o t h e a n i m a l depends on 28 i t s d i g e s t i b i l i t y i n t h e s m a l l i n t e s t i n e s t o r e l e a s e t h e r e q u i r e d a m i n o - a c i d s . Not many s t u d i e s have measured b o t h i n s i t u r u m i n a l and p o s t - r u m i n a l d i g e s t i o n o f p r o t e i n s o u r c e s . H v e l p l u n d , (1985) u s i n g t h e m o b i l e bag t e c h n i q u e t o measure t h e d i g e s t i b i l i t y o f n i t r o g e n p o s t - r u m i n a l l y r e p o r t e d s i g n i f i c a n t d i f f e r e n c e s i n t h e d i g e s t i b i l i t y o f N and amino-acid-N among v a r i o u s p r o t e i n supplements. The d i g e s t i b i l i t y o f N i n t h e s m a l l i n t e s t i n e s v a r i e d between 63% and 86% and t h a t f o r amino-acid-N v a r i e d between 67% and 87%, r e s p e c t i v e l y . Undegraded r a p e s e e d , f i s h , and soybean meals averaged 63%, 86% and 81% and 77%, 87% and 87%, f o r undegraded N and amino-acid-N, r e s p e c t i v e l y . The d i g e s t i b i l i t y o f e s s e n t i a l amino-acid-N and n o n - e s s e n t i a l - a m i n o -a c i d - N showed o n l y minor d i f f e r e n c e s . Work u s i n g cows c o n f i r m e d t h e r e s u l t s o b t a i n e d w i t h sheep, a l t h o u g h o n l y N - d i g e s t i b i l i t y was measured. The d i s a p p e a r a n c e of N from bags a v e r a g e d 75%, 90% and 96% f o r undegraded r a p e s e e d , f i s h and soybean meals, r e s p e c t i v e l y . A l l f e e d s t e s t e d were above 7 0% e x c e p t one f i s h meal sample which was h e a t damaged, a v e r a g i n g 11% i n p o s t - r u m i n a l d i g e s t i b i l i t y . P o s t - r u m i n a l N d i g e s t i o n was r e p o r t e d t o be h i g h e r when bags were r e c o v e r e d from f e c e s t h a n from i l e a l c a n n u l a . The N c o n t e n t and a m i n o - a c i d c o m p o s i t i o n between t h e o r i g i n a l p r o t e i n supplement and t h e rumen undegraded r e s i d u e s showed s m a l l d i f f e r e n c e s o r v a r i a t i o n f o r t h e m a j o r i t y o f a m i n o - a c i d s ( H v e l p l u n d , 1985). However i n c r e a s e s were n o t e d f o r i s o l e u c i n e , l e u c i n e , p h e n y l a l a n i n e , t h r e o n i n e , t y r o s i n e and v a l i n e w i t h t h e r e s t o f t h e a m i n o - a c i d s showing b o t h i n c r e a s e s and d e c r e a s e s , w h i c h was i n agreement w i t h 29 r e s u l t s from o t h e r s t u d i e s (Hennessy e t a l . , 1987; V a r v i k k o e t a l . , 1983; H v e l p l u n d and H e s s e l h o l t , 1987 and De Boer e t a l . , 1987). Ruminal and i n t e s t i n a l d i g e s t i b i l i t y o f N f o r soybean, c a n o l a , f i s h meal and a l f a l f a hay were 55.1, 44.6; 69.7, 24.0; 28.5, 59.2; and 68.8, 22.2% r e s p e c t i v e l y f o r t h e i n i t i a l and r e s i d u e s r e s p e c t i v e l y a t 8 hour rumen i n c u b a t i o n t i m e (de Boer e t a l . , 1987). I t was shown t h a t p r o t e i n s o u r c e s w i t h d i f f e r e n t rumen d e g r a d a b i l i t i e s had d i f f e r e n t i n t e s t i n a l n i t r o g e n d i g e s t i b i l i t y . Rumen d e g r a d a b i l i t y i n c r e a s e d w i t h t i m e w h i l e i n t e s t i n a l d i g e s t i b i l i t y d e c r e a s e d and b o t h p a r a m e t e r s d i f f e r e d among p r o t e i n s o u r c e s . More r e c e n t p u b l i s h e d f i n d i n g s s u p p o r t t h e s e e a r l i e r f i n d i n g s (Erasmus e t a l . , 1990 and Erasmus e t a l . , 1994). These w o r k e r s a l s o r e p o r t e d s i g n i f i c a n t d i f f e r e n c e s among f e e d s t u f f s i n t h e d i g e s t i b i l i t y o f t h e f e e d p r o t e i n , a m i n o - a c i d p r o f i l e o f un d e g r a d a b l e p r o t e i n and a b s o r b a b l e a m i n o - a c i d p r o f i l e . However, t h e r e s e a r c h e r s r e p o r t e d t h a t t h e i r s t u d y a l s o i n d i c a t e d t h a t t h e a m i n o - a c i d p r o f i l e o f a b s o r b a b l e p r o t e i n was much more s i m i l a r t o t h e p r o f i l e f o r t h e undegraded r e s i d u e s t h a n t o t h e o r i g i n a l f e e d p r o t e i n . D i f f e r e n c e s i n i n t e s t i n a l d i g e s t i b i l i t y seem t o be r e l a t e d t o t h e d e g r a d a b i l i t y i n t h e rumen and a l s o f i b e r c o n t e n t i n t h e p a r t i c u l a r p r o t e i n supplement ( H v e l p l u n d , 1985; H v e l p l u n d and H e s s e l h o l t , 1987; de Boer e t a l . , 1987 and Erasmus e t a l . , 1994). The h i g h e r t h e rumen d e g r a d a b i l i t y t h e lower was t h e i n t e s t i n a l d i g e s t i b i l i t y and m a t e r i a l s w i t h h i g h e r f i b e r had l o w e r i n t e s t i n a l d i g e s t i b i l i t i e s . T h i s i s e x p e c t e d because some o f t h e p r o t e i n t h a t 30 i s r u m i n a l l y u n d e g r a d a b l e i s bound t o c e l l - w a l l s and t h a t p o r t i o n p a s s e s o u t as c e l l - w a l l bound i n d i g e s t e d r e s i d u e ( H v e l p l u n d , 1985 and de Boer e t a l . , 1987) The i m p o r t a n c e o f t h e d i g e s t i b i l i t y o f u n d e g r a d a b l e p r o t e i n a f t e r t r e a t m e n t was a l s o demonstrated i n t h e e x p e r i m e n t s o f H v e l p l u n d , (1985) and Erasmus e t a l . , (1994). H v e l p l u n d , (1985) r e p o r t e d d e c r e a s e s i n i n t e s t i n a l n i t r o g e n and a l s o a m i n o - a c i d s o f undegraded-N when soybean meal was t r e a t e d w i t h 0.5% formaldehyde when compared t o t h e o r i g i n a l soybean meal. Heat damaged f i s h meal averaged 11% compared t o 9 0% w i t h w e l l p r e s e r v e d f i s h meal i n i n t e s t i n a l d i g e s t i b i l i t y o f undegradable p r o t e i n . K i n g e t a l . (1990) and Erasmus e t a l . (1994) r e p o r t e d reduced i n t e s t i n a l d i g e s t i b i l i t y o f b l o o d meal when compared t o o t h e r f e e d s w i t h a low d e g r a d i b i l i t y i n s p i t e o f b l o o d meal d e l i v e r i n g more feed-N t o t h e duodenum. T h i s d i f f e r e n c e was a t t r i b u t e d t o d i f f e r e n c e s i n d r y i n g methods used r e s u l t i n g i n o v e r p r o t e c t i o n o f t h e p r o t e i n . I t i s t h e r e f o r e i m p o r t a n t t h a t p r o c e s s i n g s h o u l d n ot r e s u l t i n o v e r p r o t e c t i o n o f t h e p r o t e i n and t h a t i t i s i m p o r t a n t t o a s s e s s t h e i n t e s t i n a l d i g e s t i b i l i t y o f such m a t e r i a l . A l t h o u g h , most o f t h e s e e x p e r i m e n t s came up w i t h v a l u a b l e d a t a and t h e r e i s some g e n e r a l agreement among r e s u l t s , u s e f u l n e s s o f t h e d a t a i s re d u c e d due t o d i f f e r e n c e s i n a c t u a l v a l u e s o b t a i n e d . There i s c o n s i d e r a b l e v a r i a t i o n among l a b o r a t o r i e s i n measurement of p r o t e i n u t i l i z a t i o n and t h e s e d i f f e r e n c e s can be a c c o u n t e d f o r by d i f f e r e n c e s i n methods used by each l a b o r a t o r y even under s t a n d a r d i z e d c o n d i t i o n s (Beever and C o t t r i l l , 1994). 31 1.2. PERFORMANCE STUDIES 1.2.1. MATCHING OF CARBOHYDRATE AND PROTEIN SOURCES VARYING IN RATE OF STARCH AND PROTEIN DEGRADABILITY. U n t i l a few y e a r s ago, r e l a t i v e l y l i t t l e a t t e n t i o n was p a i d t o t h e r o l e o f c a r b o h y r a t e s i n d i e t s o f d a i r y c a t t l e o t h e r t h a n t h a t s t r u c t u r a l c a r b o h y d r a t e s i n roughages a c t e d as a s o u r c e o f f i b e r w i t h i m p o r t a n t s t a b i l i z i n g p r o p e r t i e s f o r rumen f e r m e n t a t i o n and t h a t c a b o h y d r a t e s i n roughages and c o n c e n t r a t e s were an i m p o r t a n t energy y i e l d i n g p a r t o f t h e d i e t ( B a l d w i n and Koong, 1977)• De V i s s e r and H i n d l e , (1990) r e p o r t e d d i f f e r e n c e s i n t h e r u m i n a l d e g r a d a t i o n c h a r a c t e r i s t i c s o f NSC l i k e s t a r c h and s u g a r s and SC l i k e f i b e r . R u s s e l l and H e s p e l l , (1981) and more r e c e n t l y Henning e t a l . (1991), o b s e r v e d t h a t o p t i m a l m i c r o b i a l p r o t e i n s y n t h e s i s r e s u l t s from synchronous u t i l i z a t i o n o f r u m i n a l l y degraded p r o t e i n and c a r b o h y d r a t e s from d i e t a r y i n g r e d i e n t s . P r o t e i n d e g r a d a t i o n i n t h e rumen u s u a l l y exceeds c a r b o h y d r a t e a v a i l a b i l i t y and p r o t e i n wastage o c c u r s (NRC, 1985). On t h e o t h e r hand p r o t e i n d e g r a d a t i o n might be t o o slow t o s u p p o r t o p t i m a l r u m i n a l d i g e s t i o n o f c a r b o h y d r a t e s . I n b o t h c a s e s , d e p r e s s i o n i n m i c r o b i a l p r o t e i n s y n t h e s i s o c c u r s . The p r i n c i p l e o f n u t r i e n t s y n c h r o n i c i t y i s based on t h e p r e m i s e t h a t p r o v i s i o n o f a v a i l a b l e energy and p r o t e i n a t c o o r d i n a t e d r a t e s and i n t h e r i g h t p r o p o r t i o n s s h o u l d a l l o w m i c r o b e s t o o b t a i n s i m u l t a n e o u s l y ATP, NH3, AAs and d i p e p t i d e s ( o l i g o p e p t i d e s ) needed f o r c e l l s y n t h e s i s and r e s u l t i n b e t t e r u t i l i z a t i o n o f n u t r i e n t s i n t h e rumen as w e l l as i n c r e a s i n g t h e s u p p l y o f m i c r o b i a l p r o t e i n t o t h e s m a l l i n t e s t i n e (Oldham, 1984). 32 C a r b o h y d r a t e and p r o t e i n synchrony s t u d i e s i n N o r t h A m e r i c a have c o n c e n t r a t e d on b a r l e y , c o r n and t o some e x t e n t sorghum as a major NSC s o u r c e s w i t h f i s h meal (FM), d r i e d - b r e w e r s - g r a i n (DBG), c a n o l a meal (CSM) , u r e a (U) , o r soybean meal (SBM) as p r o t e i n supplements (DePeters and T a y l o r , 1985; McCarthy e t a l . , 1989; Casper and S c h i n g o e t h e 1989; H e r r e r a - S a l d a n a and Huber, 1989; H e r r e r a - S a l d a n a e t a l . , 1990a; A l d r i c h e t a l . , 1993 and K h o r a s a n i e t a l . , 1994). O t h e r s have emphasized b a l a n c i n g f o r s t r u c t u r a l c a r b o h y d r a t e s i n t h e d i e t s (MacGregor e t a l . , 1983). I n Europe where g r a i n p r o d u c t i o n o r use as a n i m a l f e e d i s not as h i g h as i n N o r t h A m e r i c a , t h e c o n c e n t r a t e p o r t i o n o f t h e f e e d i s u s u a l l y compounded from a g r o - b y p r o d u c t s such as b e e t p u l p , wheat m i d d l i n g s , hominy, b r a n s , p a l m - k e r n e l and a l s o p r o c e s s e d c e r e a l s t o mention a few (De V i s s e r and H i n d l e , 1990). Johnson, (1976) and Nocek and R u s s e l l , (1988) s u g g e s t e d t h a t a c o m b i n a t i o n o f r a p i d l y and s l o w l y degraded c a r b o h y d r a t e s s h o u l d s u p p o r t maximum m i c r o b i a l y i e l d . T h i s e f f e c t was demonstrated i n b o t h i n v i t r o and i n s i t u s t u d i e s , where i n c r e a s e d i n t a k e o f paper and wheat s t a r c h t o g e t h e r s t i m u l a t e d m i c r o b i a l y i e l d ( O f f e r , e t a l . , 1978 and NRC, 1985). Oldham (1984) a n a l y s e d d a t a from d i f f e r e n t e x p e r i m e n t s , and found t h a t b a r l e y s u p p o r t e d h i g h e r b a c t e r i a l y i e l d t h a n c o r n g r a i n when f e d t o d a i r y cows a t moderate i n t a k e s o f d i e t s w i t h 10 o r 40% hay. An e a r l i e r s t u d y by 0 r s k o v e t a l . (1971) a l s o r e p o r t e d g r e a t e r m i c r o b i a l p r o t e i n q u a n t i t y (DAPA) i n abomasal f l u i d f o r b a r l e y compared t o c o r n w i t h u r e a as t h e n i t r o g e n s o u r c e . I n c o n t r a s t , S p i c e r e t a l . (1986), found no 33 i n f l u e n c e o f d r y r o l l e d sorghum v e r s u s d r y r o l l e d c o r n v e r s u s s t e a m - f l a k e d b a r l e y on m i c r o b i a l y i e l d i n s t e e r s f e d 20% f o r a g e d i e t s . Recent s t u d i e s u t i l i z i n g d i e t s s y n c h r o n i z e d f o r c a r b o h y d r a t e and p r o t e i n , have produced c o n f l i c t i n g r e s u l t s . McCarthy e t a l . (1989) d i d not ob s e r v e any d i f f e r e n c e s i n e f f i c i e n c y o f m i c r o b i a l p r o t e i n s y n t h e s i s (g/kg, o r g a n i c m a t t e r , a p p a r e n t o r t r u l y d i g e s t e d ) o r t o t a l passage o f N t o t h e duodenum. M i c r o b i a l p r o t e i n s y n t h e s i s and m i c r o b i a l p r o t e i n f l o w t o t h e duodenum was h i g h e r f o r cows f e d b a r l e y t h a n c o r n . T h i s was a t t r i b u t e d t o t h e h i g h e r d i g e s t i o n o f o r g a n i c m a t t e r t h a t o c c u r r e d i n t h e rumen, i n s p i t e o f low r u m i n a l NH3-N c o n c e n t r a t i o n s . These f i n d i n g s a r e i n agreement w i t h t h o s e o f 0 r s k o v e t a l . (1971) and Lee e t a l . (1986). I n c o n t r a s t , i n v i v o s t u d i e s w i t h sheep and c o n t i n o u s c u l t u r e s t u d i e s by H u s s e i n e t a l . (19 91a,b) i n d i c a t e d t h a t t h e r e were no s i g n i f i c a n t d i f f e r e n c e s i n b a c t e r i a l p r o t e i n s y n t h e s i s , e f f i c i e n c y , N f l o w and t o t a l AA f l o w t o t h e s m a l l i n t e s t i n e s between cows f e d b a r l e y (B) o r c o r n (C) based d i e t s w i t h SBM o r FM as p r o t e i n supplements. There was however a tendency f o r h i g h e r m i c r o b i a l p r o t e i n y i e l d on C-SBM t h a n B-SBM and f o r c o r n d i e t s t h a n b a r l e y . These f i n d i n g s a r e i n agreement w i t h t h e i r c o n t i n o u s c u l t u r e f i n d i n g s , a l t h o u g h t o t a l AAs, e s s e n t i a l amino a c i d s (EAAs) and non-e s s e n t i a l amino a c i d s (NEAAs) f l o w s were s i g n i f i c a n t l y h i g h e r f o r c o r n o r FM t h a n b a r l e y o r SBM d i e t s . They c o n c l u d e d from t h e s e s t u d i e s t h a t c o r n o r FM has a s i g n i f i c a n t e f f e c t on m a n i p u l a t i n g AAs l e a v i n g t h e rumen. 34 The above r e p o r t e d r e s u l t s do not agree w i t h t h o s e o f o t h e r w o r k e r s who have r e p o r t e d s i g n i f i c a n t l y h i g h e r m i c r o b i a l p r o t e i n s y n t h e s i s f o r b a r l e y - c o t t o n - s e e d meal (B-CSM) d i e t t h a n b a r l e y - d r y -b r e w e r s - g r a i n s (B-DBG) o r milo(M-CSM) o r M-DBG d i e t s ( H e r r e r a -S a l d a n a and Huber, 1989) and b a r l e y t h a n c o r n based d i e t s (Owens and Bergen, 1983) . S n i f f e n and R o b i n s o n , (1987) r e p o r t e d h i g h e r m i c r o b i a l p r o t e i n e f f i c i e n c i e s f o r c o r n t h a n wheat d i e t s . D i f f e r e n c e s i n r e p o r t e d r e s u l t s c o u l d be e x p l a i n e d by a number o f f a c t o r s , i n c l u d i n g c h e m i c a l and p h y s i o l o g i c a l (Hoover and S t o k e s , 1991). M a j o r c h e m i c a l and p h y s i o l o g i c a l m o d i f i e r s o f rumen f e r m e n t a t i o n a r e rumen pH and t u r n - o v e r r a t e and o t h e r n u t r i t i o n a l l y r e l a t e d c h a r a c t e r i s t i c s such as l e v e l o f f e e d i n t a k e , f e e d i n g s t r a t e g i e s , f o r a g e l e n g t h and q u a l i t y , and f o r a g e : c o n c e n t r a t e r a t i o s . S n i f f e n and R o b i n s o n , (1987) n o t e d t h a t , i n t e r a c t i o n s between f e e d i n t a k e , l e v e l o f p r o d u c t i o n , t y p e o f roughage s o u r c e (legume vs g r a s s ) , form (hay vs s i l a g e ) and amount of f o r a g e i n c l u d e d , a l l m o d i f y t h e r e l a t i v e a b i l i t i e s o f g r a i n s t o s u p p o r t m i c r o b i a l growth i n v i v o . S t u d i e s d e a l i n g w i t h r e p l a c e m e n t o f f o r a g e w i t h g r a i n i n t h e d i e t i n d i c a t e a d e c r e a s e i n e f f i c i e n c y o f m i c r o b i a l p r o t e i n s y n t h e s i s when a h i g h e r p r o p o r t i o n o f f o r a g e i s r e p l a c e d by g r a i n (Mathers and M i l l e r , 1981 and Owens and Bergen, 1983). I n s p i t e of t h e d e c r e a s e d e f f i c i e n c y , t h e t o t a l m i c r o b i a l - N f l o w t o t h e duodenum was o f t e n i n c r e a s e d when g r a i n was added. T h i s was a t t r i b u t e d t o t h e i n c r e a s e d OM d i g e s t i o n i n t h e rumen w h i c h more t h a n o f f - s e t t h e d e c r e a s e d e f f i c i e n c y (Hoover and S t o k e s , 1991). D i f f e r e n c e s i n t y p e o f c a r b o h y d r a t e s o u r c e may 35 e x p l a i n d i f f e r e n c e s i n f l o w o f N t o t h e duodenum. These s t u d i e s s u g g e s t t h a t optimum f l o w o f m i c r o b i a l p r o t e i n and t o t a l AAs t o t h e duodenum may be a f f e c t e d by b o t h t y p e and s o u r c e o f c a r b o h y d r a t e s and t h a t f u r t h e r s t u d i e s a r e needed t o i d e n t i f y t h e c o m b i n a t i o n s t h a t w i l l r e s u l t i n t h e optimum m i c r o b i a l e f f i c i e n c y and rumen d i g e s t i b i l i t y . O t her workers (MacGregor e t a l . , 1983 and S t o k e s e t a l . , 1991a,b) have l o o k e d a t t h e e f f e c t o f d i f f e r e n t r a t i o s o f NSC:DIP on m i l k p r o d u c t i o n . T h i s i s because NSC has a major i n f l u e n c e on t o t a l c a r b o h y d r a t e d i g e s t i o n and DIP a f f e c t s b o t h c a r b o h y d r a t e d i g e s t i o n and m i c r o b i a l e f f i c i e n c y ( S t o k e s e t a l . , 1991a). Stokes e t a l . (1991b) i n v e s t i g a t e d t h e e f f e c t o f NSC:SC r a t i o and l e v e l o f DIP on m i c r o b i a l y i e l d and rumen parameters i n l a c t a t i n g d a i r y cows. Three d i e t s were f o r m u l a t e d t o p r o v i d e h i g h , medium, and low l e v e l s o f DIP and NSC r e s p e c t i v e l y v i z 25, 37, and 54% NSC. The p r o t e i n and c a r b o h y d r a t e d i g e s t i o n and m i c r o b i a l y i e l d were p r e d i c t e d from c o n t i n u o u s c u l t u r e r e s u l t s ( S t o k e s e t a l . , 1991a) t o be i n t h e o r d e r o f d i e t I > d i e t 2 > d i e t 3 ( S t o k e s e t a l . , 1991b). There were no s i g n i f i c a n t d i f f e r e n c e s between d i e t 1 and d i e t 2 i n e i t h e r p r o t e i n o r c a r b o h y d r a t e d i g e s t i o n o r m i c r o b i a l y i e l d . D i e t 3 r e s u l t e d i n s i g n i f i c a n t l y l e s s m i c r o b i a l y i e l d t h a n d i e t 1 and 2 i n d i c a t i n g t h e low l e v e l s o f a v a i l a b l e p r o t e i n and c a r b o h y d r a t e . T h i s d e m o n s t r a t e s t h e importance o f h a v i n g adequate amounts o f NSC and DIP i n t h e d i e t f o r m i c r o b i a l growth. I t must be n o t e d t h a t d i e t s used i n t h i s e x periment were f o r m u l a t e d t o c o n t a i n s i m i l a r r a t i o s o f a v a i l a b l e p r o t e i n and c a r b o h y d r a t e ; t h e r e f o r e , no 36 s i g n i f i c a n t d i f f e r e n c e s i n m i c r o b i a l e f f i c i e n c i e s were e x p e c t e d i n s p i t e o f d i e t 3 h a v i n g a w i d e r r a t i o . These r e s u l t s a r e not i n agreement w i t h t h e i r e a r l i e r s t u d i e s u s i n g t h e c o n t i n u o u s c u l t u r e t e c h n i q u e ( S t o k e s e t a l . , 1991a). I n t h e s e c o n t i n u o u s c u l t u r e s t u d i e s , c a r b o h y d r a t e d i g e s t i o n and m i c r o b i a l p r o t e i n s y n t h e s i s e f f i c i e n c y responded l i n e a r l y t o t h e l e v e l o f DIP w i t h i n each NSC l e v e l . I n c r e a s i n g NSC as a p r o p o r t i o n o f c a r b o h y d r a t e had a p o s i t i v e e f f e c t on t o t a l c a r b o h y d r a t e d i g e s t e d and was n o t r e l a t e d t o m i c r o b i a l e f f i c i e n c y . T h i s i s s u p p o r t e d by i n v i v o s t u d i e s i n v o l v i n g l a c t a t i n g d a i r y cows a t h i g h i n t a k e s (McCarthy e t a l . , 1989 and H e r r e r a - S a l d a n a e t a l . , 1990a). There i s a l i m i t e d number o f s t u d i e s d e a l i n g w i t h l a c t a t i n g cows a t h i g h f e e d i n t a k e s , i n which i n f o r m a t i o n i s a v a i l a b l e t o q u a n t i t a t i v e l y a s s e s s b o t h m i c r o b i a l y i e l d , e f f i c i e n c y and AAs f l o w r e s p o n s e s t o v a r y i n g d i e t a r y NSC, DIP, and t o t a l c a r b o h y d r a t e . However, b o t h i n v i t r o and i n v i v o d a t a a r e i n g e n e r a l agreement c o n c e r n i n g t h e i n f l u e n c e o f c a r b o h y d r a t e and p r o t e i n on rumen m i c r o b i a l growth. N o n - s t r u c t u r a l c a r b o h y d r a t e as a p r o p o r t i o n o f t o t a l c a r b o h y d r a t e d i g e s t e d i n t h e rumen seems t o be more i m p o r t a n t . T h e r e f o r e , as NSC l e v e l i n c r e a s e s , t h e concommitant i n c r e a s e i n c a r b o h y d r a t e d i g e s t e d w i l l enhance d a i l y m i c r o b i a l p r o t e i n y i e l d by p r o v i d i n g more energy f o r growth (Hoover and S t o k e s , 1991). 37 1.2.2. MILK PRODUCTION. S e v e r a l r e s e a r c h e r s (McCarthy e t a l . , 1989; Casper and Sc h i n g o e t h e , 1989 and Casper e t a l . , 1990) have r e p o r t e d d e c r e a s e d m i l k p r o d u c t i o n and d r y m a t t e r i n t a k e (DMI) o f cows f e d b a r l e y compared t o t h o s e f e d c o r n . O t h e r s , (DePeters and T a y l o r , 1985 and G r i n g s e t a l . , 1992) d i d n o t o b s e r v e t h i s r e s p o n s e . Nocek and Tamminga, (1991) have r e c e n t l y p u b l i s h e d on t h e e f f e c t o f s t a r c h s o u r c e on m i l k p r o d u c t i o n . They noted t h a t t h e magnitude o f m i l k y i e l d r e s p o n s e was v a r i a b l e among s t u d i e s . Changes i n m i l k c o m p o s i t i o n were m a i n l y i n f a t c o n t e n t . I n t h e s t u d i e s by McCarthy e t a l . , (1989), m i l k p r o d u c t i o n was s i g n i f i c a n t l y h i g h e r f o r cows f e d c o r n d i e t s t h a n b a r l e y . They a t t r i b u t e d t h i s i n c r e a s e d p r o d u c t i o n t o h i g h energy i n t a k e s w h i c h were used f o r m i c r o b i a l p r o t e i n and m i l k l a c t o s e s y n t h e s i s . M i c r o b i a l p r o t e i n s y n t h e s i s e f f i c i e n c y was not a f f e c t e d by c o r n o r b a r l e y d i e t s , i n c o m b i n a t i o n w i t h SBM o r FM; however p r o t e i n f l o w t o t h e duodenum was h i g h e r f o r cows f e d b a r l e y t h a n c o r n . I f m i l k p r o d u c t i o n was h i g h e r on c o r n d i e t s , t h e n c o r n d i e t s were a b l e t o p r o v i d e enough r u m i n a l d e g r a d a b l e c a r b o h y d r a t e f o r m i c r o b i a l s y n t h e s i s as w e l l as s u f f i c i e n t u n d e g r a d a b l e p r o t e i n . I n c o n t r a s t , H e r r e r a - S a l d a n a and Huber (1989) r e p o r t e d h i g h e r m i l k p r o d u c t i o n on b a r l e y based d i e t s t h a n c o r n . T h i s was a t t r i b u t e d t o i n c r e a s e d DM and s t a r c h i n t a k e s and a l s o h i g h e r m i c r o b i a l p r o t e i n s y n t h e s i s ( H e r r e r a - S a l d a n a e t a l . , 1990a). I t i s however argued t h a t t h e s t a r c h c o n t e n t o f t h e b a r l e y d i e t s was h i g h e r t h a n t h e o t h e r t h r e e d i e t s . Q 38 European s t u d i e s (De V i s s e r and H i n d l e , 1990; De V i s s e r e t a l . , 1991; Tamminga e t a l . , 1991 and De V i s s e r e t a l . , 1992;) have c o n c e n t r a t e d on r e p l a c e m e n t of b a r l e y by a g r o - b y p r o d u c t s such as b e e t p u l p . A t a c e r t a i n l e v e l o f i n c l u s i o n i n t h e d i e t , b e e t p u l p has been shown t o g i v e s i m i l a r m i l k y i e l d t o b a r l e y . No measurement o f m i c r o b i a l y i e l d and a m i n o - a c i d s f l o w were a t t e m p t e d i n t h e s e s t u d i e s . I t appears from t h e r e v i e w of l i t e r a t u r e t h a t more s t u d i e s a r e needed d e a l i n g w i t h t h e a s p e c t of c a r b o h y d r a t e and p r o t e i n s o u r c e s y n c h r o n i z a t i o n . I n a d d i t i o n not many s t u d i e s have been done under Canadian c o n d i t i o n s . However, i n t e r e s t i n c a r b o h y d r a t e and p r o t e i n s y n c h r o n i z a t i o n s t u d i e s i s i n c r e a s i n g ( S n i f f e n e t a l . , 1992; R u s s e l l e t a l . , 1992; O'Connor e t a l . , 1993 and K h o r a s a n i e t a l . , 1994) I t was h y p o t h e s i s e d t h a t ; 1. N o n - s t r u c t u r a l - c a r b o h y d r a t e s ( s t a r c h ) from d i f f e r e n t s o u r c e s w i l l degrade a t d i f f e r e n t r a t e s , 2. P r o c e s s i n g by s t e a m - r o l l i n g w i l l i n c r e a s e t h e r a t e o f s t a r c h d e g r a d a t i o n and r e l e a s e by c e r e a l g r a i n s , 3. C e l l - w a l l (NDF) from d i f f e r e n t roughages and a g r o - b y p r o d u c t s degrade a t d i f f e r e n t r a t e s , 4. D i e t s matched f o r d i f f e r i n g r a t e s o f c a r b o h y d r a t e and p r o t e i n d e g r a d a t i o n w i l l s u p p o r t d i f f e r e n t l e v e l s o f m i l k p r o d u c t i o n . 39 1.3. REFERENCES AFRC. 1992. T e c h n i c a l Committee on Responses t o N u t r i e n t s . R e p o r t No. 9 N u t r i t i v e Requirements of Ruminant A n i m a l s : P r o t e i n . N u t r i t i o n A b s t r a c t s and Reviews ( s e r i e s B ) , 62, 787. A l d r i c h , J.M., L.D. M u l l e r , G.A. V a r g a, and L.C. G r i e l , J r . 1993. N o n s t r u c t u r a l c a r b o h y d r a t e and p r o t e i n e f f e c t on rumen f e r m e n t a t i o n , n u t r i e n t f l o w and performance o f d a i r y cows. J . D a i r y S c i . 76:1091. A n n i s o n , E.F. 1956. N i t r o g e n m e t a b o l i s m i n t h e sheep. Biochem. 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Oldham, J.D. 1984. P r o t e i n - e n e r g y i n t e r r e l a t i o n s h i p i n d a i r y cows. J . D a i r y S c i . 67:1090. O p s t v e d t , J . , R. M i l l e r , R.W. Hardy, and J . S p i n e l l i . 1984. Heat-i n d u c e d changes i n s u l f h y d r y l groups and d i s u l f i d e bonds i n f i s h p r o t e i n and t h e i r e f f e c t on p r o t e i n and amino a c i d d i g e s t i b i l i t y i n ra i n b o w t r o u t . J . A g r i c . Food Chem. 32:929. 0 r s k o v , E.R., C. F r a s e r , and I . MacDonald. 1979. D i g e s t i o n o f c o n c e n t r a t e s i n sheep: E f f e c t s o f rumen f e r m e n t a t i o n o f b a r l e y and maize d i e t s on p r o t e i n d i g e s t i o n . J . A g r i c . S c i . (Camb): 92:499. 45 Owens, F.N., and W.G. Bergen. 1983a. N i t r o g e n m e t a b o l i s m o f r u m i n a n t : H i s t o r i c a l p e r s p e c t i v e , c u r r e n t u n d e r s t a n d i n g and f u t u r e i m p l i c a t i o n s . J . Anim. 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A n e t c a r b o h y d r a t e and p r o t e i n system f o r e v a l u a t i n g c a t t l e d i e t s : I I . C a r b o h y d r a t e and p r o t e i n a v a i l a b i l i t y . J . Anim. S c i . 70:3562. S n i f f e n , C.J., and P.H. Robinson. 1987. Symposium: P r o t e i n and f i b e r d i g e s t i o n , passage, and u t i l i z a t i o n i n l a c t a t i n g cows. M i c r o b i a l growth and f l o w as i n f l u e n c e d by d i e t a r y m a n i p u l a t i o n s . J . D a i r y S c i . 70:425. S p i c e r , L.A., C.B. Th e u r e r , J . Sowe and T.H. Noon. 1986. Ruminal and p o s t r u m i n a l u t i l i z a t i o n of n i t r o g e n and s t a r c h from sorghum g r a i n - , c o r n - , and b a r l e y - b a s e d d i e t s by beef s t e e r s . J . Anim. S c i . 62:521. S t e r n , M.D., G.A. Varga, J.H. C l a r k , J .L. F i r k i n s , J.T. Huber, and D.L. P a l m q u i s t . 1994. Symposium: M e t a b o l i c r e l a t i o n s h i p i n s u p p l y o f n u t r i e n t s f o r m i l k p r o t e i n s y n t h e s i s . E v a l u a t i o n o f c h e m i c a l and p h y s i c a l p r o p e r t i e s o f fe e d s t h a t a f f e c t m e t a b o l i s m i n t h e rumen. J . D a i r y S c i . 77:2762. S t o k e s , S.R., W.H. Hoover, T.K. M i l l e r , and R.P. M a n s k i . 1991a. Impact o f c a r b o h y d r a t e and p r o t e i n l e v e l on b a c t e r i a l m e t a b o l i s m i n c o n t i n o u s c u l t u r e . J . D a i r y S c i . 74:854. S t o k e s , S.R., W.H. Hoover, T.K. M i l l e r , and R. B l a u w e i k e l . 1991b. Ruminal d i g e s t i o n and m i c r o b i a l u t i l i z a t i o n o f d i e t s v a r y i n g i n t y p e o f c a r b o h y d r a t e and p r o t e i n . J . D a i r y S c i . 74:871. Tamminga, S., A.M. Van Vuren, C.J. Van Der K o e l e n , R.S. K e t e l a a r and P.L. van Der J o g t . 199 0. Ruminal b e h a v i o r o f s t r u c t u r a l c a r b o h y d r a t e s , n o n - s t r u c t u r a l c a r b o h y d r a t e s and c r u d e p r o t e i n from c o n c e n t r a t e i n g r e d i e n t s i n d a i r y cows. Neth. J . A g r i c . S c i . 38:513. T i l l e y , J.M.A. , and R.A. T e r r y . 1963. A two s t a g e t e c h n i q u e f o r t h e i n v i t r o d i g e s t i o n o f f o r a g e c r o p s . J . B r . G r a s s l . Soc. 18:104. Van S o e s t , P . J. 1986. S o l u b l e c a r b o h y d r a t e s . C o r n e l l N u t r i t i o n C o n f e r e n c e f o r f e e d M a n u f a c t u r e r s . S y r a c u s e M a r r i o t t , E a s t S y r a c u s e , pp. 73. Van S o e s t , P . J . 1982. N u t r i t i o n a l E c o l o g y o f t h e Ruminant. 2nd ed., C o r n e l l U n i v e r s i t y P r e s , I t h a c a . V a r v i k k o , T., J.E. L i n d b e r g , J . S e t a l a , and L. s y r j a l a - Q u i s t . 1983. The e f f e c t o f formaldehyde t r e a t m e n t o f soya bean and r a p e s e e d meal on t h e amino a c i d p r o f i l e s and a c i d - p e p s i n s o l u b i l i t y o f rumen undegraded p r o t e i n . J . A g r i c . Sci.(Camb). 101:603. V e r i t e , R., and Peyraund, J.L. 1989. P r o t e i n : The PDI System. In: J a r r i g e , R. (ed.) Ruminant N u t r i t i o n . INRA p u b l i c a i o n . V e r s a i l l e s , p. 33. 47 W a l t z , D.M., and M.D. S t e r n , 1989. E v a l u a t i o n o f v a r i o u s methods f o r p r o t e c t i n g soya-bean p r o t e i n from d e g r a d a t i o n by rumen b a c t e r i a . Anim. Feed S c i . Tech. 25:111. W i l l i a m s , A.P., 1986. L a b o r a t o r y methods o f d e t e r m i n i n g p r o t e i n d e g r a d a b i l i t y i n r u m i n a n t s . R e s e a r c h and Development i n A g r i c u l t u r e , 3:1. W i l l i a m s , J.M. 1968. The c h e m i c a l e v i d e n c e f o r t h e s t r u c t u r e o f s t a r c h . I n : S t a r c h and i t s d e r i v a t i v e s . R a d l e y , J.A. ( E d . ) , 4 t h . ed., pp 91-138. Chapman and H a l l L t d . , London, U.K. W r i g h t , D.E., and R.E. Hungate. 1967. Amino a c i d c o n c e n t r a t i o n s i n rumen f l u i d . A p p l . M i c r o b i o l . 15:148. 48 CHAPTER 2. THE EFFECT OF STEAM-ROLLING CORN, BARLEY AND WHEAT ON IN VITRO STARCH RELEASE AND IN SITU DEGRADABILITY OF DRY MATTER, CRUDE PROTEIN AND STARCH. 2.0. ABSTRACT. Three groups o f f e e d s t u f f s , c e r e a l s , roughages and a g r o -b y p r o d u c t s were i n c u b a t e d i n s i t u f o r 2, 3, 6, 12, 24, 36, and 48 h i n 2 cows and i n 3 p e r i o d s . The t h r e e f e e d groups were randomly a s s i g n e d t o p e r i o d s w i t h i n a cow. Ruminal d e g r a d a b i l i t y d a t a was s u b j e c t e d t o an i t e r a t i v e p r o c e d u r e u s i n g t h e f o l l o w i n g e q u a t i o n , P = a + b(l-e (" c ( t" l a 8 ) )) f o r t > l a g where; a = r a p i d l y d e g r a d a b l e f r a c t i o n ; b = s l o w l y d e g r a d a b l e f r a c t i o n ; c = r a t e c o n s t a n t o f b; t = t i m e o f i n c u b a t i o n ; l a g = l a g t i m e . S t a t i s t i c a l a n a l y s i s was h a n d l e d s e p a r a t e l y f o r each group o f f e e d s t u f f s . C e r e a l d a t a were h a n d l e d as a 3 x 2 f a c t o r i a l a n a l y s i s w i t h c e r e a l and p r o c e s s i n g as main e f f e c t s . S i x t r e a t m e n t s were i n v o l v e d ; u n p r o c e s s e d c o r n (UPC), b a r l e y (UPB), wheat. (UPW) and t h e i r s t e a m - r o l l e d c o u n t e r p a r t s , c o r n (SRC), b a r l e y (SRB) and wheat (SRW). Dry m a t t e r , CP and s t a r c h d i s a p p e a r a n c e from n y t e x p o l y e s t e r bags were r a p i d f o r a l l c e r e a l s under c o n s i d e r a t i o n , though d i f f e r e n c e s e x i s t e d . About 80% o f DM had d i s a p p e a r e d by 12 h and s t a r t e d t o l e v e l o f f between 12 and 24 h. S t a r c h was most r a p i d l y degraded f o r a l l f e e d s t u f f s such t h a t by 12 h, a t l e a s t 80% o f c o r n and 9 0% o f b a r l e y and wheat s t a r c h had d i s a p p e a r e d and a l l r e a c h e d a p l a t e a u by t h e 24 h i n c u b a t i o n . Steam r o l l i n g r e s u l t e d i n d e c r e a s i n g (P<0.0001) t h e r a t e o f DM (P<0.0007), CP (P<0.003) and s t a r c h (P<0.0091) d e g r a d a t i o n i n t h e 49 rumen o f cows and t h e r e s p o n s e was not dependent on t y p e o f c e r e a l f o r t h e t h r e e p a r a m e t e r s . Average r e s p o n s e due t o steam r o l l i n g f o r DM, s t a r c h and CP was 15.54+0.98 %/h, 22.92+0.98 %/h; 19.26+1.08 %/h, 25.03+1.08 %/h; and 15.08+0.45 %/h, 18.15+0.45 %/h, r e s p e c t i v e l y f o r t h e p r o c e s s e d and u n p r o c e s s e d g r a i n s , r e s p e c t i v e l y . Type o f c e r e a l a l s o s i g n i f i c a n t l y a f f e c t e d t h e r a t e o f DM (0.0371), s t a r c h (P<0.0.002) and CP (P<0.0001) d e g r a d a t i o n o f t h e g r a i n s . Corn t r e a t m e n t had lower r a t e o f DM d e g r a d a t i o n compared t o b a r l e y (P<0.0137) but not wheat (P>0.0918), w h i l e b a r l e y and wheat were s i m i l a r (P<0.1993). Average r e s p o n s e t o t y p e o f c e r e a l was 16.68+0.99, 19.49±0.99 and 21.52±0.99 %/h f o r c o r n , wheat and b a r l e y , r e s p e c t i v e l y . Rate o f s t a r c h d e g r a d a t i o n was s i g n i f i c a n t l y l o w e r f o r c o r n compared t o wheat (P<0.0083) and b a r l e y (P<0.0007) and wheat was lower t h a n b a r l e y (P<0.0436). V a l u e s f o r r a t e o f s t a r c h d e g r a d a t i o n averaged 15.74+1.32, 22.97+1.32 and 27.73+1.32 %/h f o r c o r n , wheat and b a r l e y , r e s p e c t i v e l y . F o r CP, c o r n had lo w e r r a t e o f CP d e g r a d a t i o n compared t o wheat (P<0.0001) and b a r l e y (P<0.0008) w h i l e b a r l e y was lower t h a n wheat (P<0.0032). Rate o f d e g r a d a t i o n o f CP averaged 12.13+0.56, 20.71+0.56, and 16.99+0.56 %/h f o r c o r n , wheat and b a r l e y , r e s p e c t i v e l y . I n v i t r o s t a r c h r e l e a s e by a m y l o g l u c o s i d a s e t e n d e d t o i n c r e a s e w i t h i n c r e a s i n g i n c u b a t i o n t i m e f o r a l l g r a i n s . Steam r o l l i n g t e n d e d t o i n c r e a s e i n v i t r o s t a r c h r e l e a s e when i n c u b a t e d w i t h a m y l o g l u c o s i d a s e enzyme a t each i n c u b a t i o n t i m e f o r a l l g r a i n s . 50 Data such as t h e s e can be used t o rank f e e d s a c c o r d i n g t o t h e i r s t a r c h d e g r a d a b i l i t y and t h e r e f o r e can be used i n c a r b o h y d r a t e and p r o t e i n s y n c h r o n i z a t i o n o f d i e t s . I f steam r o l l i n g r e d u c e d s t a r c h d e g r a d a t i o n t h e n t h e p r o c e s s can be used t o a t t e n u a t e t h e s t a r c h d e g r a d a b i l i t y o f t h o s e f e e d s w i t h h i g h r u m i n a l d e g r a d a b i l i t y which would r e s u l t i n n e g a t i v e e f f e c t s i f n o t matched c o r r e c t l y w i t h a p r o t e i n s o u r c e . 2.1. INTRODUCTION. C a r b o h y d r a t e s a r e a major s o u r c e o f d i e t a r y energy f o r b o t h l i v e s t o c k and humans and c o n s t i t u t e about 60-80% o f t y p i c a l d a i r y r a t i o n (Nocek and R u s s e l l , 1988 and Nocek and Tamminga, 1991). They a r e a l a r g e d i v e r s e group o f s i m p l e and complex c h e m i c a l compounds (Van S o e s t , 1982 and Van S o e s t , 1986). C a r b o h y d r a t e s a r e t y p i c a l l y d i v i d e d i n t o s t r u c t u r a l c a r b o h y d r a t e s ( h e m i - c e l l u l o s e , c e l l u l o s e , p e c t i n s ) w h i c h c o n s t i t u e n t s o r i g i n a t e from p l a n t c e l l - w a l l s , and n o n - s t r u c t u r a l c a r b o h y d r a t e s ( s u g a r s , o l i g o s a c c h a r i d e s , s t a r c h e s ) w h i c h c o n s t i t u e n t s o r i g i n a t e from c e l l - c o n t e n t s . S t r u c t u r a l c a r b o h y d r a t e s and t h e i r components degrade a t lower r a t e s t h a n NSCs; a l s o NSCs w i t h i n t h e same group, such as s t a r c h , a l s o degrade a t d i f f e r e n t r a t e s . T h i s i s d e t e r m i n e d i n p a r t by d i f f e r e n c e s i n t h e p h y s i c a l and c h e m i c a l s t r u c t u r e o f d i f f e r e n t c a r b o h y d r a t e s w h i c h i n f l u e n c e t h e r a t e and e x t e n t o f i n v i t r o rumen d i g e s t i o n and en z y m a t i c ( M a l e s t e i n e t a l . , 1988; Cone e t a l . , 1989 and Cone and V l o t , 1990) and i n v i t r o gas p r o d u c t i o n ( H a l e , 1970 and T r e i e t 51 a l . , 1970), i n s i t u r u m i n a l (Galyean e t a l . , 1981; S p i c e r e t a l . , 1986; T h e u r e r , 1986; H e r r e r a - S a l d a n a e t a l . , 1990b and Tamminga e t a l . , 1990) and r u m i n a l i n v i v o ( H u n t i n g t o n , 1994) d e g r a d a t i o n c h a r a c t e r i s t i c s . M a l e s t e i n e t a l . , (1988), Cone e t a l . , (1989) and Cone and V l o t , 1990) u s i n g an i n v i t r o p r o c e d u r e showed a c o n s t a n t r a n k i n g i n degree o f d e g r a d a b i l i t y o f d i f f e r e n t s t a r c h s o u r c e s upon 6 h i n c u b a t i o n w i t h pure enzymes o r rumen f l u i d from cows f e d e i t h e r a hay o r hay p l u s c o n c e n t r a t e d i e t . Unprocessed maize was l e s s degraded t h a n wheat and wheat was l e s s degraded t h a n b a r l e y . Steam-f l a k i n g and p o p p i n g s i g n i f i c a n t l y i n c r e a s e d t h e d e g r a d a b i l i t y o f t h e s e g r a i n s . A g r o - b y p r o d u c t s such as wheat m i d d l i n g s and c o r n g l u t e n meal were more d e g r a d a b l e t h a n t h e i r c o r r e s p o n d i n g c e r e a l s . F o r a l l samples, s t a r c h d e g r a d a t i o n was h i g h e r when t h e f e e d s were i n c u b a t e d i n t h e rumen o f cows f e d a h a y - c o n c e n t r a t e d i e t t h a n a hay d i e t a l o n e . These r e s u l t s a r e i n agreement i n terms o f r a n k i n g o f t h e c e r e a l s w i t h i n s i t u s t u d i e s ( H e r r e r a - S a l d a n a e t a l . , 1990b; Fiems e t a l . , 1990 and Tamminga e t a l . , 1990). H e r r e r a - S a l d a n a e t a l . , (1990b) r e p o r t e d t h a t c o r n , m i l o and o a t s had s i g n i f i c a n t l y l o wer r a t e s o f s t a r c h d e g r a d a t i o n t h a n wheat o r b a r l e y . Wheat and b a r l e y were s i m i l a r , w i t h wheat h a v i n g a h i g h e r r a t e o f d r y m a t t e r and s t a r c h d e g r a d a t i o n . Among a l l t h e g r a i n s o a t s had t h e h i g h e s t r a p i d l y d e g r a d a b l e f r a c t i o n o f s t a r c h compared t o t h e r e s t o f t h e g r a i n s . B a r l e y and wheat had s i m i l a r amounts o f r a p i d l y d e g r a d a b l e f r a c t i o n o f s t a r c h but h i g h e r t h a n c o r n and m i l o w h i c h were v e r y low. A r i e l i e t a l . (1995) have r e p o r t e d a s i m i l a r r a n k i n g o f rumen d e g r a d a t i o n c h a r a c t e r i s t i c s o f d r y m a t t e r and s t a r c h of c o r n , b a r l e y , wheat and sorghum. These d i f f e r e n c e s i n s t a r c h d e g r a d a t i o n a r e due t o i n h e r e n t p h y s i c a l and c h e m i c a l d i f f e r e n c e s among d i f f e r e n t g r a i n s ( F r e n c h , 1973; Moran, 1982 and Rooney and P f l u g f e l d e r , 1986). P h y s i c a l and c h e m i c a l b a r r i e r s t o r u m i n a l d i g e s t i o n can be m o d i f i e d by many p r o c e s s e s such as g r i n d i n g (Galyean e t a l . , 1981 and Fiems e t a l . , 1990), steam f l a k i n g (Fiems e t a l . , 1990; M alcolm and K i e s l i n g , 1993), p o p p i n g ( M a l e s t e i n e t a l . , 1988 and Cone and V l o t , 1990), and steam r o l l i n g (Engstrom e t a l . , 1992) w h i c h a r e g e n e r a l l i v e s t o c k f e e d and human foods p r o c e s s i n g p r o c e d u r e s . T h i s d i f f e r e n c e i n d e g r a d a t i o n r a t e s o f c e r e a l g r a i n s has been c i t e d as b e i n g r e s p o n s i b l e f o r t h e d i f f e r e n c e s i n m i c r o b i a l p r o t e i n p r o d u c t i o n when c e r e a l s a r e f e d i n c o m b i n a t i o n w i t h p r o t e i n s o u r c e s o f s i m i l a r o r d i f f e r e n t r u m i n a l d e g r a d a b i l i t y (Nocek and R u s s e l l , 1988; H e r r e r a - S a l d a n a e t a l . , 1990a; Nocek and Tamminga, 1990 and Hoover and S t o k e s , 1991) r e s u l t i n g i n d i f f e r e n c e s i n m i l k p r o d u c t i o n (McCarthy e t a l . , 1989 and H e r r e r a - S a l d a n a e t a l . , 1990a). I n a d d i t i o n , newly proposed p r o t e i n r a t i o n i n g systems r e q u i r e an adequate and comprehensive d e s c r i p t i o n o f r u m i n a l and i n t e s t i n a l b e h a v i o r of c a r b o h y d r a t e s and p r o t e i n from d i f f e r e n t s o u r c e s i n o r d e r t o a p p r o p r i a t e l y s y n c h r o n i z e p r o t e i n w i t h c a r b o n r e l e a s e (ARC, 1984; NKJ, 1985; V e r i t e and Peyraund, 1989 and AFRC, 1992). T h i s i n f o r m a t i o n i s t h e r e f o r e i m p o r t a n t i n f o r m u l a t i o n o f d i e t s , m a t c h i n g r a t e s and e x t e n t o f r u m i n a l d e g r a d a t i o n of c a r b o h y d r a t e s and p r o t e i n t o maximize m i c r o b i a l p r o t e i n s y n t h e s i s . 53 The purpose o f t h i s e x periment was t o d e t e r m i n e e f f e c t o f c e r e a l t y p e and steam r o l l i n g on DM, s t a r c h and CP i n s i t u d e g r a d a t i o n c h a r a c t e r i s t i c s and i n v i t r o s t a r c h r e l e a s e by a m y l o g l u c o s i d a s e enzyme. 2.2.0. MATERIALS AND METHODS. 2.2.1. Source and description of feedstuffs and i n i t i a l handling. Twelve f e e d s t u f f s , c o n s i s t i n g o f c e r e a l s , roughages ( c o r n -g r a s s s i l a g e - C G r S , o r c h a r d g r a s s hay-OGrH and a l f a l f a hay-ALFH) and a g r o - b y p r o d u c t s (wheat millrun-WMR, r y e d i s t i l l e r s grains-RDG and b e e t pulp-BP) were o b t a i n e d from t h e Vancouver a r e a o f B r i t i s h C olumbia. C e r e a l s ; u n p r o c e s s e d c o r n , b a r l e y and wheat and t h e i r c o r r e s p o n d i n g s t e a m - r o l l e d c o u n t e r p a r t s were s u p p l i e d by E a s t C h i l l i w a c k A g r i c u l t u r a l C o - o p e r a t i v e , C h i l l i w a c k , B.C. A l l c e r e a l s were whole g r a i n s . The g r a i n s were steam r o l l e d a t 70°C f o r 30 m i n u t e s under a t m o s p h e r i c p r e s s u r e and r o l l i n g was done u s i n g r o l l e r s w i t h 5.7 grooves/cm (14 g r o o v e s / i n c h ) r e s u l t i n g i n f l a t r o l l e d g r a i n s . These f e e d s were s e l e c t e d because t h e y a r e commonly used i n t h e d i e t s o f ruminant a n i m a l s and t h e y c o n t r i b u t e d i f f e r e n t l y t o t h e energy economy o f t h e a n i m a l and t h e r e f o r e a comprehensive s t u d y o f t h e i r d e g r a d a b i l i t y i n t h e rumen w i t h r e s p e c t t o c a r b o h y d r a t e s i s i m p o r t a n t . A l l c e r e a l g r a i n s were i m m e d i a t e l y ground t h r o u g h a 2 mm s c r e e n t o f a c i l i t a t e s a m p l i n g and t h e n r e d u c e d t o 1 mm s i z e u s i n g a W i l e y M i l l , model #3 and C h r i s t y and N o r r i s , r e s p e c t i v e l y . A l l 54 samples were t h e n d r i e d i n a f o r c e d a i r oven a t 60°C f o r 48 h. R e s i d u a l DM d e t e r m i n a t i o n was l a t e r done on 1.0 g o f d r i e d ground samples and t h i s was done a t 105°C o v e r n i g h t . The b u l k o f t h e samples were packed i n 5 kg bags and s t o r e d a t room t e m p e r a t u r e f o r p r o x i m a t e a n a l y s i s , NDF and s t a r c h a n a l y s i s and a l s o i n v i t r o and i n s i t u s t u d i e s . 2.2.2. Cows, diets and nylon bags. Two d a i r y cows (average w e i g h t = 518 kg) f i t t e d w i t h b oth rumen (10 cm i n t e r n a l d i a m e t e r ) and duodenal c a n n u l a e (Bar Diamond I n c . , Parma, Idaho, USA) were used f o r rumen i n c u b a t i o n s t u d i e s . Cows were t e t h e r e d i n t i e s t a l l s and had f r e e a c c e s s t o w a t e r . They were o f f e r e d a TMR t w e l v e t i m e s d a i l y u s i n g an e l e c t r i c a l c o n t i n u o u s f e e d e r c a l i b r a t e d t o drop f e e d e v e r y 2 h f o r 17 seconds. T h i s was done t o m a i n t a i n a c o n t i n u o u s and even f e r m e n t a t i o n i n t h e rumen t o mimic a c o n t i n u o u s t y p e o f f e e d i n g system t h a t i s c h a r a c t e r i s t i c o f some farms and t h i s has been shown t o i n c r e a s e e f f i c i e n c y o f m i c r o b i a l p r o t e i n s y n t h e s i s under i n v i t r o system (Henning e t a l . , 1991). The d i e t was d e s i g n e d i n such a way t h a t t h e m a j o r i t y o f t h e f e e d s t u f f s under t e s t were i n c o r p o r a t e d . T h i s e n s u r e s a b a l a n c e o f m i c r o - o r g a n i s m s i n t h e rumen which a r e r e s p o n s i b l e f o r d i g e s t i o n o f d i f f e r e n t k i n d s o f n u t r i e n t s . The c o n c e n t r a t e p o r t i o n o f t h e d i e t was a 16% t e x t u r e d commercial d a i r y f e e d (40%) ( O t t e r Feed Co-op, A l d e r g r o v e , B.C). C o r n - g r a s s s i l a g e , (50:50), l o n g chopped a l f a l f a and o r c h a r d g r a s s hay made up t h e roughage p o r t i o n (60%) o f t h e d i e t . Q u a n t i t y o f f e e d o f f e r e d per day was c a l c u l a t e d a t 1.65% body w e i g h t and good q u a l i t y hay a l o n e c o u l d have s a t i s f i e d t h e n u t r i e n t r e q u i r e m e n t s o f t h e cows. S i n c e f e e d s t u f f s under i n v e s t i g a t i o n were from d i f f e r e n t s o u r c e s t h e e s t i m a t e d i n t a k e was d i v i d e d between roughage and c o n c e n t r a t e i n t h e r a t i o n o t e d above. The cows were g i v e n 8.53 kg/d (16% t e x t u r e d commercial d a i r y f e e d = 3.41 kg, CGrS =2.56 kg, ALFH and OGrH =1.28 kg) DM o f a TMR. The r a t i o o f c o r n -g r a s s s i l a g e t o hay and t h a t o f a l f a l f a t o o r c h a r d g r a s s hay was 1:1. T a b l e 1 shows t h e p r o p o r t i o n s o f i n g r e d i e n t s used i n t h e d i e t s f e d t o t h e cows. The f e e d i n g r e d i e n t s were pre-weighed and mixed t w i c e w e e k l y and s p r e a d on t h e f e e d t r o u g h s a t 13 3 0 and 013 0 h. F e e d i n g t r o u g h s measured about 2.0 x 0.15 x 0.2m ( l e n g t h x w i d t h x h e i g h t ) and were r a i s e d about 2m above ground. Conveyor b e l t s wrapped around l e n g t h - w i s e and l y i n g on t h e f l o o r o f t h e f e e d i n g t r o u g h s were used t o drop t h e f e e d a t t i m e d i n t e r v a l s . On each end o f t h e t r o u g h s t h e b e l t s passed over moving s h a f t s w i t h one s i d e f i t t e d w i t h a motor. The motor was c o n n e c t e d t o an e l e c t r o n i c t i m e r i n o r d e r t o r e g u l a t e d r o p p i n g o f t h e f e e d . A t each m i x i n g , a l l i n g r e d i e n t s were sampled s e p a r a t e l y and s t o r e d i n p l a s t i c bags i n a f r e e z e r f o r f u r t h e r p r o c e s s i n g and c h e m i c a l a n a l y s i s . A c o m m e r c i a l d a i r y v i t a m i n - m i n e r a l mix was g i v e n a t 0.2% o f t h e DM i n t a k e . The v i t a m i n - m i n e r a l mix ( D a i r y P r i d e P-20, Van Waters and Rogers L t d , A b b o t s f o r d , B.C., Canada) c o n t a i n e d v i t a m i n A, v i t a m i n D, v i t a m i n E, mono ammonium phosphate, sodium s e l e n i t e , c o b a l t s u l p h a t e , copper o x i d e , z i n c o x i d e , c a l c i u m i o d a t e , manganese o x i d e , magnesium o x i d e , m o l a s s e s , a n i s e f l a v o u r #98037 and a 56 g u a r a n t e e d a n a l y s i s o f phosphorus 20.0%, i o d i n e 200 mg/kg, c o b a l t 150 mg/kg, copper 4000 mg/kg, z i n c 6000 mg/kg, manganese 2500 mg/kg, magnesium 6.0%, f l o u r i n e ( m a x ) 2000 mg/kg, v i t a m i n A(min) 500000 IU/kg, v i t a m i n D(min) 50000 IU/kg, v i t a m i n E(min) 500 IU/kg, i r o n 8000 mg/kg and s e l e n i u m 35mg/kg. C o b a l t i o d i z e d s a l t b l o c k ( S i f t o Canada I n c . M i s s i s s a u g a , O n t a r i o ) was a l s o a v a i l a b l e t o cows a t a l l t i m e s . A t t h e end o f t h e e x p e r i m e n t a l l f e e d samples were thawed o v e r n i g h t . Feed (16% t e x t u r e d commercial d a i r y f e e d , OGrH, ALFH and CGrS) i n g r e d i e n t s were ground t h r o u g h a 2 mm s c r e e n t o reduce p a r t i c l e s i z e so as t o f a c i l i t a t e m i x i n g and s a m p l i n g u s i n g a W i l e y M i l l (model #3). A l l samples were t h e n ground t h r o u g h a 1 mm s c r e e n u s i n g C h r i s t y and N o r r i s . C o r n - g r a s s s i l a g e was f i r s t d r i e d a t 60°C f o r 48 h b e f o r e b e i n g ground. A l l d r y i n g a t 60°C were done t o p r e v e n t any p o s s i b l e l o s s o f v o l a t i l e n i t r o g e n and p o s s i b l e c o m p l e x i n g between c a r b o h y d r a t e and p r o t e i n f r a c t i o n s , w h i c h may o c c u r a t h i g h e r t e m p e r a t u r e . The samples were t h o r o u g h l y mixed s e p a r a t e l y u s i n g a Hobart commercial dough m i x e r and t h e n a subsample t a k e n on which DM a n a l y s i s was done. The samples were s t o r e d i n a c o o l e r f o r c h e m i c a l a n a l y s i s ( T a b l e 2 ) . N y l o n bags were made from n y t e x p o l y e s t e r m a t e r i a l o b t a i n e d from Behnsen G r a p h i c s (Vancouver, B.C). The bags measured 22x9 cm i n t e r n a l d i a m e t e r and had an average pore s i z e o f 50+2 jum. Glue was f i r s t a p p l i e d as a s t r i p about 0.2 cm from t h e edges o f t h e f a b r i c l e a v i n g one s i d e open of each p o t e n t i a l bag and t h e n a d o u b l e seem was made by s t i c h i n g l e a v i n g t h e s t r i p o f g l u e i n between. The open 57 s i d e was hemmed and a s m a l l n y l o n s t r i n g p u t i n s i d e t h e hem. The bags were p u t under some w e i g h t s t o h a s t e n s t i c k i n g t o g e t h e r o f t h e bag's s i d e s . The bottom c o r n e r s o f t h e bags were round so t h a t f e e d m a t e r i a l d i d n o t accumulate and compact i n t h e c o r n e r s . 2.2.3. Experimental design. A t h r e e p e r i o d s w i t c h - b a c k d e s i g n was used i n v o l v i n g two a n i m a l s and t h r e e groups o f f e e d s t u f f s (Cochran and Cox, 1969). Each group o f t h e t e s t f e e d was s e q u e n t i a l l y i n c u b a t e d once i n each cow i n two d i f f e r e n t p e r i o d s o f t h e t h r e e p e r i o d s . The a n i m a l s were f e d t h e e x p e r i m e n t a l d i e t f o r a t l e a s t one month b e f o r e t h e e x p e r i m e n t a l p e r i o d s s t a r t e d , t o g e t t h e a n i m a l s used t o t h e d i e t and s t a b i l i s e t h e rumen environment. 2.2.4.0. Incubation procedures. 2.2.4.1. Rumen incubation. F i v e grams o f d r i e d ground t e s t f e e d s samples ( c e r e a l s - UPC, UPW, UPB, SRC, SRW and SRB; roughages-CGrs, OGrH and ALFH; a g r o -byproducts-WMR, RDG and BP) , were q u a n t i t a t i v e l y weighed i n t o i n c u b a t i o n bags ( d e n s i t y ; 2 5 . 3 mg/cm2) i n d u p l i c a t e f o r each f e e d p e r i n c u b a t i o n t i m e t o g i v e 2 bags/feed/cow/time. A l l bags were n u m e r i c a l l y l a b e l l e d f o r i d e n t i f i c a t i o n and t h e n washed, d r i e d f o r a few h o u r s and p u t i n a d e s s i c a t o r b e f o r e t a k i n g t h e i r w e i g h t s . The bags were t i g h t l y s e c u r e d u s i n g t h e n y l o n s t r i n g i n s i d e t h e hem t o s t o p m a t e r i a l from coming out o f t h e bags. The bags were t h e n t i e d t o a few common m e t a l r i n g s o f about 2.5 cm i n d i a m e t e r . The 58 r i n g s were t h e m s e l v e s t h e n s e c u r e d t o hooks. A l l t h e hooks were t i e d t o a s i n g l e m a i n l i n e n y l o n s t r i n g m e a suring about 1.0 m. A p l a s t i c b o t t l e c o n t a i n i n g about 3 00 g o f sand was t i e d t o each n y l o n s t r i n g t o a c t as a rumen s u s p e n s i o n d e v i c e (RSD). T h i s p r o c e d u r e was done f o r each i n c u b a t i o n t i m e and a n i m a l , f o r t h e t e s t m a t e r i a l under c o n s i d e r a t i o n . E i g h t i n c u b a t i o n t i m e s , 0, 2, 3, 6, 12, 24, 36, and 48 h were i n v o l v e d . The bags were i n s e r t e d i n t o t h e rumen i n r e v e r s e o r d e r i . e . 48 h bags were p l a c e d f i r s t , f o l l o w e d by 36 h and down t o 2 h i n c u b a t i o n . A l l t h e bags were t h e n removed from t h e rumen a t once i n o r d e r t o a l l o w f o r washing o f t h e bags a t t h e same t i m e and a l s o any d i f f e r e n c e s t h a t might be i n t r o d u c e d due t o d i f f e r e n c e s i n exposure t o t h e atmosphere a f t e r d r y i n g t h e bags. A l l b a t c h e s o f bags were w e t t e d by s p r i n k l i n g lukewarm t a p wa t e r b e f o r e b e i n g i n s e r t e d i n t o t h e rumen t o p r e v e n t i n f l a t i o n o f bags when p u t i n t h e rumen. I n c u b a t i o n s s t a r t e d an hour a f t e r t h e f e e d had been g i v e n . Each b a t c h o f bags was pushed i n t o t h e l i q u i d s t r a t a o f t h e m i d - v e n t r a l r e g i o n o f t h e rumen. A f t e r removal from t h e rumen, a l l bags were p l a c e d i n t o a bu c k e t o f v e r y c o l d t a p water t o remove e x c e s s d i g e s t a m a t e r i a l a d h e r i n g t o t h e bags but a l s o t o s t o p f e r m e n t a t i o n . Four bags p e r t e s t f e e d were i n c l u d e d i n t h e washing t o a c t as t h e 0 h d i s a p p e a r a n c e . The z e r o h bags were washed by immersing t h e bags i n t a p w a t e r f o r 15 minutes and t h e n washed t o g e t h e r w i t h rumen i n c u b a t e d bags. 59 E v e r y t h i n g was t r a n s p o r t e d t o t h e A n i m a l S c i e n c e department l a b o r a t o r y and t h o r o u g h l y washed under r u n n i n g t a p w a t e r , u n t i l t h e wate r r a n c l e a r . The bags were t h e n s p r e a d on p e r f o r a t e d aluminium f o i l and d r i e d i n a f o r c e d a i r oven a t 60°C f o r 48 h. The bags were p u t i n t h e d e s i c c a t o r b e f o r e b e i n g weighed. The d r i e d i n c u b a t e d samples were c o m p o s i t e d b e f o r e b e i n g ground t h r o u g h a 1.0 mm s c r e e n u s i n g a Brinkman m i c r o g r i n d e r , and t h e n packed i n t o s m a l l p o l y e t h y l e n e sample bags and s t o r e d a t room t e m p e r a t u r e f o r CP and s t a r c h a n a l y s i s . 2.2.4.2. A n a l y t i c a l procedures. P r o x i m a t e a n a l y s i s and d e t e r g e n t - f i b e r s (DF's) o f t h e t e s t m a t e r i a l s and i n g r e d i e n t s o f t h e TMR f e d t o cows were a n a l y s e d a c c o r d i n g t o AOAC (1984) and Waldern (1971) and Van S o e s t e t a l . (1991), r e s p e c t i v e l y . D r i e d i n c u b a t e d c o m p o s i t e t e s t samples were a n a l y s e d f o r DM, CP and s t a r c h . Crude p r o t e i n was a n a l y s e d a t P a c i f i c A g r i c u l t u r e R e s e a r c h C e n t r e ( A g a s s i z , B.C. Canada) u s i n g a Leco N i t r o g e n D e t e r m i n a t o r FP-428 (Leco C o r p o r a t i o n , S t . J o s e p h , M I ) . S t a r c h was a n a l y s e d a c c o r d i n g t o t h e method o f MacRae and Arm s t r o n g , (1968), w i t h m o d i f i c a t i o n s a c c o r d i n g t o X i o n g e t a l . (1990). S t a r c h a n a l y s i s was done by i n i t i a l l y g e l a t i n i z i n g samples i n a 4.5+0.05 a c e t a t e b u f f e r s o l u t i o n ( X i o n g , e t a l . , 1990) u s i n g an a u t o c l a v e (STERILIZER; B a r n s t e a d S t i l l and S t e r i l i z e r Co., Bo s t o n , M a s s a c h u s e t t s , Model # 0745 02131) f o r 90 min. s e t a t 124°C (MacRae and A r m s t r o n g , 1968) f o l l o w e d by i n c u b a t i n g w i t h 1 ml 60 a m y l o g l u c o s i d a s e (Rhizopus mold) enzyme (Sigma, No. A-7255) i n a C o n t r o l l e d Environment I n c u b a t o r Shaker (New B r u n s w i c k S c i e n t i f i c Co., I n c . , Edson, N.J., U.S.A) f o r 16-20 h t o r e l e a s e a - l i n k e d g l u c o s e p o l y m e r s . The i n c u b a t e d samples were t h e n d e p r o t e i n i z e d and f i l t e r e d . An a l i q u o t o f t h e f i l t r a t e was used f o r s t a r c h a n a l y s i s by c o l o r development t h r o u g h t h e copper r e d u c t i o n method. S t a r c h p e r c e n t (%) was c a l c u l a t e d a c c o r d i n g t o MacRae and A r m s t r o n g (19 68) as shown below; A. a - l i n k e d g l u c o s e polymers = GC x V/100 x 1/W ( E q u a t i o n 2.1); a. a - l i n k e d g l u c o s e polymers i n mg/g, b. GC = g l u c o s e c o n c e n t r a t i o n i n mg/100 ml from s t a n d a r d c u r v e , c. V = volume ( d i l u t i o n t o 25 ml) i n m l , d. W = sample d r y w e i g h t i n g, B. % s t a r c h =• ( a - l i n k e d g l u c o s e polymers (mg/g) )/l,110x100 ( E q u a t i o n 2.2); 2.2.4.3. Treatment of r e s u l t s and s t a t i s t i c a l a nalysis. A l l s t a r c h c o n t e n t a n a l y s i s o f t e s t m a t e r i a l s i n v o l v i n g t e n r e p l i c a t i o n s were done i n o r d e r t o v a l i d a t e our m o d i f i e d s t a r c h a n a l y s i s method. T h i s was done by c a l c u l a t i n g t h e mean, range o f v a l u e s , s t a n d a r d d e v i a t i o n (SD), and c o e f f i c i e n t o f v a r i a t i o n (CV) . D i s a p p e a r a n c e d a t a were f i t t e d t h r o u g h i t e r a t i v e p r o c e d u r e s a c c o r d i n g t o t h e f o l l o w i n g m o d i f i e d m a t h e m a t i c a l e q u a t i o n o f 0 r s k o v and Macdonald (1979) w i t h a l a g phase: p = a + b ( l - e ( c ( t l a g ) ) ) f o r t > l a g ( E q u a t i o n 2.3); where p i s t h e d i s a p p e a r a n c e (%) a f t e r t , a i s t h e f r a c t i o n which d i s a p p e a r s r a p i d l y (%), b i s t h e s l o w l y d e g r a d a b l e f r a c t i o n (%), c i s t h e f r a c t i o n a l r a t e o f d e g r a d a t i o n (k d, %/h) o f f r a c t i o n b, and t i s t i m e (h) o f i n c u b a t i o n . The a, b, c and l a g were e s t i m a t e d by an i t e r a t i v e l e a s t - s q u a r e p r o c e d u r e (Appendix 1) u s i n g g e n e r a l l i n e a r Model (GLM) o f t h e s t a t i s t c a l a n a l y s i s system (SAS) (1990) package. E f f e c t i v e d e g r a d a b i l i t y (EFDEG) was t h e n c a l c u l a t e d from t h e e s t i m a t e s o f a, b and c assuming a f r a c t i o n a l o u t f l o w r a t e o f s o l i d s from t h e rumen ( k f ) o f 5 %/h, because d e g r a d a b i l i t y o f any n u t r i e n t i s a f u n c t i o n o f b o t h d i g e s t i o n and f r a c t i o n a l r a t e o f passage o f s o l i d s . The f o l l o w i n g e q u a t i o n was used t o c a l c u l a t e e f f e c t i v e d e g r a d a b i l i t y (Appendix 1) : EFDEG = a + ( ( (be) e(-c*l-'ag)) / (c + k f ) e (- ( c + k f ) l a g ) ( E q u a t i o n 2.4); where a, b and c a r e as d e f i n e d above. 62 D e g r a d a t i o n c h a r a c t e r i s t i c s d a t a was s t a t i s t i c a l l y a n a l y s e d as a 3 x 2 f a c t o r i a l e x periment (Cochran and Cox, 1969) w i t h c e r e a l and p r o c e s s i n g as main e f f e c t s u s i n g GLM o f SAS package (1990) and LSD was used f o r mean s e p a r a t i o n when t h e i n t e r a c t i o n was s i g n i f i c a n t . 2.2.4.4. Enzyme i n v i t r o starch release procedure. The t e c h n i q u e was adapted from t h a t o f X i o n g e t a l . (1990) and M a t h i s o n e t a l . (1991). T r i p l i c a t e samples (0.2g) o f g r a i n were weighed i n t o 50 ml d i g e s t i o n t u b e s c o n t a i n i n g 15 ml o f a c e t a t e b u f f e r (.2 M, pH 4.50). A m y l o g l u c o s i d a s e (Rhizopus mold) enzyme (1 ml) was added t o each tube and i n c u b a t e d i n an E n v i r o n m e n t a l C o n t r o l l e d E l e c t r i c I n c u b a t o r i n c l u d i n g 3, 6, 12, 24, and 36 h. The r e a c t i o n was stopped by p u t t i n g t h e t u b e s i n a c o l d i c e b a t h . The samples were t h e n d e p r o t e i n i z e d by a d d i n g 2 mis o f 10% ZnS0 4.H 20 f o l l o w e d by 1.0 ml o f 0.5% NaOH and t h e n mixed. A l l t r e a t m e n t s were t h e n d i l u t e d t o 25 ml w i t h d e i o n i z e d w a t e r and f i l t e r e d t h r o u g h a pre-weighed f i l t e r paper (WHATMAN # 40) . The f i l t r a t e was a n a l y s e d f o r s t a r c h u s i n g t h e s t a r c h a n a l y s i s method as p r e v i o u s l y d e s c r i b e d . 2.3.0. RESULTS AND DISCUSSION. 2.3.1. General observations. The c h e m i c a l c o m p o s i t i o n o f c o r n , wheat and b a r l e y and t h e i r c o r r e s p o n d i n g s t e a m - r o l l e d c o u n t e r p a r t s i s g i v e n i n T a b l e 3 and t h a t f o r s t a r c h i s g i v e n i n T a b l e 4. There was v e r y l i t t l e v a r i a t i o n i n DM, OM and EE c o n t e n t among t h e c e r e a l t r e a t m e n t s . Wide v a r i a t i o n was o b s e r v e d i n CP, NDF, t o t a l n o n - s t r u c t u r a l c a r b o h y d r a t e s (TNC) , and ash c o n t e n t and t h i s seem t o be r e l a t e d t o t y p e o f c e r e a l ( T a b l e 3) . V a l u e s f o r CP, NDF, ash and EE a r e s i m i l a r t o t y p i c a l v a l u e s f o r c o r n , b a r l e y and wheat r e p o r t e d e l s e w h e r e ( H e r r e r a - S a l d a n a e t a l . , 1990b; NRC, 1989; M a l c o l m and K i e s l i n g , 1993). S t a r c h c o n t e n t a l s o v a r i e d a c c o r d i n g t o t y p e o f c e r e a l and p r o c e s s i n g ( T a b l e 4) . S t a r c h was h i g h e s t f o r c o r n , medium f o r wheat and l e a s t f o r b a r l e y c e r e a l s a v e r a g i n g 71.96%, 60.07% and 56.30% f o r c o r n , wheat and b a r l e y . Wide v a r i a t i o n i n range, SD and CV were a l s o o b s e r v e d among c e r e a l t y p e s . I t appears t h a t , t h e h i g h e r t h e f i b e r c o n t e n t , t h e h i g h e r was t h e SD and CV. H e r r e r a S a l d a n a e t a l . (1990b) and K a r t c h n e r and T h e u r e r , (1991) r e p o r t e d s i m i l a r o b s e r v a t i o n s . However, t h e SD and CV r e p o r t e d were somewhat lo w e r f o r b a r l e y and c o r n t r e a t m e n t s t h a n r e p o r t e d h e r e . K a r t c h n e r and T h e u r e r , (1981) r e p o r t e d i n c r e a s e d v a r i a t i o n among i n d i v i d u a l e s t i m a t e s o f s t a r c h as t h e c e l l u l o s e c o n t e n t o f t h e m a t e r i a l i n c r e a s e d . I t i s p o s s i b l e t h a t i t i s d i f f i c u l t t o a c h i e v e t h o r o u g h m i x i n g o f f e e d i n g r e d i e n t s h i g h i n f i b e r c o n t e n t r e s u l t i n g i n s e p a r a t i o n o f f e e d p a r t i c l e s making r e p r e s e n t a t i v e s a m p l i n g d i f f i c u l t ( H e r r e r a - S a l d a n a e t a l . , 1990b). S t a r c h v a l u e s r e p o r t e d i n t h i s s t u d y a r e s i m i l a r t o o t h e r s ( H e r r e r a - S a l d a n a e t a l . , 1990b; H u n t i n g t o n , 1994 and de Smet e t a l . , 1995) but d i f f e r e n t t o M a l c o l m and K i e s l i n g , (1993) who r e p o r t e d much h i g h e r v a l u e s and o u t o f t h e range r e p o r t e d by H u n t i n g t o n , (1994). S l i g h t i n c r e a s e s i n s t a r c h 64 c o n t e n t o b s e r v e d (Table 4) due t o steam r o l l i n g ; t h i s a g r e e s w i t h M a l c o l m and K i e s l i n g , (1993) f o r c o r n , wheat and sorghum b u t not b a r l e y and G a l y e a n e t a l . (1981) f o r c o r n , and sorghum. The i n c r e a s e i n s t a r c h was s m a l l e r f o r c o r n t h a n wheat and b a r l e y . V a r i a t i o n among r e p l i c a t e s i n DM, CP and s t a r c h i n s i t u d i s a p p e a r a n c e were l a r g e f o r a l l g r a i n s i n e a r l y i n c u b a t i o n t i m e s and became s m a l l e r by 24 h i n c u b a t i o n . The s m a l l e r v a r i a t i o n i n r e p l i c a t e s a f t e r 24 h i n c u b a t i o n would mean t h a t i n t h i s s t u d y , i n s i t u d e g r a d a t i o n o f DM, CP and s t a r c h was i n f l u e n c e d by a c t u a l f e e d c h a r a c t e r i s t i c s and l e a s t i n f l u e n c e d by o t h e r f a c t o r s such as a n i m a l and p e r i o d (Van der K o e l e n e t a l . , 1992). S i m i l a r o b s e r v a t i o n s have been r e p o r t e d by o t h e r s , a l t h o u g h v a r i a t i o n s t a r t e d b e i n g s m a l l e r by 48 h i n c u b a t i o n (Van d e r K o e l e n e t a l . , 1992 and de Smet e t a l . , 1995) . D i s a p p e a r a n c e o f DM and s t a r c h were most r a p i d f o r a l l f e e d s compared t o p r o t e i n d i s a p p e a r a n c e . By 12 h, 80% o f DM had d i s a p p e a r e d and was s t a r t i n g t o l e v e l o f f between 12 and 24 h. S t a r c h was most r a p i d f o r a l l f e e d s t u f f s such t h a t by 12 h, between 80% and 90% on average had d i s a p p e a r e d from c o r n , b a r l e y and wheat t r e a t m e n t s , r e a c h i n g asymptote by 24 h. Most o f t h e DM i n c e r e a l g r a i n s i s i n t h e form o f s t a r c h and t h i s can be as h i g h as 75% o f DM ( H u n t i n g t o n , 1994 and F r e n c h , 1973) . S i n c e DM d i s a p p e a r a n c e p a r a l l e d t h a t o f s t a r c h and p r o t e i n , t h i s i s an i n d i c a t i o n o f t h e s i g n i f i c a n t c o n t r i b u t i o n o f s t a r c h d i s a p p e a r a n c e t o DM d i s a p p e a r a n c e (Varga and Hoover, 1983). 65 2.3.2.0 Dry Matter degradation c h a r a c t e r i s t i c s . 2.3.2.1. Rapidly degradable f r a c t i o n of DM. Steam r o l l i n g s i g n i f i c a n t l y (P<0.0012) r e d u c e d t h e r a p i d l y d e g r a d a b l e f r a c t i o n o f DM f o r a l l g r a i n s (39.89+0.58% vs 44.61+0.58 %) . Type o f c e r e a l a l s o s i g n i f i c a n t l y (P<0.0001) a f f e c t e d t h e r a p i d l y d e g r a d a b l e f r a c t i o n o f DM. The r a p i d l y d e g r a d a b l e f r a c t i o n o f DM f o r c o r n (31.17+0.71%) was s i g n i f i c a n t l y l o w e r (P<.0001) t h a n f o r wheat (49.24+0.71%) and b a r l e y (46.33+0.71%) and b a r l e y was lo w e r (P<0.0271) t h a n wheat. S i m i l a r r a n k i n g f o r u n p r o c e s s e d g r a i n s was r e p o r t e d by H e r r e r a - S a l d a n a e t a l . (1990b) and de Smet e t a l . (1995) and was a l s o m a i n t a i n e d among steam r o l l e d g r a i n s i n t h i s s t u d y ( T a b l e 5 ) . The v a l u e f o r UPB ( T a b l e 5) i s s i m i l a r t o 47.0% r e p o r t e d by H e r r e r a - S a l d a n a e t a l . (1990b), w h i l e UPC and UPW were h i g h e r and l o w e r ( T a b l e 5) r e s p e c t i v e l y i n t h i s s t u d y t h a n r e p o r t e d by H e r r e r a - S a l d a n a e t a l . (1990b), (18.6% and 61.1%, r e s p e c t i v e l y ) . V a l u e s r e p o r t e d by de Smet e t a l . (1995) were much lo w e r t h a n r e p o r t e d i n t h i s s t u d y and H e r r e r a - S a l d a n a e t a l . (1990b). de Smet e t a l . (1995) used g r a i n s ground t h r o u g h a 2.0 mm s c r e e n as opposed t o 1.0 mm s c r e e n used i n t h i s s t u d y and H e r r e r a - S a l d a n a e t a l . (1990b) w h i l e bag pore s i z e was t h e same i n a l l t h e s t u d i e s . D i f f e r e n c e s i n t h e q u a n t i t y of r a p i d l y d e g r a d a b l e f r a c t i o n w i t h i n an e x p e r i m e n t and among e x p e r i m e n t s may be e x p l a i n e d by d i f f e r e n c e s i n t h e s o l u b i l i t y o f DM components o f t h e d i f f e r e n t c e r e a l g r a i n s and e x p e r i m e n t a l p r o c e d u r a l d i f f e r e n c e s , r e s p e c t i v e l y as noted above. Wheat and b a r l e y c o n t a i n more s o l u b l e n u t r i e n t s t h a n c o r n (Aman and Hesselman, 1984 and Salomonsson e t a l . , 1984). I n 66 c o n t r a s t t o t h e s e f i n d i n g s Malcolm and K i e s l i n g , (1993) d i d not f i n d d i f f e r e n c e s i n t h e r a p i d l y d e g r a d a b l e f r a c t i o n o f DM f o r ground and steam f l a k e d c o r n , b a r l e y and wheat e x c e p t f o r a s i g n i f i c a n t d e c r e a s e f o r sorghum. I n a d d i t i o n t h e r e was not much d i f f e r e n c e i n t h i s f r a c t i o n a c r o s s c e r e a l s w h i c h averaged o f 24% (Malcolm and K i e s l i n g , 1993). 2.3.2.2. Slowly degradable f r a c t i o n of DM. The q u a n t i t y o f t h e s l o w l y d e g r a d a b l e f r a c t i o n was s i g n i f i c a n t f o r t y p e o f c e r e a l (P<0.0001) and approached s i g n i f i c a n c e (P<0.0556) f o r steam r o l l i n g w h i l e i n t e r a c t i o n was n o t s i g n i f i c a n t (P<0.0904). Steam r o l l i n g t ended t o i n c r e a s e t h e s l o w l y d e g r a d a b l e f r a c t i o n o f DM and t h i s averaged 50.32+0.98% and 47.03+0.98% f o r t h e p r o c e s s e d and u n p r o c e s s e d group, r e s p e c t i v e l y . The r e d u c t i o n i n t h e r a p i d l y d e g r a d a b l e f r a c t i o n f o r p r o c e s s e d g r a i n s seems t o be r e f l e c t e d i n t h e i n c r e a s e d s l o w l y d e g r a d a b l e f r a c t i o n . T h i s s i g n i f i c a n t r e d u c t i o n i n t h e r a p i d l y d e g r a d a b l e f r a c t i o n o f t h e g r a i n s due t o steam r o l l i n g s u g g e s t s t h a t some s o l u b l e DM was s h i f t e d t o e i t h e r t h e s l o w l y o r t o t a l l y u n d e g r a d a b l e f r a c t i o n o r b o t h (Chalupa and S n i f f e n , 1994). Corn t r e a t m e n t s (62.03+1.20%) had s i g i n i f i c a n t l y h i g h e r (P<0.0001) l e v e l s o f t h e s l o w l y d e g r a d a b l e f r a c t i o n when compared t o wheat (42.11+1.20%) o r b a r l e y (41.88+1.20%) wh i c h were t h e m s e l v e s s i m i l a r (P>0.8977) . I t was e x p e c t e d t h a t c o r n w i t h a low r a p i d l y d e g r a d a b l e f r a c t i o n would have a h i g h e r s l o w l y d e g r a d a b l e f r a c t i o n t h a n wheat and b a r l e y . There i s l a c k o f d a t a i n l i t e r a t u r e 67 f o r DM, s t a r c h and CP s l o w l y d e g r a d a b l e f r a c t i o n . However, Dewhurst e t a l . ( 1 9 9 5 ) r e p o r t e d a v a l u e o f 5 1 . 1 % f o r wheat g r a i n (15.3% C P); compare w i t h 41.1% (no shown i n t a b l e 5) f o r u n p r o c e s s e d wheat g r a i n . 2.3.2.3. Rate o f d e g r a d a t i o n o f DM. The r a t e o f DM d i s a p p e a r a n c e (k d) f o r t h e s l o w l y d e g r a d a b l e f r a c t i o n was a l s o s i g n i f i c a n t l y a f f e c t e d by b o t h c e r e a l t y p e (P<0.0371) and steam r o l l i n g (P<0.0007) and t h e e f f e c t was not dependent on t y p e o f c e r e a l (P>0.1181) ( T a b l e 5 ) . F o r a l l t h r e e c e r e a l s , steam r o l l i n g s i g n i f i c a n t l y (P<0.0007) r e d u c e d t h e r a t e o f DM d e g r a d a b i l i t y and t h e s e averaged 15.54+0.81 %/h and 22.92+0.81 %/h; an unexpected r e s u l t . Among t h e c e r e a l s , as e x p e c t e d , c o r n t r e a t m e n t s (16.68+0.99 %/h) had lower r a t e o f DM d e g r a d a t i o n t h a n b a r l e y (P<0.0137) and tended t o be l o w e r when compared t o wheat (P<0.0918). No s i g n i f i c a n t d i f f e r e n c e s were o b s e r v e d i n r a t e o f DM d e g r a d a t i o n between wheat and b a r l e y (P>0.1993). The v a l u e s f o r b a r l e y and wheat t r e a t m e n t s were 21.52+0.99 and 19.49+0.99 %/h, r e s p e c t i v e l y . S i m i l a r r e s u l t s f o r u n p r o c e s s e d c o r n v e r s u s u n p r o c e s s e d wheat o r b a r l e y have been found ( H e r r e r a - S a l d a n a e t a l . , 1990b; G r i n g s e t a l . , 1992; Fiems e t a l . , 1993; de Smet e t a l . , 1995 and A r i e l i e t a l . , 1995). That t h e r a t e s o f DMD f o r b a r l e y and wheat i n t h i s s t u d y a r e s i m i l a r ( T a b l e 5) was unexpected and i n s h a r p c o n t r a s t t o o v e r whelming e v i d e n c e t h a t t h e r e v e r s e was t r u e from t h e above r e p o r t s . The r e a s o n f o r t h i s d i s c r e p a n c y i n our r e s u l t s i s not 68 q u i t e a p p a r e n t . However, i t must be mentioned h e r e t h a t , i n s p i t e o f wheat n u m e r i c a l l y h a v i n g a h i g h e r r a t e o f DMD t h a n b a r l e y , t h e r a t e s were s t a t i s t i c a l l y t h e same as r e p o r t e d by H e r r e r a - S a l d a n a e t a l . (1990b) w h i c h i s i n agreement w i t h our f i n d i n g s ( T a b l e 5 ) . I t may be s p e c u l a t e d t h a t t h e wheat and b a r l e y v a r i e t y may have had s i m i l a r p r o p e r t i e s . G r i n g s e t a l . (1992) r e p o r t e d v a l u e s f o r r a t e o f DMD r a n g i n g from 20 t o 36 %/h f o r a x b a r l e y v a r i e t y w i t h g r a i n d e n s i t i e s a v e r a g i n g from 0.66 kg/L (44 lb/bu) t o 0.79 kg/L (53 lb/bu) and Flachowsky e t a l . (1992) r e p o r t e d v a l u e s r a n g i n g from 5 t o 16 % / h r f o r 12 d i f f e r e n t v a r i e t i e s o f b a r l e y . Among t h e steam r o l l e d c e r e a l s c o r n and b a r l e y but not wheat, m a i n t a i n e d t h e same o r d e r as f o r u n p r o c e s s e d g r a i n s . I t c o u l d be p o s s i b l e t h a t steam r o l l i n g c o u l d have a f f e c t e d SRW more n e g a t i v e l y t h a n SRC. The r e s u l t s t h a t steam r o l l i n g r e d u c e d t h e r a t e o f DMD f o r each g r a i n i s i n agreement w i t h o t h e r p r e v i o u s r e p o r t s (Fiems e t a l . , 1990; M a l c o l m and K i e s l i n g , 1993 and A r i e l i e t a l . , 1995). Engstrom e t a l . (1992) r e p o r t e d h i g h e r (P<0.01) DMD f o r d r y r o l l e d t h a n steam r o l l e d b a r l e y a t 0, 8 and 24 h o f i n c u b a t i o n i n s a c c o . I n o t h e r work, Malcolm and K i e s l i n g , (1993) r e p o r t e d i n t e r c h a n g e s i n r a n k i n g o f DM d i s a p p e a r a n c e a t d i f f e r e n t i n c u b a t i o n t i m e s a f t e r steam f l a k i n g o f s i m i l a r g r a i n s i n c l u d i n g sorghum. 2.3.2.4. Lag t i m e o f DM d e g r a d a t i o n . R e s u l t s f o r l a g t i m e of DMD were q u i t e v a r i a b l e ( T a b l e 5) . The steam r o l l i n g e f f e c t was not s i g n i f i c a n t (P>0.96) w h i l e t y p e o f c e r e a l (P<0.0101) and i n t e r a c t i o n (P<0.0439) were s i g n i f i c a n t . The 69 i n t e r a c t i o n o c c u r r e d because steam r o l l i n g r e d u c e d t h e l a g t i m e f o r c o r n and b a r l e y though t h i s was not s i g n i f i c a n t (P>0.4258 and P>0.1131, r e s p e c t i v e l y ) but not f o r wheat w h i c h was i n c r e a s e d and was s i g n i f i c a n t (P<0.0398). The v a l u e s f o r u n p r o c e s s e d g r a i n s averaged 1.61+0.25%, 1.40+0.25% and 1.05+0.25% f o r UPC, UPW and UPB, r e s p e c t i v e l y and t h e v a l u e s f o r p r o c e s s e d g r a i n s averaged 1.31+0.25%, 2.30+0.25% and 0.41+0.25% f o r SRC, SRW and SRB, r e s p e c t i v e l y . 2.3.2.5. E f f e c t i v e d e g r a d a b i l i t y o f DM. R e s u l t s f o r e f f e c t i v e d e g r a d a b i l i t y o f DM i n d i c a t e t h a t b o t h c e r e a l t y p e (P>0.1681) and i n t e r a c t i o n (P>0.2550) were not s i g n i f i c a n t , w h i l e steam r o l l i n g was s i g n i f i c a n t (P<0.0222)(Table 5 ) . Steam r o l l i n g d e c r e a s e d t h e e f f e c t i v e d e g r a d a b i l i t y o f DM f o r a l l g r a i n s . The average v a l u e s f o r p r o c e s s e d and u n p r o c e s s e d g r a i n s were 75.45+1.12% and 80.29+1.12%, r e s p e c t i v e l y . A r i e l i e t a l . (1995) d i d not f i n d d i f f e r e n c e s i n e f f e c t i v e d e g r a d a b i l i t y o f DM f o r s i m i l a r g r a i n s ; u n t r e a t e d , e x t r u d e d o r expanded. The v a l u e s f o r t h e s e w o r k e r s averaged over 8 0% compared t o above 7 0% i n t h i s s t u d y . G r i n g s e t a l . (1992) obse r v e d s i m i l a r r a n k i n g f o r b a r l e y and c o r n a l t h o u g h e f f e c t i v e d e g r a d a b i l i t y f o r c o r n was around 55% wh i c h i s much lo w e r t h a n r e p o r t e d h e r e ( T a b l e 5 ) , b u t v a l u e s f o r b a r l e y were i n t h e same (77.8%, d e n s i t y o f 0.79 kg/L) range as r e p o r t e d i n t h i s s t u d y ( T a b l e 5 ) . 70 2.3.3.0. Starch degradation c h a r a c t e r i s t i c s . 2.3.3.1. Rapidly degradable f r a c t i o n of starch. A summary o f t h e r e s u l t s f o r s t a r c h d e g r a d a t i o n c h a r a c t e r i s t i c s i s shown i n T a b l e 6. C e r e a l t y p e and steam r o l l i n g s i g n i f i c a n t l y (P<0.0002 and P<0.0289) a f f e c t e d t h e q u a n t i t y o f t h e r a p i d l y d e g r a d a b l e f r a c t i o n o f s t a r c h and t h e r e s p o n s e t o steam r o l l i n g was n o t dependent on t h e t y p e o f c e r e a l (P<0.3741). Steam r o l l i n g r e d u c e d t h e l e v e l o f t h e r a p i d l y d e g r a d a b l e f r a c t i o n f o r a l l g r a i n s . P r o c e s s e d and unp r o c e s s e d g r a i n s averaged 44.84+2.16% and 53.58+2.16%, r e s p e c t i v e l y . Corn t r e a t m e n t s had s i g n i f i c a n t l y l o w e r l e v e l o f t h e r a p i d l y d e g r a d a b l e f r a c t i o n compared t o wheat (P<0.0002) and b a r l e y (P<0.0001), w h i l e wheat and b a r l e y were s i m i l a r (P>0.7417). The average v a l u e s f o r c o r n , wheat and b a r l e y were, 2 8.06+2.65, 59.14+2.65 and 60.43+2.65%, r e s p e c t i v e l y . A s i m i l a r r a n k i n g has been r e p o r t e d by o t h e r s ( H e r r e r a - S a l d a n a e t a l . , 1990b and Tamminga e t a l . , 1990) , when UPC was compared t o e i t h e r b a r l e y o r wheat, but t h e r a n k i n g f o r b a r l e y and wheat i n t h i s s t u d y i s d i f f e r e n t from t h e above quoted r e p o r t s . I t must be mentioned h e r e t h a t a l t h o u g h r e p o r t s show a h i g h e r v a l u e f o r wheat t h a n b a r l e y , H e r r e r a - S a l d a n a e t a l . (1990b) r e p o r t e d no s i g n i f i c a n t d i f f e r e n c e s i n t h e l e v e l o f t h e r a p i d l y d e g r a d a b l e f r a c t i o n o f s t a r c h . V a l u e s f o r steam r o l l e d g r a i n s i n d i c a t e d a s i g n i f i c a n t l y lower v a l u e f o r SRC t h a n e i t h e r b a r l e y o r wheat ( T a b l e 6 ) . The v a l u e f o r UPB r e p o r t e d i n t h i s s t u d y i s s i m i l a r t o t h a t r e p o r t e d by H e r r e r a - S a l d a n a e t a l . (1990b) and Tamminga e t a l . (1990), w h i l e a h i g h e r v a l u e f o r UPC and UPW a r e 71 r e p o r t e d h e r e ( T a b l e 6) t h a n e l s e w h e r e ( H e r r e r a - S a l d a n a e t a l . , 1990b and Tamminga e t a l . , 1990). However t h e v a l u e f o r UPC r e p o r t e d h e r e ( T a b l e 6) i s s i m i l a r t o t h a t r e p o r t e d by G r i n g s e t a l . (1992) f o r ground c o r n . V a r i a t i o n i n t h e q u a n t i t y o f t h e r a p i d l y s o l u b l e f r a c t i o n a c r o s s e x p e r i m e n t s may l i k e l y be r e l a t e d t o d i f f e r e n c e s i n washing p r o c e d u r e s o f z e r o h bags, and d i f f e r e n c e s among c e r e a l s can be e x p l a i n e d by i n h e r e n t p h y s i c a l and c h e m i c a l d i f f e r e n c e s ( F r e n c h , 1973; Rooney and P f l u g f e l d e r , 1986, and H u n t i n g t o n , 1994) o f t h e c e r e a l s t h e m s e l v e s , r e s u l t i n g i n d i f f e r e n c e s i n water s o l u b i l i t y o f t h e g r a i n (Aman and Hesselman, 1984 and Salomonsson e t a l . , 1984). 2.3.3.2. Slowly degradable f r a c t i o n of starch. The q u a n t i t y o f t h e s l o w l y d e g r a d a b l e f r a c t i o n o f s t a r c h was s i g n i f i c a n t l y a f f e c t e d by b o t h t y p e o f c e r e a l (P<0.0001) and p r o c e s s i n g (P<0.0204) and t h e re s p o n s e o f steam r o l l i n g was not dependent on t y p e o f c e r e a l (P<0.3 684). Steam r o l l i n g i n c r e a s e d t h e s l o w l y d e g r a d a b l e f r a c t i o n f o r a l l g r a i n s , m i m i c k i n g t h e r e s u l t f o r t h e r a p i d l y d e g r a d a b l e f r a c t i o n ( T a b l e 6 ) . P r o c e s s e d g r a i n s a v e r a g e d 53.38+1.85% compared t o 45.18+1.85% f o r u n p r o c e s s e d g r a i n s . Wheat and b a r l e y t r e a t m e n t s had s i m i l a r (P>0.5684) q u a n t i t y o f t h e s l o w l y d e g r a d a b l e f r a c t i o n and were b o t h l o w e r (P<0.0001) t h a n c o r n t r e a t m e n t . The v a l u e s f o r wheat and b a r l e y were 39.62+2.17% and 37.68+2.17%, r e s p e c t i v e l y compared t o 70.53+2.17% f o r c o r n . Corn s t a r c h i s more r e s i s t a n t t o d i s i n t e g r a t i o n i n t h e rumen t h a n 72 b a r l e y and wheat, r e s u l t i n g i n h i g h e r q u a n t i t y o f t h i s f r a c t i o n f o r c o r n t h a n wheat and b a r l e y . V a r i a t i o n i n t h e q u a n t i t y o f t h e s l o w l y d e g r a d a b l e f r a c t i o n o f s t a r c h may i n p a r t e x p l a i n t h e v a r i a t i o n o b s e r v e d i n t h e s l o w l y d e g r a d a b l e f r a c t i o n o f DM. 2.3.3.3. Rate o f d e g r a d a t i o n o f s t a r c h . The r a t e o f s t a r c h d e g r a d a t i o n f o r t h e s l o w l y d e g r a d a b l e f r a c t i o n f o r a l l g r a i n s i s summarized i n T a b l e 6. R e s u l t s i n d i c a t e t h a t t y p e o f c e r e a l (P<0.002) and p r o c e s s i n g (P<0.0091) e f f e c t s were s i g n i f i c a n t and t h e e f f e c t o f steam r o l l i n g d i d not depend on t y p e o f g r a i n (P>0.1380). Steam r o l l i n g s i g n i f i c a n t l y r educed (P<0.0091) t h e r a t e o f s t a r c h d e g r a d a t i o n f o r a l l g r a i n s and t h e p r o c e s s e d and u n p r o c e s s e d g r a i n s averaged 19.2 6+1.08 and 25.03+1.08 %/h. Rate o f s t a r c h d e g r a d t i o n was s i g n i f i c a n t l y l o w e r f o r c o r n t r e a t m e n t s t h a n f o r b o t h wheat (P<0.0083) and b a r l e y (P<0.0007) as e x p e c t e d and wheat was lower (P<0.0436) t h a n b a r l e y . These r e s u l t s , i n terms o f r a n k i n g o f t h e g r a i n s , a r e i n agreement w i t h p r e v i o u s r e p o r t s f o r r a t e o f d e g r a d a t i o n o f t h e s l o w l y d e g r a d a b l e f r a c t i o n o f s t a r c h ( G r i n g s e t a l . , 1992; H e r r e r a - S a l d a n a e t a l . , 1990b and A r i e l i e t a l . , 1995) o r t h e p o t e n t i a l l y d e g r a d a b l e f r a c t i o n (Tamminga e t a l . , 1990). The r a n k i n g o f t h e g r a i n s d i d n o t change among t h e u n p r o c e s s e d g r a i n s (Table 6) . The h i g h e r r a t e o f d e g r a d a t i o n o f b a r l e y and wheat t r e a t m e n t s compared t o c o r n t r e a t m e n t s can be e x p l a i n e d by i n h e r e n t d i f f e r e n c e s i n t h e p h y s i c a l and c h e m i c a l make up o f t h e s t a r c h i n c e r e a l g r a i n s ( F r e n c h , 1973; Rooney and P f l u g f e l d e r , 1986, and H u n t i n g t o n , 1994) r e s u l t i n g i n d i f f e r e n c e s i n wa t e r s o l u b i l i t y o f t h e g r a i n s (Aman and Hesselman, 1984 and Salomonsson e t a l . , 1984). The r e s u l t t h a t steam r o l l i n g d e c r e a s e d t h e r a t e o f s t a r c h d e g r a d a t i o n i n s i t u c o n f l i c t s e a r l i e r r e p o r t s ( G a l y e a n e t a l . , 1981; T h u e r e r , 1986 and Thomas e t a l . , 1988) and a l s o d a t a from i n v i t r o s t u d i e s w i t h pure enzymes and rumen f l u i d (Cone and V l o t , 1990) and a l s o i n c r e a s e d i n v i t r o s t a r c h r e l e a s e (Fiems e t a l . , 1990; M a t h i s o n e t a l . , 1991 and Malcolm and K i e s l i n g , 1993) and i n v i v o s t u d i e s (Thuerer, 1986 and H u n t i n g t o n , 1994) . I n c o n t r a s t d a t a t h a t show p r o c e s s i n g such as steam f l a k i n g (Fiems e t a l . , 1990) and steam r o l l i n g (Engstrom e t a l . , 1993) and o t h e r steam a p p l y i n g p r o c e s s e s ( A r i e l i e t a l . , 1995) r e s u l t e d i n r e d u c e d r a t e o f s t a r c h d e g r a d a b i l i t y has p r e v i o u s l y been r e p o r t e d . Engstrom e t a l . (1992) r e p o r t e d s i g n i f i c a n t l y l o wer v a l u e s f o r steam r o l l e d b a r l e y a t 0, 8 and 24 h o f i n c u b a t i o n i n s a c c o i n c o n f l i c t t o t h e i r f i n d i n g s f o r g l u c o s e r e l e a s e by a m y l o g l u c o s i d a s e enzyme. They s p e c u l a t e d t h a t d i f f e r e n c e s i n p a r t i c l e s i z e d i s t r i b u t i o n w i t h i n each g r a i n , w i t h d r y r o l l e d b a r l e y h a v i n g a h i g h e r number o f s m a l l p a r t i c l e s t h a n steam r o l l e d b a r l e y r e s u l t i n g i n more p a r t i c l e s d i s a p p e a r i n g a t 0 h i n c u b a t i o n from d r y r o l l e d b a r l e y t h a n steam r o l l e d b a r l e y . M a l c o l m and K i e s l i n g , (1993) r e p o r t e d v a r i a b l e r e s u l t s due t o g r i n d i n g and steam f l a k i n g (100°C, 25 m i n u t e s , a t a t m o s p h e r i c p r e s s u r e ) f o r t h e s e same c e r e a l s i n c l u d i n g sorghum f o r DMD a t d i f f e r e n t i n c u b a t i o n t i m e s . S i n c e t h e g r e a t e s t e f f e c t on DMD i s from s t a r c h d i s a p p e a r a n c e , by i m p l i c a t i o n i t c o u l d be c o n c l u d e d 74 t h a t s t a r c h d i s a p p e a r a n c e f o l l o w e d a s i m i l a r t r e n d . However, t h e i r r e s u l t s i n d i c a t e d t h a t t e m p e r a t u r e a t whi c h b i r e f r i g e n c e i s l o s t were l o w e r f o r steam f l a k e d g r a i n s t h a n ground g r a i n s a l t h o u g h t h e d i f f e r e n c e was s m a l l f o r c o r n . I n a n o t h e r r e p o r t f o r t h e same c e r e a l g r a i n s (Fiems e t a l . , 1990), steam f l a k i n g (95-100°C, 30 m i n u t e s , a t a t m o s p h e r i c p r e s s u r e ) was r e p o r t e d t o have c o n s i s t e n t l y r e d u c e d DM and CP d i s a p p e a r a n c e a t a l l i n c u b a t i o n t i m e s . Fiems e t a l . (1990) i n f e r r e d from t h e i r r e s u l t s t h a t s t a r c h d i s a p p e a r a n c e may have been a f f e c t e d i n a s i m i l a r way b e i n g i n c o n f l i c t w i t h t h e i r g e l a t i n i z a t i o n d a t a which i n d i c a t e d steam f l a k i n g i n c r e a s e d s t a r c h r e l e a s e d by a m y l o g l u c o s i d a s e enzyme. More r e c e n t l y , A r i e l i e t a l . (1995) r e p o r t e d a s i g n i f i c a n t r e d u c t i o n i n t h e r a t e o f s t a r c h d e g r a d a t i o n due t o e x p a n s i o n ( a t 125°C) o r e x t r u s i o n ( a t 115°C) o f c o r n , b a r l e y and wheat, a l t h o u g h t h e r e d u c t i o n was not s i g n i f i c a n t f o r c o r n and t h e r e was no o b s e r v a b l e change f o r sorghum. The f i n d i n g s o f t h e above quoted e x p e r i m e n t s a r e i n agreement w i t h t h e f i n d i n g s of t h i s e x p e r i m e n t i n s p i t e o f t h e f a c t t h a t t h e steam r o l l i n g t e m p e r a t u r e i n t h i s e x p e r i m e n t was lower (70°C) t h a n i n a l l o f t h e o t h e r e x p e r i m e n t s , a l l o t h e r c o n d i t i o n s b e i n g s i m i l a r . A number o f f a c t o r s may e x p l a i n t h e r e d u c t i o n i n s t a r c h d i s a p p e a r a n c e due t o steam a p p l i c a t i o n . Fiems e t a l . (1990) s p e c u l a t e d t h a t r e t r o g r a d a t i o n o f g e l a t i n i z e d s t a r c h and f o r m a t i o n o f s t a r c h - p r o t e i n complexes may be r e s p o n s i b l e f o r t h e re d u c e d s t a r c h d e g r a d a b i l i t y . There i s a l s o a p o s s i b i l i t y t h a t steam r o l l i n g may m o d i f y t h e e f f e c t o f g r i n d i n g r e s u l t i n g i n a steam 75 r o l l e d g r a i n w i t h a lower f r a c t i o n o f v e r y s m a l l p a r t i c l e s t h a n d r y r o l l e d o r ground u n p r o c e s s e d samples, r e s u l t i n g i n h i g h e r r a p i d l y d e g r a d a b l e f r a c t i o n (Engstrom e t a l . , 1992). I n a n o t h e r s t u d y , steam r o l l i n g a t low p r e s s u r e ( a t m o s p h e r i c o r 1.4 kg/cm 2) was r e p o r t e d t o have d e c r e a s e d s t a r c h d e g r a d a b i l i t y (Osman, e t a l . , 1970). T h i s i s p o s s i b l e t o have happened i n t h i s e x p e r i m e n t s i n c e steam r o l l i n g was done a t a t m o s p h e r i c p r e s s u r e . The d i f f e r e n c e s between s t u d i e s t h a t show s i g n i f i c a n t i n c r e a s e i n DM and s t a r c h d e g r a d a b i l i t y (Galyean e t a l , 1981 and Thomas e t a l , 1988) o f c e r e a l g r a i n s a f t e r steam r o l l i n g and t h o s e i n c o n f l i c t (Fiems e t a l , 1990, malcolm and K i e s l i n g , 1993, Engstrom e t a l , 1992 and A r i e l i e t a l , 1995) i n c l u d i n g t h i s r e p o r t , may e x p l a i n e d by t h e way t h e two groups t r e a t e d t h e i r t e s t f e e d s t u f f s . The former used steam r o l l e d c o r n and c r a c k e d c o r n t h a t had been r e t a i n e d on a 4 o r 2 mm s i e v e t h e r e b y r e d u c i n g number o f f i n e p a r t i c l e s , and t h e l a t e r used g r a i n s t h a t had been ground a f t e r steam r o l l i n g o r l e f t u n p r o c e s s e d . U s i n g m a t e r i a l t h a t had been r a t a i n e d on a s i e v e would t e n d t o reduce t h e e f f e c t o f g r i n d i n g on t h e z e r o hour i n c u b a t i o n due t o d i f f e r e n c e s i n number o f v e r y s m a l l p a r t i c l e s f o r t h e d i f f e r e n t g r a i n s i n s p i t e o f t h e g r a i n s h a v i n g been ground u s i n g t h e same s c r e e n s i z e . That g r i n d i n g o f g r a i n s t h r o u g h t h e same s c r e e n s i z e r e s u l t s i n d i f f e r e n t p a r t i c l e s i z e d i s t r i b u t i o n (Fiems e t a l , 1990) would t e n d t o mask t h e e f f e c t o f steam r o l l i n g . Dewhurst e t a l . (1995) have r e c e n t l y q u e s t i o n e d t h e e f f e c t i v e n e s s o f t h e n y l o n bag p r o c e d u r e i n e v a l u a t i n g c o n c e n t r a t e s 7 6 w h i c h have a p p r e c i a b l e l e v e l s o f water s o l u b l e f r a c t i o n . C e r t a i n l y more r e s e a r c h i s r e q u i r e d t o e x p l o r e t h i s d i s c r e p a n c y between i n s a c c o and i n v i t r o and i n v i v o d a t a . 2.3.3.4. Lag t i m e o f s t a r c h d e g r a d a t i o n . Lag t i m e f o r s t a r c h d i s a p p e a r a n c e v a r i e d among t h e g r a i n s and was s i g n i f i c a n t l y a f f e c t e d by c e r e a l t y p e (P<0.0061) and p r o c e s s i n g (P<0.0068); however t h e r e s p o n s e t o steam r o l l i n g was dependent on t y p e o f c e r e a l (P< 0 . 0 0 1 ) ( T a b l e 6 ) . The i n t e r a c t i o n o c c u r r e d because steam r o l l i n g s i g n i f i c a n t l y r e d u c e d t h e l a g t i m e f o r c o r n (P<0.0004) and b a r l e y (P<0.016) but not f o r wheat, wh i c h was s i g n i f i c a n t l y (P<0.0175) i n c r e a s e d . Among t h e u n p r o c e s s e d g r a i n s , UPC had t h e l o n g e s t t i m e (Table 6) and was s i g n i f i c a n t l y d i f f e r e n t t o UPW (P<0.0003) and UPB (P<0.0017), w h i c h were s i m i l a r (P>0.0768). The v a l u e s were 3.99, 0.91, and 1.79 h f o r UPC, UPW and UPB, r e s p e c t i v e l y . The l o n g e r t i m e on UPC i s e x p e c t e d when compared t o wheat and b a r l e y because c o r n s t a r c h i s more r e s i s t a n t t o d e g r a d a t i o n t h a n t h e o t h e r 2, because o f d i f f e r e n c e s i n p h y s i c a l and c h e m i c a l make up ( F r e n c h , 1973; Rooney and P f l u g f e l d e r , 1986, and H u n t i n g t o n , 1994). Among t h e p r o c e s s e d m a t e r i a l s , SRW had t h e l o n g e s t l a g t i m e when compared t o SRC (P<0.0378) and SRB (P<0.0044), and SRC l a g t i m e was l o n g e r t h a n SRB b u t t h i s was not s i g n i f i c a n t (P<0.1253). The v a l u e s averaged 1.16, 2.24 and 0.43 h f o r c o r n , wheat and b a r l e y , r e s p e c t i v e l y . D i f f e r e n c e s i n l a g t i m e among c e r e a l s f o r s t a r c h may i n p a r t e x p l a i n t h e d i f f e r e n c e s i n l a g t i m e f o r DMD. 77 2.3.3.5. E f f e c t i v e d e g r a d a b i l i t y o f s t a r c h . R e s u l t s f o r t h e e f f e c t i v e d e g r a d a b i l i t y o f s t a r c h a r e shown i n T a b l e 6. C e r e a l t y p e was s i g n i f i c a n t (P<0.0001) w h i l e , steam r o l l i n g approached s i g n i f i c a n c e (P<0.0994) and t h e i n t e r a c t i o n was n o t s i g n i f i c a n t (P>0.1903). Steam r o l l i n g t e n d e d t o r e d u c e d t h e e f f e c t i v e d e g r a d a b i l i t y o f steam r o l l e d g r a i n s when compared t o t h e u n p r o c e s s e d g r a i n s . Steam r o l l e d g r a i n s a veraged 83.92+0.75% compared t o 85.98+0.75%. R e s u l t s f o r wheat and b a r l e y agree w i t h A r i e l i e t a l . (1995) who a l s o r e p o r t e d r e d u c e d e f f e c t i v e d e g r a d a b i l i t y o f s t a r c h when t h e s e same c e r e a l s were s u b j e c t e d t o e x p a n s i o n and e x t r u s i o n a l t h o u g h t h e s e t r e a t m e n t s a r e d i f f e r e n t from steam r o l l i n g . A l t h o u g h UPC had a f a s t e r r a t e o f s t a r c h d e g r a d a t i o n t h a n SRC t h i s d i d not r e s u l t i n a h i g h e r e f f e c t i v e d e g r a d a b i l i t y t h a n SRC and t h i s c o u l d be a t t r i b u t e d t o t h e l o n g e r l a g t i m e o b s e r v e d on UPC. I n terms o f e f f e c t o f c e r e a l t y p e , c o r n t r e a t m e n t had s i g n i f i c a n t l y l o wer (P<0.0001) e f f e c t i v e d e g r a d a b i l i t y t h a n wheat and b a r l e y , w h i l e wheat and b a r l e y were s i m i l a r (P>0.3429) as e x p e c t e d . Corn, wheat and b a r l e y t r e a t m e n t s averaged 75.21+0.92, 89.15+0.92 and 90.49+0.92% r e s p e c t i v e l y . I n s p i t e o f c o r n h a v i n g t h e h i g h e s t a v a i l a b l e m a t e r i a l f o r t h e s l o w d e g r a d a b l e f r a c t i o n , t h e low r a t e o f d e g r a d a t i o n i n t h e rumen r e s u l t e d i n lower e f f e c t i v e d e g r a d a b i l i t y and t h i s e x p l a n a t i o n i s t r u e f o r b o t h steam r o l l e d and u n p r o c e s s e d g r a i n s . T h i s would mean more energy would be a v a i l a b l e f o r m i c r o b i a l p r o t e i n s y n t h e s i s from b a r l e y o r wheat t h a n 78 c o r n . D i f f e r e n c e s i n e f f e c t i v e d e g r a d a b i l i t y o f s t a r c h would p a r t l y e x p l a i n d i f f e r e n c e s o b s e r v e d f o r DM e f f e c t i v e d e g r a d a b i l i t y . 2.3.4.0 Protein degradation c h a r a c t e r i s t i c s . 2.3.4.1. Rapidly degradable f r a c t i o n of CP. The summary o f r e s u l t s o f t h e p r o t e i n d e g r a d a t i o n c h a r a c t e r i s t i c s f o r c e r e a l g r a i n s i s shown i n T a b l e 7. Type o f c e r e a l , steam r o l l i n g and t h e i n t e r a c t i o n were s i g n i f i c a n t (P<0.0007, P<0.0001 and P<0.0115, r e s p e c t i v e l y ) f o r t h e r a p i d l y d e g r a d a b l e f r a c t i o n . Steam r o l l i n g s i g n i f i c a n t l y r educed t h e r a p i d l y d e g r a d a b l e f r a c t i o n f o r a l l g r a i n s but t h e e x t e n t d i f f e r e d among t h e g r a i n s . The d e c r e a s e was h i g h e r i n b a r l e y g r a i n , l ower f o r c o r n and l e a s t f o r wheat g r a i n . T h i s a g r e e s w i t h o b s e r v a t i o n s f o r t h e same g r a i n s a f t e r e x t r u s i o n o r e x p a n s i o n o r steam f l a k i n g ( H e r r e r a - S a l d a n a e t a l . , 1990b and A r i e l i e t a l . , 1995). Among u n p r o c e s s e d g r a i n s , t h e r a p i d l y d e g r a d a b l e f r a c t i o n f o r UPC tended t o be l o w e r t h a n UPW (P<0.0536) and UPB (P<0.0002) and UPW was l o w e r when compared t o UPB (P<0.0013). T h i s r e s u l t was t h e same when SRC was compared t o SRW (P<0.0176) o r SRB (P<0.0253) which were s i m i l a r (P>0.7853). R a n k i n g o f c o r n t r e a t m e n t i n r e l a t i o n t o b a r l e y and wheat agree s w i t h p r e v i o u s r e p o r t s (Fiems e t a l . , 1990; Tamminga e t a l . , 1990; H e r r e r a - S a l d a n a e t a l . , 1990b and G r i n g s e t a l . , 1992). V a l u e s f o r u n p r o c e s s e d and steam r o l l e d g r a i n s were; 20.55%, 29.46% and 50.49% f o r UPC, UPW and UPB r e s p e c t i v e l y and 6.52%, 18.59% and 17.53% f o r SRC, SRW and SRB r e s p e c t i v e l y ( T a b l e 7 ) . Most o f t h e v a l u e s f a l l i n t h e same g e n e r a l range as p r e v i o u s r e p o r t s (Fiems e t a l . , 1990; 79 H e r r e r a - S a l d a n a e t a l . , 1990b and Tamminga e t a l . , 1990), e x c e p t f o r SRC and SRB which were lower and h i g h e r r e s p e c t i v e l y t h a n u s u a l l y r e p o r t e d ( T a b l e 7) . The d e c r e a s e d l e v e l o f t h e r a p i d l y d e g r a d a b l e f r a c t i o n o f p r o t e i n a f t e r a p p l y i n g h e a t may have r e s u l t e d from f o r m a t i o n o f r e s i s t a n t complexes between c e l l w a l l and s o l u b l e p r o t e i n s . F o r m a t i o n o f a r t i f a c t l i g n i n may i n c r e a s e c e l l w a l l c o n t e n t when g r a i n s a r e t h e r m a l l y t r e a t e d above 65°C ( M a t h i s o n e t a l . , 1991 and Malcolm and K i e s l i n g , 1993) and i t i s a l s o p o s s i b l e t h a t r e s i s t a n t complexes were formed between p r o t e i n and s o l u b l e s u g a r s (Fiems e t a l . , 1990). G r a i n s used i n t h i s s t u d y were steam r o l l e d a t 7 0°C w h i c h i s h i g h e r t h a n 65°C, making i t p o s s i b l e f o r t h e f o r m a t i o n o f a r t i f a c t l i g n i n and complexes o f p r o t e i n and s o l u b l e s u g a r s . D i f f e r e n c e s i n s o l u b i l i t y o f p r o t e i n s from d i f f e r e n t c e r e a l s o u r c e s i s r e l a t e d t o p h y s i c a l and c h e m i c a l p r o p e r t i e s o f t h e m a t e r i a l due t o s p e c i e s , v a r i e t a l and p r o c e s s i n g d i f f e r e n c e s t o mention a few (Kakade, 1974; W a l l and P a u l i s , 1975, and S t e r n e t a l . , 1994). C e r e a l s c r o p s such as b a r l e y and wheat though h i g h i n g l u t e l i n s and p r o l a m i n s l i k e c o r n , a l s o have a h i g h c o n t e n t o f alb u m i n s and g l o b u l i n s t o o . A lbumin and g l o b u l i n p r o t e i n have a h i g h c o n t e n t o f b a s i c and a c i d i c a m i n o - a c i d s making t h e s e p r o t e i n s h i g h l y s o l u b l e (Kakade, 1974) i n w a t e r . G l u t e l i n s and p r o l a m i n s a r e more r e s i s t a n t t o d i s i n t e g r a t i o n t h a n a l b u m i n s and g l o b u l i n s (Kakade, 1974; W a l l and P a u l i s , 1975; S t e r n e t al.,1994 and Romagnolo e t a l . , 1994) 80 2.3.4.2. S l o w l y d e g r a d a b l e f r a c t i o n o f CP. The s l o w l y d e g r a d a b l e f r a c t i o n f o r p r o t e i n was a l s o s i g n i f i c a n t l y a f f e c t e d by p r o c e s s i n g (P<0.0069) and i n t e r a c t i o n (P<0.0286), w h i l e t y p e o f c e r e a l e f f e c t approached s i g n i f i c a n c e (P<0.1058) ( T a b l e 7 ) . Steam r o l l i n g s i g n i f i c a n t l y i n c r e a s e d and ten d e d t o i n c r e a s e t h e s l o w l y d e g r a d a b l e f r a c t i o n f o r b a r l e y (P<0.0023) and c o r n (P<0.088), r e s p e c t i v e l y , b u t n o t wheat (P>0.9047). The r e s u l t s f o r wheat were unexpected. The d e c r e a s e d r a p i d l y d e g r a d a b l e f r a c t i o n r e s u l t e d i n a c o n c o m i t t a n t i n c r e a s e i n t h e q u a n t i t y o f t h e t h e s l o w l y d e g r a d a b l e f r a c t i o n f o r c o r n and b a r l e y but n o t wheat (Table 7 ) . The i n c r e a s e i n t h i s f r a c t i o n due t o steam r o l l i n g may be r e l a t e d t o t h e f o r m a t i o n o f r e s i s t a n t complexes formed between s o l u b l e s u g a r s and p r o t e i n s , (Fiems e t a l . , 1990 and M a t h i s o n e t a l . , 1991). Our r e s u l t s agree w i t h Fiems e t a l . (1990) who deduced from p r o t e i n d i s a p p e a r a n c e c u r v e s . Among u n p r o c e s s e d m a t e r i a l s , UPW was h i g h e r i n t h e s l o w l y d e g r a d a b l e f r a c t i o n when compared t o b a r l e y (P<0.0047) and tended t o be h i g h e r t h a n c o r n (P<0.0576), and UPC tended t o be h i g h e r (P<0.0883) t h a n b a r l e y . V a l u e s were 66.63%, 55.08% and 45.06% f o r wheat, c o r n and b a r l e y ( T able 7) . D i f f e r e n c e s i n t h e s l o w l y d e g r a d a b l e f r a c t i o n were a l s o o b s e r v e d f o r steam r o l l e d g r a i n s but d i f f e r e n c e s were not s i g n i f i c a n t (P>0.05). R a n k i n g was SRB, SRW and SRC and t h e i r v a l u e s were 70.07%, 66.02% and 65.12%, r e s p e c t i v e l y ( T a b l e 7 ) . S i n c e p r o t e i n i s a component o f DM, u i t does c o n t r i b u t e t o t h e v a r i a t i o n o b s e r v e d i n t h e s l o w l y d e g r a d a b l e f r a c t i o n o f DM. 81 2.3.4.3. Rate o f d e g r a d a t i o n o f CP. The r a t e o f d e g r a d a t i o n f o r t h e s l o w l y d e g r a d a b l e f r a c t i o n o f p r o t e i n was s i g n i f i c a n t l y a f f e c t e d by t y p e o f c e r e a l (P<0.0001) and p r o c e s s i n g (P<0.003) w h i l e i n t e r a c t i o n was n o t s i g n i f i c a n t (P<0.0778) ( T a b l e 7 ) . Steam r o l l i n g d e c r e a s e d t h e r a t e o f d e g r a d a t i o n o f t h e s l o w l y d e g r a d a b l e f r a c t i o n o f p r o t e i n f o r a l l g r a i n s b u t was o n l y s i g n i f i c a n t f o r c o r n (P<0.043) and wheat (P<0.0028). R e s u l t s f o r c o r n and wheat agree w i t h p r e v i o u s r e p o r t s (Fiems e t a l . , 1990 and A r i e l i e t a l . , 1995) f o r t h e same g r a i n s . However e x t r u s i o n o f b a r l e y and e x p a n s i o n o f sorghum r e s u l t e d i n s i m i l a r r a t e s o f d e g r a d a t i o n as t h e c o n t r o l ( A r i e l i e t a l . , 1995). Among t h e u n p r o c e s s e d g r a i n s , UPW was degraded f a s t e r t h a n b o t h UPC (P<0.0001) and UPB (P<0.0017) and UPB was f a s t e r t h a n UPC p r o t e i n (P<0.0009). The r a t e o f d e g r a d a t i o n averaged 23.43+0.79 %/h, 17.48±0.79 %/h, and 13.55+0.79 %/h, f o r UPW, UPB and UPC, r e s p e c t i v e l y ( T a b l e 7 ) . T h i s r a n k i n g was n o t m o d i f i e d among t h e steam r o l l e d g r a i n s . V a l u e s f o r t h e r a t e o f d e g r a d a t i o n were 18.00±0.79 %/h, 16.50+0.79 %/h and 10.70±0.79 %/h f o r SRW, SRB and SRC, r e s p e c t i v e l y ( T a b l e 7) . R a n k i n g o f t h e g r a i n s f o r b o t h u n p r o c e s s e d and steam r o l l e d g r a i n s agree w i t h p r e v i o u s r e p o r t s (Fiems e t a l . , 1990; G r i n g s e t a l . , 1992 and A r i e l i e t a l . , 1995). The v a l u e f o r UPC i s somewhat h i g h e r t h a n p r e v i o u s l y r e p o r t e d ( G r i n g s e t a l . , 1992) and t h a t e s t i m a t e d by Tamminga e t a l . (1990) but s i m i l a r t o t h e 9.0 %/h r e p o r t e d by A r i e l i e t a l . (1995) . G r i n g s e t a l . (1992) and A r i e l i e t a l . (1995) r e p o r t e d s i m i l a r v a l u e s f o r b a r l e y and wheat r e s p e c t i v e l y w h i l e Tamminga e t a l . (1990) 82 e s t i m a t e d t h e r a t e t o be around 2 0 %/h f o r wheat w h i c h i s s i m i l a r t o t h e 23.43 %/h f o r UPW r e p o r t e d i n t h i s s t u d y ( T a b l e 7 ) . R a t e s f o r expanded and e x t r u d e d g r a i n s were much lo w e r ( A r i e l i e t a l . , 1995) t h a n r e p o r t e d h e r e (Table 7) f o r steam r o l l e d m a t e r i a l s . The r e d u c e d r a t e o f d e g r a d a t i o n may be r e l a t e d t o f o r m a t i o n o f r e s i s t a n t complexes such as a r t i f a c t l i g n i n formed between p r o t e i n and s u g a r s i n p r e s e n c e o f heat (Fiems e t a l . , 1990; Malc o l m and K i e s l i n g , 1993 and M a t h i s o n e t a l . , 1991). D i f f e r e n c e s i n r a t e o f d e g r a d a t i o n f o r t h e 3 g r a i n t y p e s i s r e l a t e d t o d i f f e r e n c e s i n t h e d i s t r i b u t i o n o f p r o t e i n t y p e s o f t h e s e g r a i n s (Kakade, 1974; W a l l and P a u l i s , 1975; Romagnolo e t a l . , 1994 and S t e r n e t a l . , 1994). 2.3.4.4. Lag ti m e o f CP d e g r a d a t i o n . The l a g t i m e o f p r o t e i n d e g r a d a t i o n was s i g n i f i c a n t l y (P<0.0001) a f f e c t e d by c e r e a l t y p e (P<0.0001) and p r o c e s s i n g (P<0.0003) but t h e e x t e n t o f r e s p o n s e by t h e 3 g r a i n s was a l s o s i g n i f i c a n t (P<0.0001) (Table 7 ) . The i n t e r a c t i o n o c c u r r e d because Steam r o l l i n g r e s u l t e d i n reduced (P<0.0291) l a g w h i l e t h a t f o r b a r l e y and wheat were i n c r e a s e d but was o n l y s i g n i f i c a n t f o r wheat (P<0.0001). The l o n g e r l a g phase f o r c o r n t r e a t m e n t s when compared t o UPW, SRB and UPB i s e x p e c t e d as w e l l as t h a t f o r wheat and b a r l e y c o m p a r i s o n , however, t h e v a l u e f o r SRW was u n e x p e c t e d l y h i g h . P o s s i b l e f o r m a t i o n o f p r o t e i n - c a r b o h y d r a t e r e s i s t a n t complexes as p r e v i o u s l y s p e c u l a t e d would reduce t h e s o l u b i l i t y o f he a t t r e a t e d p r o t e i n s r e s u l t i n g i n a l o n g e r l a g phase. 83 2.3.4.5. E f f e c t i v e d e g r a d a b i l i t y o f CP. A summary of r e s u l t s f o r t h e e f f e c t i v e d e g r a d a b i l i t y o f p r o t e i n a r e shown i n T a b l e 7. E f f e c t i v e d e g r a d a b i l i t y o f CP was s i g n i f i c a n t l y a f f e c t e d by t y p e o f c e r e a l (P<0.0001) and p r o c e s s i n g (P<0.0001) and t h e i n t e r a c t i o n was not s i g n i f i c a n t (P>0.05). Steam r o l l i n g r e s u l t e d i n a s i g n i f i c a n t r e d u c t i o n i n t h e e f f e c t i v e d e g r a d a b i l i t y o f a l l g r a i n s ; c o r n (P<0.0344) wheat (P<0.0004) and b a r l e y (P<0.0031). The average e f f e c t i v e d e g r a d a b i l i t y o f p r o c e s s e d and u n p r o c e s s e d g r a i n s were 55.72+1.39% and 72.43%+l.39%, r e s p e c t i v e l y . T h i s was e x p e c t e d c o n s i d e r i n g t h a t most p r o t e i n from steam r o l l e d g r a i n s would by-pass rumen m i c r o b i a l d e g r a d a t i o n as i n d i c a t e d by t h e s i g n i f i c a n t l y l owered r a t e o f d e g r a d a t i o n (Table 7) • Fo r t h e d i f f e r e n t c e r e a l s , c o r n t r e a t m e n t s had s i g n i f i c a n t l y l o w e r q u a n t i t y o f e f f e c t i v e d e g r a d a b i l i t y t h a n wheat (P<0.0.0001) and b a r l e y (P<0.0001) w h i l e wheat was lower (P<0.045) t h a n b a r l e y . The t r e a t m e n t s averaged 47.30+1.72, 69.41+1.72 and 75.50+1.72%. Among t h e u n p r o c e s s e d g r a i n s , c o r n (UPC) had a s i g n i f i c a n t l y l o wer e f f e c t i v e d e g r a d a b i l i t y when compared t o UPW (P<0.0001) and UPB (P<0.0001) w h i c h were s i m i l a r (P>0.5862) among t h e u n p r o c e s s e d g r a i n s ( T a b l e 7 ) . The r a n k i n g was t h e same f o r steam r o l l e d g r a i n b u t SRB had a s i g n i f i c a n t l y h i g h e r (P<0.0241) e f f e c t i v e d e g r a d a b i l i t y t h a n SRW. The h i g h e r r a p i d l y d e g r a d a b l e f r a c t i o n f o r b a r l e y and wheat t h a n c o r n t r e a t m e n t s may e x p l a i n d i f f e r e n c e s i n e f f e c t i v e d e g r a d a b i l i t y . Most o f t h e c o r n p r o t e i n escapes t o t h e s m a l l i n t e s t i n e s . S i m i l a r r a n k i n g f o r c o r n v e r s u s wheat o r b a r l e y 84 was p r e v i o u s l y r e p o r t e d ( G r i n g s e t a l . , 1992 and A r i e l i e t a l . , 1995). R e s u l t s f o r e f f e c t i v e d e g r a d a b i l i t y by A r i e l i e t a l . (1995) a r e v a r i a b l e w i t h r e s p e c t t o t h e r m a l p r o c e s s i n g . E x p a n s i o n and e x t r u s i o n r e s u l t e d i n h i g h e r e f f e c t i v e d e g r a d a b i l i t y f o r b a r l e y , wheat, c o r n and sorghum which i s i n c o n f l i c t w i t h our r e s u l t s . T h i s i s i n t e r e s t i n g because r a t e s f o r t h e r m a l l y p r o c e s s e d m a t e r i a l s were l o w e r t h a n u n p r o c e s s e d g r a i n s . I t i s p o s s i b l e t h a t e x t r u s i o n and e x p a n s i o n may have an e f f e c t on o t h e r n u t r i e n t components compared t o t h o s e a f f e c t e d by steam r o l l i n g . Dry r o l l e d b a r l e y a t 3 d i f f e r e n t b u s h e l w e i g h t s averaged over 70% ( G r i n g s e t a l . , 1992) f a l l i n g i n between t h e v a l u e s f o r t h e 2 b a r l e y t r e a t m e n t s . G r i n g s e t a l . (1992) and A r i e l i e t a l . (1995) r e p o r t e d a s i m i l a r v a l u e f o r ground c o r n , (44%) which a l s o f e l l between t h e two c o r n t r e a t m e n t s . The h i g h e r e f f e c t i v e d e g r a d a b i l i t y o f CP f o r wheat and b a r l e y would mean t h a t more n i t r o g e n would be a v a i l a b l e f o r m i c r o b i a l p r o t e i n s y n t h e s i s i n t h e rumen t h a n from c o r n . 2.3.5. I n v i t r o s t a r c h r e l e a s e . The r e s u l t s f o r t h e r e l e a s e o f s t a r c h from u n p r o c e s s e d and steam r o l l e d g r a i n s a r e summarised i n T a b l e 8. The r e l e a s e o f s t a r c h i n c r e a s e d f o r a l l s i x g r a i n s w i t h i n c r e a s i n g i n c u b a t i o n t i m e . T h i s a g r e e s w i t h p r e v i o u s r e p o r t s f o r d r y r o l l e d and steam r o l l e d b a r l e y g r a i n ( M a t h i s o n e t a l . , 1991 and Engstrom e t a l . , 1992) . Steam r o l l i n g i n c r e a s e d t h e r e l e a s e o f s t a r c h f o r a l l t h e 3 g r a i n s , b e i n g i n agreement w i t h p r e v i o u s r e p o r t s (Fiems e t a l . , 1990; M a t h i s o n e t a l . , 1991; Engstrom e t a l . , 1992 and M a l c o l m and 85 K i e s l i n g , 1993) f o r s i m i l a r g r a i n s . T h i s was e x p e c t e d because a m y l o g l u c o s i d a s e does not a t t a c k u n g e l a t i n i z e d s t a r c h e a s i l y (MacRae and Armstrong, 19 6 8 ) . The improvement i n s t a r c h r e l e a s e a f t e r steam r o l l i n g a t each i n c u b a t i o n t i m e was h i g h f o r c o r n t h a n b a r l e y and wheat which showed s m a l l changes o n l y . The l o w e r degree o f g e l a t i n i z a t i o n o f b a r l e y and wheat when compared t o c o r n t h e r e f o r e , s u g g e s t s t h a t b a r l e y and wheat do n o t e x h i b i t as much s t a r c h g e l a t i n i z a t i o n when s u b j e c t e d t o h e a t as does c o r n s u g g e s t i n g t h a t b a r l e y and wheat s t a r c h a r e more s u s c e p t i b l e t o enzyme a t t a c k t h a n c o r n s t a r c h even b e f o r e a p p l i c a t i o n o f steam. T h i s a g r e e s w i t h p r e v i o u s r e p o r t s f o r c o r n , sorghum, b a r l e y and wheat (Walker e t a l . , 1970 and M a l c o l m and K i e s l i n g , 1993), m i c r o n i z e d wheat (Aimone and Wagner, 1977) and c o r n , and wheat (Fiems e t a l . , 1990). I t i s t h e r e f o r e r e a s o n a b l e t o s u g g e s t t h a t , steam t r e a t m e n t i s more b e n e f i c i a l f o r g r a i n s w i t h low s t a r c h d e g r a d a b i l i t y t h a n t h o s e w i t h h i g h s t a r c h d e g r a d a b i l i t y . The i n c r e a s e i n s t a r c h r e l e a s e due t o steam r o l l i n g i s as a r e s u l t o f g e l a t i n i z a t i o n , w hich i s a measure o f t h e s t a r c h g r a n u l e d i s r u p t i o n . G r a i n s from d i f f e r e n t s o u r c e s g e l a t i n i z e a t d i f f e r e n t t e m p e r a t u r e s and t h i s i s r e l a t e d t o t h e p h y s i c a l and c h e m i c a l s t r u c t u r e o f t h e s t a r c h s o u r c e (Moran, 1983 and Rooney and P f l u g f e l d e r , 1986). Thermal t r e a t m e n t o f g r a i n s i n t h e p r e s e n c e of m o i s t u r e i n c r e a s e s s w e l l i n g o f t h e s t a r c h g r a n u l e r e s u l t i n g i n changes i n b o t h t h e c h e m i c a l and p h y s i c a l s t r u c t u r e o f s t a r c h . T h i s a l l o w s f o r more enzymes t o e n t e r t h e i n t e r i o r o f t h e s t a r c h 86 m o l e c u l e s t h e r e b y e nhancing e n z y m a t i c h y d r o l y s i s o f s t a r c h ( F r e n c h , 1973; Moran, 1982 and Rooney and P f l u g f e l d e r , 1986). R e s u l t s f o r s t a r c h r e l e a s e (TAble 8) c o n f l i c t w i t h i n s acco d a t a , ( T a b l e 6) , i n which i t was o b s e r v e d t h a t steam r o l l i n g d e c r e a s e d t h e r a t e o f DM and s t a r c h d e g r a d a t i o n f o r a l l g r a i n s . These f i n d i n g s a r e s i m i l a r t o o t h e r p r e v i o u s r e p o r t s i n w h i c h such c o n f l i c t was a l s o r e p o r t e d (Fiems e t a l . , 1990; Engstrom e t a l . , 1992 and M a l c o l m and K i e s l i n g , 1993). Engstrom e t a l . (1992) s p e c u l a t e d t h a t c o n f l i c t between i n s a c c o and enzyme s t a r c h r e l e a s e d a t a may be r e l a t e d t o t h e f a c t t h a t , i n s p i t e o f d r y i n g g r a i n s t o t h e same m o i s t u r e c o n t e n t u n p r o c e s s e d m a t e r i a l c o n t a i n e d more s m a l l p a r t i c l e s s i n c e more DM d i s a p p e a r e d from 0 h bags (Engstrom e t a l . , 1992) . T h i s i s t r u e f o r our i n s a c c o d a t a ( T a b l e 6) w h i c h i n d i c a t e s h i g h e r 0 h v a l u e s f o r u n p r o c e s s e d g r a i n s t h a n steam r o l l e d g r a i n s . T h i s m o d i f y i n g e f f e c t o f g r i n d i n g has a l r e a d y been d i s c u s s e d e a r l i e r under s e c t i o n 2.3.3.3. More r e s e a r c h i s needed t o e l u c i d a t e t h i s c o n f l i c t . Dewhurst e t a l . (1995) have r e c e n t l y q u e s t i o n e d t h e e f f i c a c y o f t h e n y l o n bag t e c h n i q u e f o r d e t e r m i n a t i o n o f d e g r a d a b i l i t y f o r c o n c e n t r a t e s w h i c h c o n t a i n a p p r e c i a b l e l e v e l s o f w a t e r s o l u b l e m a t e r i a l s o r s m a l l p a r t i c l e s w h i c h may l e a v e t h e bag unfermented. 2.4.0. SUMMARY AND CONCLUSION. Steam r o l l i n g o f c o r n , wheat and b a r l e y s i g n i f i c a n t l y d e c r e a s e d t h e r a p i d l y d e g r a d a b l e f r a c t i o n , e f f e c t i v e d e g r a d a b i l i t y 87 and r a t e o f d e g r a d a t i o n f o r DM, CP and s t a r c h but i n c r e a s e d t h e s l o w l y d e g r a d a b l e f r a c t i o n . V a l u e s f o r t h e r a p i d l y d e g r a d a b l e f r a c t i o n , r a t e o f d e g r a d a t i o n and e f f e c t i v e d e g r a d a b i l i t y f o r DM, CP and s t a r c h were lower f o r c o r n t h a n wheat and b a r l e y . There was no d i f f e r e n c e i n t h e r a t e o f s t a r c h d e g r a d a t i o n between steam r o l l e d b a r l e y and wheat. Corn t r e a t m e n t v a l u e s were l o w e r t h a n b a r l e y and wheat f o r t h e s l o w l y d e g r a d a b l e f r a c t i o n o f DM, s t a r c h and CP. 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I n g r e d i e n t s o f t h e d i e t consumed by r u m i n a l l y f i s t u l a t e d cows used f o r t h e i n s i t u e x p e r i m e n t s (DM b a s i s ) . I n g r e d i e n t Roughage 60 Chopped a l f a l f a hay 15 Chopped o r c h a r d g r a s s hay 15 C o r n - g r a s s s i l a g e 30 C o n c e n t r a t e 4 0 D a i r y t e x t u r e d f e e d (16% CP) 40 R o l l e d b a r l e y 47 Beet p u l p 3 R o l l e d c o r n 1 M o l a s s e s 2 Commercial p e l l e t e d p r o t e i n v i t a m i n -m i n e r a l mix 1 46 •canola meal, Rye d i s t i l l e r s g r a i n s , meat-meal, f e a t h e r - m e a l , wheat m i l l r u n , m o l a s s e s , s a l t , l i m e s t o n e , v i t a m i n - m i n e r a l premix. (A s p e c i a l f o r m u l a t i o n f o r t h e f e e d company and p r o p o r t i o n s o f t h e i n g r e d i e n t s a r e c o n f i d e n t i a l ) . 94 T a b l e 2. C h e m i c a l c o m p o s i t i o n o f i n g r e d i e n t s used i n t h e d i e t consumed by r u m i n a l l y f i s t u l a t e d cows used f o r i n s i t u s t u d y (DM b a s i s ) . I n g r e d i e n t N u t r i e n t Chopped Chopped Co r n - D a i r y a l f a l f a o r c h a r d g r a s s t e x t u r e d hay hay s i l a g e f e e d (16 %) DM 95.23 98.17 97. 02 97.54 OM 89 .93 93 .40 94 . 06 93 . 76 CP 19.87 6.77 11.35 15.89 NDF 41.29 61.40 56.92 16.75 ADF 34 . 58 37 . 56 33.75 9 .23 S t a r c h 4.98 13.71 19.07 45.87 Ash 10.07 6. 60 5.94 6.24 Ca 1. 54 0.20 0.20 1.22 P 0.24 0.30 0.32 0.27 GE, k c a l / g . 4.42 4.33 4.83 4.35 T a b l e 3. C h e m i c a l c o m p o s i t i o n o f c e r e a l g r a i n s used i n i n s i t u and i n v i t r o e x p e r i m e n t s (DM b a s i s ) . F e e d s t u f f s 1 N u t r i e n t SRC UPC SRB UPB SRW UPW DM 95. 06 95.02 96. 06 96.61 93.05 96.70 OM 98 . 61 98.65 97.11 97 . 00 98.17 97.97 CP 9.50 8.98 12.43 12.61 15.92 14.85 NDF 9.47 8 . 37 20. 09 19.33 13.68 12.45 TNC2 77.54 79 . 66 61.29 63.52 66.81 66.00 Ash 1.39 1.35 2.89 3.00 1.83 2.03 EE 2 .10 1. 64 1.30 1.54 1.76 1. 65 , S R C = s t e a m - r o l l e d c o r n , UPC=unprocessed c o r n , S R B=steam-rolled b a r l e y , UPB=unprocessed b a r l e y , SRW=steam-rolled wheat, UPW=unprocessed wheat. 2TNC=Total N o n - s t r u c t u r a l C a r b o h y d r a t e = DM - (CP + NDF + EE + Ash) 95 T a b l e 4. S t a r c h c o n t e n t o f t e s t f e e d s t u f f s and v a l i d a t i o n o f s t a r c h a n a l y s i s method (DM b a s i s ) . Item F e e d s t u f f 1 No. o f S t a r c h Range S.D. C V , r e p s . c o n t e n t , o f % % DM v a l u e s SRC 10 72.35 67-78 3 .57 4.93 UPC 10 71. 57 62-79 6.59 9.21 SRW 10 61. 08 57-66 3.10 5.06 UPW 10 59 . 05 55-66 3 .14 5.32 SRB 10 58 . 34 48-69 7 . 38 12.65 UPB 10 54.26 44-66 6.60 12.17 xSee T a b l e 3 96 T a b l e 5. The e f f e c t o f t y p e of c e r e a l and s t e a m - r o l l i n g on i n s i t u d r y m a t t e r d e g r a d a t i o n c h a r a c t e r i s t i c s o f c o r n , b a r l e y and wheat i n c u b a t e d i n t h e rumen o f d a i r y cows. C e r e a l D e g r a d a t i o n c h a r a c t e r i s t i c s g r a i n s 1 2,3 a% b% K d%/h EFDEG% C e r e a l t y p e 1 Corn 31.17 62.03 16.68 75.42 Wheat 49.24 41.11 19.49 79.33 B a r l e y 46.33 41.88 21.52 78.86 SE 4 0.71 1.20 0.99 1.37 P r o c e s s 1 SR 39.89 50.32 15.54 75.45 Unprocessed 44.61 47.03 22.92 80.29 SE 0.58 0.98 0.81 1.12 P v a l u e s 5 C 0.0001 0.0001 0.0371 0.1681 P 0.0012 0.0556 0.0007 0.0222 C*P 0.0622 0.0904 0.1181 0.2550 •C e r e a l Type = Corn, wheat, and b a r l e y P r o c e s s = S t e a m - r o l l i n g (SR) and u n p r o c e s s e d . 2 a = r a p i d l y d e g r a d a b l e f r a c t i o n , b = s l o w l y d e g r a d a b l e f r a c t i o n , k d = f r a c t i o n a l r a t e o f d e g r a d a t i o n o f f r a c t i o n b, lag= l a g t i m e , EFDEG = e f f e c t i v e d e g r a d a b i l i t y a t 5 %/h f r a c t i o n a l o u t f l o w r a t e . 3means i n t h e same column w i t h d i f f e r e n t l e t t e r s a r e s i g n i f i c a n t l y d i f f e r e n t . 4SE = s t a n d a r d e r r o r ( c e r e a l t y p e , n=4 and p r o c e s s , n=6). 5 E f f e c t s ; C = c e r e a l t y p e , P = p r o c e s s i n g ( s t e a m - r o l l i n g ) C*P = i n t e r a c t i o n . 97 T a b l e 6. The e f f e c t o f t y p e of c e r e a l and s t e a m - r o l l i n g on i n s i t u s t a r c h d e g r a d a t i o n c h a r a c t e r i s t i c s o f c o r n , b a r l e y and wheat i n c u b a t e d i n t h e rumen o f d a i r y cows. D e g r a d a t i o n c h a r a c t e r i s t i c s 2 , 3 a% b% K d%/h EFDEG% C e r e a l Type 1 Corn 28.06 70.53 15.74 75.21 Wheat 59.14 39.62 22.97 89.15 B a r l e y 60.43 37.68 27.73 90.49 SE 4 2.65 2.17 1.32 0.92 P r o c e s s 1 P r o c e s s i n g 44.84 53.38 19.26 83.92 Unprocessed 53.58 45.18 25.03 85.98 SE 2.16 1.85 1.08 0.75 P v a l u e 5 C 0.0002 0.0001 0.002 0.0001 P 0.0289 0.0204 0.0091 0.0994 C*P 0.3741 0.3684 0.138 0.1903 C e r e a l Type = Corn, wheat, and b a r l e y P r o c e s s = s t e a m - r o l l i n g (SR) and u n p r o c e s s e d . 2a = r a p i d l y d e g r a d a b l e f r a c t i o n , b = s l o w l y d e g r a d a b l e f r a c t i o n , k d = f r a c t i o n a l r a t e o f d e g r a d a t i o n o f f r a c t i o n b, lag= l a g t i m e , EFDEG = e f f e c t i v e d e g r a d a b i l i t y a t 5 %/h f r a c t i o n a l o u t f l o w r a t e . 3means i n t h e same column w i t h d i f f e r e n t l e t t e r s a r e s i g n i f i c a n t l y d i f f e r e n t . 4SE = s t a n d a r d e r r o r ( c e r e a l t y p e , n=4 and p r o c e s s , n=6). 5 E f f e c t s ; C = c e r e a l t y p e , P = p r o c e s s i n g ( s t e a m - r o l l i n g ) C*P = i n t e r a c t i o n . 98 T a b l e 7. The e f f e c t o f t y p e o f c e r e a l and s t e a m - r o l l i n g on i n s i t u c r u d e p r o t e i n d e g r a d a t i o n c h a r a c t e r i s t i c s o f c o r n , b a r l e y and wheat i n c u b a t e d i n t h e rumen o f d a i r y cows. C e r e a l D e g r a d a t i o n C h a r a c t e r i s t i c s 2 ' 3 g r a i n s 1 a% b% K d%h Lag h EFDEG% SRC 6 . 52d 65 . 12a 10 .70 4 . 02b 42 . 66 UPC 20 . 55c 55 . 08b 13 . 55 4.96c 51 .96 SRW 18 .59c 66 . 02a 18 . 00 5.86d 57 . 14 UPW 29 .46b 66 . 63a 23 .43 1. 00a 81 . 69 SRB 17 . 53c 70 . 07a 16 . 50 1. 52a 67 . 35 UPB 50 • 49a 45 . 06c 17 .48 1.10a 83 .65 SE 4 2. 63 3 . 49 0. 79 0.23 2 . 41 P v a l u e s 5 C 0 . 0007 0 . 1058 0 .0001 0. 0001 0 . 0001 P 0 .0001 0 . 0069 0 . 003 0.0003 0 .0001 C*P 0 .0115 0 . 0286 0 . 0778 0.0001 0 .0524 !SRC = steam r o l l e d c o r n , UPC = u n p r o c e s s e d c o r n , SRW = steam r o l l e d wheat, UPW = u n p r o c e s s e d wheat, SRB = steam r o l l e d b a r l e y UPB = u n p r o c e s s e d b a r l e y 2 a = r a p i d l y d e g r a d a b l e f r a c t i o n , b = s l o w l y d e g r a d a b l e f r a c t i o n , k d = f r a c t i o n a l r a t e o f d e g r a d a t i o n o f f r a c t i o n b, lag= l a g t i m e , EFDEG = e f f e c t i v e d e g r a d a b i l i t y a t 5 %/h f r a c t i o n a l o u t f l o w r a t e , 'means i n t h e same column w i t h d i f f e r e n t l e t t e r s a r e s i g n i f i c a n t l y d i f f e r e n t . 4SE = s t a n d a r d e r r o r ( n = 2 ) . 5P v a l u e s ; C = C e r e a l t y p e , P = p r o c e s s i n g ( s t e a m - r o l l i n g ) C*P = i n t e r a c t i o n . 99 T a b l e 8 . I n v i t r o s t a r c h r e l e a s e (% o f DM) by steam r o l l e d and u n p r o c e s s e d c e r e a l g r a i n s i n c u b a t e d w i t h a m y l o g l u c o s i d a s e enzyme. I n c u b a t i o n C e r e a l G r a i n 1 t i m e , h. : SRC UPC SRW UPW SRB UPB 3 60.43 48 . 19 40.33 40.81 48.6 30.26 SD 2 1.70 1. 52 1. 19 1. 82 1.42 1 6 63 .30 58 . 39 45.68 46. 25 53 .96 33 . 2 SD 2 .32 1. 61 2.85 2 . 42 1.45 0.57 12 72.72 60. 10 53 . 95 49.19 56.16 33 . 63 SD 2 . 04 2 . 65 2 .49 0.78 1.20 0.46 24 75. 05 60.91 55.54 52.03 57.63 42 .90 SD 0.76 1.82 1.55 1.58 1.55 1.17 36 81.53 64.91 56 . 06 53 . 59 57.86 43 .33 SD 1.84 1.85 2 . 08 2.45 2.87 1.90 JSRC = steam r o l l e d c o r n , UPC = u n p r o c e s s e d c o r n , SRW = steam r o l l e d wheat, UPW = u n p r o c e s s e d wheat, SRB = steam r o l l e d b a r l e y UPB = u n p r o c e s s e d b a r l e y 2SD = s t a n d a r d d e v i a t i o n (n=3). 100 CHAPTER 3. IN SITU DEGRADABILITY OF DRY MATTER AND NEUTRAL DETERGENT FIBER OF THREE ROUGHAGES AND AGRO-BYPRODUCTS USED AS LIVESTOCK FEEDS. 3.0. ABSTRACT. Roughages ( c o r n - g r a s s s i l a g e - C G r S , o r c h a r d g r a s s hay-OGrH and a l f a l f a hay-ALFH) o r a g r o - b y p r o d u c t s (wheat millrun-WMR, r y e d i s t i l l e r s grains-RDG and beet pulp-BP) were i n c u b a t e d i n t h e rumen o f two d a i r y cows. Each f e e d group was i n c u b a t e d i n each cow i n two p e r i o d s . D u p l i c a t e 5 g samples o f t h e f e e d s were weighed i n t o n y t e x p o l y e s t e r bags p e r i n c u b a t i o n t i m e and t h e n i n c u b a t e d i n t h e rumen f o r , 2, 3, 6, 12, 24, 36, and 48 h. Cows were f e d t o t a l mixed r a t i o n (TMR) e v e r y 2 h u s i n g a c o n t i n o u s f e e d i n g system. S t a t i s t i c a l a n a l y s i s on t h e d e g r a d a t i o n c h a r a c t e r i s t i c s was done s e p a r a t e l y f o r roughages and a g r o - b y p r o d u c t s . A two way a n a l y s i s o f v a r i a n c e was used f o r d a t a a n a l y s i s and Duncan m u l t i p l e range t e s t was used f o r mean s e p a r a t i o n and t e s t e d f o r s i g n i f i c a n c e a t 0.05 l e v e l . F o r a g r o - b y p r o d u c t s , t h e r a t e o f DM and NDF d i s a p p e a r a n c e o f RDG was s i g n i f i c a n t l y h i g h e r (P<0.05) t h a n WMR and BP wh i c h were s i m i l a r (P>0.05). Rate o f DM d e g r a d a t i o n f o r WMR, BP and RDG averaged 11.21+1.44, 12.27+1.44 and 28.69+1.44 %/h, r e s p e c t i v e l y ; NDF, 8.56+1.68, 8.68+1.68 and 19.32+1.68 %/h, r e s p e c t i v e l y . E f f e c t i v e d e g r a d a b i l i t y o f DM was s i m i l a r (P>0.05) f o r RDG and BP (80.75+0.37 and 80.64+0.37%, r e s p e c t i v l e y ) and b o t h were h i g h e r (P<0.05) t h a n WMR (67.56+0.37%). However, e f f e c t i v e d e g r a d a b i l i t y 101 o f NDF was h i g h e r f o r BP t h a n RDG (63.36+0.43 v s 48.04+0.43%) and WMR, and RDG was h i g h e r t h a n (P<0.05) WMR (48.04+0.43 vs 33.51±0.43%). S i g n i f i c a n t d i f f e r e n c e s were o b s e r v e d (P<0.05) i n t h e r a t e o f d e g r a d a t i o n o f DM and NDF among t h e t h r e e roughages. R a t e o f DM d i s a p p e a r a n c e was h i g h e r (P<0.05) f o r ALFH (15.15+0.51 %/h) t h a n CGrS (6.29+0.51 %/h) and OGrH (6.58.0+0.51 %/h) wh i c h were s i m i l a r (P>0.05). However, t h e r a t e o f NDF d i s a p p e a r a n c e was s i m i l a r (P>0.05) f o r ALFH and CGrS but b o t h s i g n i f i c a n t l y d i f f e r e n t (P<0.05) t o OGrH and v a l u e s averaged 7.87+0.44, 7.67+0.44 and 6.95+0.44 %/h, r e s p e c t i v e l y . The e f f e c t i v e d e g r a d a b i l i t y o f DM was h i g h e s t (P<0.05) f o r ALFH (62.05±0.57%), medium f o r OGrH (43.92±0.57%) and l o w e s t f o r CGrS (40.81+0.57%). However, t h e e f f e c t i v e d e g r a d a b i l i t y o f NDF was was s i m i l a r (P>0.05) f o r OGrH (28.67+0.40%) and ALFH (27.67+0.40%) w h i c h were s i g n i f i c a n t l y h i g h e r (P<0.05) t h a n t h a t o f CGrS (20.96±0.40%). V a r i a b i l i t y i n t h e r a t e o f d e g r a d a t i o n and e f f e c t i v e d e g r a d a b i l i t y o f DM and NDF can be e x p l o i t e d i n d i e t f o r m u l a t i o n f o r m a t c h i n g c a r b o h y d r a t e and p r o t e i n r e l e a s e i n t h e rumen t o promote e f f i c i e n t rumen m i c r o b i a l p r o t e i n s y n t h e s i s . A p o r t i o n o f t h a t c a r b o h y d r a t e comes from roughages and a g r o - b y p r o d u c t s which can a v e r t t h e n e g a t i v e e f f e c t s a s s o c i a t e d w i t h c o n c e n t r a t e f e e d i n g and can a l s o be a r e l i a b l e s o u r c e o f s l o w l y d e g r a d a b l e c a r b o h y d r a t e . 102 3.1. INTRODUCTION. Roughage i s a v e r y i m p o r t a n t component i n t h e d i e t o f d a i r y cows and o t h e r r u m i n a n t s i n g e n e r a l and may c o n s t i t u t e 35-100% o f t h e r a t i o n DM depending on t h e s t a g e o f p r o d u c t i o n (NRC, 1989). They a r e t r a d i t i o n a l l y t h e major s o u r c e o f f i b e r (Van S o e s t , 1982 and Beauchemin e t a l . , 1994), however, a g r o - b y p r o d u c t s w i t h h i g h f i b e r c o n t e n t s have a l s o been i n c o r p o r a t e d i n d i e t s f o r a l o n g t i m e and a r e becoming i n c r e a s i n g l y i m p o r t a n t ( S u t t o n e t a l . , 1987; De V i s s e r and H i n d l e , 1990; De V i s s e r e t a l . , 1991; Swain and Armamento, 1994) complementing t r a d i t i o n a l roughages o r s t a r c h y f e e d s . F i b e r c o n t e n t and s o u r c e i n t h e d i e t i s an i m p o r t a n t d e t e r m i n a n t o f DMI, gut f u n c t i o n and r u m i n a l environment p a r t i c u l a r l y when d i e t s h i g h i n s t a r c h a r e f e d , w i t h s i g n i f i c a n t i mpact on m i l k y i e l d and m i l k f a t (Van S o e s t , 1982; Nocek and R u s s e l l , 1988 and Poore e t a l . , 1993). N e u t r a l d e t e r g e n t f i b e r (NDF) has been p r o p o s e d as an a l t e r n a t i v e t o t h e crud e f i b e r a n a l y s i s o f t h e p r o x i m a t e a n a l y s i s f o r d e t e r m i n i n g t o t a l f i b e r c o n t e n t o f f e e d s ( G o e r i n g and Van S o e s t , 1970) and f o r f o r m u l a t i n g d i e t s t o maximize DMI and t h e r e f o r e m i l k p r o d u c t i o n (Mertens, 1983). The c o n c e p t can be extended f u r t h e r t o s t r u c t u r a l (SC) v e r s u s n o n - s t r u c t u r a l c a r b o h y d r a t e s (NSC). N o n - s t r u c t u r a l c a r b o h y d r a t e s i n t h e d i e t come from g r a i n , h i g h i n s t a r c h and t e n d t o have t h e o p p o s i t e e f f e c t t o t h a t o f f i b e r on r u m i n a l pH, gut f u n c t i o n i n g and end p r o d u c t s o f f e r m e n t a t i o n and t h e r e f o r e m i l k f a t (Nocek and R u s s e l l , 1988). 103 F i b e r and NSC i n t e r a c t i n t h e rumen, i m p a c t i n g on performance o f young g r o w i n g beef a n i m a l s ( F o s t e r e t a l . , 1993 and G a l l o w a y e t a l . , 1993) and l a c t a t i n g d a i r y cows by c o n t r o l o f t h e energy s u p p l y f o r m i c r o b i a l growth (Nocek and R u s s e l l , 1988; H e r r e r a - S a l d a n a and Huber, 1989 and H e r r e r a - S a l d a n a e t a l . , 1990a). S t r u c t u r a l c a r b o h y d r a t e s a r e d i g e s t e d a t a s l o w e r r a t e t h a n NSC (Van S o e s t , 1982 and Van S o e s t , 1986). The v a l u e o f f i b e r depends on i t s q u a l i t y and t h i s i s dependent on many f a c t o r s among them, p l a n t s p e c i e s , growing c o n d i t i o n s , m a t u r i t y , h a r v e s t and s t o r a g e and p r e s e r v a t i o n methods and p h y s i c a l form a t t h e t i m e o f f e e d i n g (Van S o e s t , 1982). These f a c t o r s a f f e c t t h e r e l e a s e o f energy i n t h e rumen r e q u i r e d f o r m i c r o b i a l p r o t e i n s y n t h e s i s . V arga and Hoover, (1983) and Tamminga e t a l . (1990) have r e p o r t e d major d i f f e r e n c e s among f e e d s t u f f s i n t h e r a t e and e x t e n t o f breakdown o f NDF and an i n c r e a s e i n m i l k p r o d u c t i o n and p r o t e i n w i t h d i e t s h a v i n g a f a s t e r r a t e o f NDF d i s a p p e a r a n c e . Legumes have been shown t o produce g r e a t e r l i v e w e i g h t g a i n s and m i l k y i e l d s i n r u m i n a n t s t h a n do g r a s s e s a t s i m i l a r DM and OM d i g e s t i b i l i t i e s (Waldo and J o r g e n s e n , 1981) . D i e t s c o n t a i n i n g e i t h e r a l f a l f a hay, c o r n s i l a g e o r bermuda g r a s s hay b a l a n c e d t o 36% NDF r e s u l t e d i n h i g h e r DMI and m i l k y i e l d on a l f a l f a hay i n s p i t e o f l o w e r NE o f l a c t a t i o n when compared t o c o r n s i l a g e and bermuda g r a s s . S i m i l a r r e s u l t s have been r e p o r t e d f o r o t h e r roughages (Poore e t a l . , 1993; Holden e t a l . , 1994 and R u i z e t a l . , 1995) . DMI and m i l k p r o d u c t i o n were h i g h e r f o r a l f a l f a hay t h a n 104 o r c h a r d g r a s s hay f o r d i e t s f o r m u l a t e d t o c o n t a i n 42% NDF, a l t h o u g h t h e NDF and ADF d i g e s t i b i l i t i e s were h i g h e r f o r o r c h a r d g r a s s t h a n a l f a l f a hay ( R u i z e t a l . , 1995). However, Poore e t a l . (1993) r e p o r t e d no d i f f e r e n c e s i n p r o d u c t i o n c h a r a c t e r i s t i c s f o r d i e t s c o n t a i n i n g wheat s t r a w o r a l f a l f a hay a t 32% o f t h e d i e t DM (22% f o r a g e NDF) c o n t e n t and b a l a n c e d f o r f e e d NDF and rumen d e g r a d a b l e s t a r c h b u t passage r a t e f o r s o l i d s and l i q u i d s were s l o w e r f o r s t r a w t h a n a l f a l f a hay w i t h no e f f e c t on chewing t i m e and NDF d i g e s t i b i l i t y . These r e p o r t s s u g g e s t t h a t o t h e r f a c t o r s b e s i d e s p e r c e n t NDF i n t h e d i e t a f f e c t m i l k p r o d u c t i o n and t h e d i f f e r e n c e s i n p r o d u c t i o n a r e a f u n c t i o n o f f o r a g e q u a l i t y and a p r o p e r b a l a n c e between n o n - s t r u c t u r a l c a r b o h y d r a t e and NDF i n t h e d i e t . Nocek and R u s s e l l (1988) r e p o r t e d t h a t m i l k y i e l d was maximized when t h e r a t i o o f NSC t o NDF was between 0.9 and 1.2. Poore e t a l . (1993) have p r o p o s e d t h a t a r a t i o o f 1:1 f o r a g e NDF ( i n d i e t ) t o rumen d e g r a d a b l e s t a r c h w i l l maximize performance by l a c t a t i n g d a i r y cows. Knowledge o f c a r b o h y d r a t e d e g r a d a b i l i t y i n t h e rumen i s i m p o r t a n t i n s e l e c t i o n o f energy s o u r c e s ( c a r b o h y d r a t e ) t h a t w i l l match t h e r e l e a s e o f n i t r o g e n ( p r o t e i n ) f o r e f f i c i e n t m i c r o b i a l p r o t e i n s y n t h e s i s . The purpose o f t h i s e x periment was t o d e t e r m i n e i n s i t u d e g r a d a t i o n c h a r a c t e r i s t i c s o f some commonly used roughages ( a l f a l f a hay, o r c h a r d g r a s s hay and c o r n - g r a s s s i l a g e ) and a g r o -b y p r o d u c t s (wheat m i l l r u n , r y e d i s t i l l e r s g r a i n and b e e t p u l p ) . 105 3.2.0. MATERIALS AND METHODS. 3.2.1. Source and description of feedstuffs and i n i t i a l handling. C o r n - g r a s s s i l a g e (CGrS) (50:50), O r c h a r d g r a s s hay (OGrH) and a l f a l f a hay (ALFH) were o b t a i n e d from Vancouver a r e a i n B r i t i s h C o lumbia. The hays were used f o r l a c t a t i n g d a i r y cows a t t h e U n i v e r s i t y farm, South campus ( U n i v e r s i t y o f B r i t i s h Columbia, Dept. o f A n i m a l S c i e n c e ) and had been o b t a i n e d from a p r i v a t e l o c a l f a r m e r . C o r n - g r a s s s i l a g e was o r i g i n a l l y o b t a i n e d from A g r i c u l t u r e Canada R e s e a r c h s t a t i o n i n A g a s s i z (B.C). The two s i l a g e s were e n s i l e d s e p a r a t e l y and l a t e r mixed a t 50:50 r a t i o . The a l f a l f a hay appeared t o have been i n mid-bloom and t h e o r c h a r d g r a s s hay appeared t o be i n f u l l bloom. Wheat m i l l r u n (WMR), r y e d i s t i l l e r s g r a i n (RDG) and beet p u l p (BP) (molassed and p e l l e t e d ) , were s u p p l i e d by E a s t C h i l l i w a c k A g r i c u l t u r a l C o - o p e r a t i v e , C h i l l i w a c k , B.C. C h a r a c t e r i s t i c a l l y , WMR l o o k e d crumbly and s h i n y s m a l l p a r t i c l e s o f g r a i n and f i b e r f l a k e s c o u l d be seen. Rye d i s t i l l e r s g r a i n s were g r a n u l a t e d and l i g h t b r o w n i s h i n c o l o r and t h e BP was molassed and p e l l e t e d and of a dark g r e y c o l o u r . A g r o - b y p r o d u c t s , ALFH and OGrH were i m m e d i a t e l y ground t h r o u g h a 2.0 mm s c r e e n u s i n g a W i l e y M i l l (model #3) t o f a c i l i t a t e m i x i n g and s a m p l i n g and t h e n reduced t o 1.0 mm s i z e u s i n g a C h r i s t y and N o r r i s m i l l . A l l samples were t h e n d r i e d i n a f o r c e d a i r oven a t 60°C f o r 48 h. A second DM a n a l y s i s was l a t e r done on 1.0 g samples a t 105°C o v e r n i g h t . The b u l k o f t h e samples were packed i n p o l y e t h y l e n e bags f o r p r o x i m a t e a n a l y s i s and NDF a n a l y s i s . The 106 samples were s t o r e d a t room t e m p e r a t u r e u n t i l t h e i r use f o r i n s i t u s t u d i e s . C o r n - g r a s s s i l a g e was f i r s t d r i e d a t 60°C f o r 48 h and t h e n p r e p a r e d f o r use i n t h e same way as a g r o - b y p r o d u c t s . 3.2.2. Cows, d i e t s and nylon bags. D e t a i l s o f h a n d l i n g and c a r e o f cows, p r e p a r a t i o n o f d i e t s and i n i t i a l p r e p a r a t i o n o f t e s t samples and i n c u b a t i o n p r o c e d u r e s f o r t h e n y l o n bag s t u d i e s have been d e s c r i b e d i n t h e p r e v i o u s c h a p t e r . 3.2.3. A n a l y t i c a l Procedures. P r o x i m a t e and f i b e r a n a l y s i s methods f o r f e e d i n g r e d i e n t s have been d e s c r i b e d i n Chapter 2. D r i e d i n c u b a t e d samples were h a n d l e d as d e s c r i b e d i n Chapter 2 and NDF was a n a l y s e d a c c o r d i n g t o Waldern (1971). A l l c h e m i c a l a n a l y s e s were done i n d u p l i c a t e . 3.2.4. Treatment of re s u l t s and s t a t i s t i c a l analysis. Dry m a t t e r and NDF d i s a p p e a r a n c e from t h e n y l o n bags were c a l c u l a t e d as t h e d i f f e r e n c e between what was p u t i n and what remained i n t h e bags. D e g r a d a t i o n c h a r a c t e r i s t i c s , r a p i d l y d e g r a d a b l e f r a c t i o n % ( a ) , s l o w l y d e g r a d a b l e f r a c t i o n % ( b ) , l a g t i m e h, r a t e o f d e g r a d a t i o n (k d) %/h and e f f e c t i v e d e g r a d a b i l i t y a t 5 %/h f r a c t i o n a l o u t f l o w r a t e % (EFDEG), were c a l c u l a t e d a c c o r d i n g t o t h e e q u a t i o n o f 0 r s k o v and MacDonald (1979) . S t a t i s t i c a l a n a l y s i s was done s e p a r a t e l y f o r roughages and a g r o - b y p r o d u c t s . The d a t a were a l l a n a l y s e d as a two way a n a l y s i s a c c o r d i n g t o Cochran 107 and Cox (1969) u s i n g GLM o f SAS (1990) and Duncan m u l t i p l e range t e s t was used f o r mean s e p a r a t i o n . 3.3.0. RESULTS AND DISCUSSION. 3.3.1. C h e m i c a l c o m p o s i t i o n . C h e m i c a l c o m p o s i t i o n o f t h e t h r e e a g r o - b y p r o d u c t s i s shown i n T a b l e 9. There was not much v a r i a b i l i t y i n DM, OM, and ash c o n t e n t o f t h e f e e d s , a v e r a g i n g 95.09%, 89.10% and 5.99%, r e s p e c t i v e l y . CP, ADF, NDF and h e m i - c e l l u l o s e showed more v a r i a t i o n among o r between t h e f e e d s . RDG was h i g h e s t i n p r o t e i n c o n t e n t (29.64%) and l o w e s t f o r BP (10.36%) and i n t e r m e d i a t e f o r WMR (18.84%). N e u t r a l d e t e r g e n t f i b e r was h i g h f o r RDG and BP a v e r a g i n g 31.85% and 28.36% r e s p e c t i v e l y and WMR was h i g h e s t (40.38%) wh i c h most l i k e l y i s a r e f l e c t i o n o f p r o c e s s i n g . These v a l u e s a r e t y p i c a l o f such by-p r o d u c t s (NRC, 1989). The p r o t e i n c o n t e n t o f a l l t h e s e m a t e r i a l s have been c o n c e n t r a t e d a f t e r t h e raw m a t e r i a l under went p r o c e s s i n g . C h e m i c a l c o m p o s i t i o n o f roughages i s shown i n T a b l e 9. There was v e r y l i t t l e d i f f e r e n c e among f e e d s t u f f s i n c o n t e n t o f DM, OM, ash and EE though CGrS was always much lo w e r i n DM and OM compared t o t h e r e s t o f t h e f e e d s . ALFH was h i g h e s t i n p r o t e i n c o n t e n t (19.90%) and l o w e s t f o r OGrH (6.74%) and i n t e r m e d i a t e f o r CGrS (11.26%). N e u t r a l d e t e r g e n t f i b e r was h i g h f o r b o t h OGrH and CGrS a v e r a g i n g 61.33% and 56.92%, r e s p e c t i v e l y and ALFH was 41.34% which i s i n d i c a t i v e o f t h e i r m a t u r i t y . D i f f e r e n c e s i n f i b e r t y p e and c e l l - c o n t e n t d e r i v a t i v e s o f f e e d s t u f f s such as c e l l u l o s e , hemi-108 c e l l u l o s e , l i g n i n , f i b e r - b o u n d n i t r o g e n , p e c t i n s and CP, s u g a r s , EE, r e s p e c t i v e l y , g i v e each f e e d i n d i v i d u a l c h a r a c t e r i s t i c s t h a t may c o n t r i b u t e t o d i f f e r e n c e s i n r u m i n a l d e g r a d a t i o n c h a r a c t e r i s t i c s (Van S o e s t , 1982; Buxton and J o r g e n s e n , 1988 and Shaver e t a l . , 1988). 3.3.2. DM and NDF degradation c h a r a c t e r i s t i c s of agro-byproducts. I n s i t u d e g r a d a t i o n c h a r a c t e r i s t i c o f DM and NDF f o r WMR, RDG and BP a r e shown i n T a b l e 10. The DM d i s a p p e a r a n c e o f WMR was g e n e r a l l y l o w e r a t a l l i n c u b a t i o n t i m e s compared t o RDG and BP. The DM d i s a p p e a r a n c e o f RDG was most r a p i d among t h e t h r e e , l e v e l l i n g o f f by 12 h, w h i l e DM d i s a p p e a r a n c e o f BP was s t i l l i n c r e a s i n g . The p e r c e n t a g e o f t h e r a p i d l y d e g r a d a b l e f r a c t i o n o f DM was h i g h f o r a l l t h e f e e d s (Table 10) and s i g n i f i c a n t d i f f e r e n c e s (P<0.05) were o b s e r v e d among t h e f e e d s . More m a t e r i a l d i s a p p e a r e d i n i t i a l l y (P<0.05) from RDG (57.62+0.72%) t h a n BP (52.67+0.72%) and d i s a p p e a r a n c e was l e a s t (P<0.05) f o r WMR (46.60+0.72%). Wide v a r i a t i o n i n t h e s l o w l y d e g r a d a b l e f r a c t i o n was o b s e r v e d f o r DM. The s l o w l y d e g r a d a b l e f r a c t i o n o f RDG was s i g n i f i c a n t l y l o w e r t h a n BP (27.78+1.00% vs 42.74+1.00%) b u t s i m i l a r t o WMR (30.96+1.00%) ( T a b l e 10). The r a t e o f DM d e g r a d a t i o n of t h e s l o w l y d e g r a d a b l e f r a c t i o n was s i g n i f i c a n t l y h i g h e r (P<0.05) f o r RDG t h a n WMR o r BP w h i c h were s i m i l a r (P>0.05). The average r a t e o f DM d e g r a d a t i o n was 28.69+1.44 109 %/h f o r RDG as a g a i n s t 11.21+1.44 %/h and 12.27+1.44 %/h f o r WMR and BP, r e s p e c t i v e l y ( T able 10). Lag t i m e was s i m i l a r (P>0.05) f o r WMR and RDG b u t b o t h were s i g n i f i c a n t l y l o wer (P<0.05) t h a n BP ( T a b l e 10) and l a g t i m e f o r NDF f o l l o w e d a s i m i l a r t r e n d . E f f e c t i v e d e g r a d a b i l i t y o f DM (5%/h f r a c t i o n a l o u t f l o w r a t e ) was h i g h e r (P<0.05) f o r RDG and BP t h a n t h a t o f WMR ( T a b l e 10) . The v a l u e s o f e f f e c t i v e d e g r a d a b i l i t y o f DM were 80.75+0.37%, 80.64+0.37% and 67.56+0.37% f o r RDG, BP and WMR, r e s p e c t i v e l y . C omparative d a t a f o r WMR and RDG w i t h r e s p e c t t o d e g r a d a t i o n c h a r a c t e r i s t i c s i s s c a r c e . However, because o f new i n t e r e s t i n BP, d a t a i s s l o w l y a c c u m u l a t i n g (Varga and Hoover, 1983; De V i s s e r and H i n d l e , 1990 and De V i s s e r e t a l . 1991 and Swain and Armentano, 1994) . A few r e p o r t s on beet p u l p i n s i t u d e g r a d a t i o n c h a r a c t e r i s t i c s a r e i n agreement. The 12.27+1.44 %/h r a t e o f DM d e g r a d a t i o n i s s i m i l a r t o 11.40+0.0832 %/h r e p o r t e d by Dewhurst e t a l . (1995) and 8.7 %/h r e p o r t e d by Swain and Armentano, (1994) f o r molassed sugar beet f e e d and d e h y d r a t e d b e e t p u l p r e s p e c t i v e l y . However, t h e l e v e l o f t h e r a p i d l y d e g r a d a b l e f r a c t i o n and t h e s l o w l y d e g r a d a b l e f r a c t i o n were b o t h l o w e r t h a n r e p o r t e d by Dewhurst e t a l . (1995) (52.67+0.72% vs 63.2+0.018%; 42.74+1.00% vs 59.70+0.0187 %) r e s p e c t i v e l y ( T able 1 0 ) . I n c o n t r a s t t o t h e above r e s u l t s , Swain and Armantano, (1994) r e p o r t e d l o w e r and h i g h e r v a l u e s o f BP r a p i d l y d e g r a d a b l e and s l o w l y d e g r a d a b l e f r a c t i o n s (15.3+7.6% and 8 0.6+7.6% r e s p e c t i v e l y ; mean+SD) and Souvant e t a l . 110 (1985) r e p o r t e d a 12% v a l u e f o r t h e r a p i d l y d e g r a d a b l e f r a c t i o n s i m i l a r t o Swain and Armentano, (1994). S i n c e t h e c h e m i c a l c o m p o s i t i o n o f BP (molassed p e l l e t e d ) used i n t h i s s t u d y was s i m i l a r t o t h a t used by Dewhurst e t a l . (1995) d i f f e r e n c e s i n t h e r a p i d l y d e g r a d a b l e f r a c t i o n may be r e l a t e d t o t h e q u a n t i t y o f molasses added. A d d i t i o n o f molasses may a l s o e x p l a i n t h e h i g h e r r a p i d l y d e g r a d a b l e f r a c t i o n v a l u e s i n t h i s s t u d y and o t h e r s (Dewhurst e t a l . , 1995) t h a n t h o s e r e p o r t e d by Souvant e t a l . (1985) and Swain and Armentano, (1994) as mo l a s s e s would c o n t r i b u t e s i g n i f i c a n t l y t o t h i s f r a c t i o n . O ther r e a s o n s c o u l d be r e l a t e d t o d i f f e r e n c e s i n t h e washing p r o c e d u r e . I n our s t u d y 0 h d i s a p p e a r a n c e was d e t e r m i n e d by s o a k i n g i n wa t e r f o r 15 minutes f o u r bags p e r f e e d and t h e n hand washing t h e bags under t a p water t o g e t h e r w i t h t h e r u m i n a l l y i n c u b a t e d samples, u n t i l t h e t a p water became c l e a r , w h i l e Dewhurst e t a l . (1995) soaked t h e bags i n c o l d w a t e r t h e n c o l d r i n s e c y c l e i n h o u s e - h o l d l a u n d r y machine f o r 40 mi n u t e s and Souvant e t a l . (1985) o n l y w e t t e d t h e bags f o r 30 m i n u t e s . I n o t h e r work t h e r a p i d l y s o l u b l e f r a c t i o n o f DM f o r d r i e d b e e t p u l p was r e p o r t e d as 6.3% compared t o 34.5% f o r p r e s s e d beet p u l p (De V i s s e r e t a l . , 1991). De V i s s e r e t a l . (1991) s p e c u l a t e d t h a t t h e l a r g e d i f f e r e n c e i n t h e l e v e l o f t h e r a p i d l y d e g r a d a b l e f r a c t i o n may be due t o s w e l l i n g o f d r y p a r t i c l e s o f beet p u l p , i n c r e a s i n g p a r t i c l e s i z e and t h e r e f o r e r e d u c i n g t h e number o f v e r y s m a l l p a r t i c l e s w hich c o u l d be r i n s e d out o f t h e bag. T h i s p r o b a b l y n e v e r happened i n our case s i n c e t h i s f r a c t i o n was r e a s o n a b l y h i g h . D i f f e r e n c e s i n DM d e g r a d a t i o n c h a r a c t e r i s t i c s may be e x p l a i n e d by a number o f r e a s o n s , i n c l u d i n g i n i t i a l s o u r c e o f t h e b y p r o d u c t , and p r o c e s s i n g . A l l p r o c e s s i n g methods i n v o l v e d r e m o v a l o f a l a r g e p o r t i o n o f t h e s o l u b l e c a r b o h y d r a t e e s p e c i a l l y RDG. Among t h e t h r e e methods, m a l t i n g would have more impact on t h e c h e m i c a l c o m p o s i t i o n and r u m i n a l d e g r a d a t i o n c h a r a c t e r i s t i c s . The p r o t e i n and f i b e r c o n t e n t , and r a t e o f p r o t e i n d e g r a d a b i l i t y o f RDG a r e h i g h e r and l o w e r r e s p e c t i v e l y t h a n t h e u n p r o c e s s e d p a r e n t r y e g r a i n (NRC, 1989). Both p r o t e i n and f i b e r w i l l impact t h e r u m i n a l DM b e h a v i o r o f RDG s i g n i f i c a n t l y . On t h e o t h e r hand, t h e m i l l i n g p r o c e s s o f wheat r e s u l t e d i n a s m a l l i n c r e a s e i n CP c o n t e n t compared t o an u n p r o c e s s e d wheat, w h i c h a l s o shows a t h r e e f o l d i n c r e a s e i n c r u d e f i b e r c o n t e n t a f t e r m i l l i n g p r o c e s s (NRC, 1989) because t h e p r o c e s s removes most of s t a r c h y p o r t i o n o f t h e g r a i n . Up t o 75% o f t h e DM i s s t a r c h i n c e r e a l s . The removal o f s t a r c h y m a t e r i a l would r e d u c e t h e g r e a t i n f l u e n c e i t e x e r t s on DM d e g r a d a t i o n c h a r a c t e r i s t i c s . B oth s t a r c h and p r o t e i n i n wheat a r e h i g h l y d e g r a d a b l e ( H e r r e r a - S a l d a n a e t a l . , 1990a). However s i n c e t h e r e i s l i t t l e change i n c o n c e n t r a t i o n o f CP and w i t h p r o b a b l e c h e m i c a l changes due t o p r o c e s s i n g , t h e impact o f CP on DM d e g r a d a t i o n would be t h e same as u n p r o c e s s e d wheat g r a i n . T h i s t h e n would i m p l y t h a t t h e d e g r a d a b i l i t y o f f i b e r would be paramount i n i n f l u e n c i n g DM d e g r a d a t i o n c h a r a c t e r i s t i c s . P r e s s i n g o f s o l u b l e c a r b o h y d r a t e s from BP r e s u l t e d i n s i m i l a r c o n t e n t o f CP t o u n p r e s s e d b e e t - r o o t w h i l e t h a t f o r c r u d e f i b e r i n c r e a s e d two f o l d t o r e l a t i v e l y h i g h q u a n t i t i e s (NRC, 1989). L i k e 112 WMR, BP DM d e g r a d a t i o n may be r e l a t e d t o t h e i n c r e a s e d f i b e r c o n t e n t (NRC, 1989). M a l t i n g o f c e r e a l g r a i n r e s u l t s i n p h y s i c a l and c h e m i c a l changes due t o h y d r a t i o n c a u s i n g s w e l l i n g o f s t a r c h and f i b e r and a l s o h e a t o f f e r m e n t a t i o n due t o m i c r o b i a l a c t i o n r e s u l t i n g i n some o f t h e p r o t e i n b e i n g bound t o f i b e r . I n a d d i t i o n , t h e d r y i n g p r o c e s s has t h e most s i g n i f i c a n t impact on t h e d e g r a d a t i o n o f CP i n RDG ( W a l l and P a u l i s , 1978). D i s t i l l e r s g r a i n s have a re d u c e d CP d e g r a d a b i l i t y when compared t o t h e p a r e n t m a t e r i a l because o f t h e r e a s o n mentioned i n t h e p r e c e e d i n g s t a t e m e n t (NRC, 1989). T h i s may e x p l a i n t h e lower r a p i d l y s o l u b l e f r a c t i o n o f NDF i n RDG when compared t o BP though s i m i l a r t o WMR (T a b l e 10) . I t i s u n l i k e l y t h a t t h e lo w e r r a p i d l y d e g r a d a b l e s o l u b l e f r a c t i o n o f WMR was due t o b i n d i n g o f f i b e r t o p r o t e i n s i n c e t h e p r o c e s s r e s u l t s i n l e s s e f f e c t on t h e CP c o n t e n t o f wheat. The h i g h l e v e l s o f t h e r a p i d l y d e g r a d a b l e f r a c t i o n i n BP r e l a t i v e t o WMR and RDG i s r e l a t e d t o t h e p e c t i n c o n t e n t o f t h e f i b e r . Beet p u l p i s h i g h i n c e l l w a l l c o n t e n t and a l s o h i g h i n p e c t i n m a t e r i a l which i s r e c o v e r e d i n NDF (Van S o e s t , 1982). P e c t i n b e l o n g s t o s t r u c t u r a l c a r b o h y d r a t e s b u t i s h i g h l y d e g r a d a b l e i n t h e rumen, making t h e f i b e r o f BP h i g h l y d e g r a d a b l e when compared t o o t h e r m a t e r i a l s o f s i m i l a r f i b e r c o n t e n t . I n t h i s s t u d y , t h e r a t e o f DM d e g r a d a t i o n o f BP was s i m i l a r t o WMR b u t s i g n i f i c a n t l y l o wer t h a n RDG (T a b l e 1 0 ) , w h i l e t h e s l o w l y d e g r a d a b l e f r a c t i o n was h i g h e r f o r BP t h a n RDG and WMR. E f f e c t i v e DM d e g r a d a b i l i t y was h i g h e r f o r RDG t h a n b o t h BP and WMR, however b o t h RDG and BP were e x t e n s i v e l y degraded a v e r a g i n g 80% compared t o 68% on WMR. The v a r i a t i o n o b s e r v e d i n r u m i n a l d e g r a d a t i o n c h a r a c t e r i s t i c s o f NDF may p a r t l y e x p l a i n t h e v a r i a t i o n i n i n s i t u d e g r a d a t i o n o f DM. The r a t e o f NDF d e g r a d a t i o n p a r a l l e l e d t h a t o f DM i n t h i s s t u d y and t h e r a t e o f d e g r a d a t i o n NDF was a s s o c i a t e d w i t h DM i n s i t u d e g r a d a t i o n (Varga and Hoover, 1983). Source o f m a t e r i a l and p r o c e s s i n g e f f e c t s a r e t h e l i k e l y f a c t o r s t h a t may e x p l a i n t h e v a r i a t i o n i n NDF d e g r a d a t i o n c h a r a c t e r i s t i c s . I n s p i t e o f t h e low CP d e g r a d a b i l i t y o f RDG, t h e r a t e o f d e g r a d a b i l i t y o f NDF was s t i l l h i g h e r t h a n t h a t o f WMR and BP which have h i g h and medium CP d e g r a d a b i l i t y . T h i s may i n d i c a t e l e s s e f f e c t o f CP c o n t e n t on r a t e o f DM d e g r a d a b i l i t y . However, CP c o n t e n t would be i m p o r t a n t i n i n f l u e n c i n g e f f e c t i v e d e g r a d a b i l i t y . V a rga and Hoover, (1983) found no r e l a t i o n s h i p between %CP c o n t e n t and NDF r a t e o f d e g r a d a t i o n f o r a d i v e r s e group o f f e e d s t u f f s and a low b u t p o s i t i v e r e l a t i o n s h i p e x i s t e d between t h e e x t e n t o f NDF d e g r a d a t i o n and %CP c o n t e n t ( r = .46, P<0.03). I n t h i s s t u d y b o t h DM and NDF r a t e o f d e g r a d a t i o n f o r BP were much lo w e r t h a n RDG but s i m i l a r t o WMR, y e t t h e e f f e c t i v e d e g r a d a b i l i t y was h i g h e r t h a n RDG and WMR. T h i s d a t a s t r e n g t h e n s p r e v i o u s f i n d i n g s t h a t t h e amount o f NDF degraded i s not n e c e s s a r i l y r e l a t e d t o t h e r a t e o f d e g r a d a t i o n (Varga and Hoover, 1983). Of t h e t h r e e b y p r o d u c t s t e s t e d , DM and NDF d i s a p p e a r a n c e i n RDG was most r a p i d i n r e a c h i n g an asymptote, WMR was not as r a p i d but a l s o l e v e l l e d e a r l y when compared t o BP. S i m i l a r o b s e r v a t i o n s f o r d i s t i l l e r s g r a i n s and beet p u l p and o t h e r 114 f e e d s t u f f s from d i f f e r e n t backgrounds have been r e p o r t e d (Varga and Hoover, 1983). I n s i t u d a t a on t h e r a t e o f c e l l - w a l l d e g r a d a t i o n o f a g r o -b y p r o d u c t f e e d s t u f f s such as BP i s l a c k i n g . Swain and Armentano (1994) r e p o r t e d a r a t e o f 8.0+2.6 %/h wh i c h i s s i m i l a r t o t h e 8.68+1.68 %/h r e p o r t e d i n t h i s s t u d y . I n c o n t r a s t , Varga and Hoover, (1983) and De V i s s e r e t a l . (1992) r e p o r t e d a l o w e r r a t e o f NDF d e g r a d a t i o n f o r BP t h a n r e p o r t e d i n t h i s s t u d y b u t t h e v a l u e i s i n t h e same g e n e r a l a r e a (5.3 %/h vs 8.68 % / h ) . The d i f f e r e n c e s may be r e l a t e d t o v a r i e t y d i f f e r e n c e s o f t h e b e e t p u l p w h i c h may l i k e l y have d i f f e r e n t NDF c o n t e n t between t h i s s t u d y and t h a t o f Varga and Hoover, (1983). I n c o n f l i c t t o our f i n d i n g s f o r BP and RDG, Varga and Hoover, (1983) r e p o r t e d a s l i g h t l y l o w e r r a t e o f NDF d e g r a d a t i o n f o r d i s t i l l e r s ( u n s p e c i f i e d o r i g i n a l s o u r c e ) g r a i n s t h a n BP. I t i s p o s s i b l e t h a t t h e i r s o u r c e o f d i s t i l l e r s g r a i n was c o r n . De V i s s e r e t a l . (1992) r e p o r t e d a l o w e r NDF r a t e o f d e g r a d a t i o n f o r maize r e l a t i v e t o BP b u t t h e BP NDF r a t e o f d e g r a d a t i o n was lower t h a n f o r a c e r e a l l i k e b a r l e y w h i c h f a l l s under s i m i l a r b o t a n i c a l group w i t h r y e . There i s v i r t u a l l y no d a t a on t h e d e g r a d a t i o n c h a r a c t e r i s t i c s f o r WMR. I n t h i s s t u d y , WMR was s i m i l a r t o BP i n terms o f DM and NDF r a t e o f d e g r a d a t i o n but y i e l d e d much lo w e r d i g e s t e d m a t e r i a l s i n c e most o f t h e d i g e s t i b l e p o r t i o n ( s t a r c h ) has been removed. 115 3.3.3. DM and NDF d e g r a d a t i o n c h a r a c t e r i s t i c s of roughages. I n s i t u d e g r a d a t i o n c h a r a c t e r i s t i c s f o r t h e roughages a r e shown i n T a b l e 11. S i g n i f i c a n t d i f f e r e n c e s (P<0.05) i n t h e d e g r a d a t i o n c h a r a c t e r i s t i c s of DM and NDF were o b s e r v e d . The r a p i d l y d e g r a d a b l e f r a c t i o n (a%) and r a t e o f DM d e g r a d a t i o n , (K d) were h i g h e r (P<0.05) f o r ALFH t h a n b o t h OGrH and CGrS, w h i c h had s i m i l a r v a l u e s f o r t h e s e same pa r a m e t e r s . The r a t e o f DM d e g r a d a t i o n o f ALFH was 15.15+0.51 %/h and OGrH and CGrS were, 6.58+0.51 and 6.29+0.51 %/h, r e s p e c t i v e l y . Averages f o r t h e r a p i d l y d e g r a d a b l e f r a c t i o n were 38.00+1.98%, 24.54+1.98% and 21.62+1.98% f o r ALFH, OGrH and CGrS, r e s p e c t i v e l y . These v a l u e s a r e s i m i l a r t o 36%, 29% and 22% f o r t h e same roughages as r e p o r t e d by M i r e t a l . (1991). A l l roughages had s i g n i f i c a n t l y d i f f e r e n t q u a n t i t i e s o f t h e s l o w l y d e g r a d a b l e f r a c t i o n (b) o f DM and t h e s e averaged 42.56+1.55, 38.27+1.55% and 34.19+1.55% OGrH, CGrS and ALFH, r e s p e c t i v e l y . The r a n k i n g f o r t h e s l o w l y d e g r a d a b l e f r a c t i o n between a l f a l f a hay and o r c h a r d g r a s s was m a i n t a i n e d i n t h i s s t u d y ( T a b l e 11) as w e l l as i n M i r e t a l . (1991). The 34% v a l u e f o r a l f a l f a hay as r e p o r t e d by M i r e t a l . (1991) i s s i m i l a r t o t h a t r e p o r t e d i n t h i s s t u d y ( T a b l e 11) and a l s o Shaver e t a l . (1988) f o r a f u l l bloom a l f a l f a hay; b u t t h e o r c h a r d g r a s s hay v a l u e (53%) was h i g h e r t h a n t h e v a l u e o f 43% r e p o r t e d h e r e . D i f f e r e n c e s i n t h e 2 v a l u e s may be due t o d i f f e r e n c e s i n m a t u r i t y between t h e two o r c h a r d g r a s s hays used i n t h e e x p e r i m e n t s . The more r e s i s t a n t p o r t i o n o f t h e c e l l c o n t e n t s as 116 w e l l as c e l l - w a l l c o n t e n t make up a p o r t i o n o f t h e s l o w l y d e g r a d a b l e f r a c t i o n . S i g n i f i c a n t d i f f e r e n c e s were (P<0.05) o b s e r v e d i n t h e l a g t i m e (h) among t h e t h r e e roughages. Lag t i m e was l o n g e r f o r OGH (4.33+0.28 h ) , t h a n f o r CGrS (2.11+0.28 h) and ALFH (1.37+0.28 h ) . These r e s u l t s agree w i t h t h o s e by M i r e t a l . (1991) i n terms o f r a n k i n g . Lag t i m e f o r OGrH but n o t ALFH was s i m i l a r t o t h a t r e p o r t e d by M i r e t a l . (1991). A lower l a g c o u l d be an i n d i c a t i o n o f t h e p r e s e n c e o f a h i g h c o n t e n t o f s o l u b l e m a t e r i a l w h i c h can r e s u l t i n b o t h l o s s e s from t h e bag o f v e r y s m a l l p a r t i c l e s as w e l l as t h a t w h i c h a c t u a l l y i s r a p i d l y d e g r a d a b l e i n t h e rumen ( 0 r s k o v , e t a l . , 1980). V a l u e s f o r t h e r a t e o f DM d e g r a d a b i l i t y r e p o r t e d by M i r e t a l . (1991) were 16.0, 6.0 and 2.0 %/h f o r a l f a l f a hay, o r c h a r d g r a s s and pure c o r n s i l a g e , r e s p e c t i v e l y . The r a t e s f o r a l f a l f a hay and o r c h a r d g r a s s hay a r e s i m i l a r t o t h o s e r e p o r t e d i n t h i s s t u d y ( T a b l e 11) . The v a l u e f o r s i l a g e r e p o r t e d h e r e ( T a b l e 11) i s h i g h e r t h a n t h a t r e p o r t e d by M i r e t a l . (1991). The s i l a g e i n t h i s s t u d y was a 50:50% m i x t u r e o f c o r n and g r a s s s i l a g e as opposed t o pure c o r n s i l a g e used by M i r e t a l . (1991) . The a d d i t i o n o f a g r a s s s i l a g e t o c o r n s i l a g e i n c r e a s e d t h e r a t e o f DM d i s a p p e a r a n c e i n s i t u . V a l u e s f o r r a p i d l y d e g r a d a b l e f r a c t i o n a veraged 36%, 29% and 22% r e s p e c t i v e l y f o r ALFH, OGrH and maize s i l a g e ( M i r e t a l . 1991) compared t o t h i s e x p e r i m e n t , 38%, 24.54% and 21.62% f o r ALFH, OGrH, CGrS ( T a b l e 1 1 ) . 117 The s l o w l y degraded f r a c t i o n o f DM f o r ALFH was l e a s t among t h e t h r e e , b u t r e s u l t e d i n s i g n i f i c a n t l y h i g h e r (P<0.05) e f f e c t i v e d e g r a d a b i l i t y , t h a n OGrH and CGrS. Averages f o r e f f e c t i v e d e g r a d a b i l i t y were 62.05±.57%, 43.92±0.57% and 40.81±0.57% f o r ALFH, OGrH and CGrS r e s p e c t i v e l y . The h i g h e f f e c t i v e d e g r a d a b i l i t y o f ALFH was t h e r e s u l t o f t h e h i g h r a t e o f d e g r a d a t i o n and r a p i d l y d e g r a d a t i o n f r a c t i o n and a l s o lower l a g phase when compared t o CGrS and OGrH. NDF d e g r a d a t i o n c h a r a c t e r i s t i c s showed d i f f e r e n c e s i n terms o f r a n k i n g o f t h e t h r e e roughages (Table 11) . A l f a l f a hay w h i c h had t h e h i g h e s t r a p i d l y d e g r a d a b l e DM, had a lo w e r (P<0.05) r a p i d l y d e g r a d a b l e f r a c t i o n o f NDF compared t o OGrH and CGrS w h i c h were s i m i l a r t o OGrH. The s l o w l y d e g r a d a b l e NDF was h i g h e r (P<0.05) f o r OGrH t h a n ALFH and CGrS, which were a l s o s i g n i f i c a n t l y d i f f e r e n t from each o t h e r w i t h ALFH b e i n g h i g h e r (P<0.05) t h a n CGrS. The average v a l u e s f o r s l o w l y d e g r a d a b l e f r a c t i o n and e f f e c t i v e d e g r a d a b i l i t y were 43.74+1.05%, 33.98+1.05% and 26.66+1.05% and 28.53+.40, 27.67+0.40 and 20.96+0.4 0% f o r OGrH, ALFH and CGrS, r e s p e c t i v e l y . A l t h o u g h t h e r a t e o f DM d e g r a d a t i o n f o r ALFH was 2x more t h a n t h a t f o r OGrH and CGrS, NDF r a t e o f d e g r a d a t i o n was s i m i l a r (P>0.05) t o t h a t o f CGrS but s t i l s i g n i f i c a n t l y h i g h e r t h a n OGrH. The r e s u l t f o r ALFH and CGrS when compared t o OGrH w i t h r e s p e c t t o r a t e o f NDF d e g r a d a t i o n a r e as e x p e c t e d s i n c e OGrH was o f low q u a l i t y as i n d i c a t e d by t h e low and h i g h CP and NDF c o n t e n t s (CP and NDF; 6.74 and 61.33%, r e s p e c t i v e l y ) . V a l u e s f o r r a t e o f NDF 118 d e g r a d a t i o n were 7.87+0.44 %/h, 7.67+0.44 %/h and 6.95+0.44 %/h f o r ALFH, CGrS and OGrH, r e s p e c t i v e l y . The l a g t i m e f o r NDF was l e a s t (P<0.05) f o r ALFH (1.57+0.15 h ) , l o n g e s t f o r CGrS (11.3 0+0.15 h) and l o n g e r f o r OGrH (10.29+0.15 h) (P<0.05). Lower l a g t i m e v a l u e s were r e p o r t e d by Varga and Hoover, (1983) f o r a l f a l f a hay and o r c h a r d g r a s s hay. Lag t i m e f o r a l f a l f a hay and o r c h a r d g r a s s hay r e p o r t e d were 4.32 and 0.90 h r e s p e c t i v e l y w h i c h were h i g h e r and much lower r e s p e c t i v e l y t h a n r e p o r t e d i n t h i s s t u d y ( T a b l e 11) . D i f f e r e n c e s i n r e s u l t s r e p o r t e d h e r e and t h o s e o f Varga and Hoover, (1983) may be e x p l a i n e d by d i f f e r e n c e s i n m a t u r i t y o f t h e roughages used. R e s u l t s f o r r a t e o f NDF d e g r a d a t i o n were s i m i l a r t o t h o s e o f Varga and Hoover, (1983). N e u t r a l d e t e r g e n t f i b e r i n a l f a l f a hay was r e p o r t e d t o degrade f a s t e r t h a n NDF i n b o t h o r c h a r d g r a s s hay (7.8 v s 5.6 %/h) and pure c o r n s i l a g e averaged 8.2 %/h (Varga and Hoover, 1983). These v a l u e s a r e s i m i l a r t o t h o s e r e p o r t e d i n t h i s s t u d y f o r ALFH and OGrH (Table 11) . These f i n d i n g s have been c o n f i r m e d w i t h i n s i t u (Shaver e t a l . , 1988) , i n v i t r o (Mertens and L o f t e n , 1980 and Buxton and R u s s e l l , 1988) and i n v i v o s t u d i e s (Holden e t a l . , 1994). C e l l - w a l l s from a l f a l f a hay degrades f a s t e r t h a n c e l l w a l l s from o r c h a r d g r a s s hay (Buxton and R u s s e l l , 1988) . The d i f f e r e n c e i n r a p i d l y d e g r a d a b l e f r a c t i o n o f DM i n a l f a l f a hay ( T a b l e 11) when compared t o o t h e r f o r a g e s may be p a r t l y due t o t h e d i f f e r e n c e s i n m a t u r i t y (Shaver e t a l . , 1988) . The p r o t e i n and NDF c o n t e n t o f a l f a l f a hay were 19% and 39%, r e s p e c t i v e l y , w h i c h were h i g h e r and lower r e s p e c t i v e l y t h a n f o r OGrH and CGrS. A l a r g e 119 p o r t i o n o f t h e r a p i d l y d e g r a d a b l e f r a c t i o n i n a l f a l f a would be h i g h i n c e l l - c o n t e n t s such as p r o t e i n s , s u g a r s and t o a s m a l l e x t e n t s t a r c h w h i c h a r e more r e a d i l y d e g r a d a b l e t h a n t h e c e l l - w a l l . I n a d d i t i o n a l f a l f a hay has broad l e a v e s w h i c h t e n d t o be b r i t t l e when h a r v e s t e d and d r i e d and w i l l t e n d t o p u l v e r i s e r e s u l t i n g i n v e r y f i n e p a r t i c l e d u r i n g g r i n d i n g . A l f a l f a hay i s t h e r e f o r e l i k e l y t o have a l a r g e p o r t i o n o f p a r t i c l e s w h i c h would come ou t o f t h e bag w i t h o u t n e c e s s a r i l y b e i n g s o l u b l e ( 0 r s k o v e t a l . , 1980). On t h e o t h e r hand ALFH had t h e l o w e s t (P<0.05, T a b l e 11) l e v e l o f t h e NDF r a p i d l y d e g r a d a b l e f r a c t i o n compared t o OGrH and CGrS and t h e r a t e o f NDF d e g r a d a t i o n was e q u a l t o CGrS but n o t OGrH. T h i s seems t o mean t h a t t h e h i g h l e v e l o f t h e r a p i d l y d e g r a d a b l e f r a c t i o n and r a t e o f DM d e g r a d a t i o n shown by a l f a l f a hay i s n o t s i g n i f i c a n t l y a f f e c t e d by t h e s o l u b i l i t y and r a t e o f d i g e s t i o n o f NDF compared t o CGrS and OGrH. D i f f e r e n c e s i n t h e r a t e o f NDF d i g e s t i o n i n s i t u can be e x p l a i n e d on t h e b a s i s o f t h e i n h i b i t o r y e f f e c t s o f l i g n i n on d i g e s t i o n o f h e m i - c e l l u l o s e and i t s n e g a t i v e r e l a t i o n s h i p t o d i g e s t i o n o f c e l l u l o s e and h e m i c e l l u l o s e (Van S o e s t , 1982 and Buxton and R u s s e l l , 1988). Buxton and R u s s e l l , (1988) r e p o r t e d t h a t t h e a p p a r e n t i n h i b i t i o n by l i g n i n o f c e l l - w a l l d i g e s t i o n was 62% g r e a t e r i n g r a s s e s t h a n i n legumes b e f o r e m a t u r i t y . I t was o b s e r v e d t h a t t h e i n h i b i t o r y e f f e c t s o f l i g n i n were not r e l a t e d t o i t s c o n t e n t . L i g n i n on a p e r u n i t l i g n i n b a s i s was more i n h i b i t o r y t o d i g e s t i o n o f g r a s s e s t h a n legumes. T h i s i s p a r t i c u l a r l y so i n immature l o w - l i g n i n c e l l w a l l s i n which a u n i t o f l i g n i n p r o t e c t s 120 more c a r b o h y d r a t e t h a n i n h i g h l y l i g n i f i e d mature c e l l w a l l s (Smith e t a l . , 1972; Van S o e s t , 1982 and Buxton and R u s s e l l , 1988) and t h i s e x p l a i n s why legumes a l t h o u g h w i t h a low c o n t e n t o f NDF but h i g h i n l i g n i n , d i g e s t f a s t e r t h a n g r a s s e s (Smith e t a l . , 1972 and Buxton and R u s s e l l , 1988). I n v i t r o r a t e o f c e l l u l o s e d i g e s t i o n was h i g h e r f o r d e l i g n i f i e d o r c h a r d g r a s s (Darcy and B e y l e a , 1980) and a l f a l f a hay t h a n i n t a c t hays ( B e y l e a e t a l . , 1983). T h i s may a l s o i n p a r t e x p l a i n t h e lo w e r l a g phase o f NDF o b s e r v e d on a l f a l f a hay t h a n CGrS and OGrH ( T a b l e 11) w h i c h a r e graminae i n o r i g i n . I n h e r e n t s p e c i e s d i f f e r e n c e s between legumes and g r a s s e s i n c h e m i c a l and p h y s i c a l c e l l - w a l l c o n s t i t u e n t s and o r remov a l o f c e l l - w a l l p r o t e i n s , c e l l - w a l l a l t e r a t i o n by g r i n d i n g and h y d r a t i o n a l l c o n t r i b u t e t o v a r i a t i o n i n l a g t i m e s (Darcy and B e y l e a , 1980; Shaver e t a l . , 1988 and Buxton and R u s s e l l , 1988). 121 3.4.0. SUMMARY AND CONCLUSION. The r a t e o f DM and NDF d e g r a d a t i o n was h i g h e r f o r RDG t h a n BP and WMR. RDG and BP had s i g n i f i c a n t l y h i g h e r l e v e l s o f h i g h l y s o l u b l e f r a c t i o n though d i f f e r e n t , when compared t o WMR. The s l o w l y d e g r a d a b l e f r a c t i o n was c o n s i s t e n t l y h i g h e r f o r BP DM and NDF t h a n RDG and WMR. Though e f f e c t i v e d e g r a d a b i l i t y o f DM f o r RDG and BP were d i f f e r e n t t h e y were b o t h e x t e n s i v e l y d e g r a d a b l e compared t o WMR. Beet p u l p had t h e h i g h e s t e f f e c t i v e d e g r a d a b i l i t y f o r NDF. Lag t i m e s f o r DM and NDF were h i g h e r f o r BP t h a n WMR and RDG. The l e v e l o f h i g h l y d e g r a d a b l e f r a c t i o n , r a t e o f d e g r a d a t i o n and e f f e c t i v e d e g r a d a b i l i t y of DM were s i g n i f i c a n t l y h i g h e r f o r ALFH t h a n CGrS and OGrH w h i l e t h e r a t e o f NDF d e g r a d a t i o n o f ALFH was s i m i l a r t o CGrS but s i g n i f i c a n t l y h i g h e r t h a n OGrH. However, i n s p i t e o f s i m i l a r r a t e o f NDF d e g r a d a t i o n , t h e amount d i g e s t e d i n OGrH and ALFH was s i g n i f i c a n t l y h i g h e r CGrS; l o n g e r NDF l a g t i m e s were n o t e d f o r CGrS and OGrH r e l a t i v e t o ALFH. V a r i a t i o n i n t h e d e g r a d a t i o n c h a r a c t e r i s t i c s o f DM and NDF such as shown by roughages and a g r o - b y p r o d u c t s can be e x p l o i t e d i n r a t i o n f o r m u l a t i o n f o r r u m i n a n t s (Mertens, 1983). E f f i c i e n t m i c r o b i a l growth r e q u i r e s s u f f i c i e n t and s u s t a i n e d r e l e a s e o f n u t r i e n t s i n t h e rumen. A l f a l f a hay, OGrH and CGrS have been used as roughages i n c o m b i n a t i o n t a k i n g advantage o f t h i s v a r i a b i l i t y . The i n s i t u r u m i n a l b e h a v i o r o f b y p r o d u c t s i s l e s s w e l l known, but a l l i n d i c a t i o n s a r e t h a t t h e y show wide v a r i a t i o n (Varga and Hoover, 1983; Souvant e t a l . , 1985 and Dewhurst e t a l . , 1995). 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The e s t i m a t i o n o f p r o t e i n d e g r a d a b i l i t y i n t h e rumen from i n c u b a t i o n measurements w e i g h t e d a c c c o r d i n g t o r a t e o f passage. J . A g r i c . S c i . (Camb.), 92:499. 125 Poore, M.H., J.A. Moore, T.P. Eck, R.S. S w i n g l e , and C.B. T h e u r e r . 1993. E f f e c t o f f i b e r and r u m i n a l s t a r c h d e g r a d a b i l i t y on t h e s i t e and e x t e n t o f d i g e s t i o n i n d a i r y cows. J . D a i r y S c i . 76:2244. R u i z , T.M., E. B e r n a l , C.R. S t a p l e s , L.E. S o l l e n b e r g e r , and R.N. G a l l a g e r . 1995. E f f e c t o f d i e t a r y n e u t r a l d e t e r g e n t f i b e r c o n c e n t r a t i o n and f o r a g e s o u r c e on performance o f l a c t a t i n g cows. J . D a i r y S c i . 7 8 : 3 0 5 . SAS U s e r ' s Guide. 1990. SAS i n s t i t u t e , I n c . , Cary, NC. Shaver, R.D., L.D. S a t t e r , and A. J o r g e n s e n . 1988. Impact of f o r a g e c o n t e n t on d i g e s t i o n and d i g e s t i b l e passage i n l a c t a t i n g d a i r y cows. J . D a i r y S c i . 71:1556. Sm i t h , L.W., H.K. G o e r i n g , and C.H. Gordon. 1972. R e l a t i o n s h i p o f f o r a g e c o m p o s i t i o n w i t h r a t e s o f c e l l w a l l d i g e s t i o n and i n d i g e s t i b i l i t y o f c e l l w a l l s . J . D a i r y S c i . 55:1140. Souvant, D., D. B e r t r a n d and S. G i g e r . 1985. V a r i a t i o n and p r e v i s i o n o f t h e i n sacco d r y m a t t e r d i g e s t i o n o f c o n c e n t r a t e s and b y p r o d u c t s . Anim. Feed S c i . Tech. 13:7. S u t t o n , J.D., J.A. B i n e s , S.V. Morant, and D.J. Napper. 1987. A c o m p a r i s o n o f s t a r c h y and f i b r o u s c o n c e n t r a t e s f o r m i l k p r o d u c t i o n , energy u t i l i z a t i o n and hay i n t a k e by F r i e s i a n cows. J . A g r i c . S c i . (Camb), 109:135. Swain, S.M., and L.E. Armentano. 1994. Q u a n t i t a t i v e e v a l u a t i o n o f f i b e r from n o n - f o r a g e s o u r c e s used t o r e p l a c e a l a f a l f a s i l a g e . J . D a i r y S c i . 7 7 : 2 3 1 8 . Tamminga, S., A.M. Van Vuren, C.J. Van Der K o e l e n , R.S. K e t e l a a r and P.L. Van Der J o g t . 1990. Ruminal b e h a v i o r o f s t r u c t u r a l c a r b o h y d r a t e s , n o n - s t r u c t u r a l c a r b o h y d r a t e s and c r u d e p r o t e i n from c o n c e n t r a t e i n g r e d i e n t s i n d a i r y cows. Neth. J . A g r i c . S c i . 3 8 : 5 1 3 . Van S o e s t , P . J . 1982. N u t r i t i o n a l E c o l o g y o f t h e Ruminants. 2nd ed., C o r n e l l U n i v e r s i t y P r e s s , I t h a c a . Van S o e s t , P . J . 1986. S o l u b l e c a r b o h y d r a t e s . C o r n e l l N u t r i t i o n C o n f e r e n c e f o r f e e d M a n u f a c t u r e r s . S y r a c u s e M a r r i o t t , E a s t S y r a c u s e , pp. 73. V a r g a , G.A., and W.H. Hoover. 1983. R a t e and e x t e n t o f n e u t r a l d e t e r g e n t f i b e r d e g r a d a t i o n o f f e e d s t u f f s i n - s i t u . J . D a i r y S c i . 66:1209. Waldern, D.E. 1971. A r a p i d m i c r o - d i g e s t i o n p r o c e d u r e f o r n u e t r a l and a c i d d e t e r g e n t f i b e r . Can. J . Anim. S c i . 51:67. 126 Waldo, D.R., and N.A. J o r g e n s e n . 1981. Forages f o r h i g h a n i m a l p r o d u c t i o n . N u t r i t i o n a l f a c t o r s and e f f e c t s o f c o n s e r v a t i o n . J . D a i r y S c i . 64:1207. W a l l , J.S., and J.W. P a u l i s . 1978. Corn and sorghum g r a i n p r o t e i n s . Page 135, in 'Advances i n C e r e a l S c i e n c e and Technology. V o l . I I ' . Y. Pomeranz, ed. Am. As s o c . C e r e a l C h e m i s t s . S t . P a u l , MN. 127 3.6.0. TABLES. T a b l e 9. C h e m i c a l c o m p o s i t i o n o f a g r o - b y p r o d u c t s and roughages used i n i n s i t u experiment(DM b a s i s ) . N u t r i e n t F e e d s t u f f 1 DM OM CP ADF NDF H C e l l Ash EE TNC WMR 94 77 94 16 18 84 14 .30 40 38 26 08 5 84 2 51 33 09 RDG 93 35 95 54 29 64 12 83 31 85 19 02 4 46 2 56 31 49 BP 97 14 92 33 10 36 18 18 28 36 10 18 7 67 0 43 53. 18 ALFH 95 23 91 57 19 90 34 58 41 34 6 76 8 43 1 28 29 05 OGrH 98 17 93 54 6 74 37 56 61 33 23 77 6 46 1 44 24. 03 CGrS 97 02 92 44 11 26 33 75 56 92 23 17 7 56 1 33 22 93 1VMR = wheat m i l l r u n , RDG = r y e d i s t i l l e r s g r a i n s , BP = be e t p u l p , ALFH = a l f a l f a hay, OGrH = o r c h a r d g r a s s hay and CGrS = c o r n - g r a s s s i l a g e 2TNC=Total n o n - s t r u c t u r a l c a r b o h y d r a t e = DM - (CP + NDF + EE + Ash) 128 T a b l e 10. I n s i t u d e g r a d a t i o n c h a r a c t e r i s t i c s o f d r y m a t t e r and n e u t r a l d e t e r g e n t f i b e r o f wheat m i l l r u n , r y e d i s t i l l e r s g r a i n and beet p u l p 1 . D e g r a d a t i o n A g r o - b y p r o d u c t s 3 C h a r a c t e r i s t i c s 2 WMR RDG BP SE 4 DM a (%) 46.60c 57.62a 52.67b 0.72 b (%) 30.96b 27.78b 42.74a 1.00 k d(%/h) 11.21b 27.69a 12.27b 1.44 l a g (h) 0.26b 0.33b 1.61a 0.48 EFDEG (%) 0.05 %/h 67.56b 80.75a 80.64a 0.37 NDF a (%) 7.65b 8.89b 27.68a 1.97 b (%) 42.09c 50.24b 61.83a 1.86 k d(%) 8.56b 19.32a 8.68b 1.68 l a g (h) 0.24b 0.35b 1.91a 0.41 EFDEG (%) 0.05 %/h 33.51c 48.04b 63.36a 0.43 !WMR = Wheat m i l l r u n , RDG = r y e d i s t i l l e r s g r a i n , BP = b e e t p u l p . 2a = r a p i d l y d e g r a d a b l e f r a c t i o n , b = s l o w l y d e g r a d a b l e f r a c t i o n , k d = f r a c t i o n a l r a t e o f d e g r a d a t i o n o f f r a c t i o n b, lag= l a g t i m e , EFDEG = e f f e c t i v e d e g r a d a b i l i t y a t 5 %/h f r a c t i o n a l o u t f l o w r a t e . 3Means i n t h e same row w i t h d i f f e r e n t l e t t e r s a r e s i g n i f i c a n t l y d i f f e r e n t (P<0.05). 4SE = s t a n d a r d e r r o r (n=2) 129 T a b l e 11. I n s i t u d e g r a d a t i o n c h a r a c t e r i s t i c s o f d r y m a t t e r and n e u t r a l d e t e r g e n t f i b e r o f c o r n - g r a s s s i l a g e , o r c h a r d g r a s s hay and a l f a l f a hay 1. D e g r a d a t i o n roughage : C h a r a c t e r i s t i c s 2 CGrS OGrH ALFH SE 4 DM a (%) 21.62b 24.54b 38.00a 1.98 b (%) 38.27b 42.56a 34.19c 1. 55 k d(%/h) 6.29b 6.58b 15.15a 0.51 l a g (h) 2 . l i b 4.33a 1.37b 0.28 EFDEG (%) 40.81c 43.92b 62.05a 0.57 NDF a (%) 11.79a 13 .32a 8.50b 0.74 b (%) 26.66c 43 .74a 33.98b 1. 05 k d(%/h) 7.67ab 6.95b 7.87a 0. 44 l a g (h) 11.30a 10.29b 1.57c 0.15 EFDEG (%) 20.96b 28 .53a 27.67a 0.40 ^ G r S = c o r n - g r a s s s i l a g e , OGrH = o r c h a r d g r a s s hay, ALFH = a l f a l f a hay. 2 a = r a p i d l y d e g r a d a b l e f r a c t i o n , b = s l o w l y d e g r a d a b l e f r a c t i o n , k d = f r a c t i o n a l r a t e o f d e g r a d a t i o n o f f r a c t i o n b, lag= l a g t i m e , EFDEG = e f f e c t i v e d e g r a d a b i l i t y a t 5 %/h f r a c t i o n a l o u t f l o w r a t e . 3Means i n t h e same row w i t h d i f f e r e n t l e t t e r s a r e s i g n i f i c a n t l y d i f f e r e n t (P<0.05). 4SE = s t a n d a r d e r r o r (n=2) 130 CHAPTER 4. THE EFFECT OF DIETS MATCHED FOR RATE OF DEGRADATION OF CARBOHYDRATE AND PROTEIN ON MILK PRODUCTION CHARACTERISTICS OF DAIRY COWS. 4.0. ABSTRACT. Twelve l a c t a t i n g m u l t i p a r o u s H o l s t e i n cows a v e r a g i n g 150 d (40-291 d) po s t p a r t u m , were randomly a s s i g n e d t o one o f f o u r c o n c e n t r a t e d i e t s ; s t e a m - r o l l e d c o r n - f i s h meal (SRC-FM), steam-r o l l e d c o r n - c a n o l a meal (SRC-CM), s t e a m - r o l l e d b a r l e y - f i s h meal (SRB-FM) o r s t e a m - r o l l e d b a r l e y - c a n o l a meal (SRB-CM), i n a t h r e e p e r i o d / f o u r t r e a t m e n t s s w i t c h - b a c k d e s i g n . C o n c e n t r a t e d i e t s were f e d a t a 50:50 r a t i o w i t h a l f a l f a hay (ALFH) and t h e t o t a l f e e d p e r day was a l l o c a t e d a c c o r d i n g t o body w e i g h t , m i l k p r o d u c t i o n and b u t t e r - f a t as p e r NRC, (1989) s t a n d a r d s . Each p e r i o d l a s t e d f o r 28 days s p l i t i n t o a 14 d adju s t m e n t , 7 d i n t a k e and 7 d d i g e s t i b i l i t y and m e t a b o l i s m s e c t i o n s . Cows were f i r s t k e p t i n t h e f r e e s t a l l s e c t i o n o f t h e ba r n f o r t h e f i r s t 14 d t o a d j u s t t o t h e d i e t . S i x cows were t h e n moved t o t h e s t a n c h i o n s e c t i o n o f t h e b a r n f o r i n t a k e s t u d i e s f o r 7d and t h e n moved back t o t h e f r e e s t a l l b a r n . The r e m a i n i n g 6 cows were t h e n moved t o t h e s t a n c h i o n s e c t i o n o f t h e b a r n and o n l y 4 were used f o r a 7 d d i g e s t i b i l i t y and me t a b o l i s m s t u d y . A c o m p u t e r i z e d f e e d i n g system was used f o r c o n c e n t r a t e and ALFH was f e d 4x/day i n t h e f r e e - s t a l l b a r n and f e e d i n g f o r b o t h c o n c e n t r a t e and hay changed t o 4x/day s e p a r a t e l y and i n d i v i d u a l l y f o r each cow when moved t o t h e s t a n c h i o n b a r n . Feed i n t a k e , d i g e s t i b i l i t y and m i l k p r o d u c t i o n (MP) f o r t h e l a s t 5 days o f each p e r i o d were c o n s i d e r e d f o r s t a t i s t i c a l a n a l y s i s . 131 M i l k i n g o f cows was 2x/day (0330 and 1530 h) and samples f o r c o m p o s i t i o n a n a l y s e s were c o l l e c t e d on 2 c o n s e c u t i v e days. A c t u a l d a i l y DMI and DMI (%B.Wt.), were n o t a f f e c t e d by (P>0.05) e i t h e r s o u r c e o f c a r b o h y d r a t e o r p r o t e i n i n t h e d i e t and av e r a g e d ; 23.74, 23.77, 23.84, and 23.54 kg/cow/d; 3.63, 3.65, 3.65, and 3.61 %BWt.; f o r SRC-FM, SRC-CM, SRB-FM, and SRB-CM, r e s p e c t i v e l y . S t a r c h i n t a k e approached s i g n i f i c a n c e (P<0.11) f o r p r o t e i n s o u r c e w h i l e NDF and h e m i - c e l l u l o s e , and ADF i n t a k e were h i g h e r f o r SRB t h a n SRC (P<0.05) and f o r CM t h a n FM (P<0.05), r e s p e c t i v e l y . B a r l e y based d i e t s promoted h i g h e r a c t u a l m i l k y i e l d s and e f f i c i e n c y o f f e e d u t i l i z a t i o n (MP:DMI) t h a n c o r n d i e t s (P<0.01): 25.76, 25.07, 27.59, and 27.40 kg/d: 1.07, 1.04, 1.14, and 1.16, f o r SRC-FM, SRC-CM, SRB-FM and SRB-CM, r e s p e c t i v e l y . S i g n i f i c a n t d i f f e r e n c e s (P<0.05) were d e t e c t e d i n p e r c e n t f a t and s o l i d s - n o t -f a t ; 2.99 and 9.05 f o r b a r l e y ; and 3.54 and 8.69 f o r c o r n . I n a d d i t i o n f e e d i n g b a r l e y based d i e t s r e s u l t e d i n h i g h e r y i e l d o f t o t a l s o l i d s , SNF and p r o t e i n t h a n c o r n d i e t s . DM, OM, s t a r c h , CP, NDF and h e m i - c e l l u l o s e d i g e s t i b i l i t y were s i g n i f i c a n t l y h i g h e r (P<0.05) f o r t h e b a r l e y d i e t s t h a n c o r n . These d a t a showed a b e n e f i c i a l e f f e c t f o r a c t u a l m i l k p r o d u c t i o n , e f f i c i e n c y o f f e e d u t i l i z a t i o n , DMD and OMD, s t a r c h and f i b e r d i g e s t i b i l i t y when d i e t was matched f o r h i g h rumen s t a r c h and p r o t e i n a v a i l a b i l i t y and a l s o when d i e t w i t h h i g h rumen s t a r c h a v a i l a b i l i t y was f e d w i t h p r o t e i n s o u r c e o f moderate rumen p r o t e i n a v a i l a b i l i t y 132 4.1. INTRODUCTION. Ruminants, u n l i k e m o n o - g a s t r i c a n i m a l s , d e r i v e t h e i r p r o t e i n needs from p r o t e i n o f m i c r o b i a l o r i g i n s y n t h e s i s e d i n t h e rumen and t h a t p o r t i o n o f d i e t a r y p r o t e i n t h a t escapes rumen d e g r a d a t i o n . W h i l s t m i c r o b i a l p r o t e i n s u p p l y i s o f t e n s u f f i c i e n t t o meet p r o t e i n needs (Van S o e s t , 1982), t h i s i s not t r u e f o r h i g h p r o d u c i n g d a i r y cows and young growing s t e e r s (ARC, 1980 and NRC, 1989). T h i s i s a l s o t r u e f o r energy needs (NRC, 1989). I t has been s u g g e s t e d t h a t t h e i n c r e a s e d needs f o r p r o t e i n by h i g h p r o d u c i n g cows and f a s t g r o w i n g s t e e r s can be met by p r o v i d i n g p a r t o f t h e d i e t a r y p r o t e i n i n a form w h i c h i s u n d e g r a d a b l e i n t h e rumen b u t a v a i l a b l e i n t h e s m a l l i n t e s t i n e s , t h u s i n c r e a s i n g a m i n o - a c i d (AA) s u p p l i e d t o t h e s m a l l i n t e s t i n e s (ARC, 1980 and NRC, 1989). F e e d i n g t h i s s u p p l e m e n t a l p r o t e i n i s one o f t h e most e x p e n s i v e but most i m p o r t a n t a s p e c t s o f d a i r y c a t t l e n u t r i t i o n . T h e r e f o r e , i t would be p r u d e n t t o maximize rumen m i c r o b i a l p r o t e i n s y n t h e s i s t o i n c r e a s e AA s u p p l y t o t h e s m a l l i n t e s t i n e s and maximize t h e e f f i c i e n c y o f u t i l i z i n g r u m i n a l undegradable p r o t e i n . The most c r i t i c a l n u t r i e n t components t o o p t i m i z e t h e e f f i c i e n c y o f m i c r o b i a l p r o t e i n s y n t h e s i s a r e energy (ATP), a carbon (C) s o u r c e and a n i t r o g e n s o u r c e (N) ( S n i f f e n e t a l . , 1983; Nocek and R u s s e l l , 1988). E f f i c i e n c y o f m i c r o b i a l p r o t e i n s y n t h e s i s , however, r e q u i r e s t h a t b o t h C and N be a v a i l a b l e w i t h i n t h e same t i m e frame and i n p r o p o r t i o n a t e amounts (Nocek and R u s s e l l , 1988; H e r r e r a - S a l d a n a e t a l . , 1990b; Nocek and Tamminga, 1991 and Hoover and S t o k e s , 1991). 133 S t a r c h e s and p r o t e i n s from d i f f e r e n t s o u r c e s have been found t o degrade a t d i f f e r e n t r a t e s ( S p i c e r e t a l . , 1986; Casper and S c h i n g o e t h e , 1989; M a l e s t e i n e t a l . , 1988 and H e r r e r a - S a l d a n a e t a l . , 1990b). S e v e r a l r e s e a r c h e r s (Casper and S c h i n g o e t h e , 1989; McCarthy e t a l . , 1989 and Casper e t a l . , 1990) have r e p o r t e d d e c r e a s e d m i l k p r o d u c t i o n and d r y m a t t e r i n t a k e (DMI) o f cows f e d b a r l e y compared t o t h o s e f e d c o r n . O t h e r s , (DePeters e t a l . , 1985 and G r i n g s e t a l . , 1992) d i d not o b s e r ve t h i s r e s p o n s e . Nocek and Tamminga, (1991) have r e c e n t l y p u b l i s h e d d a t a from d i f f e r e n t e x p e r i m e n t s on t h e e f f e c t o f s t a r c h s o u r c e on m i l k p r o d u c t i o n . They n o t e d t h a t t h e magnitude o f m i l k y i e l d r e s p onse was v a r i a b l e among s t u d i e s . Changes i n m i l k c o m p o s i t i o n were m a i n l y i n f a t c o n t e n t . I n t h e s t u d i e s by McCarthy e t a l . (1989), m i l k p r o d u c t i o n was s i g n i f i c a n t l y h i g h e r f o r cows f e d c o r n d i e t s t h a n b a r l e y d i e t s . They a t t r i b u t e d t h i s i n c r e a s e d p r o d u c t i o n t o a h i g h energy i n t a k e w h i c h was used f o r m i c r o b i a l p r o t e i n s y n t h e s i s and m i l k l a c t o s e s y n t h e s i s . E f f i c i e n c y o f m i c r o b i a l p r o t e i n s y n t h e s i s was not a f f e c t e d by c o r n o r b a r l e y d i e t s , i n c o m b i n a t i o n w i t h SBM o r FM; however p r o t e i n f l o w t o t h e duodenum was h i g h e r f o r cows f e d b a r l e y t h a n c o r n . I f m i l k p r o d u c t i o n was h i g h e r on c o r n d i e t s , t h e n c o r n d i e t s were a b l e t o p r o v i d e enough r u m i n a l d e g r a d a b l e c a r b o h y d r a t e f o r m i c r o b i a l s y n t h e s i s but a l s o an adequate q u a n t i t y o f q u a l i t y u n d e g r a d a b l e p r o t e i n . I n c o n t r a s t , H e r r e r a - S a l d a n a and Huber, (1989) r e p o r t e d h i g h e r m i l k p r o d u c t i o n on b a r l e y based d i e t s t h a n c o r n . T h i s was 134 a t t r i b u t e d t o i n c r e a s e d DM and s t a r c h i n t a k e s and a l s o h i g h e r m i c r o b i a l p r o t e i n s y n t h e s i s ( H e r r e r a - S a l d a n a and Huber, 1989 and H e r r e r a - S a l d a n a e t a l . , 1990a). However, s t a r c h i n t a k e s were confounded w i t h t h e f a c t t h a t s t a r c h c o n t e n t on b a r l e y d i e t s was h i g h e r t h a n on t h e o t h e r t h r e e d i e t s ( H e r r e r a - S a l d a n a e t a l . , 1990a). I t i s t h e o r i z e d t h a t d i e t s a p p r o p r i a t e l y matched f o r d i f f e r i n g r a t e s o f c a r b o h y d r a t e and p r o t e i n d e g r a d a t i o n w i l l s u p p o r t h i g h e r m i l k p r o d u c t i o n , e s p e c i a l l y on d i e t s matched f o r h i g h rumen a v a i l a b i l i t i e s when compared w i t h d i e t s unmatched i n rumen a v a i l a b i l i t i e s o r low i n rumen a v a i l a b i l i t i e s o f c a r b o h y d r a t e and p r o t e i n . The main o b j e c t i v e of t h e ex p e r i m e n t was t o d e t e r m i n e t h e e f f e c t o f f e e d i n g d i e t s matched f o r d i f f e r e n t r a t e s o f c a r b o h y d r a t e and p r o t e i n d e g r a d a t i o n on n u t r i e n t i n t a k e , a p p a r e n t t o t a l t r a c t d i g e s t i b i l i t y , r u m i n a l and b l o o d p a r a m e t e r s and m i l k p r o d u c t i o n c h a r a c t e r i s t i c s o f l a c t a t i n g d a i r y cows. 4.2.0. MATERIALS AND METHODS. 4.2.1. D i e t s . Four complete d i e t s were f o r m u l a t e d a t 50:50 ( c o n c e n t r a t e : r o u g h a g e ) r a t i o . S t e a m - r o l l e d b a r l e y (SRB) and steam-r o l l e d c o r n (SRC) s e r v e d as s o u r c e s o f h i g h l y and s l o w l y d e g r a d a b l e c a r b o h y d r a t e r e s p e c t i v e l y , i n c o m b i n a t i o n w i t h e i t h e r c a n o l a meal (CM) o r f i s h meal (FM) as s o u r c e s o f h i g h l y and s l o w l y d e g r a d a b l e p r o t e i n , r e s p e c t i v e l y . The f e e d i n g r e d i e n t s were chosen because 135 t h e r e a r e commonly used i n d a i r y c a t t l e r a t i o n s and a l s o f o r t h e i r wide d i f f e r e n c e s i n t h e r a t e o f s t a r c h ( T a b l e 6) and p r o t e i n d e g r a d a t i o n (Madsen, 1985). A l l t h e i n g r e d i e n t s were p r e p a r e d a t A g r i c u l t u r e Canada R e s e a r c h S t a t i o n F e e d m i l l ( A g a s s i z , BC). The b a r l e y and c o r n g r a i n were s t e a m - r o l l e d a t a p p r o x i m a t e l y 75 °C ( p r e s s u r e , 15 P s i ) . The g r a i n s used i n t h i s e x p e r i m e n t and t h o s e used i n t h e c h a p t e r 2 f o r n y l o n bag s t u d i e s a r e from d i f f e r e n t s o u r c e s . B o t h FM and CM had been ground and a b i n d e r added b e f o r e p e l l e t i n g and f e e d i n g . A l l d i e t s were f o r m u l a t e d t o c o n t a i n 16% CP and 1.7 M c a l / k g , n e t energy of l a c t a t i o n (NE L ) o f DM on average. A l f a l f a hay was t h e roughage p o r t i o n o f t h e d i e t . I n g r e d i e n t c o m p o s i t i o n , c h e m i c a l c o m p o s i t i o n o f t h e major d i e t a r y i n g r e d i e n t s and c a l c u l a t e d c h e m i c a l c o m p o s i t i o n o f t h e d i e t s a r e shown t a b l e s 12, 13 and 14 r e s p e c t i v e l y . 4.2.2. Cow management and e x p e r i m e n t a l d e s i g n . Twelve m u l t i p a r o u s l a c t a t i n g H o l s t e i n , 150 d (40-291 d) p o s t p a r t u m w i t h average m i l k p r o d u c t i o n o f 29 d (19-45 kg/d) cows were used i n a t h r e e p e r i o d - s w i t c h - b a c k d e s i g n (Lucas, 1956). A f o u r t r e a t m e n t - t h r e e p e r i o d sequence was chosen (Appendix 2) . The t r e a t m e n t s were a s s i g n e d t o numbers (1-4) w h i c h were t h e n used f o r r a n d o m i z a t i o n . The cows were th e m s e l v e s randomly a s s i g n e d t o t h e sequences s e p a r a t e l y f o r each p e r i o d . Weight o f cows was t a k e n b e f o r e t h e s t a r t o f t h e e x p e r i m e n t and a t t h e end o f each e x p e r i m e n t a l p e r i o d . Water and c o b a l t i o d i z e d s a l t b l o c k were a v a i l a b l e a t a l l t i m e s . The cows were i n i t i a l l y housed i n t h e f r e e 136 s t a l l s e c t i o n o f t h e ba r n d u r i n g t h e a d j u s t m e n t p e r i o d days and a l t e r n a t e groups o f 6 cows were t h e n moved t o t h e s t a n c h i o n s e c t i o n o f t h e b a r n f o r e i t h e r i n t a k e o r d i g e s t i b i l i t y and m e t a b o l i s m s t u d i e s f o r 5 days. 4.2.3. N y l o n bag s t u d i e s . N y l o n bag s t u d i e s , as o u t l i n e d i n c h a p t e r 2, were done f o r s e v e r a l f e e d i n g r e d i e n t s (SRC, SRB, FM, CM and ALFH) . The cows were i n d i v i d u a l l y f e d a s t a n d a r d c o n c e n t r a t e (3.0 kg/d-16% d a i r y t e x t u r e d feed) and roughage d i e t (5.5 kg/d-60% A l f a l f a hay and 40 % g r a s s hay) f o u r t i m e s / d a y . The bags used i n t h e s t u d y measured 10x5 cm i n t e r n a l d i a m e t e r and had an average p o r e s i z e o f 52+2 /Lim. The edges were h e a t s e a l e d l e a v i n g one w i d t h s i d e open. The i n c u b a t i o n t i m e s i n v o l v e d were 0, 2, 4, 8, 12, 18, 24, 36, and 48 h. Feed samples were ground t h r o u g h a 2.0 mm s c r e e n u s i n g a W i l e y M i l l (model #3) . Two-three grams o f d r i e d t e s t m a t e r i a l were q u a n t i t a t i v e l y weighed i n t o i n c u b a t i o n bags (40-60mg/cm2) f o r each i n c u b a t i o n t i m e . The bags were t i g h t l y s e c u r e d u s i n g o r d i n a r y o f f i c e r u b b e r bands t o s t o p m a t e r i a l from coming out o f t h e bags. The bags were t h e n p u t i n b i g p o l y e s t e r mesh bags m e a s u r i n g 25x4 0 cm w i t h a p o r e - s i z e o f 3 mm t o a l l o w rumen f l u i d go i n and o u t . The s m a l l i n c u b a t i o n n y l o n bags were removed from t h e b i g bags and washed i n a washing machine 4-5 t i m e s a f t e r f i l l i n g t h e machine w i t h w a t e r and a g i t a t e d f o r about 5 m i n u t e s / t i m e . The washed bags were d r i e d i n a f o r c e d a i r oven a t 55°C t i l l c o n s t a n t w e i g h t . Four 137 bags p e r t e s t f e e d were i n c l u d e d i n t h e washing t o a c t as z e r o hour d i s a p p e a r a n c e a f t e r i n i t i a l l y washing them i n w a t e r a t 39°C f o r 30 m i n u t e s and t h e n washed t o g e t h e r w i t h r u m i n a l l y i n c u b a t e d bags. The d r i e d d u p l i c a t e i n c u b a t e d samples were c o m p o s i t e d f o r each cow d u r i n g g r i n d i n g t h r o u g h a 0.5 mm s c r e e n u s i n g a Brinkman m i c r o g r i n d e r , and s t o r e d under room t e m p e r a t u r e f o r c h e m i c a l a n a l y s i s . Zero hour and rumen i n c u b a t e d samples f o r SRC and SRB were a n a l y s e d f o r DM and s t a r c h w h i l e FM and CM were a n a l y s e d f o r DM and CP. The a l f a l f a hay was a n a l y s e d f o r DM, CP and NDF. The rumen d e g r a d a t i o n c h a r a c t e r i s t i c s o f c e r e a l s and p r o t e i n supplements were a n a l y s e d s e p a r a t e l y u s i n g t - t e s t (Cochran and Cox, 1969) a c c o r d i n g t o GLM o f t h e S t a t i s t i c a l A n a l y s i s I n s t i t u t e (SAS, 1990) . 4.2.4. Nutrient intake and apparent t o t a l t r a c t d i g e s t i b i l i t y . The cows were i n d i v i d u a l l y f e d c o n c e n t r a t e s w i t h a computer c o n t r o l l e d g r a i n f e e d e r w h i l e i n t h e f r e e s t a l l b a r n and t h e amount o f f e e d consumed was computer r e c o r d e d . The f e e d was a l l o c a t e d t o each cow a c c o r d i n g t o body w e i g h t , a c t u a l m i l k p r o d u c t i o n and b u t t e r f a t p e r c e n t a g e a t t h e s t a r t o f each p e r i o d . A l f a l f a hay was f e d ad l i b i t u m from common f e e d bunks f o r a l l cows and was f e d f o u r t i m e s p e r day a t 0800, 1330, 2000 and 0130 h. C o n c e n t r a t e s were sampled e v e r y o t h e r day and hay was sampled e v e r y day. A sample of weigh-back was t a k e n d a i l y d u r i n g t h e e x p e r i m e n t a l p e r i o d . A f t e r a 10 d a d j u s t m e n t t o t h e d i e t , s i x cows were t r a n s f e r r e d t o t h e s t a n c h i o n b a r n where t h e y were i n d i v i d u a l l y s e c u r e d and f e d 138 a d - l i b i t u m f o r 3 days o f t h e e x p e r i m e n t a l s t a g e t o e s t a b l i s h i n d i v i d u a l i n t a k e s . I n t a k e was measured f o r 7 days and t h e n t h e cows were moved back t o t h e f r e e s t a l l b a r n . A p p r o p r i a t e a l l o t m e n t s ( a c c o r d i n g t o body w e i g h t , m i l k p r o d u c t i o n l e v e l and b u t t e r f a t ) o f c e r e a l and a p r o t e i n supplement were weighed and mixed b e f o r e b e i n g o f f e r e d , s e p a r a t e from hay. Hay was f e d a d - l i b i t u m and i n t a k e r e c o r d e d . The cows were f e d f o u r t i m e s p e r day as p r e v i o u s l y mentioned f o r hay. A f t e r 7 days o f i n t a k e measurement, cows were t a k e n back t o t h e f r e e s t a l l b a r n and t h e r e m a i n i n g s i x were moved t o t h e s t a n c h i o n b a r n f o r d i g e s t i b i l i t y and m e t a b o l i s m s t u d i e s f o r t h e l a s t 7 days o f each p e r i o d . These cows were f e d c l o s e t o t h e i r maximum i n t a k e l e v e l . T h i s was a c h i e v e d by e s t a b l i s h i n g maximum i n t a k e w i t h i n 2 t o 3 days. D i g e s t i b i l i t y and m e t a b o l i c s t u d i e s were done i n t h e l a s t 5 days o f each p e r i o d . One cow from each d i e t a r y t r e a t m e n t was randomly chosen f o r d i g e s t i b i l i t y and m e t a b o l i s m s t u d i e s . Weigh back samples were t a k e n d a i l y f o r each cow w h i l e i n t h e s t a n c h i o n b a r n . One cow from t h e d i g e s t i b i l i t y group was removed due t o an i n j u r y t o t h e l e g s and was r e p l a c e d by a n o t h e r from t h e same group. The t o t a l number o f cows used f o r f e e d i n t a k e and m i l k p r o d u c t i o n c h a r a c t e r i s t i c s d a t a was 11. C o n t i n u o u s f e e d i n g o f cows was adopted t o mimic farm c o m p u t e r i s e d f e e d i n g c o n d i t i o n s and ensure a c o n t i n u o u s s u p p l y o f energy and n i t r o g e n t o t h e rumen which has been shown t o i n c r e a s e e f f i c i e n c y o f b a c t e r i a l growth i n v i t r o (Henning e t a l . , 1991). The t o t a l f e c a l c o l l e c t i o n p r o c e d u r e was used f o r d i g e s t i b i l i t y s t u d i e s . Wooden boxes were p l a c e d b e h i n d each cow as 139 f e c a l c o l l e c t i n g v e s s e l s . U r i n e cups, f a s t e n e d w i t h a h a r n e s s t o each cow, a l l o w e d f o r s e p a r a t i o n o f u r i n e from f e c e s . The u r i n e was d i r e c t e d i n t o b u c k e t s u s i n g vacuum c l e a n e r hose. Feces f o r each cow were weighed d a i l y , t h o r o u g h l y mixed and about 2-3kg sample was k e p t f o r f u r t h e r p r o c e s s i n g and a n a l y s i s . The samples were s t o r e d i n a f r e e z e r . A t t h e end o f t h e e x p e r i m e n t , t h e samples were thawed, mixed t h o r o u g h l y u s i n g a commercial dough m i x e r f o r each cow and p e r i o d . A sub-sample f o r c h e m i c a l a n a l y s i s was t a k e n on w h i c h DM, OM and n u t r i e n t a n a l y s e s were performed a c c o r d i n g t o methods p r e v i o u s l y mentioned. ' A t t h e end o f each e x p e r i m e n t a l p e r i o d , g r a i n , p r o t e i n supplements and hay f e e d samples were c o m p o s i t e d and subsampled. A l f a l f a hay samples i n c l u d i n g weigh-backs were f i r s t chopped i n a s h r e d d e r - g r i n d e r (Mighty Mac Compost Shredder g r i n d e r , Amerind M a c k i s s i c , P a r k e r F o r d . PA) w i t h a 2.5 cm s c r e e n t o reduce p a r t i c l e s i z e and t h e r e f o r e f a c i l i t a t e s u b s a m p l i n g . C o n c e n t r a t e mix and hay weigh-back from t h e s t a n c h i o n b a r n f e e d i n g were c o m p o s i t e d s e p a r a t e l y f o r each cow and p e r i o d . An amount s u f f i c i e n t f o r t h e r e q u i r e d c h e m i c a l a n a l y s e s and n y l o n bag s t u d i e s was d r i e d i n a f o r c e d a i r - o v e n a t 60°C f o r 48 h b e f o r e b e i n g ground u s i n g a 1.0 mm s c r e e n . D u p l i c a t e ground samples were c o m p o s i t e d and t h o r o u g h l y mixed f o r each f e e d o r weigh-back, f o r each a n i m a l and each p e r i o d b e f o r e b e i n g subsampled and packed i n p o l y e t h y l e n e sample bags. A l l samples were s t o r e d a t room t e m p e r a t u r e f o r a p p r o p r i a t e c h e m i c a l a n a l y s e s . 140 4.2.5. A n a l y t i c a l p r o c e d u r e s . Methods f o r c h e m i c a l a n a l y s i s o f f e e d , weigh-back and f e c a l samples a r e as d e s c r i b e d i n Chapter 2. Weigh-back samples were a n a l y s e d f o r a l l n u t r i e n t s e x c e p t GE, EE, Ca and P. C a l c i u m (Ca), and phosphorus (P) were a n a l y s e d a c c o r d i n g t o t h e methods o f Heckman (1967) and P a r k i n s o n and A l l e n , (1975). Feed, weigh-back and f e c a l d a t a were used t o c a l c u l a t e v o l u n t a r y f e e d and n u t r i e n t i n t a k e and t o t a l a p p a r e n t d i g e s t i b i l i t y . NDF f o r c o n c e n t r a t e and weigh-back was a n a l y s e d by c o m b i n i n g t h e Ankom f i l t e r bag t e c h n i q u e (FTB) (Komarek, 1993) and t h e NDF p r o c e d u r e a c c o r d i n g t o Waldern, (1971). Samples (0.35g) were weighed i n t o pre-weighed Ankom made N y l o n bags (5cm x 5cm). The mouths o f t h e bags were sown (double seam) u s i n g a h o u s e - h o l d sewing machine t o p r e v e n t m a t e r i a l from g e t t i n g out o f t h e bags and t h e n weighed. The bags were r e f l u x e d f o r an hour i n a beaker c o n t a i n i n g t h e r e q u i r e d amount of NDF s o l u t i o n (3 5ml/bag). A f t e r one hour t h e bags were washed i n an e x c e s s amount of h o t w a t e r . A l l bags were d r i e d i n a f o r c e d a i r oven a t 105°C o v e r n i g h t , d e s i c c a t e d and t h e n weighed. A l l c h e m i c a l a n a l y s e s were done i n d u p l i c a t e . Feed i n t a k e and a p p a r e n t d i g e s t i b i l i t y was c a l c u l a t e d a c c o r d i n g t o t h e f o l l o w i n g f o r m u l a e : V o l u n t a r y i n t a k e / d a y = q u a n t i t y o f f e e d g i v e n - q u a n t i t y o f weigh-back ( E q u a t i o n 4.2);. D i g e s t i b i l i t y C o e f f i c i e n t = ( ( I N - FN)/IN)*100 ( E q u a t i o n 4.3); 141 where, IN = I n t a k e ( n u t r i e n t ) , FN = f e c a l ( n u t r i e n t ) . 4.2.6. Rate o f passage. L i q u i d and p a r t i c u l a t e m a t t e r f l o w r a t e s were measured u s i n g c o b a l t - e t h y l e n e d i a m i n e t e t r a a c e t i c a c i d (Co-EDTA) and chromium mordanted f i b e r , r e s p e c t i v e l y . Co-EDTA was p r e p a r e d a c c o r d i n g t o Uden e t a l (1980) and a d m i n i s t e r e d as a s i n g l e dose on t h e f i r s t day o f f e c a l c o l l e c t i o n . 37.5g o f Co-EDTA (5g o f Co) was f i r s t d i s s o l v e d i n 1 l i t e r o f d e i o n i z e d w a t e r and f l u s h e d down i n t o t h e rumen u s i n g a R h e i n h a r d o r a l t u b e . About 2 l i t e r s o f water was f l u s h e d down t h e tube f o l l o w i n g marker a d m i n i s t r a t i o n i n o r d e r t o make s u r e t h a t a l l o f th e marker went i n t o t h e a n i m a l . Chromium-mordanted f i b e r was a l s o p r e p a r e d a c c o r d i n g t o Uden e t a l . (1980). A s m a l l amount o f f e e d was mixed w i t h lOOg (3g Cr) of Cr-mordanted f i b e r . I n a d d i t i o n , a s m a l l amount o f molasses ( B l a c k s t r a p M o l a s s e s , p r o d u c t o f West I n d i e s , Croby M o l a s s e s C o . l t d , ST.Johns NB, Canada) was added and mixed t o improve f i b e r a c c e p t a b i l i t y . The a n i m a l s were o b s e r v e d f o r any r e f u s a l s . Only one cow showed r e l u c t a n c e t o consume a l l t h e marker m i x t u r e . The l e f t -o v e r marker was weighed and a sample s t o r e d f o r Cr a n a l y s i s . F e c a l c o l l e c t i o n f o r marker e s t i m a t i o n s t a r t e d 12 h a f t e r marker a d m i n i s t r a t i o n and t h e r e a f t e r , a t t h r e e hour i n t e r v a l s up t o 72 h p o s t d o s i n g a f t e r w hich a 6 h i n t e r v a l was f o l l o w e d f o r a f u r t h e r 142 52 h. F e c a l samples were t a k e n as gr a b samples. Sampled f e c e s were s c r a p e d i n t o a c o l l e c t i n g b u cket o r t o one o f t h e s i d e s o f t h e f e c a l c o l l e c t i o n box o r a p l a s t i c c o v e r was p u t on t o p o f t h e o l d f e c e s t o a v o i d m i x i n g w i t h t h e new ones. Samples were p u t i n p l a s t i c bags and s t o r e d i n a f r e e z e r . A t t h e end o f t h e ex p e r i m e n t t h e samples were thawed and d r i e d a t 60°C f o r 48 h and ground t h r o u g h a 1.0 mm s c r e e n u s i n g a W i l e y m i l l . The samples were s t o r e d a t room t e m p e r a t u r e f o r marker a n a l y s e s . Samples f o r f e c a l c o b a l t c o n c e n t r a t i o n were p r e p a r e d by a s h i n g 0.5 g o f f e c a l m a t e r i a l a t 500°C o v e r n i g h t . F i v e ml o f 4 N HC1 was added a f t e r t h e samples had c o o l e d . The m i x t u r e was a l l o w e d t o s i t f o r 30 m i n u t e s a t room t e m p e r a t u r e b e f o r e d i l u t i n g w i t h 15 ml d e i o n i z e d w a t e r and s u b s e q u e n t l y c e n t r i f u g i n g a t 10,000 x g f o r 10 m i n u t e s . C o b a l t a b s o r p t i o n was r e a d u s i n g an a i r - a c e t y l e n e flame w i t h a P e r k e n Elmer Atomic A b s o r p t i o n S p e c t r o p h o t o m e t e r (Model 4000 Perken-Elmer C o r p o r a t i o n Norwalk, CT) ( C h r i s t i a n and Feldman, 1970). I t was r e a d a t 241 nm wa v e l e n g t h . Chromium samples were p r e p a r e d by w e i g h i n g 0.5 g o f f e c a l m a t e r i a l i n t o pre-weighed 50 ml er l y n m e y e r f l a s k . T h i r t y mis o f 4 M HN03 was added and samples were l e f t t o s i t f o r 4 h o u r s a t room t e m p e r a t u r e . The samples were t h e n h e a t e d t o 7 5°C f o r 12 h, c o o l e d and t h e g r o s s w e i g h t t a k e n so as t o d e t e r m i n e t h e amount o f r e m a i n i n g s o l u t i o n . A f t e r t h a t t h e samples were c e n t r i f u g e d a t 12,000 x g f o r 10 m i n u t e s . The s u p e r n a t a n t was decanted i n t o t e s t - t u b e s and r e a d d i r e c t l y . A p p r o p r i a t e d i l u t i o n s f o r samples w i t h a r e a d i n g h i g h e r 143 t h a n t h e h i g h e s t s t a n d a r d were made w i t h d e i o n i z e d w a t e r . The Cr c o n c e n t r a t i o n was d e t e r m i n e d u s i n g a t o m i c a b s o r p t i o n s p e c t r o s c o p y ( C h r i s t i a n and Feldman, 1970 and Fenton and Fen t o n , 1979) as f o r Co a n a l y s i s and r e a d a t 357.7 nm wav e l e n g t h . The r a t e o f passage was c a l c u l a t e d as t h e r a t e o f d e c l i n e i n t h e n a t u r a l l o g a r i t h m o f c o b a l t o r chromium c o n c e n t r a t i o n i n t h e f e c e s a f t e r peak c o n c e n t r a t i o n . I t was assumed t h a t one d e f e c a t i o n o c c u r r e d m i d p o i n t i n t h e i n t e r v a l between c o l l e c t i o n s as proposed by F a i c h n e y , (198 0) 4.2.7. B l o o d Sampling. B l o o d samples were t a k e n on t h e l a s t day o f each e x p e r i m e n t a l p e r i o d b e f o r e t h e a f t e r - n o o n f e e d i n g and 2.5 h a f t e r f e e d i n g from t h e f o u r cows on t h e met a b o l i s m s t u d y . The b l o o d was c o l l e c t e d i n 10 ml h e p a r i n i z e d t u b e s from t h e c o c c y g e a l v e i n . I t was i m m e d i a t e l y c e n t r i f u g e d a t 2000 x g f o r 10 m i n u t e s . The serum was d e c a n t e d i n t o s m a l l v i a l s , s t o r e d i n a f r e e z e r and l a t e r a n a l y s e d f o r b l o o d - u r e a -n i t r o g e n (BUN) and b l o o d g l u c o s e (BG) u s i n g Kodak Ektachem DT s l i d e s ( C l i n i c a l P r o d u c t s D i v i s i o n , Eastman Kodak Co., R o c h e s t e r , NY) . 4.2.8. Rumen s a m p l i n g . Rumen f l u i d was c o l l e c t e d on t h e l a s t day a t t h e same t i m e as b l o o d s a m p l i n g . Samples were c o l l e c t e d j u s t b e f o r e t h e a f t e r - n o o n f e e d i n g and 2.5 h t h e r e a f t e r . A r u b b e r t u b e p e r f o r a t e d on one end was used t o c o l l e c t t h e f l u i d a f t e r a p p l y i n g vacuum u s i n g a vacuum 144 pump. A R e i n h a r d p i p e was f i r s t p l a c e d i n t o t h e t h r o a t o f t h e a n i m a l b e f o r e t h e r u b b e r t u b i n g was pushed i n t o t h e rumen. The pH of t h e f l u i d was i m m e d i a t e l y measured u s i n g a pH meter. The samples were s t o r e d i n a f r e e z e r a t - 2 0 ° C . B e f o r e a n a l y s i s t h e rumen samples were thawed a t room t e m p e r a t u r e and c e n t r i f u g e d a t 27,000 g f o r 10 mi n u t e s a t 4°C (McCarthy e t a l . , 1989) . Ten ml o f t h e s u p e r n a t a n t was t r e a t e d w i t h 2 ml o f 25% metap h o s p h o r i c a c i d . The s u p e r n a t a n t was used f o r rumen-ammonia-nitrogen (rumen NH3-N) a n a l y s i s a c c o r d i n g t o Chaney and Marbach, (1962) u s i n g a T e c h n i c o n A u t o a n a l y s e r I I (as a m a n i f o l d and p r o p o r t i o n i n g pump) a c c o r d i n g t o t h e method o f W a l l and Gehrke, (1975). The rumen NH3-N was a n a l y s e d d i r e c t l y w i t h o u t pre-wet d i g e s t i o n . V o l a t i l e f a t t y a c i d s (VFA's) were a n a l y s e d a c c o r d i n g t o E r w i n e t a l . (1961). 4.2.9. M i l k p r o d u c t i o n and c o m p o s i t i o n . A l l cows on t h e t r i a l were m i l k e d t w i c e d a i l y s t a r t i n g a t 0330 and 1530 h and m i l k w e i g h t was r e c o r d e d f o r each cow. M i l k samples from b o t h a.m. and p.m. m i l k i n g s were t a k e n f o r each cow on 2 c o n s e c u t i v e days i n t h e l a s t 5 days o f each p e r i o d . A p o t a s s i u m d i c h r o m a t e p i l l , a p r e s e r v a t i v e , was added t o each sample tu b e a t t h e t i m e o f c o l l e c t i n g t h e samples. The morning and a f t e r - n o o n samples were i m m e d i a t e l y c o m p o s i t e d f o r each cow and each day i n each p e r i o d . The samples were f r o z e n and l a t e r a n a l y s e d f o r m i l k p r o t e i n , f a t , t o t a l - s o l i d s (TS) and s o l i d s - n o t - f a t (SNF). M i l k f a t and p r o t e i n were a n a l y s e d a t t h e D a i r y Herd Improvement S e r v i c e s 145 l a b o r a t o r y ( A b b o t s f o r d , BC). T o t a l s o l i d s (TS) were d e t e r m i n e d by a r e g u l a r DM d e t e r m i n a t i o n (AOAC, 1984). A 10 ml sample o f a w e l l -mixed m i l k sample was oven d r i e d i n an a l u m i n i u m pan a t 100°C f o r 24 h. S o l i d s - n o t - F a t (SNF) was c a l c u l a t e d by t h e d i f f e r e n c e between TS and f a t c o n t e n t . Y i e l d s o f t h e above m i l k components were c a l c u l a t e d f o r t h e l a s t 5 days of each p e r i o d by a v e r a g i n g t h e c o n t e n t v a l u e s f o r t h e two m i l k s a m p l i n g days. M i l k p r o d u c t i o n v a l u e s were used t o c a l c u l a t e 3.5% f a t - c o r r e c t e d - m i l k (3.5% FCM) and s o l i d s - c o r r e c t e d m i l k (SCM) ( T y r r e l l and R e i d , 1965), y i e l d o f f a t and p r o t e i n and m i l k p o d u c t i o n g r o s s e f f i c i e n c i e s . The g r o s s e f f i c i e n c y was c a l u l a t e d as t h e r a t i o o f m i l k p r o d u c t i o n ( a c t u a l o r 3.5% FCM) t o d r y m a t t e r o r o r g a n i c m a t t e r i n t a k e . 3.5%FCM=(0.4255xlbs m i l k ) + [ 1 6 . 4 2 5 x ( % f a t / 1 0 0 ) x l b s m i l k ) ( E q u a t i o n 4.4); SCM=(12.3xlbs f a t ) + ( 6 . 5 6 x l b s SNF)-(0.0752xM) ( E q u a t i o n 4.5); 4.2.10. S t a t i s t i c a l analysis. I n t a k e , d i g e s t i b i l i t y , b l o o d , r u m i n a l and m i l k c h a r a c t e r i s t i c s d a t a were s u b j e c t e d t o a n a l y s i s o f v a r i a n c e u s i n g t h e G e n e r a l L i n e a r Model p r o c e d u r e (SAS I n s t i t u t e , Cary, NC, 1990). The s t a t i s t i c a l model used t o h a n d l e s w i t c h - b a c k d e s i g n s u s i n g t h e SAS package (Sanders and Gaynor, 1987) and i s shown below; Yjki = M + C o w j + bjPk + P e r i o d k + T r t , + Ejkl ( E q u a t i o n 4.6); 146 Where: Yjkl = o b s e r v e d r e s p o n s e o f t h e j * cow i n t h e k ^ p e r i o d r e c e i v i n g t h e 1th t r e a t m e n t , fi = o v e r a l l mean, CoWj = e f f e c t o f t h e j * i n d i v i d u a l cow, bj = p a r t i a l r e g r e s s i o n c o e f f i c i e n t o f t h e r e s p o n s e v a r i a b l e on p e r i o d f o r t h e j * cow, P k = k"1 p e r i o d , P e r i o d k = ( c l a s s v a r i a b l e ) e f f e c t o f t h e k* p e r i o d ( e s t i m a t e s environment p e r i o d e f f e c t t h r o u g h o u t t h e s t u d y , T r t , = e f f e c t o f t h e 1th t r e a t m e n t ; Ejkl = random e r r o r a s s o c i a t e d w i t h t h e j k l * o b s e r v a t i o n ( e s t i m a t e d from p o o l i n g o f h i g h e r o r d e r i n t e r a c t i o n i n v o l v i n g p e r i o d , t r e a t m e n t , and cow, w h i c h i s c o n s i s t e n t w i t h t h e e r r o r t e rm components d e s c r i b e d by L u cas, (1956). The bjP k term was o m i t t e d when a n a l y s i n g f o r d i g e s t i b i l i t y , r u m i n a l and b l o o d d a t a . A two way a n a l y s i s o f v a r i a n c e was used t o a n a l y s e t h e d a t a and o r t h o g o n a l c o n t r a s t s ( p r e - p l a n n e d comparison) were used t o compare t h e e f f e c t o f c a r b o h y d r a t e and p r o t e i n s o u r c e and whether t h e r e was an i n t e r a c t i o n between t h e two a c c o r d i n g t o Cochran and Cox, (1969). S i m p l e c o - v a r i a n c e a n a l y s i s was used t o h a n d l e r u m i n a l and b l o o d d a t a a c c o r d i n g t o Cochran and Cox (1969) . The b e f o r e f e e d i n g o b s e r v a t i o n (0 h) was used as a c o v a r i a t e t o t h e 2.5 h p o s t f e e d i n g o b s e r v a t i o n . V a l u e s f o r VFAs o f one cow on BFM i n p e r i o d (0 h) were v e r y low and was t h e r e f o r e n o t c o n s i d e r e d i n t h e a n a l y s i s . L e a s t s i g n i f i c a n t d i f f e r e n c e was used f o r t h e i n t e r a c t i o n f o r a l l d a t a . 4.3.0. RESULTS AND DISCUSSION. 4.3.1. I n s i t u T r i a l . T a b l e s 15a and 15b show t h e rumen d e g r a d a t i o n c h a r a c t e r i s t i c s o f f e e d i n g r e d i e n t s used i n t h e m i l k p r o d u c t i o n t r i a l . Note t h a t comparisons were made on a w i t h i n s o u r c e o f c a r b o h y d r a t e o r p r o t e i n b a s i s . A l f a l f a hay was not i n c l u d e d i n t h e s t a t i s t i c a l a n a l y s i s ( T a b l e 15a). I t i s however i m p o r t a n t t o mention t h a t v a l u e s f o r t h e r a t e o f d e g r a d a t i o n o f DM and NDF i n c l u d i n g e x t e n t o f d e g r a d a t i o n o f DM f o r a l f a l f a hay a r e s i m i l a r t o t h o s e r e c e n t l y r e p o r t e d by A l h a d r a m i and Huber, (1992) and Beauchemin e t a l . (1994) f o r a l f a l f a hay o f s i m i l a r c h e m i c a l c o m p o s i t i o n i n CP, ADF and NDF. The r a p i d l y d e g r a d a b l e NDF f r a c t i o n r e p o r t e d ( T a b l e 15a) i s s i m i l a r t o t h a t p r e v i o u s l y r e p o r t e d f o r a l f a l f a hay w i t h ADF c o n t e n t o f 38% b u t t h e r a p i d l y d e g r a d a b l e DM f r a c t i o n was h i g h e r t h a n t h a t 148 r e p o r t e d by A l h a d h r a m i and Huber, (1992). The v a l u e s f o r r a p i d l y d e g r a d a b l e f r a c t i o n and r a t e o f d e g r a d a t i o n o f DM f o r a l f a l f a hay a r e a l s o c o n s i s t e n t w i t h t h o s e r e p o r t e d i n T a b l e 11. M i r e t a l . (1991) have r e p o r t e d DM d e g r a d a t i o n c h a r a c t e r i s t i c s f o r a l f a l f a hay (n o t i d e n t i f i e d ) as 36%, 34%, 16 %/h and 2 h f o r r a p i d l y and p o t e n t i a l l y d e g r a d a b l e DM, r a t e o f d e g r a d a t i o n and l a g t i m e f o r DM, b e i n g i n c o n s i s t e n t w i t h our v a l u e s ( T a b l e 15a). However, t h e e f f e c t i v e d e g r a d a b i l i t y o f DM r e p o r t e d h e r e ( T a b l e 15a) was s i m i l a r t o t h a t r e p o r t e d by M i r e t a l . (1991) a t a f r a c t i o n a l o u t f l o w r a t e o f 5 %/h. The most l i k e l y r e a s o n f o r t h i s i s t h a t t h e hays were o f d i f f e r e n t m a t u r i t y . C e r e a l (SRC and SRB) d e g r a d a t i o n c h a r a c t e r i s t i c s a r e shown i n T a b l e 15a. Ex c e p t f o r a l a c k o f s i g n i f i c a n c e (P>0.05) o f l a g and s l o w l y d e g r a d a b l e f r a c t i o n o f DM and s t a r c h , a l l d e g r a d a t i o n c h a r a c t e r i s t i c s were s i g n i f i c a n t l y h i g h e r (P<0.05) f o r SRB t h a n SRC ( T a b l e 15a). Most o f t h e s e d e g r a d a t i o n c h a r a c t e r i s t i c s a r e c o n s i s t e n t w i t h o t h e r f i n d i n g s ( H e r r e r a - S a l d a n a e t a l . , 1990b; Tamminga e t a l . , 1990; H u s s e i n e t a l . , 1991a and G r i n g s e t a l . , 1992). V a l u e s f o r d e g r a d a t i o n r a t e s o f DM and s t a r c h were s i m i l a r t o t h o s e r e p o r t e d by H e r r e r a - S a l d a n a e t a l . (1990b) and G r i n g s e t a l . (1992) f o r c o r n . V a l u e s f o r t h e s e c h a r a c t e r i s t i c s were h i g h e r f o r b a r l e y i n our case t h a n r e p o r t e d by t h e s e w o r k e r s . E f f e c t i v e d e g r a d a b i l i t y a t an o u t f l o w r a t e o f 9.0 %/h f o r DM r e p o r t e d i n t h i s s t u d y , f a l l s w i t h i n t h e range o f v a l u e s r e p o r t e d by G r i n g s e t a l . (1992) f o r b o t h c o r n and b a r l e y a t a r a t e o f passage o f 8.0 %/h. 149 However e f f e c t i v e d e g r a d a b i l i t y f o r s t a r c h was somewhat lo w e r i n our case t h a n t h a t r e p o r t e d by G r i n g s e t a l . (1992). The s i g n i f i c a n t l y h i g h e r (P<0.05) v a l u e s o f DM d e g r a d a t i o n c h a r a c t e r i s t i c s o f SRB t h a n SRC would s u g g e s t a h i g h d i g e s t i b i l i t y o f OM as a r e s u l t o f h i g h e r r u m i n a l n u t r i e n t d e g r a d a b i l i t y such as CP ( T a b l e 15a). D i f f e r e n c e s i n n u t r i e n t d e g r a d a t i o n c h a r a c t e r i s t i c s between b a r l e y and c o r n can be a t t r i b u t e d t o d i f f e r e n c e s i n t h e t y p e o f s t a r c h e s and p r o t e i n (Kakade 1974; H u n t i n g t o n , 1994; Romagnolo e t a l . , 1994 and S t e r n e t a l . , 1994) and n e u t r a l d e t e r g e n t f i b e r d e g r a d a t i o n r a t e has been r e p o r t e d t o be h i g h e r f o r b a r l e y t h a n c o r n i n s p i t e o f c o r n h a v i n g had a h i g h e r s o l u b l e f r a c t i o n (De V i s s e r e t a l . , 1992). The s t a r c h i n b a r l e y i s m a i n l y o f a f l o u r y waxy t y p e and has a h i g h e r c o n t e n t o f a m y l o p e c t i n s t h a n c o r n s t a r c h ( F r e n c h , 1973; Rooney and P f l u g f e l d e r , 1986 and H u n t i n g t o n , 1994). I n g e n e r a l , waxy t y p e o f s t a r c h e s ( h i g h c o n t e n t o f a m y l o p e c t i n ) e a s i l y s w e l l i n he a t e d w a t e r , t h e r e b y a l l o w i n g f o r an easy e n z y m a t i c a t t a c k r e s u l t i n g i n f a s t e r r a t e s o f i n v i t r o o r i n v i v o o r i n s i t u d i g e s t i o n t h a n non-waxy s t a r c h e s ( H u n t i n g t o n , 1994) . i n ' a d d i t i o n b a r l e y has a h i g h e r c o n t e n t o f r a p i d l y s o l u b l e m a t e r i a l (DM) t h a n c o r n (Table 15; H e r r e r a - S a l d a n a e t a l . , 1990b and G r i n g s e t a l . , 1992) due t o t h e h i g h c o n t e n t o f s i m p l e c a r b o h y d r a t e s and n i t r o g e n (Aman and Hesselman, 1984). P r o t e i n s i n b a r l e y , wheat and c o r n a r e m a i n l y p r o l a m i n s and g l u t e l i n s w h i c h r e s i s t rumen d e g r a d a t i o n but o n l y b a r l e y and wheat have s u b s t a n t i a l amounts o f albumins and g l o b u l i n s w h i c h a r e h i g h l y s o l u b l e . Corn on t h e o t h e r hand has t r a c e amounts o f a l b u m i n s and 150 c o n t a i n s low amounts o f g l o b u l i n s when compared t o b a r l e y and wheat (Kakade, 1974; W a l l and P a u l i s , 1978; W i l s o n e t a l . , 1981; S p i c e r e t a l . , 1986 and' Romagnolo e t a l . , 1994). These d i f f e r e n c e s i n q u a n t i t y o f t y p e s o f p r o t e i n s a c c o u n t s f o r d i f f e r e n c e s i n d e g r a d a b i l i t y o f p r o t e i n s o f c e r e a l s w h i c h c o n t r i b u t e s t o t h e v a r i a t i o n o b s e r v e d i n DM d e g r a d a t i o n c h a r a c t e r i s t i c s . D i f f e r e n c e s i n d e g r a d a t i o n c h a r a c t e r i s t i c s o f b a r l e y and c o r n i n d i f f e r e n t e x p e r i m e n t s a r e l i k e l y t o be a r e f l e c t i o n o f d i f f e r e n c e s among s t a r c h , v a r i e t y , l o c a t i o n , y e a r , g r a i n d e n s i t y , p r o c e s s i n g , c l i m a t i c c o n d i t i o n s and agronomic p r a c t i c e s ( G r i n g s e t a l . , 1992; Flachowsky e t a l . , 1992; Engstrom e t a l . , 1992 and H u n t i n g t o n , 1994) b u t a l s o methodology, w h i c h i s r e s p o n s i b l e f o r d i f f e r e n c e s i n d e g r a d a t i o n c h a r a c t e r i s t i c s between SRC and SRB used f o r t h e l a c t a t i n g d a i r y cows t r i a l and t h e i n s i t u s t u d i e s o f c e r e a l s i n Ch a p t e r 2. D i f f e r e n c e s i n q u a n t i t y o f r a p i d l y d e g r a d a b l e f r a c t i o n i n T a b l e 5 and 6 compared t o T a b l e 15a f o r b a r l e y and c o r n can be e x p l a i n e d by d i f f e r e n c e s i n t h e methods f o r d e t e r m i n a t i o n o f t h i s f r a c t i o n as d e s c r i b e d i n m a t e r i a l s and methods o f C h a p t e r s 2 and 4. The h i g h e r q u a n t i t y o f r a p i d l y d e g r a d a b l e f r a c t i o n f o r SRB and SRC g r a i n s i n t a b l e 15a compared t o t a b l e 5 and t a b l e 6, may a l s o p a r t l y e x p l a i n t h e lower q u a n t i t y o f s l o w l y d e g r a d a b l e f r a c t i o n i n T a b l e 15a t h a n T a b l e 5 and 6. However, i n s p i t e o f t h e h i g h e r q u a n t i t y o f t h e r a p i d l y d e g r a d a b l e f r a c t i o n o f DM o r s t a r c h i n T a b l e 15a t h a n i n T a b l e 5 and 6, t h a t d i d n o t t r a n s l a t e i n t o h i g h e r r a t e s o f d e g r a d a t i o n o f t h e two p a r a m e t e r s . The d i f f e r e n c e s i n t h e r a t e o f DM and S t a r c h d e g r a d a t i o n c o u l d be r e l a t e d t o some 151 d i f f e r e n c e s i n s i z e o f t h e bags, q u a n t i t y o f sample i n t h e bags, washing p r o c e d u r e s o f t h e bags, and a l s o f r e q u e n c y o f f e e d i n g w h i l e q u a n t i t y o f f e e d and pore s i z e o f t h e bags remained c o n s t a n t as d e s c r i b e d C h a p t e r s 2 and 4. D e g r a d a t i o n c h a r a c t e r i s t i c s o f p r o t e i n s o u r c e s used as f e e d i n g r e d i e n t s a r e shown i n T a b l e 15b. E x c e p t f o r t h e r a p i d l y d e g r a d a b l e s o l u b l e f r a c t i o n f o r DM and CP, a l l p a r a m e t e r s were s i g n i f i c a n t l y h i g h e r f o r CM t h a n FM (P<0.05), b e i n g i n agreement w i t h e a r l i e r r e p o r t s ( H v e l p l u n d , 1985; NRC, 1989; H u s s e i n e t a l . , 1991a and K h o r a s a n i e t a l . , 1994). Why t h e r a p i d l y s o l u b l e f r a c t i o n (DM and CP) and l a g (CP) f o r FM i s h i g h e r (P<0.05) and lower (P<0.05) r e s p e c t i v e l y t h a n t h a t f o r CM i s unknown and t h e r e s u l t was u n e x p e c t e d . D i f f e r e n c e s i n d e g r a d a t i o n c h a r a c t e r i s t i c s o f CM and FM can be a t t r i b u t e d t o d i f f e r e n c e s i n t y p e s o f p r o t e i n s found i n t h e s e supplements and a l s o e x t e r n a l a r t i f i c i a l l y m o d i f y i n g p r o c e s s e s such as a p p l i c a t i o n o f h e a t , p e l l e t i n g and o i l e x t r a c t i o n method. O i l c r o p s such as CM c o n t a i n albumins and g l o b u l i n s w h i c h have a h i g h c o n t e n t o f b a s i c and a c i d i c a m i n o - a c i d s and t h e s e p r o t e i n s a r e h i g h l y s o l u b l e (Kakade, 1974) . F i s h meal on t h e o t h e r hand g e n e r a l l y r e s i s t s d e g r a d a t i o n , i t s r u m i n a l d e g r a d a b i l i t y i s r e d u c e d by h e a t i n g d u r i n g t h e d r y i n g p r o c e s s . Heat d u r i n g d r y i n g o f FM p r o t e i n has been shown t o i n d u c e f o r m a t i o n o f S-S c r o s s - l i n k i n g from s u l f h y d r y l o x i d a t i o n (Opstvedt e t a l . , 1984) r e s u l t i n g i n i n c r e a s e d numbers of d i s u l f i d e bonds and d e c r e a s e d r u m i n a l p r o t e o l y s i s o f FM p r o t e i n (Chen e t a l . , 1987). 152 D i f f e r e n c e s i n d e g r a d a t i o n c h a r a c t e r i s t i c s as found i n t h i s e x p e r i m e n t and many o t h e r s , have a s i g n i f i c a n t impact on t h e s i t e and e x t e n t o f d i g e s t i o n , r u m i n a l and b l o o d p a r a m e t e r s , s u p p l y o f n u t r i e n t s t o t h e s m a l l i n t e s t i n e and subsequent m e t a b o l i s m and a n i m a l performance. 4.3.2.0. Intake. 4.3.2.1. E f f e c t of carbohydrate source. Source o f c a r b o h y d r a t e d i d not a f f e c t (P>.10) t h e consumption o f DM, OM, CP and s t a r c h ( T able 16). T o t a l i n t a k e s o f ADF and NDF were a l s o n o t a f f e c t e d by c a r b o h y d r a t e s o u r c e ( T a b l e 16) . Dry m a t t e r i n t a k e s as a c t u a l t o t a l and p e r c e n t body w e i g h t averaged 23.72 kg/cow/day and 3.64% r e s p e c t i v e l y f o r t h e f o u r d i e t s b e i n g s i m i l a r t o i n t a k e s r e p o r t e d by McCarthy e t a l . (1989) f o r s i m i l a r d i e t s . Our f i n d i n g s i n t h i s e x periment d i f f e r from o t h e r s , Casper and S c h i n g o e t h e . (1989), McCarthy e t a l . (1989) and Casper e t a l . (1990) who found t h a t cows consumed l e s s o f b a r l e y - b a s e d d i e t s t h a n c o r n based d i e t s w i t h a l f a l f a hay and c o r n s i l a g e as roughage and f e d i n c o m b i n a t i o n w i t h s o u r c e s o f p r o t e i n w i t h d i f f e r e n t d e g r a d a b i l i t y r a t e s . G r i n g s e t a l (1992) and De P e t e r s and T a y l o r , (1985) r e p o r t e d no d i f f e r e n c e s f o r cows i n m i d - l a c t a t i o n w h i l e K h o r a s a n i e t a l . (1994) r e p o r t e d a s i g n i f i c a n t i n t e r a c t i o n between c a r b o h y d r a t e and p r o t e i n s o u r c e f o r t o t a l DM i n t a k e w i t h cows on cor n - b a s e d d i e t s consuming more t h a n t h o s e on b a r l e y d i e t s when f e d w i t h a h i g h l y d e g r a d a b l e s o u r c e o f p r o t e i n . 153 T o t a l i n t a k e o f NDF (P<0.006) and h e m i - c e l l u l o s e (P<0.0001), c o n c e n t r a t e NDF and h e m i - c e l l u l o s e i n t a k e s were a l l s i g n i f i c a n t l y (P<0.01) a f f e c t e d by c e r e a l t y p e ( T a b l e 1 6 ) . Cows f e d SRB c o n c e n t r a t e consumed i n e x c e s s of 2x t h e amount o f NDF and hemi-c e l l u l o s e consumed by cows f e d SRC based c o n c e n t r a t e . T o t a l i n t a k e o f ADF t e n d e d t o be h i g h e r (P<0.13) on SRB t h a n SRC ( T a b l e 1 6 ) . The d i f f e r e n c e s between SRB and SRC i n i n t a k e o f f i b e r m a t e r i a l may be e x p l a i n e d on t h e b a s i s o f d i f f e r e n c e s i n c h e m i c a l c o m p o s i t i o n w i t h b a r l e y g r a i n and b a r l e y based d i e t s b e i n g h i g h e r i n f i b e r t h a n c o r n ( T a b l e 13 and 14) s i n c e t o t a l DM i n t a k e s were s i m i l a r among d i e t s ( T a b l e 16). The NDF and h e m i - c e l l u l o s e c o n t e n t ( T a b l e 13) o f SRB (29.71 and 23.14%, r e s p e c t i v e l y . ) were about 2x more t h a n t h a t o f SRC (14.68 and 10.94%, r e s p e c t i v e l y ) w h i l e t h e same par a m e t e r s averaged 3 6.09% and 13.37% f o r SRB based d i e t s b e i n g h i g h e r t h a n c o r n based d i e t s which averaged 29.06% and 7.19% ( T a b l e 1 4 ) . These f i n d i n g s a r e d i f f e r e n t from t h o s e o f McCarthy e t a l . (1989) who r e p o r t e d no d i f f e r e n c e s w h i l e G r i n g s e t a l . (1992) i n d i c a t e d t h a t cows on a c o r n d i e t consumed more NDF t h a n cows on b a r l e y . There i s a p o s s i b i l i t y t h a t f i b e r d i g e s t i o n c o u l d have been d e p r e s s e d on b a r l e y d i e t s i n t h e e x p e r i m e n t o f G r i n g s e t a l . (1992) due t o low r u m i n a l pH r e s u l t i n g from h i g h e r r u m i n a l d e g r a d a b i l i t y o f b a r l e y s t a r c h t h a n c o r n t h e r e b y a f f e c t i n g c e l l u l o l y t i c a c t i v i t y o f b a c t e r i a . They d i d not measure pH i n t h e i r e x p e r i m e n t . T e r r y e t a l . (1969) i n d i c a t e d t h a t o p t i o m a l pH f o r c e l l u l o l y t i c a c t i v i t y o f b a c t e r i a i n t h e rumen i s about 6.8 and r u m i n a l f i b e r d i g e s t i o n i s 154 d e c r e a s e d as pH o f t h e rumen f l u i d d e c l i n e s p a r t i c u l a r l y i f below 6.0 ( S t e w a r t , 1977). P r o t e i n and s t a r c h i n t a k e were n ot s i g n i f i c a n t l y a f f e c t e d (P>0.05) by s o u r c e o f c a r b o h y d r a t e (Table 1 6 ) . T o t a l p r o t e i n and s t a r c h i n t a k e i n t h i s e x periment averaged 4.17 and 7.27 kg/cow/day r e s p e c t i v e l y . 4.3.2.2. E f f e c t of protein source. Dry m a t t e r , OM, CP, NDF and h e m i - c e l l u l o s e i n t a k e s were n ot s i g n i f i c a n t l y a f f e c t e d by (P>0.10) p r o t e i n s o u r c e ( T a b l e 1 6 ) . Cows on CM consumed more (P<0.10) ADF t h a n on FM (T a b l e 1 6 ) . S i n c e t h e DM i n t a k e s were s i m i l a r among d i e t s t h i s r e s u l t may i n p a r t be e x p l a i n e d by t h e h i g h ADF c o n t e n t o f SRB and CM compared t o c o r n ( T a b l e 13) l e t a l o n e FM which c o n t a i n s no b o t a n i c a l f i b e r . T h i s r e s u l t i s d i f f e r e n t from t h a t o f McCarthy e t a l . (1989) who showed no s i g n i f i c a n t d i f f e r e n c e s i n ADF i n t a k e due t o p r o t e i n s o u r c e . O v e r a l l , t h e r e s u l t s of i n t a k e r e p o r t e d h e r e a r e s i m i l a r t o McCarthy e t a l . (1989) i n wh i c h s o u r c e o f c a r b o h y d r a t e r a t h e r t h a n p r o t e i n had a major i n f l u e n c e on most changes i n n u t r i e n t i n t a k e ( T a b l e 1 6 ) . 4.3.3.0. Dry matter, organic matter and nutrient d i g e s t i b i l i t y . 4.3.3.1. E f f e c t of carbohydrate source. Dry m a t t e r and o r g a n i c m a t t e r i n t a k e s o f cows d u r i n g t h e d i g e s t i b i l i t y t r i a l were not s i g n i f i c a n t l y (P>0.05) a f f e c t e d by c a r b o h y d r a t e s o u r c e (Table 17) and t h e s e averaged 21.85 and 20.52 155 kg/cow/day f o r a l l d i e t s r e s p e c t i v e l y and i s i n agreement w i t h T a b l e 16, a l t h o u g h t h e a c t u a l v a l u e s a r e l o w e r ( T a b l e 17) t h a n i n T a b l e 16. A p p a r e n t d i g e s t i b i l i t i e s f o r DM, OM, CP, s t a r c h , NDF and hemi-c e l l u l o s e were s i g n i f i c a n t l y (P<0.10) h i g h e r on t h e SRB d i e t s t h a n t h e SRC based d i e t s (Table 17) b e i n g i n agreement w i t h t h e r e s u l t s r e p o r t e d by H e r r e r a - S a l d a n a e t a l . (1990b) f o r a l l p arameters e x c e p t f i b e r s u s i n g b a r l e y and m i l o based d i e t s . There were no s t a t i s t i c a l d i f f e r e n c e s (P>0.10) i n t o t a l t r a c t a p p a r e n t d i g e s t i b i l i t y o f ADF by cows consuming e i t h e r SRB o r SRC based d i e t s ( T a b l e 17) . The r e s u l t s r e p o r t e d i n t h i s e x p e r i m e n t f o r DM and OM i n t a k e and ADF d i g e s t i b i l i t y a r e d i f f e r e n t from t h e r e s u l t s r e p o r t e d by D e Peters and T a y l o r , (1985) and McCarthy e t a l . (1989) , f o r d a i r y cows and S p i c e r e t a l . (1986) f o r g r o w i n g s t e e r s b u t a g r e e s w i t h McCarthy e t a l . (1989) f o r t o t a l t r a c t a p p a r e n t s t a r c h and p r o t e i n d i g e s t i b i l i t y ( T a b l e 17) . More s t a r c h and p r o t e i n were d i g e s t e d on SRB t h a n SRC based d i e t s . D e P e t e r s and T a y l o r , (1985) and McCarthy e t a l . (1989) r e p o r t e d no s i g n i f i c a n t d i f f e r e n c e i n t o t a l t r a c t d i g e s t i b i l i t i e s o f DM and OM i n s p i t e o f f i n d i n g s i g n i f i c a n t d i f f e r e n c e s i n a p p a r e n t t o t a l t r a c t d i g e s t i b i l i t i e s o f s t a r c h ( b a r l e y h i g h e r t h a n c o r n ) , NDF ( c o r n h i g h e r t h a n b a r l e y ) and p r o t e i n ( b a r l e y h i g h e r t h a n c o r n ) . I n our s t u d i e s t h e s i g n i f i c a n t l y h i g h e r d i g e s t i b i l i t i e s o f s t a r c h , CP, NDF and h e m i - c e l l u l o s e o f SRB based d i e t s o v e r SRC 156 based d i e t s was a l s o m a n i f e s t e d i n t h e h i g h e r DM and OM d i g e s t i b i l i t i e s ( T a b l e 17). The h i g h e r p r o t e i n d i g e s t i b i l i t y on SRB d i e t s t h a n SRC d i e t s can be e x p l a i n e d i n p a r t by t h e f a c t t h a t p r o t e i n i n b o t h b a r l e y and CM i s h i g h l y d e g r a d a b l e w h i l e c o r n and FM a r e l e s s d e g r a d a b l e i n t h e rumen ( H e r r e r a - S a l d a n a e t a l . 1990a,b). The r e s u l t s f o r s t a r c h d i g e s t i b i l i t y i n a l l e x p e r i m e n t s t e s t i f y t o t h e f i n d i n g t h a t b a r l e y s t a r c h i s more d e g r a d a b l e t h a n t h a t o f c o r n ( T a b l e 15;, H e r r e r a - S a l d a n a e t a l . , 1990a,b and G r i n g s e t a l . , 1992). About 80% o f b a r l e y s t a r c h i s d i g e s t e d i n t h e rumen compared t o about 50% o f c o r n w i t h t h e r e v e r s e b e i n g t r u e f o r p o s t -r u m i n a l d i g e s t i o n i n which about 4 0% o f c o r n i s d i g e s t e d compared t o about 20% o f b a r l e y (McCarthy e t a l . , 1989). T h i s has i m p l i c a t i o n on m i l k p r o d u c t i o n w i t h r e s p e c t t o g l u c o s e and VFA's p r o v i s i o n t o t h e a n i m a l . 4.3.3.2. E f f e c t o f s o u r c e o f p r o t e i n . A p p a r e n t d i g e s t i b i l i t i e s f o r a l l p a r a m e t e r s were not s i g n i f i c a n t l y a f f e c t e d (P>0.10) by p r o t e i n s o u r c e ( T a b l e 1 7 ) . The s l i g h t l y e l e v a t e d s t a r c h and p r o t e i n a p p a r e n t d i g e s t i b i l i t i e s i n FM d i e t s when compared t o CM d i e t s may be r e l a t e d t o h i g h e r (P<0.07) r a t e o f passage of p a r t i c u l a t e m a t t e r on CM d i e t s t h a n FM based d i e t s ( T a b l e 17) . These r e s u l t s agree w i t h t h o s e r e p o r t e d by McCarthy e t a l . (1989) and H e r r e r a - S a l d a n a e t a l . (1990b) f o r a l l n u t r i e n t s e x c e p t NDF. Source of c a r b o h y d r a t e r a t h e r t h a n p r o t e i n 157 s o u r c e was t h e predominant f a c t o r a f f e c t i n g t o t a l t r a c t d i g e s t i b i l i t i e s o f n u t r i e n t s . 4.3.4.0. Ruminal VFAs, NH3-N and pH. I n g e n e r a l , t h e r a p i d and e x t e n s i v e r u m i n a l d e g r a d a t i o n o f s t a r c h and p r o t e i n on a l l d i e t s and a l s o f i b e r on b a r l e y based d i e t s r e s u l t e d i n f a i r l y h i g h c o n c e n t r a t i o n s o f t o t a l v o l a t i l e f a t t y a c i d s (VFAs) i n t h e r u m i n a l f l u i d e s p e c i a l l y when CM based d i e t s were f e d (T a b l e 18) . Rumen f l u i d pH was n o t s i g n i f i c a n t l y a f f e c t e d by t h e s o u r c e o f c a r b o h y d r a t e o r p r o t e i n (P>0.05) and averaged 7.0, c l o s e t o 6.8 and above 6.0 c o n s i d e r e d t o be o p t i m a l f o r c e l l u l o l y t i c b a c t e r i a a c t i v i t y ( T e r r y e t a l . , 1969) and d e p r e s s i o n o f f i b e r d i g e s t i b i l i t y ( S t e w a r t , 1977) r e s p e c t i v e l y . The l o w e s t pH was 6.2 0 on SRC-FM wh i c h a l s o had t h e l o w e s t c o n c e n t r a t i o n o f t o t a l VFAs, why t h i s i s so i s n o t c l e a r . S i n c e t h e s e pH v a l u e s were c l o s e t o 6.8 and above 6.0 and t h a t r a t e o f passage f o r s o l i d s and l i q u i d were s i m i l a r among d i e t s , t h e low f i b e r d i g e s t i b i l i t y ( T a ble 17) ob s e r v e d on SRC d i e t s may be r e l a t e d t o some o t h e r unknown f a c t o r s . Low pH v a l u e s were r e s p o n s i b l e f o r low f i b e r d i g e s t i b i l i t y on a l l d i e t s b u t a l s o when b a r l e y d i e t s were compared t o c o r n (McCarthy e t a l . , 1989) I n t h i s s t u d y p r o t e i n s o u r c e s i g n i f i c a n t l y a f f e c t e d (P<0.03) t h e t o t a l c o n c e n t r a t i o n o f r u m i n a l VFAs w i t h CM based d i e t s b e i n g h i g h e r (78.43 v e r s u s 72.80 mM/1) t h a n FM based d i e t s ( T a b l e 18). These r e s u l t s a r e i n agreement w i t h t h o s e r e p o r t e d by H e r r e r a -s a l d a n a and Huber, (1989) f o r c o t t o n seed meal v e r s u s d r y brewers 158 g r a i n , H u s s e i n e t a l . (1991b) f o r soybean meal v e r s u s FM and a l s o A l d r i c h e t a l . (1993) f o r CM/SBM v e r s u s b l o o d meal. T o t a l VFAs c o n c e n t r a t i o n was shown t o i n c r e a s e l i n e a r l y as d e g r a d a b l e i n t a k e p r o t e i n i n c r e a s e d i n c o n t i n u o u s c u l t u r e s ( S t o k e s e t a l . , 1991a). O t h e r s have r e p o r t e d no s i g n i f i c a n t d i f f e r e n c e s (Casper and S c h i n g o e t h e , 1989 and K h o r a s a n i e t a l . , 1994) w h i l e McCarthy e t a l . (1989) r e p o r t e d s i g n i f i c a n t c a r b o h y d r a t e and p r o t e i n e f f e c t s as w e l l as i n t e r a c t i o n e f f e c t s f o r s i m i l a r p r o t e i n s o u r c e s . Source of c a r b o h y d r a t e had no s i g n i f i c a n t (P>0.05) e f f e c t on t o t a l VFA c o n c e n t r a t i o n (Table 1 8 ) , i n agreement w i t h t h e r e s u l t s o f H e r r a r a - s a l d a n a and Huber, (1989), H u s s e i n e t a l . (1991a,b) and A l d r i c h e t a l . (1993). There was a s i g n i f i c a n t i n t e r a c t i o n (P<0.05) between s o u r c e o f c a r b o h y d r a t e and p r o t e i n i n c o n c e n t r a t i o n o f a c e t a t e , b u t y r a t e , v a l e r a t e and a l s o a c e t a t e : p r o p i o n a t e ( T a b l e 18) . The i n t e r a c t i o n i n a c e t a t e c o n c e n t r a t i o n o c c u r r e d because when CM r e p l a c e d FM on c o r n d i e t s more a c e t a t e was produced t h a n when CM r e p l a c e d FM on b a r l e y d i e t s . I t was e x p e c t e d t h a t more a c e t a t e w i l l be produced on b a r l e y based d i e t s t h a n c o r n based d i e t s c o n s i d e r i n g t h e h i g h f i b e r d i g e s t i b i l i t y on b a r l e y d i e t s . There was however tendency towards h i g h e r a c e t a t e l e v e l s on b a r l e y d i e t s t h a n on c o r n d i e t s b u t t h i s was an i n s i g n i f i c a n t s m a l l i n c r e a s e . K h o r a s a n i e t a l . (1994) r e p o r t e d no s i g n i f i c a n t d i f f e r e n c e s i n a c e t a t e c o n c e n t r a t i o n i n s p i t e o f t h e f a c t t h a t d i e t s w i t h h i g h s t a r c h d e g r a d a b i l i t y had h i g h e r c o n t e n t o f f i b e r t h a n d i e t s w i t h low s t a r c h d e g r a d a b i l i t y . 159 P r o p i o n a t e was s i g n i f i c a n t l y a f f e c t e d by b o t h s o u r c e o f c a r b o h y d r a t e (P<0.0001) and p r o t e i n (P<0.0001). Cows consuming b a r l e y d i e t s had h i g h e r a c e t a t e c o n c e n t r a t i o n t h a n t h o s e consuming c o r n d i e t s (17.4 4 vs 15.23%). The h i g h e r m o l a r p e r c e n t o f p r o p i o n a t e on b a r l e y based d i e t s t h a n c o r n d i e t s i s c o n s i s t e n t w i t h h i g h s t a r c h f e r m e n t a t i o n o f b a r l e y i n t h e rumen ( T a b l e 15a). The h i g h p r o p i o n a t e c o n c e n t r a t i o n on b a r l e y d i e t s may p a r t l y e x p l a i n t h e h i g h e r m i l k p r o d u c t i o n on t h e s e d i e t s t h a n c o r n d i e t s ( T able 19) . P r o p i o n a t e i s g l u c o g e n i c and must have r e s u l t e d i n h i g h e r g l u c o s e p r o d u c t i o n w h i c h went i n l a c t o s e p r o d u c t i o n ; L a c t o s e i s t h e main m i l k c a r b o h y d r a t e . The h i g h p r o p i o n a t e c o n c e n t r a t i o n on b a r l e y d i e t s a l s o t r a n s l a t e d i n t o l ower m i l k f a t p e r c e n t a g e ( T a b l e 19) w h i c h i s s u p p o r t e d by t h e lower A:P r a t i o s on b a r l e y d i e t s t h a n c o r n d i e t s ( T a b l e 18). H e r r e r a - S a l d a n a e t a l . (1990a) a l s o r e p o r t e d low A:P r a t i o s w h i c h r e s u l t e d i n low m i l k f a t p e r c e n t a g e s ( H e r r e r a -S a l d a n a and Huber, 1989). The d a t a f o r p r o p i o n a t e i s i n agreement w i t h K h o r a s a n i e t a l (1994) who r e p o r t e d s i g n i f i c a n t e f f e c t s f o r b o t h s o u r c e o f c a r b o h y d r a t e and p r o t e i n but d i d not f i n d any d i f f e r e n c e s i n t h e A:P r a t i o and m i l k f a t p e r c e n t a g e s . McCarthy e t a l (1989) r e p o r t e d s i g n i f i c a n t i n t e r a c t i o n f o r a c e t a t e and p r o p i o n a t e c o n c e n t r a t i o n and t h e A:P r a t i o s , w h i l e A l d r i c h e t a l (1993) r e p o r t e d no s i g n i f i c a n t d i f f e r e n c e s i n a c e t a t e and p r o p i o n a t e c o n c e n t r a t i o n but A:P r a t i o s were s i g n i f i c a n t f o r both s o u r c e o f c a r b o h y d r a t e and p r o t e i n . B u t y r a t e molar p e r c e n t was not a f f e c t e d by e i t h e r s o u r c e o f c a r b o h y d r a t e o r p r o t e i n but i n t e r a c t i o n was s i g n i f i c a n t (P<0.03). 160 ( T a b l e 18) . The i n t e r a c t i o n i n b u t y r a t e c o n c e n t r a t i o n o c c u r r e d because more b u t y r a t e was produced when CM r e p l a c e d FM on b a r l e y d i e t s t h a n when CM r e p l a c e d FM on c o r n d i e t s . O ther workers r e p o r t e d no d i f f e r e n c e s ( H e r r e r a - S a l d a n a and Huber, 1989; McCarthy e t a l . , 1989, and K h o r a s a n i e t a l . , 1994) i n c o n c e n t r a t i o n o f b u t y r a t e w h i l e o t h e r s have r e p o r t e d s i g n i f i c a n t c a r b o h y d r a t e s o u r c e e f f e c t (Casper and S c h i n g o e t h e , 1989 and A l d r i c h e t a l . , 1993) w i t h d i e t s o f low s t a r c h d e g r a d a t i o n b e i n g h i g h e r t h a n d i e t s o f h i g h s t a r c h d e g r a d a b i l i t y . A l t h o u g h McCarthy e t a l . (1989) and H e r r e r a -S a l d a n a and Huber (1989) r e p o r t e d no d i f f e r e n c e s i n b u t y r a t e c o n c e n t r a t i o n , t h e r e was however a tendency toward h i g h b u t y r a t e c o n c e n t r a t i o n on d i e t s w i t h c a r b o h y d r a t e s o u r c e o f s l o w s t a r c h d e g r a d a b i l i t y . There was tendency toward h i g h e r b u t y r a t e c o n c e n t r a t i o n on c o r n d i e t s t h a n b a r l e y i n t h i s e x p e r i m e n t b u t t h i s i n c r e a s e was not s i g n i f i c a n t . I s o b u t y r a t e and i s o v a l e r a t e m o lar p e r c e n t a g e s were s i g n i f i c a n t l y a f f e c t e d (P<0.01) by s o u r c e o f c a r b o h y d r a t e and p r o t e i n ( T a b l e 18) . I n b o t h c a s e s c o r n based d i e t s r e s u l t e d i n h i g h e r m o l a r p e r c e n t a g e s t h a n b a r l e y based d i e t s (1.7 v s 0.59 molar %, i s o b u t y r a t e ; 1.90 vs 0.9 molar %, i s o v a l e r a t e ) . I s o v a l e r a t e r e s u l t s agree w i t h t h o s e r e p o r t e d f o r d a i r y cows f o r s i m i l a r d i e t s (Casper and S c h i n g o e t h e , 1989) 'and sheep ( H u s s e i n e t a l . , 1991b). I n c o n t r a s t A l d r i c h e t a l . (1993) r e p o r t e d h i g h e r c o n c e n t r a t i o n o f i s o v a l e r a t e f o r d i e t s c o n t a i n i n g h i g h l y d e g r a d a b l e n o n - s t r u c t u r a l c a r b o h y d r a t e (NSC) t h a n t h o s e c o n t a i n i n g l e s s d e g r a d a b l e NSC. T h i s d i f f e r e n c e may be e x p l a i n e d by d i f f e r e n c e s i n t h e s o u r c e o f NSC. I n 161 t h i s s t u d y and many o t h e r s (Casper and S c h i n g o e t h e , 1989 and McCarthy e t a l . , 1989) c o r n and b a r l e y were t h e l e s s and h i g h l y d e g r a d a b l e c a r b o h y d r a t e s o u r c e r e s p e c t i v e l y w h i l e A l d r i c h e t a l . , (1993) used e a r c o r n and h i g h m o i s t u r e s h e l l e d c o r n f o r t h e same. Other w o r k e r s (McCarthy e t a l . , 1989, and K h o r a s a n i e t a l . , 1994) r e p o r t e d no d i f f e r e n c e s i n c o n c e n t r a t i o n o f i s o v a l e r a t e . As f o r i s o b u t y r a t e , r e p o r t s a r e c o n f l i c t i n g . Casper and S c h i n g o e t h e , (1989), A l d r i c h e t a l . (1993) and K h o r a s a n i e t a l . (1994) have r e p o r t e d no c a r b o h y d r a t e e f f e c t . The h i g h e r molar p e r c e n t a g e o f i s o b u t y r a t e and i s o v a l e r a t e on c o r n based d i e t s t h a n on b a r l e y based d i e t s may be r e l a t e d t o t h e h i g h e r l e v e l s o f v a l i n e and l e u c i n e as p e c u r s o r s o f i s o b u t y r a t e and i s o v a l e r a t e (Harwood and C a n a l e - P a r o l a , 1981), r e s p e c t i v e l y . More v a l i n e and l e u c i n e r e a c h e d t h e duodenum on c o r n d i e t s t h a n b a r l e y (McCarthy e t a l . , 1989), and c o r n c o n t a i n s about t h e same amount as b a r l e y w h i l e l e u c i n e i s about t w i c e as h i g h i n c o r n t h a n b a r l e y ( G r i n g s e t a l . , 1992). M o l a r p e r c e n t a g e s f o r i s o b u t y r a t e and i s o v a l e r a t e were h i g h e r f o r CM based d i e t s t h a n FM (Table 18) and t h e s e were 0.93 v s 0.81 and 1.65 v s 1.16 molar %, r e s p e c t i v e l y . R e s u l t s f o r i s o b u t y r a t e a r e c o n s i s t e n t w i t h t h o s e o f A l d r i c h e t a l . (1993) f o r l a c t a t i n g d a i r y cows and H u s s e i n e t a l . (1991b) f o r sheep. K h o r a s a n i e t a l . (1994) a l s o r e p o r t e d a p r o t e i n e f f e c t but i n t h e i r r e s u l t s i n d i c a t e d h i g h c o n c e n t r a t i o n o f i s o b u t y r a t e f o r s l o w l y d e g r a d a b l e p r o t e i n s o u r c e d i e t . I s o v a l e r a t e was shown t o be h i g h e r on SBM t h a n FM d i e t s f e d t o sheep ( H u s s e i n e t a l . , 1991b) and l a c t a t i n g d a i r y cows (McCarthy e t a l . , 1989) i n s p i t e o f t h e d i f f e r e n c e s n o t b e i n g s t a t i s t i c a l l y 162 s i g n i f i c a n t . The h i g h e r i s o b u t y r a t e and i s o v a l e r a t e on CM based d i e t s t h a n c o r n r e f l e c t s t h e h i g h e r (P<0.05) r u m i n a l CP d e g r a d a t i o n i n t h e rumen because i s o b u t y r a t e and i s o v a l e r a t e a r e d e r i v e d from t h e d e a m i n a t i o n o f branched c h a i n a m i n o - a c i d s , v a l i n e and l e u c i n e r e s p e c t i v e l y (Harwood and C a n a l e - P a r o l a , 1981). Rumen NH3-N c o n c e n t r a t i o n s were s i g n i f i c a n t l y (P<0.05) a f f e c t e d by p r o t e i n b u t not by c a r b o h y d r a t e s o u r c e ( T a b l e 1 8 ) . Cows consuming CM based d i e t s produced more rumen NH3-N t h a n t h o s e on FM based d i e t s (8.5 vs 4.7 mg/dl), s u g g e s t i n g g r e a t e r r u m i n a l f e r m e n t a b i l i t y o f p r o t e i n i n CM compared t o FM ( T a b l e 15) ( H e r r e r a -S a l d a n a e t a l . , 1990a,b and H u s s e i n e t a l . , 1991a,b). T h i s s u p p o r t s t h e f i n d i n g s and p r o p o s a l by Erdman e t a l . (1986) t h a t , t h e amount o f NH3-N i n t h e rumen and f e r m e n t a b i l i t y o f p r o t e i n a r e s t r o n g l y l i n k e d . S i m i l a r r e s u l t s were a l s o shown w i t h soybean meal v e r s u s FM w i t h c o r n o r b a r l e y u s i n g sheep ( H u s s e i n e t a l . , 1991b) and d a i r y cows ( Z e r b i n i e t a l . , 1988 and McCarthy e t a l . , 1989), c o t t o n seed meal v e r s u s d r y - b r e w e r s g r a i n s w i t h b a r l e y o r m i l o ( H e r r e r a - S a l d a n a and Huber, 1989) and soybean meal v e r s u s u r e a w i t h c o r n o r b a r l e y (Casper and S c h i n g o e t h e , (1989) and more r e c e n t l y K h o r a s a n i e t a l . (1994) f o r d a i r y cows u t i l i z i n g d i e t s a l m o s t s i m i l a r t o t h e d i e t s used i n t h i s e x p e r i m e n t . Rumen NH3-N c o n c e n t r a t i o n f o r t h e CM d i e t s was above 5 mg/dl w h i l e t h a t f o r FM was c l o s e t o 5 mg/dl. S a t t e r and S l y t e r , (1974) f o u n d from i n v i t r o s t u d i e s t h a t 5 mg/dl o f rumen NH3-N was r e q u i r e d f o r o p t i m a l m i c r o b i a l growth. I t i s u n l i k e l y i n t h i s s t u d y t h a t t h e low f i b e r d i g e s t i b i l i t y on SRC-CM d i e t s i s r e l a t e d t o rumen NH3-N 163 c o n c e n t r a t i o n s i n c e t h i s was adequate and t h a t SRB-FM w i t h a c o n c e n t r a t i o n c l o s e t o 5mg/dl had q u i t e h i g h f i b e r d i g e s t i b i l i t y . I t may be s p e c u l a t e d t h a t energy on t h e SRC-CM d i e t c o u l d have been l i m i t i n g development and p r o l i f e r a t i o n o f b a c t e r i a . R e p o r t e d v a l u e s f o r rumen NH3-N c o n c e n t r a t i o n s i n t h e l i t e r a t u r e f o r s i m i l a r d i e t s range from 8.6-16 mg/dl (Casper and S c h i n g o e t h e , 1989), 18-20.5 mg/dl ( H u s s e i n e t a l . , 1991a) 10.2-16.4 mg/dl ( H e r r e r a - S a l d a n a and Huber, 1989) 8.9-14.8 mg/dl ( A l d r i c h e t a l . , 1993), 11.97-13.57 mg/dl ( K h o r a s a n i e t a l . , 1994) and l o w e s t b e i n g 1.39-3.54 mg/dl (McCarthy e t a l . , 1989) f o r c a t t l e and 18-20.5 mg/dl ( H u s s e i n e t a l . , 1991b) f o r sheep. K h o r a s a n i e t a l . (1994) have a l s o i n d i c a t e d a minimum v a l u e o f about 4 mg/dl f o r s l o w l y d e g r a d a b l e s t a r c h and s l o w l y d e g r a d a b l e p r o t e i n d i e t . The low NH3-N c o n c e n t r a t i o n on SRC-FM and SRB-FM may n o t j u s t be due t o t h e d e g r a d a b i l i t y o f b o t h SRC and FM b u t a l s o t o t h e s y n c h r o n i c i t y and a s y n c h r o n i c i t y r e s p e c t i v e l y o f t h e d i e t s . On b o t h d i e t s t h e r e l e a s e o f c a r b o h y d r a t e i s a b l e t o cont e n d w i t h t h e r e l e a s e o f n i t r o g e n from FM. The r a t e o f s t a r c h d e g r a d a t i o n i n c o r n i s about 2x more t h a n t h e CP i n FM and c o r n i t s e l f ( T a b l e 15a,b and H u s s e i n e t a l . , 1991b) and f o r SRB-FM c o m b i n a t i o n , r a t e o f s t a r c h d e g r a d a t i o n i n b a r l e y i s 5x more t h a n i t s own CP and a l m o s t e q u a l t o t h e r a t e o f r e l e a s e o f p r o t e i n i n FM (T a b l e 15a,b and H u s s e i n e t a l . , 1991b). T h i s t h e n would s u g g e s t a h i g h e r f i x a t i o n o f NH3-N by a - k e t o - a c i d s p r o v i d e d from c a r b o h y d r a t e s o u r c e s a t a r a t e adequate t o c o n t e n d w i t h t h e r e l e a s e o f n i t r o g e n (Mahadevan e t a l . , 1982). A l d r i c h e t a l . (1993) has p u b l i s h e d d a t a s u p p o r t i n g t h e above 164 o b s e r v a t i o n . Cows on a low rumen a v a i l a b l e n o n - s t r u c t u r a l c a r b o h y d r a t e / l o w rumen a v a i l a b l e p r o t e i n showed l o w e r rumen NH3-N c o n c e n t r a t i o n compared t o t h e c o n v e r s e d i e t a r y c o m b i n a t i o n s . I t i s i m p o r t a n t t o note t h a t t h e rumen r e s u l t s s h o u l d be i n t e r p r e t e d w i t h c a u t i o n because o f t h e p o s s i b i l i t y o f s a l i v a r y c o n t a m i n a t i o n because i t was sampled once/cow/period and a stomach t u b e was used (Erdman e t a l . , 1982). I t must be borne i n mind t h a t , measured c o n c e n t r a t i o n s i n t h e rumen a r e a f u n c t i o n o f p r o d u c t i o n and u t i l i z a t i o n by rumen m i c r o b e s and t h i s may i n p a r t e x p l a i n t h e d i f f e r e n c e s i n rumen par a m e t e r s w i t h i n an experiment but a l s o among e x p e r i m e n t s . R e s u l t s f o r b l o o d parameters a r e a l s o shown i n T a b l e 18. Ca r b o h y d r a t e (P<0.05) and p r o t e i n (P<0.05) s o u r c e i n c l u d i n g i n t e r a c t i o n s were s i g n i f i c a n t (P<0.005) f o r bl o o d - u r e a - N (BUN). Cows on SRB d i e t s had lower b l o o d u r e a - n i t r o g e n (BUN) t h a n SRC based d i e t s (19.41 v s 20.92 mg/dl), and cows had more BUN on CM based d i e t s t h a n FM based d i e t s (20.62 v s 19.71, m g / d l ) . The r e s u l t f o r p r o t e i n s o u r c e i s as ex p e c t e d , r e s u l t i n g from t h e s i g n i f i c a n t l y h i g h e r p r o d u c t i o n o f NH3-N i n t h e rumen ( T a b l e 18) , when CM was f e d t h a n FM. The i n t e r a c t i o n o c c u r r e d because, when FM r e p l a c e d CM on SRC d i e t s r e s u l t e d i n h i g h e r l e v e l s o f BUN t h a n CM. T h i s was unexp e c t e d c o n s i d e r i n g t h a t SRC-FM c o m b i n a t i o n gave l o w e r rumen NH3-N ( T a b l e 1 8 ) . The h i g h e r BUN on t h e SRB-CM t h a n SRB-FM d i e t s was p o s s i b l y a r e s u l t o f t h e h i g h rumen NH3-N c o n c e n t a t i o n as w e l l as t h e h i g h p r o t e i n d e g r a d a b i l i t y i n t h e rumen o f b o t h SRB and CM ( T a b l e 15a,b) 165 s i n c e t h e BUN was lower on SRC-CM d i e t s ( T a b l e 1 8 ) . These f i n d i n g a r e i n agreement w i t h t h o s e o f Casper and S c h i n g o e t h e , (1989) f o r b a r l e y w i t h SBM o r u r e a as a p r o t e i n supplement. I n c o n t r a s t H e r r e r a - S a l d a n a and Huber, (1989) were u n a b l e t o show s i g n i f i c a n t d i f f e r e n c e s i n BUN between c o t t o n - s e e d meal and d r y brewers g r a i n f o r b a r l e y o r c o r n d i e t s , and A l d r i c h e t a l . , (1993) between h i g h r u m i n a l a v a i l a b l e and low a v a i l a b l e p r o t e i n w i t h h i g h a v a i l a b l e n o n - s t r u c t u r a l o r low a v a i l a b l e n o n - s t r u c t u r a l c a r b o h y d r a t e d i e t s . McCarthy e t a l . , (1989) and H e r r e r a - S a l d a n a and Huber, (1989) r e p o r t e d o n l y a c a r b o h y d r a t e e f f e c t as a l s o r e p o r t e d i n t h i s s t u d y . The r e s u l t t h a t FM r e s u l t e d i n h i g h e r BUN t h a n CM on SRC d i e t s c o n f l i c t s w i t h t h e f i n d i n g s o f H e r r a r a - S a l d a n a and Huber, (1989), Casper and S c h i n g o e t h e , (1989), A l d r i c h e t a l . (1993) and St o k e s e t a l . (1991a,b) who r e p o r t e d no s i g n i f i c a n t d i f f e r e n c e f o r s i m i l a r d i e t s ( i . e . low rumen a v a i l a b l e c a r b o h y d r a t e i n c o m b i n a t i o n w i t h e i t h e r h i g h o r low rumen a v a i l a b l e p r o t e i n ) . I t i s however o f i n t e r e s t t o note t h a t t h i s s t u d y and a l l o t h e r s were a b l e t o show h i g h rumen NH3-N f o r h i g h rumen a v a i l a b l e p r o t e i n and low rumen a v a i l a b l e p r o t e i n on low rumen a v a i l a b l e n o n - s t r u c t u r a l c a r b o h y d r a t e d i e t s . Veen e t a l . (1988) a l s o r e p o r t e d s i m i l a r o b s e r v a t i o n s . T h i s t h e n s u g g e s t s t h a t f a c t o r s o t h e r t h a n r u m i n a l NH3-N l e v e l a f f e c t BUN. F e e d i n g o f s l o w l y d e g r a d a b l e p r o t e i n i n c r e a s e s i n t e s t i n a l a m i n o - a c i d s which a r e s u b s q u e n t l y absorbed. I t i s p o s s i b l e t h a t t h e h i g h BUN on such d i e t s c o u l d be r e s u l t i n g from ammonia r e l e a s e d i n t h e l i v e r t h r o u g h d e a m i n a t i o n and g l u c o n e o g e n e s i s from a m i n o - a c i d s (Veen e t a l . , 1988). The most 166 s u s c e p t i b l e a m i n o - a c i d s t o g l u c o n e o g e n e s i s a r e a l a n i n e , g l u t a m i c a c i d , s e r i n e and a s p a r t i c a c i d ( L i n d s a y , 1982). A l t h o u g h b l o o d amino a c i d s were n ot measured i n t h i s e x p e r i m e n t , d i e t s (FM vs CM) w i t h s i g n i f i c a n t l y low rumen NH3-N had BUN l e v e l s i n t h e e x p e c t e d range compared t o t h o s e w i t h h i g h rumen NH3-N b u t a l s o t h e i r b l o o d g l u c o s e l e v e l s were h i g h (Table 18). I t i s p o s s i b l e t h a t cows on SRC-FM would want t o compensate f o r t h e s h o r t - f a l l i n rumen NH3-N and b l o o d g l u c o s e t h r o u g h d e a m i n a t i o n and g l u c o n e o g e n e s i s i n o r d e r t o s u p p o r t o r m a i n t a i n o p t i m a l m i l k s y n t h e s i s , i n s p i t e o f SRC s t a r c h b e i n g l e s s d e g r a d a b l e i n t h e rumen. T h i s seems t o be e v i d e n t from SRB-FM d i e t s w i t h t h e l o w e s t rumen NH3-N, and t h e unexpected normal l e v e l o f BUN showed t h e h i g h e s t b l o o d g l u c o s e ( T a b l e 1 8). The SRB and FM d i e t s would r e s u l t i n low l e v e l s o f i n t e s t i n a l g l u c o s e compared t o SRC-FM but a h i g h l e v e l o f i n t e s t i n a l amino-a c i d s , m i c r o b i a l p r o t e i n and undegradable p r o t e i n . The h i g h e r BUN and h i g h g l u c o g e n i c a m i n o - a c i d s on s l o w l y d e g r a d a b l e p r o t e i n d i e t s i n comparison w i t h h i g h l y d e g r a d a b l e p r o t e i n may be seen as an i n d i c a t i o n o f g l u c o n e o g e n e s i s (Veen e t a l . , 1988). The r e s u l t s f o r b l o o d g l u c o s e showed a s i g n i f i c a n t c a r b o h y d r a t e s o u r c e e f f e c t but a l s o a s i g n i f i c a n t i n t e r a c t i o n (P<0.01). 4.3.5.0 Rate o f passage. R e s u l t s f o r r a t e o f passage o f s o l i d s and l i q u i d d a t a a r e shown i n T a b l e 17. Source o f c a r b o h y d r a t e d i d not i n f l u e n c e t h e r a t e o f passage o f e i t h e r s o l i d s o r l i q u i d s . T h i s i s ag r e e s w i t h 167 r e s u l t s f o r i n t a k e ( T a b l e 16 and 17), w h i c h shows t h a t t h e s o u r c e o f c a r b o h y d r a t e d i d not i n f l u e n c e d r y m a t t e r i n t a k e s . However, DM and n u t r i e n t d i g e s t i b i l i t i e s were i n f l u e n c e d by s o u r c e o f c a r b o h y d r a t e w i t h b a r l e y based d i e t s b e i n g d i g e s t e d more t h a n c o r n based d i e t s . I f i n t a k e and r a t e o f passage o f s o l i d s o f t h e d i e t s was s i m i l a r among d i e t s , t h e h i g h e r d i g e s t i b i l i t y o f DM, OM and n u t r i e n t s o b s e r v e d on b a r l e y based d i e t s t h a n c o r n based d i e t s c o u l d be a t t r i b u t e d t o t h e h i g h e r rumen d i g e s t i o n o f b a r l e y t h a n c o r n ( T a b l e 15a) i n a d d i t i o n t o a b e t t e r rumen environment f o r p r o l i f e r a t i o n and development o f m i c r o o r g a n i s m s n e c e s s a r y f o r d i g e s t i o n . I n c r e a s e d r a t e o f d i g e s t a passage from t h e rumen has been shown t o i n c r e a s e f e e d i n t a k e (Baumgardt, 1970), d e c r e a s e r u m i n a l d i g e s t i o n and d e c r e a s e t o t a l t r a c t d i g e s t i b i l i t y ( H a r r i s o n e t a l . 1975; M e r t e n s , 1977). V a l u e s f o r s o l i d and l i q u i d r a t e o f passage were 5.64, 6.05, 5.43 and 8.63 %/h and t h o s e f o r l i q u i d r a t e o f passage were 11.81, 13.44, 10.42 and 10.71 %/h f o r SRC-FM, SRC-CM, SRB-FM and SRB-CM d i e t s , r e s p e c t i v e l y . The v a l u e s f o r s o l i d s r a t e o f passage a r e s i m i l a r t o t h o s e r e p o r t e d by MacGregor e t a l (1983). Source o f p r o t e i n s i g n i f i c a n t l y a f f e c t e d t h e r a t e o f passage f o r s o l i d s b u t not l i q u i d s ( T a b l e 17) . Cows consuming CM based d i e t s had h i g h e r r a t e o f passage f o r s o l i d s t h a n t h o s e cows consuming FM based d i e t s . Rate o f passage f o r s o l i d s a v e r a g e d 7.34 %/h f o r CM compared t o 5.54 %/h f o r FM based d i e t s . T h i s i s e x p e c t e d c o n s i d e r i n g t h e f a c t t h a t CM i s more d i g e s t e d i n t h e rumen t h a n FM ( T a b l e 15b). However, t h e h i g h e r r a t e o f passage f o r s o l i d s 168 f o r CM d i e t s t h a n FM d i e t s i s not s u p p o r t e d by i n c r e a s e d f e e d i n t a k e ( T a b l e 16 and 17) but a s m a l l d e p r e s s i o n i n DM, OM, and n u t r i e n t d i g e s t i b i l i t i e s was o b s e r v e d though t h i s was not s i g n i f i c a n t . 4.3.6.0. M i l k y i e l d and c o m p o s i t i o n . M i l k y i e l d b u t not 3.5% FCM and SCM was s i g n i f i c a n t l y a f f e c t e d by s o u r c e o f c a r b o h y d r a t e (Table 19) . Cows consuming SRB based d i e t s p roduced on average 2.08 kg/day more m i l k (P<0.01) t h a n cows consuming SRC based d i e t s . When m i l k y i e l d was c o r r e c t e d f o r f a t and s o l i d s , t h e s i g n i f i c a n t d i f f e r e n c e s d i s a p p e a r e d . S i n c e t o t a l DM and OM i n t a k e s d i d not show any i n f l u e n c e s o f s o u r c e o f c a r b o h y d r a t e o r p r o t e i n (Table 16, 17), t h e i n c r e a s e i n a c t u a l m i l k p r o d u c t i o n by cows on SRB based d i e t s may be e x p l a i n e d by h i g h e r DM and OM d i g e s t i b i l i t y r e s u l t i n g from h i g h n u t r i e n t c o n s t i t u e n t d i g e s t i b i l i t i e s ( T a ble 17). T h i s s h o u l d have r e s u l t e d i n a g r e a t e r s u p p l y o f d i g e s t e d n u t r i e n t s f o r m i l k s y n t h e s i s , and p o s s i b l y i n c r e a s e d m i c r o b i a l mass i n t h e rumen and t h u s p r o v i d i n g a d d i t i o n a l p r o t e i n and energy, w i t h t h e e x t r a energy g o i n g i n t o body s t o r e s ( T a b l e 1 9 ) . Y i e l d (passage t o duodenum) and e f f i c i e n c y o f b a c t e r i a l s y n t h e s i s was r e p o r t e d t o be h i g h e r f o r d i e t s matched f o r h i g h r a t e s o f b o t h NSC and p r o t e i n d e g r a d a t i o n (McCarthy e t a l . , 1989; H e r r e r a - S a l d a n a e t a l . , 1990b and A l d r i c h e t a l . , 1993). On t h e o t h e r hand, f l o w o f ammonia-non-microbial N, (McCarthy e t a l . , 1989 and A l d r i c h e t a l . , 1993) and s t a r c h were r e p o r t e d t o be h i g h e r on c o r n based d i e t s t h a n b a r l e y . I n t h e p r e s e n t t r i a l most apparent 169 n u t r i e n t , d i g e s t i b i l i t i e s were i n f l u e n c e d by c a r b o h y d r a t e r a t h e r t h a n by p r o t e i n s o u r c e and were h i g h e r f o r b a r l e y t h a n c o r n based d i e t s i r r e s p e c t i v e o f p r o t e i n s o u r c e . T h i s p o s i t i v e e f f e c t o f b a r l e y would r e s u l t i n a h i g h s u p p l y o f n u t r i e n t s f o r b o t h t h e a n i m a l and a l s o development and p r o l i f e r e a t i o n o f rumen b a c t e r i a . M i c r o b i a l growth has been shown t o be i n f l u e n c e d more by t h e f e r m e n t a t i o n o f c a r b o h y d r a t e (Nocek and R u s s e l l e t a l . , 1988 and A r g y l e and B a l d w i n , 1989) t h a n p r o t e i n . Rumen b a c t e r i a l growth on b a r l e y d i e t s was a l s o p r o b a b l y i n f l u e n c e d by t h e h i g h p r o v i s i o n o f p e p t i d e s and a m i n o - a c i d s o r b o t h because o f t h e h i g h e r r u m i n a l f e r m e n t a t i o n o f CM and a l s o p r o t e i n i n g e n e r a l on t h e s e d i e t s t h a n c o r n d i e t s ( A r g y l e and B a l d w i n , 1989). A l t h o u g h s t a r c h and non-ammonia n o n - m i c r o b i a l N were most l i k e l y h i g h e r on c o r n based d i e t s t h a n b a r l e y i t i s p o s s i b l e t h a t t h e s e m a t e r i a l s were not a v a i l a b l e o r l e s s d i g e s t e d i n t h e s m a l l i n t e s t i n e and p a s s e d t o t h e cecum where t h e y were ferm e n t e d but u n a v a i l a b l e f o r a b s o r p t i o n (McCarthy e t a l . , 1989). Response t o t h e i n c r e a s e d p r o v i s i o n o f non-ammonia-non-microbial p r o t e i n i s a l s o dependent on whether t h e a n i m a l s were i n n e g a t i v e energy b a l a n c e (Marsden, 1985). These two f a c t o r s may p r o b a b l y e x p l a i n i n p a r t d i f f e r e n c e s i n m i l k p r o d u c t i o n r e s u l t s found when b a r l e y and c o r n a r e compared. These r e s u l t s agree w i t h t h o s e o f H e r r e r a - S a l d a n a and Huber, (1989) but a r e i n c o n f l i c t w i t h t h o s e o f Casper e t a l . (1989, 1990), who r e p o r t e d h i g h e r m i l k p r o d u c t i o n f o r c o r n based d i e t s 170 compared t o b a r l e y d i e t s . I n c o n t r a s t t o t h e above, D e P e t e r s and T a y l o r , (1985), G r i n g s e t a l . (1992) and K h o r a s a n i e t a l . (1994) and A l d r i c h e t a l . (1993) r e p o r t e d no d i f f e r e n c e s i n a c t u a l m i l k p r o d u c t i o n when c o r n o r b a r l e y and when d i e t s h i g h o r low i n r a p i d l y d e g r a d a b l e c a r b o h y d r a t e were f e d t o l a c t a t i n g cows. M i l k f a t and SNF p e r c e n t a g e s were s i g n i f i c a n t l y a f f e c t e d by c a r b o h y d r a t e s o u r c e ( T a b l e 19) . Cows consuming SRC d i e t s had h i g h e r m i l k f a t c o n c e n t r a t i o n s (P<0.06) but lower SNF (P<0.06) t h a n SRB d i e t s . F a t c o n c e n t r a t i o n i s n e g a t i v e l y c o r r e l a t e d t o m i l k p r o d u c t i o n b u t a l s o h i g h s t a r c h d i g e s t i b i l i t y can d e c r e a s e m i l k f a t c o n c e n t r a t i o n ( 0 r s k o v , 1986 and Macgregor e t a l , 1983). However, t h e r e d u c e d m i l k f a t c o n c e n t r a t i o n o b s e r v e d f o r b a r l e y based d i e t s ( T a b l e 19) i s not c o n s i s t e n t w i t h t h e h i g h f i b e r c o n t e n t ( T a b l e 14) and h i g h f i b e r d i g e s t i b i l i t y ( T a ble 17) b u t a l s o l a c k o f s i g n i f i c a n c e among t h e d i e t s i n a c e t a t e c o n c e n t r a t i o n ( T a b l e 18) o b s e r v e d between b a r l e y and c o r n based d i e t s . D i v e r s i o n o f n u t r i e n t s away from m i l k f a t s y n t h e s i s towards body energy d e p o s i t i o n o c c u r r e d and t h i s i s i n d i c a t e d by i n c r e a s e d body w e i g h t g a i n s on SRB d i e t s s i n c e 3.5% FCM and SCM were s i m i l a r among d i e t s ( T a b l e 19) . A l t h o u g h not s t a t i s t i c a l l y s i g n i f i c a n t , on average, cows on b a r l e y based d i e t s tended t o g a i n w e i g h t more t h a n cows consuming c o r n based d i e t s (Table 19). MacGregor e t a l , (1983) a l s o o b s e r v e d r e d u c e d f a t p e r c e n t a g e and m i l k energy s e c r e t i o n w i t h i n c r e a s e d m i l k y i e l d b u t no change i n 4% FCM on d i e t s h i g h i n TNC compared w i t h d i e t s low i n TNC. I t must be remembered t h a t t h e r e d u c e d c o n c e n t r a t i o n of m i l k f a t and e l e v a t e d y i e l d s o f m i l k , 171 p r o t e i n SNF and i n c r e a s e d body w e i g h t g a i n ( T a b l e 19) a r e c o n s i s t e n t w i t h i n c r e a s e d g l u c o g e n i c energy s u p p l y from t h e r e a d i l y f e r m e n t a b l e c a r b o h y d r a t e o f b a r l e y d i e t s ( T a b l e 15a) and h i g h t o t a l t r a c t d i g e s t i b i l i t y o f n u t r i e n t s ( T able 17). T h i s i s a l s o suppoted by t h e h i g h e r p r o p i o n a t e p r o d u c t i o n and a l s o t h e l o w e r A:P r a t i o s ( T a b l e 1 8 ) , r e s u l t i n g i n low m i l k f a t p e r c e n t a g e ( T a b l e 19) on b a r l e y based d i e t s t h a n c o r n based d i e t s . C a r b o h y d r a t e s o u r c e had no i n f l u e n c e on p r o t e i n (%) and t o t a l s o l i d s (%) (P>0.05). McCarthy e t a l . (1989) and K h o r a s a n i e t a l . (1994) and G r i n g s e t a l . (1992) r e p o r t e d no d i f f e r e n c e s i n f a t and p r o t e i n c o n c e n t r a t i o n f o r c o r n and b a r l e y based d i e t s . H e r r e r a - S a l d a n a and Huber, (1989) r e p o r t e d h i g h e r f a t c o n c e n t r a t i o n f o r m i l o based d i e t s t h a n b a r l e y w h i c h i s i n agreement w i t h our f i n d i n g s a l t h o u g h c o r n i n s t e a d o f m i l o was used as a c a r b o h y d r a t e s o u r c e o f low s t a r c h d e g r a d a b i l i t y . Y i e l d o f p r o t e i n , t o t a l s o l i d s and SNF were a l l s i g n i f i c a n t l y a f f e c t e d by c a r b o h y d r a t e s o u r c e ( T a b l e 1 9 ) . Cows consuming SRB based d i e t s produced on average 0.1, 0.2 and 0.3 kg/day more p r o t e i n , t o t a l s o l i d s and SNF (P<0.02., P<0.002 and P<0.01, r e s p e c t i v e l y ) t h a n d i d cows consuming SRC d i e t s . No s i g n i f i c a n t d i f f e r e n c e s (P<0.05) were shown i n t h e case o f f a t y i e l d a l t h o u g h t h i s t e n d e d t o be h i g h e r f o r cows consuming SRC d i e t s . A l d r i c h e t a l . (1993) and K h o r a s a n i e t a l . (1994) r e p o r t e d d a t a t h a t f a t y i e l d was s i g n i f i c a n t l y h i g h e r f o r cows consuming d i e t s h i g h i n s l o w l y d e g r a d a b l e c a r b o h y d r a t e t h a n t h o s e r e c e i v i n g d i e t s low i n h i g h l y d e g r a d a b l e c a r b o h y d r a t e i n c o n t r a s t t o o t h e r r e s e a r c h e r s who r e p o r t e d no d i f f e r e n c e s ( H e r r e r a - S a l d a n a and Huber, 1989; McCarthy 172 e t a l . 1989, and G r i n g s e t a l . 1992). The d a t a f o r p r o t e i n y i e l d s a r e i n agreement w i t h t h o s e o f O l i v e i r a e t a l . (1993) and Chen e t a l . (1994) f o r steam f l a k e d sorghum v e r s u s d r y r o l l e d sorghum but i n c o n f l i c t w i t h r e s u l t s from McCarthy e t a l . (1989) who showed h i g h e r p r o t e i n y i e l d s f o r c o r n based d i e t s t h a n b a r l e y based d i e t s . Our f i n d i n g s f o r p r o t e i n a r e c o n s i s t e n t w i t h t h e s u g g e s t i o n t h a t i n c r e a s e d f e r m e n t a b i l i t y o f c a r b o h y d r a t e r e s u l t s i n i n c r e a s e d m i l k p r o t e i n (DePeters and Cant, 1991). The h i g h e r m i l k p r o t e i n on such d i e t s c o u l d have r e s u l t e d from i n c r e a s e d c a s e i n r a t h e r t h a n t r u e p r o t e i n , NPN o r whey p r o t e i n . K h o r a s a n i e t a l . (1994) r e p o r t e d s i g n i f i c a n t l y h i g h e r c a s e i n c o n c e n t r a t i o n b o t h as a p e r c e n t o f m i l k p r o d u c t i o n and m i l k p r o t e i n f o r b a r l e y d i e t s t h a n c o r n . However as n o t e d by D e P e t e r s and Cant, (1991) changes i n m i l k c a s e i n r e s u l t i n o p p o s i t e changes t o whey p r o t e i n ; t h e n e t e f f e c t b e i n g v e r y s m a l l changes i n t o t a l m i l k p r o t e i n (0.1 kg d i f f e r e n c e i n t h i s s t u d y ) . I n c o n t r a s t t o a l l t h e s e s t u d i e s , H e r r e r a - S a l d a n a and Huber, (1989), G r i n g s e t a l . (1992), A l d r i c h e t a l . (1993) and K h o r a s a n i e t a l . (1994), d i d n o t f i n d any d i f f e r e n c e i n p r o t e i n y i e l d . Data on SNF i n t h i s e x periement a r e c o n s t i s t e n t w i t h t h o s e o f O l i v i e r a e t a l . (1994) and Chen e t a l . (1994) but d i f f e r e n t from McCarthy e t a l . (1989) who r e p o r t e d h i g h e r SNF y i e l d s f o r cows on c o r n t h a n b a r l e y . Casper and S c h i n g o e t h e , (1989) on t h e o t h e r hand r e p o r t e d no d i f f e r e n c e s f o r s i m i l a r d i e t s . There a r e o n l y a few s t u d i e s i n w h i c h t o t a l s o l i d s were measured, however, Casper and S c h i n g o e t h e , (1989) and D e Peters and T a y l o r , (1985) showed no d i f f e r e n c e s f o r c o r n and b a r l e y d i e t s w h i c h i s n o t c o n s i s t e n t w i t h 173 t h e f i n d i n g s i n t h i s e x p e r i m e n t . H i g h e r t o t a l s o l i d s f o r t h e SRB d i e t s t h a n t h e SRC d i e t s was a r e s u l t o f t h e i n c r e a s e d m i l k p r o t e i n and SNF s i n c e f a t y i e l d was lower f o r t h e s e d i e t s . A l t h o u g h l a c t o s e was n o t measured i n t h i s e x p e r i m e n t , t h e d a t a on t o t a l s o l i d s and SNF would s u g g e s t t h a t s i g n i f i c a n t l y h i g h e r l a c t o s e y i e l d f o r t h e SRB d i e t s t h a n t h e SRC d i e t s . T h i s i s c o n s i s t e n t w i t h h i g h e r b l o o d g l u c o s e l e v e l s f o r t h e SRB d i e t s t h a n t h e SRC d i e t s ( T a b l e 18) and i s s u p p o r t e d by t h e h i g h e r p r o p i o n a t e p r o d u c t i o n on t h e s e d i e t s ( T a b l e 1 8 ) . Hardwick e t a l . (1961) i n d i c a t e d t h a t l a c t o s e i s a major r e g u l a t o r o f t h e volume of m i l k produced by mammary g l a n d s . A l t h o u g h e x p e r i m e n t s which r e p o r t e d s i g n i f i c a n t d i f f e r e n c e s i n m i l k p r o d u c t i o n i n c l u d i n g t h i s e x periment d i d n o t measure m i l k l a c t o s e ( H e r r e r a - S a l d a n a and Huber, 1989; Casper and S c h i n g o e t h e , 1989 and McCarthy e t a l . , 1989) and t h o s e t h a t r e p o r t e d no d i f f e r e n c e s i n m i l k p r o d u c t i o n found no d i f f e r e n c e s i n l a c t o s e c o n c e n t r a t i o n and y i e l d s , t h i s does not d e c l a r e t h i s s p e c u l a t i o n i n v a l i d . P r o t e i n s o u r c e i n t h i s e x periment d i d n o t a f f e c t y i e l d o f m i l k , FCM ( 3 . 5 % ) , SCM, f a t , p r o t e i n , t o t a l s o l i d s , SNF and m i l k c o m p o s i t i o n of t h e above mentioned p a r a m e t e r s ( T a b l e 19), c o n s i s t e n t w i t h t h e f i n d i n g s o f McCarthy e t a l . (1989) on a l l p a r a m e t e r s but not K h o r a s a n i e t a l . (1994) f o r p r o t e i n y i e l d and f a t p e r c e n t , Casper and S c h i n g o e t h e , (1989) f o r p r o t e i n , SNF and t o t a l s o l i d s c o n c e n t r a t i o n and A l d r i c h e t a l . (1993) f o r p r o t e i n c o n c e n t r a t i o n . E f f i c i e n c i e s f o r DM and OM c o n v e r s i o n t o m i l k i n d i c a t e d a s i g n i f i c a n t c a r b o h y d r a t e s o u r c e e f f e c t f o r m i l k p r o d u c t i o n and DM 174 and OM i n t a k e but not f o r FCM (3.5%) ( T a b l e 1 9 ) . Cows on t h e SRB d i e t s had h i g h e r e f f i c i e n c i e s t h a n cows on t h e SRC d i e t s (1.15 v e r s u s 1.06; 1.23 v e r s u s 1.13, r e s p e c t i v e l y ) . S i n c e i n t a k e o f DM and OM were s i m i l a r ( T a b l e 16 and 1 7 ) , t h e s e e f f i c i e n c y v a l u e s a r e c o n s i s t e n t w i t h t h e h i g h d i g e s t i b i l i t y o f DM, OM and t h e n u t r i e n t s on SRB d i e t s t h a n SRC d i e t s ( T able 17). H e r r e r a - S a l d a n a and Huber, (1989) however found no d i f f e r e n c e s i n e f f i c i e n c y o f DM c o n v e r s i o n t o m i l k . They a t t r i b u t e d t h e i r f i n d i n g s t o more p r o t e i n and s t a r c h from m i l o d i e t s e s c a p i n g d e g r a d a t i o n i n t h e rumen and t h e r e f o r e b e i n g a v a i l a b l e i n t h e s m a l l i n t e s t i n e s f o r e n z y m a t i c d i g e s t i o n o f f - s e t t i n g t h e l o w e r t o t a l t r a c t d i g e s t i b i l i t y . I n t h i s e x p e r i m e n t i t i s p o s s i b l e t h a t t h e lower e f f i c i e n c i e s a r e r e l a t e d t o u n c a p t u r e d rumen NH3-N on t h e SRC-CM d i e t and t h a t t h e undegraded s t a r c h and p r o t e i n SRC-FM d i d not have much t i m e t o be degraded i n t h e s m a l l i n t e s t i n e and absorbed a l t h o u g h r a t e o f passage f o r s o l i d s was s i g n i f i c a n t l y a f f e c t e d (P<0.07) by p r o t e i n s o u r c e (Table 17) . No s i g n i f i c a n t d i f f e r e n c e s (P<0.05) were o b s e r v e d f o r p r o t e i n s o u r c e i n f l u e n c e on a l l e f f i c i e n c i e s ( T a b l e 1 9 ) . 175 4.4.0. SUMMARY AND CONCLUSIONS. M a t c h i n g c a r b o h y d r a t e and p r o t e i n s o u r c e s d i f f e r i n g i n t h e r a t e o f c a r b o h y d r a t e and p r o t e i n d e g r a d a t i o n showed b e n e f i c i a l e f f e c t s f o r t h e f o l l o w i n g c h a r a c t e r i s t i c s and was dominated by t h e e f f e c t o f s o u r c e c a r b o h y d r a t e ; S t a r c h i n t a k e tended t o be h i g h e r f o r t h e FM t h a n t h e CM d i e t s w h i l e b a r l e y based d i e t s had h i g h e r s t a r c h and f i b e r i n t a k e s t h a n c o r n . B a r l e y based d i e t s had h i g h e r DM, OM, s t a r c h , CP, NDF, and h e m i - c e l l u l o s e d i g e s t i b i l i t y t h a n c o r n based d i e t s . 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E f f e c t o f d i e t a r y soybean meal and f i s h meal on p r o t e i n d i g e s t a f l o w i n h o l s t e i n cows d u r i n g e a r l y and m i d - l a c t a t i o n . J . D a i r y S c i . 71:1248. 183 4.6.0 TABLES. T a b l e 12. I n g r e d i e n t s c o m p o s i t i o n o f c o n c e n t r a t e s f e d t o l a c t a t i n g d a i r y cows as a p e r c e n t a g e o f t h e d r y m a t t e r 1 . ITEM D I E T S SRC-FM SRC-CM SRB-FM SRB-CM Steam r o l l e d corn (SRC) 89 . 95 81. 75 Steam r o l l e d barley (SRB) • • • • • 91. 09 84 . 55 F i s h meal (FM) 8 . 06 7.12 C a n o l a meal (CM) 15.15 13.51 L i m e s t o n e 1. 09 0.15 S a l t 0.99 1.10 0.85 0. 90 Vitamin-mineral mix2 0.99 1.10 0.93 0.90 Concentrates: SRC-FM, steam - r o l l e d c orn-fish meal; SRC--CM, steam-r o l l e d c o r n - c a n o l a meal; SRB-FM, s t e a m - r o l l e d b a r l e y - f i s h meal and SRB-CM, s t e a m - r o l l e d b a r l e y - c a n o l a meal. 2Phosphorus 20.0%, i o d i n e 200 mg/kg, c o b a l t 150 mg/kg, copper 4000 mg/kg, z i n c 6000 mg/kg, manganese 2500 mg/kg, magnesium 6.0%, f l o u r i n e ( m a x ) 2000 mg/kg, v i t a m i n A(min) 500000 IU/kg, v i t a m i n D (min) 50000 IU/kg, v i t a m i n E (min) 500IU/kg, i r o n 8000 mg/kg, and s e l e n i u m 3 5mg/kg. 184 T a b l e 13. N u t r i e n t a n a l y s i s o f major d i e t a r y i n g r e d i e n t s f e d t o l a c t a t i n g d a i r y cows 1. Item ALFH SRC SRB FM CM DM% 89 .37 95.01 94 . 64 96. 07 96. 04 % OF DM OM 91. 34 97 .81 98 .39 74 . 64 88. 66 CP 17.39 9.02 10.29 56. 82 33. 54 S t a r c h 3.82 74 .80 67.10 10. 66 NDF 44 . 89 14 . 68 29.71 7 . 08 26. 65 ADF 39.95 3.74 6.57 2. 31 17. 71 H/CELL 4.94 10. 94 23 .14 4. 77 9. 20 GE K c a l / g 4 .43 4.43 4 .36 4 . 35 4 . 35 EE 2.34 4 . 03 1. 69 8. 34 4. 62 Ash 8 . 66 2 . 19 1.61 25. 36 11. 34 Ca 1. 50 0. 02 0. 07 5. 70 0. 65 P 0.18 0.34 0.31 3. 55 2. 63 ^ L F H = a l f a l f a hay, SRC = s t e a m - r o l l e d c o r n , SRB = s t e a m - r o l l e d b a r l e y , FM = f i s h meal, CM = c a n o l a meal 185 T a b l e 14. C h e m i c a l a n a l y s i s o f d i e t s f e d t o l a c t a t i n g d a i r y cows 1 2. Item SRC-FM SRC-CM SRB-FM SRB-CM DM% 95.69 96. 07 95.62 96.34 % OF DM OM 88.77 91.30 92 . 97 93 . 51 CP 16. 15 16.13 15.56 15.12 S t a r c h 31.18 33 . 63 32.15 33.65 NDF 29 .32 28.80 36.13 36. 05 ADF 22.28 21.47 23 . 04 22.42 H/CELL 7.04 7 .33 13 . 09 13 . 65 NE1, 1. 53 1.61 1. 58 1. 60 Meal/ k g 3 Ash 5.46 5.92 5.16 5.50 Ca 1. 03 1.37 1. 01 0.76 P 0.38 0.50 0.37 0.42 •SRC-FM = steam-rolled corn-fish meal, SRC-CM = steam-rolled corn-canola meal, SRB-FM = steam-rolled b a r l e y - f i s h meal, SRB-CM = steam-rolled barley-canola meal. Concentrate plus a l f a l f a hay Estimated from NRC (1989) 186 T a b l e 15a. I n s i t u d i s a p p e a r a n c e o f d r y m a t t e r , s t a r c h and n e u t r a l d e t e r g e n t f i b e r i n cows o f a l f a l f a hay and c e r e a l i n g r e d i e n t s used i n r a t i o n s f o r l a c t a t i n g d a i r y cows 1 2. D e g r a d a t i o n C h a r a c t e r i s t i c s 3 ALFH 5 SRC SE 4 SRB SE P<0.05 DM a (%) b (%) k d ( % / h Lag (h) 43.90±0.43 35.16+1.17 6.32+0.02 0.00+0.00 41.38 3 6.32 6.42 0.26 0. 27 2.40 0.34 0.26 52.42 39. 09 12 . 24 0. 00 0.86 0.68 0.98 0.00 0.0066 0. 3842 0.0301 0.4226 EFDEG 0.05 0. 09 (%) 63.54+0.11 58.69+0.27 61. 50 56.13 0.87 0. 60 80.14 74 .13 0.27 0.30 0.0024 0.0013 S t a r c h a (%) b (%) k d(%/h) Lag (h) 44.83 54 . 10 5.88 1.75 1.77 2 .35 0. 11 1.46 36.31 55.87 15.26 0. 00 2 . 09 1. 87 1.34 0. 00 0.0397 0.6155 0.0200 0.3526 EFDEG 4 0.05 0. 09 (%) 71.79 63 . 38 1. 57 1. 63 78.35 71.42 0.24 0.24 0.0440 0.0397 NDF6 a(%) k d(%/h) 8.02±.10 6.29+.07 ND7 ND !ALFH = a l f a l f a hay, SRC = s t e a m - r o l l e d c o r n , SRB = s t e a m - r o l l e d b a r l e y . 2Means i n t h e same row w i t h i n c e r e a l e f f e c t a r e s i g n i f i c a n t l y d i f f e r e n t (P<0.05). 3 a = r a p i d l y d e g r a d a b l e f r a c t i o n , b = s l o w l y d e g r a d a b l e f r a c t i o n , k d = f r a c t i o n a l r a t e o f d e g r a d a t i o n o f f r a c t i o n b, lag= l a g t i m e , EFDEG = e f f e c t i v e d e g r a d a b i l i t y a t 5%/h and 9%/h f r a c t i o n a l o u t f l o w r a t e . 4SE = s t a n d a r d e r r o r (n=2) 5Mean+standard d e v i a t i o n (n=4). 6 E s t i m a t e d as s l o p e o f t h e r e g r e s s i o n o f t h e n a t u r a l l o g o f p e r c e n t a g e d e g r a d a b i l i t y v s t i m e . 7Not d e t e r m i n e d . 187 T a b l e 15b. I n s i t u d i s a p p e a r a n c e o f d r y m a t t e r and crude p r o t e i n i n cows o f FM and CM i n g r e d i e n t s used i n r a t i o n s f o r l a c t a t i n g d a i r y cows 1 2. D e g r a d a t i o n C h a r a c t e r i s t i c s 3 FM SE 4 CM SE P<0.05 DM a (%) 52.72 0.05 43.16 1.37 0.0199 b (%) 15.46 2.18 44.42 2.10 0.0108 k d ( % / h 4.33 0.70 8.34 2.27 0.0336 Lag (h) 0.00 0.00 0.00 0.00 0.4226 EFDEG 5 (%) 0.05 59.76 0.32 70.57 2.84 0.0233 0.09 57.64 0.10 64.26 2.69 0.0432 CP a(%) 48.16 0.12 36.15 2.96 0.0259 b(%) 23.73 3.94 56.90 4.43 0.0305 k d(%/h) 3.02 0.44 8.06 2.14 0.0458 Lag (h) 0.00 0.00 1.18 1.18 0.4226 EFDEG 5 (%) 0.05 57.25 0.63 69.36 2.97 0.0370 0.09 54.26 0.28 60.85 2.91 0.0421 'FM = f i s h meal, CM = c a n o l a meal. 2Means i n t h e same row w i t h i n p r o t e i n e f f e c t a r e s i g n i f i c a n t l y d i f f e r e n t (P<0.05). 3 a = r a p i d l y d e g r a d a b l e f r a c t i o n , b = s l o w l y d e g r a d a b l e f r a c t i o n , k d = f r a c t i o n a l r a t e o f d e g r a d a t i o n o f f r a c t i o n b, lag= l a g t i m e , EFDEG = e f f e c t i v e d e g r a d a b i l i t y a t 5%/h and 9%/h f r a c t i o n a l o u t f l o w r a t e . 4 S t a n d a r d e r r o r (n=2). 5EFDEG = E f f e c t i v e d e g r a d a b i l i t y . 188 T a b l e 16. L e a s t square means f o r d r y m a t t e r , o r g a n i c m a t t e r and n u t r i e n t i n t a k e s of l a c t a t i n g cows r e c e i v i n g SRC o r SRB w i t h e i t h e r FM o r CM d u r i n g t h e i n t a k e s t u d y . D I E T S 1 , 2 Main e f f e c t s SRC SRB and i n t e r a c t i o n 3 ITEM FM CM FM CM C P DMI, kg/d TOTAL 23.74+.30 23.77+.30 23.84+.36 23.54±.34 NS 4 NS CONC. 11.20+.67 10.30+.63 11.35+.73 10.51+.71 NS NS HAY 12.53±.62 13.47+.62 12.49+.73 13.03±.70 NS NS %Bwt 3.63+.05 3.65+.05 3.65+.06 3.61+.05 NS NS OMI, kg/d TOTAL 22.19±.29 22.29±.29 22.41±.33 22.20±.32 NS NS CONC 10.74+.61 10.00+.61 11.00+.71 10.30+.69 NS NS HAY ^ 11.45±.57 12.28±.57 11.41±.66 11.89±.64 NS NS N u t r i e n t s . CP, kg/d Cone 1.57+.12 1.41+.12 1.68+.14 1.55+.13 NS NS Hay, 2.47+.12 2.81+.12 2.54+.14 2.65+.13 NS NS T o t a l 4.03+.09 4.22+.09 4.22+.11 4.21+.10 NS NS S t a r c h , kg/d Cone 7.45+.39 6.62+.39 6.96±.45 6.16+.44 NS .12 T o t a l 7.91+.36 7.12+.36 7.41+.42 6.65+.41 NS .11 ADF, kg/d Hay 4.44+.34 5.27+.34 4.85+.39 5.56+.38 NS .09 T o t a l 4.85±.33 5.91+.33 5.53±.39 6.47±.38 .13 .04 NDF, kg/d Cone 1.30±.16 1.28+.16 2.93±.18 2.53±.18 .0001 NS Hay 5.57+.29 5.99+.29 5.55+.34 5.79+.33 NS NS T o t a l 6.86+.28 7.28+.28 8.18+.33 8.32+.32 .006 NS H/CELL, kg/d Cone 0.71+.07 0.78+.07 1.86+.09 1.91+.08 .0001 NS Hay 0.59+.03 0.64±.03 0.58±.04 0.61±.04 NS NS T o t a l 1.31+.06 1.42+.06 2.44+.07 2.52+.06 .0001 NS 'SRC = s t e a m - r o l l e d c o r n , SRB = s t e a m - r o l l e d b a r l e y , FM = f i s h m eal, CM = c a n o l a meal. 2Mean+se (SRC d i e t s , BFM and CCM, n=9, 7 and 8, r e s p e c t i v e l y ) . 3The i n t e r a c t i o n o f s o u r c e o f c a r b o h y d r a t e and s o u r c e o f p r o t e i n were not s i g n i f i c a n t l y d i f f e r e n t l y (P<0.10). 4NS = n o t s i g n i f i c a n t (P>0.10). 189 T a b l e 17. L e a s t square means of d r y m a t t e r and o r g a n i c m a t t e r i n t a k e s , t o t a l a p p a r e n t n u t r i e n t d i g e s t i b i l i t i e s and r a t e of passage f o r l a c t a t i n g cows f e d e i t h e r SRC o r SRB w i t h e i t h e r FM o r CM d u r i n g t h e d i g e s t i b i l i t y t r i a l . D I E T S 1,2 ITEM SRC SRB Main e f f e c t s 3 FM CM FM CM SE 4 C P I n t a k e , kg/d DM 21.97 21. 72 21. 75 21. 94 0. 64 NS 5 NS OM 20. 60 20. 34 20. 43 20. 70 0. 68 NS NS D i g e s t i b i l i t i e s DM 68 . 79 67 . 16 75. 47 74 . 39 2 .20 . 07 NS OM 71.10 69 . 22 77 . 92 75. 62 2 . 01 . 07 NS CP 75. 01 71. 71 78. 64 77. 23 1.27 .05 NS S t a r c h 92 .13 89 . 50 96. 64 95. 82 1.52 . 06 NS ADF 44.64 44 . 53 51. 62 56. 29 5.46 NS NS NDF 39.83 35. 96 53 . 87 57. 62 4 .74 .05 NS H-CE 48.20b 27 . 91c 55. 22a 65. 22a 5.42 .04 NS ROP6, %/h S o l i d phase 5. 64 6 . 05 5. 43 8 . 63 . 52 NS . 07 L i q u i d phase 11.81 13 . 44 10. 42 10. 71 . 58 NS NS XSRC = s t e a m - r o l l e d c o r n , SRB = s t e a m - r o l l e d b a r l e y , FM = f i s h meal, CM = c a n o l a meal. 2Means i n t h e same row w i t h d i f f e r e n t l e t t e r s a r e s i g n i f i c a n t l y d i f f e r e n t P<0.10. 3The i n t e r a c t i o n between s o u r c e o f c a r b o h y d r a t e and s o u r c e o f p r o t e i n s i g n i f i c a n t f o r h e m i - c e l l u l o s e (P<0.0962). 4 S E - S t a n d a r d e r r o r (n=3). 5NS-not s i g n i f i c a n t (P>0.10). 6ROP-rate o f passge. 190 TJ r d ™ . 0) « j j - H 0) 4H a) o >H a) +j c id s X u ft. £ ej co £ P4 CO £ [v. CN H CN co co CO O CO O to O o 55 o 25 o 55 • • • • • I-I o H o H O CO o CO o O O CO CO . 55 o o o 2 o o H rH H rH n O O CT\ O O CO O CO o o O o CO o 55 o o o o 55 • • • • • XI XI XI xt CN CO CN i n o o o CO i n • • • • • • * • H o o o o o o CN +1 +1 +1 + 1 + 1 +1 + 1 + 1 o co i n o CN CO CO O 0 0 ro VO CO H VO • • • • • • • • i n CO o rH rH co rH VO H H CO rd cd 0 XI XI H i n CN CO CO VO CO in o o O CO CO rH o o o o O o CN +i +i +i + 1 +1 +1 + 1 +1 i n r> CN r- CO CO i n CO vo CO CO • • • • • • • • H o H o co CO VO H H r » 0 O Xt cd cd cn CN CO i n VO H i n o o o CO • t f H O o o o o o CN +1 +1 +i +1 +1 +i +i +i CN VO CM o CO r- i n CO o CN i n H CO • • • • • • • • CO CN H H CN i n vo H H Xt Xt rd XI Xt CN CN vo •«* CN o\ r-co i n O O O co o H O O O O O O CN +1 +1 +1 +1 +1 +1 +l +1 CN i n O O vo CM co CO H CO VO CN • t • t • • • • VO CO H H H CO CN VO H H i in i » < > U cd rH o £ ft. ^ co pa -P << -P w <rj 0) cd •P o cd •H U . OH > I X I O -P O U 3 10 PH ffl H CU •P cd 3 U ' CU CU •P cd U CU rH rd > o w H rd •P 0 E-t to 25 CO 55 CO 55 CO 25 i n o co 55 o CO CO CO i n CN CN o o CN VO in CO in 55 rH I TJ co X X Ok 55 e in o o i n o in o rd CN o CN CO * VO rd cn i n • CN CN CO 55 Xt CM cd CN CO • i n CO Xt Xt 1 0) in CO i n CA 1 U <M o vo CM CM 1 CU O • • • • 1 <M CO i n i <«H cu iH t-> 1 - H o o in • co VO rH 5 0Q 6 •P c rd O •H <*H •H • C — CT> O - H H IQ V +J PH O C (0 cd 5 -P c cu ^ cu «M - H <4H CU •H 4J TJ O rH 4-) <4H c o cd o cu o r4 c o CT« 10 •H 10 TJ C 0) cd U rd Q) -P CO rd u u a) TJ •P >. •p XJ cu o rH xt >H rd o c X! •p •rH o o w c CU M -p cu a> xt e rd w o X! -P co c rd cu c o •iH +J o rd >H CU •P c •H a) x) CO ii II C • rH a> > •H •P O 0J (0 0 u o 0 3 TJ C cd (N •I II § CM 0 3 PQ -55 CO CO II X a 55 u -X • TJ a c o cd H o • CO VO -p • o — c o rH CN V CO ft. 55 ^ - r o t 191 T a b l e 19. L e a s t square means f o r m i l k p r o d u c t i o n , y i e l d components, m i l k c o m p o s i t i o n , g r o s s e f f i c i e n c i e s and body w e i g h t change f o r cows f e d SRC o r SRB w i t h e i t h e r FM o r CM. ITEM D I E T S1 SRC FM CM FM SRB Main e f f e c t s and i n t e r a c t i o n 2 CM Y i e l d , kg/d M i l k 3.5% FCM SCM F a t P r o t e i n T / s o l i d s SNF 25.76+0.58 25.07+0.58 27.59+0.68 27.40+0.65 25.01+0.99 26.51+0.99 25.88+1.16 25.22+1.12 23.94+0.45 24.56+0.45 24.99+0.53 24.78+0.51 0.91+.061 0.85+.024 3.17+.038 2.27+.080 0.95+.061 0.82+.024 3.18+.038 2.21+.080 0.87+.71 0.92+.029 3.40±.045 2.51+.094 0.85+.068 0.91+.028 3.36±.043 2.55+.091 .01 NS NS NS . 02 NS NS NS NS NS 0016 NS 0116 NS C o m p o s i t i o n , % F a t 3.32+.23 3.76+.23 3.04+.26 2.93+.25 .06 NS P r o t e i n 3.30+.05 3.23+.05 3.37+.05 3.29+.05 NS NS T / s o l i d s 12.05+.19 12.40±.19 12.00+.22 12.07±.21 NS NS SNF 8.74+.15 8.64+.15 8.96+.17 9.14+.17 .06 NS Gros s e f f i M ilk:DMI FCM:DMI Milk:OMI FCM:OMI i e n c y 1.07+.018 1.07+.051 1.15+.019 1.15+.055 1.04+.018 1.09+.051 1.11+.019 1.17+.055 1.14+.021 1.06+.059 1.22±.022 1.13+.065 1.16+.02 1.07+.057 1.23+.021 1.14+.062 .002 NS NS NS .002 NS NS NS Body w e i g h t change +5.63+11 -7.99+11 +6.91+13 +10.98+12.9 NS NS Kg/28 d 'Mean+se ( SRC d i e t s , BFM and CCM, n=9, 7 and 8, r e s p e c t i v e l y ) . 2The i n t e r a c t i o n between c a r b o h y d r a t e s o u r c e and p r o t e i n s o u r c e was no t s i g n i f i c a n t (P>0.10). 3NS = P>0.10. 192 5.0 GENERAL CONCLUSIONS AND RECOMMENDATIONS. Roughages w i l l c o n t i n u e t o be t h e b a s i c and i m p o r t a n t p o r t i o n o f t h e d i e t o f ru m i n a n t a n i m a l s f o r meat and m i l k p r o d u c t i o n . However s u p p l e m e n t a t i o n w i t h c e r e a l s and p r o t e i n s o u r c e s f o r energy and n i t r o g e n p r o v i s i o n f o r e f f i c i e n t m i c r o b i a l p r o t e i n s y n t h e s i s i s paramount t o e f f i c i e n t and economic p r o d u c t i o n o f meat and m i l k . C a r e f u l s e l e c t i o n o f energy and p r o t e i n s o u r c e s a c c o r d i n g t o t h e i r r a t e o f d i g e s t i o n i n t h e rumen i s i m p o r t a n t f o r p r o v i s i o n o f energy f o r t h e c a p t u r e o f n i t r o g e n by m i c r o b e s . Knowledge o f t h e b e h a v i o r o f f e e d components i n t h e g a s t r o -i n t e s t i n a l t r a c t i s a c c o m p l i s h e d by use o f i n v i t r o , i n s i t u and i n v i v o methods. E s s e n t i a l l y t h e f i r s t two mimic what happens i n v i v o . However, t h i s may be i m p o s s i b l e t o a c h i e v e as n e i t h e r t h e i n v i t r o n o r t h e i n s i t u e s t i m a t e s a r e t h e same as found by i n v i v o systems. I n t h i s s t u d y , steam r o l l i n g o f c e r e a l g r a i n s i n c r e a s e d t h e i n v i t r o r e l e a s e o f s t a r c h by a m y l o g l u c o s i d a s e . However i n s i t u s t u d i e s showed t h a t steam r o l l i n g o f c e r e a l s r e s u l t e d i n a d e c r e a s e d r a t e o f DM and s t a r c h d e g r a d a t i o n w h i c h was i n c o n f l i c t w i t h many p u b l i s h e d i n v i v o d a t a and t h e few i n s i t u s t u d i e s t h a t have been r e p o r t e d . S t u d i e s i n whi c h i t was c o n c l u d e d t h a t steam r o l l i n g i n c r e a s e d s t a r c h d e g r a d a t i o n , r e s e a r c h e r s used g r a i n s t h a t had been r e t a i n e d on a s c r e e n o f known s i z e , t h e r e b y removing d i f f e r e n c e s i n p a r t i c l e s i z e d i s t r i b u t i o n among t h e p r o c e s s e d and un p r o c e s s e d g r a i n s w h i l e i n t h i s s t u d y and o t h e r s w h i c h a r e i n c o n f l i c t , g r a i n s used had been ground w i t h o u t f u r t h e r s i e v i n g . 193 The i n s i t u p r o c e d u r e was a l s o used t o d e t e r m i n e d e g r a d a t i o n c h a r a c t e r i s t i c s o f a g r o - b y p r o d u c t s . NDF from RDG degrades much f a s t e r t h a n t h a t o f BP and WMR b u t BP has t h e h i g h e s t r u m i n a l a v a i l a b i l i t y . As f o r steam r o l l i n g o f c e r e a l s and c e r t a i n o t h e r c o n c e n t r a t e f e e d s o f a g r o - b y p r o d u c t n a t u r e , h i g h i n p e c t i c m a t e r i a l , t h e i n s i t u method may not be s u i t a b l e f o r t h e d e t e r m i n a t i o n o f t h e d e g r a d a t i o n o f c e r t a i n f e e d components. More r e s e a r c h i s r e q u i r e d t o p i n p o i n t f a c t o r s w h i c h a r e r e s p o n s i b l e f o r t h e reduced DM and s t a r c h d e g r a d a t i o n i n s i t u , p o s s i b l y p r o d u c t s o f m a l l a i r d r e a c t i o n and r e t r o g r a d a t i o n r e a c t i o n s and a l s o t h e g e n e r a l i n s i t u t e c h n i q u e . I n a d d i t i o n more r e s e a r c h i s r e q u i r e d t o d e t e r m i n e d e g r a d a t i o n c h a r a c t e r i s t i c s o f f e e d components e s p e c i a l l y a g r o - b y p r o d u c t s w h i c h a r e becoming i n c r e a s i n g l y i m p o r t a n t i n N o r t h A m e r i c a . From i n s i t u , i n v i t r o and m i l k p r o d u c t i o n s t u d i e s , i t was c o n c l u d e d t h a t ; 1. s t a r c h i n b a r l e y and wheat degrade much f a s t e r t h a n c o r n , 2. steam r o l l i n g o f c o r n , wheat and b a r l e y d e c r e a s e s s t a r c h d e g r a d a t i o n i n s i t u , 3. steam r o l l i n g o f c o r n , wheat and b a r l e y i n c r e a s e s i n v i t r o s t a r c h r e l e a s e by a m y l o g l u c o s i d a s e enzyme, 4. NDF from a l f a l f a hay degrades f a s t e r t h a n t h a t from c o r n - g r a s s s i l a g e and o r c h a r d g r a s s hay, 194 5. NDF from r y e d i s t i l l e r s g r a i n s degrades f a s t e r t h a n t h a t from beet p u l p and wheat m i l l r u n , w i t h b eet p u l p h a v i n g t h e h i g h e s t e f f e c t i v e d e g r a d a b i l i t y . 6. From t h e m i l k p r o d u c t i o n t r i a l , i t can be c o n c l u d e d t h a t d i e t s matched f o r h i g h r u m i n a l a v a i l a b i l i t y o f b o t h c a r b o h y d r a t e and p r o t e i n and a l s o d i e t s h i g h i n r u m i n a l a v a i l a b i l i t y o f c a r b o h y d r a t e but f e d w i t h a p r o t e i n s o u r c e o f moderate n i t r o g e n a v a i l a i b i l i t y w i l l r e s u l t i n i n c r e a s e d m i l k p r o d u c t i o n w i t h a l f a l f a hay as a roughage. T h i s a g r e e s w i t h our i n s i t u s t u d i e s when b a r l e y was compared t o c o r n and when c a n o l a meal was compared t o f i s h meal f o r r u m i n a l a v a i l a b i l i t i e s . C e r t a i n l y f u r t h e r r e s e a r c h i s r e q u i r e d t o c o n f i r m t h e s e f i n d i n g s . V a r i a b i l i t y i n d e g r a d a t i o n c h a r a c t e r i s t i c s o f c a r b o h y d a t e s and p r o t e i n s o f c e r e a l s , p r o t e i n supplements, roughages and a g r o -b y p r o d u c t s can be e x p l o i t e d i n r a t i o n f o r m u l a t i o n t o a c h i e v e a b a l a n c e between t h e adequate p r o v i s i o n o f energy and n i t r o g e n f o r e f f i c i e n t m i c r o b i a l p r o t e i n and p r o v i s i o n o f some o f t h e s e n u t r i e n t s t h r o u g h l o w e r t r a c t d i g e s t i o n . 195 6.0 APPENDICES. APPENDIX 1. SAS program used t o c a l c u l a t e d e g r a d a t i o n c h a r a c t e r i s t i c s f o r f e e d s u s i n g t h e m o d i f i e d e q u a t i o n o f 0 r s k o v and MacDonald, (1979). o p t i o n s ps=59 ls=8 0 n o c e n t e r ; *JOHN HALL-AG CANADA - 0RSKOV EQUATIONS WITH LAG PHASE SOLUTION; OPTIONS PAGESIZE=9 0; TITLE 'Dry m a t t e r A g r o b y p r o d u c t s ' ; FILENAME SASDATA ' b : i n s a b s a s . p r n ' ; DATA DMD ; INF I L E SASDATA MISSOVER; INPUT Sample T r t Cow T DMD; RUN; PROC SORT; BY t r t cow; PROC NLIN ITER=50 METHOD=MARQUARDT; BY t r t cow; PARMS A=50 B=4 0 C=.04 .05 LAG=0,2,4; BOUNDS LAG>=0; IF LAG<0.0 THEN DO; LAG = 0.0; END; I F T<LAG THEN DO ; MODEL DMD = A; DER.A = 1 . ; DER.B = 0 . ; DER.C = 0 . ; DER.LAG = 0 . ; END ; ELSE DO ; MODEL DMD = A + B*(1.-EXP(-C*(T-LAG))) ; DER.A = 1 . ; DER.B = (1.-EXP(-C*(T-LAG))) ; DER.C = B*(T-LAG)*EXP(-C*(T-LAG)) ; DER.LAG = -B*C*EXP(-C*(T-LAG)) ; END ; OUTPUT OUT=B PREDICTED=YHAT RESIDUAL=YRES PARMS=A B C LAG; PROC PRINT DATA=B noobs; d a t a baba; s e t WORK.B; f i l e tembo; pu t TRT 6 COW 9 T 13-14 DMD 20-24 YHAT 26-32 YRES 34-41 A 43-49 B 51-57 C 59-65 LAG 67-73; r u n ; PROC PLOT ; BY t r t ; 196 OPTIONS PAGESIZE=25; PLOT DMD*T=/0' YHAT*T='P' / OVERLAY ; RUN; DATA SUM(DROP= YHAT YRES ) ; OPTIONS PAGESIZE=90; •CALCULATING EFFECTIVE DEGRADABILITY; v SET B; I F T < 48 THEN DELETE; I F T > 48 THEN DELETE; *THE CALCULATED CONSTANTS ARE THE SAME FOR EACH INCUBATION TIME THIS STATEMENT DELETES ALL BUT ONE TIME; TO=LAG; Kf=.05; *Kf IS THE FRACTIONAL RATE OF PASSAGE; EFFDGRD=A+(((B*C)*EXP(C*TO))/(C+Kf))*EXP(-(C+Kf)*TO); PUT t r t A B C LAG Kf EFFDGRD; RUN; PROC PRINT ; RUN; o p t i o n s ps=59 ls=8 0 n o c e n t e r ; d a t a degrade; i n f i l e 'c:\sas\tembo'; i n p u t sample t r t cow T dmd y h a t y r e s a b c l a g ; * * * i f p e r i o d = '0' t h e n d e l e t e ; r u n ; p r o c glm; c l a s s sample t r t cow T; model a b c l a g y r e s = t r t cow; means t r t / t u k e y ; lsmeans t r t / s t d e r r p d i f f ; r u n ; p r o c glm; c l a s s t r t cow T; model dmd y h a t y r e s = t r t cow; means t r t / t u k e y ; lsmeans t r t / s t d e r r p d i f f ; r u n ; 197 APPENDIX 2. Schematic r e p r e s e n t a t i o n o f t h e a l l o c a t i o n o f d i e t s f o r a 4 t r e a t m e n t / 3 p e r i o d s w i t c h back d e s i g n used f o r t h e d a i r y cow t r i a l 1 P e r i o d Cow ID 2 3 1 2 3 8707 BFM CCM BFM 8802 CFM BCM CFM 8810 CCM CFM CCM 8817 BCM CFM BCM 8819 CFM CCM CFM 8821 BCM BFM BCM 8902 CCM BCM CCM 8908 CFM BFM CFM 8909 BFM CFM BFM 8913 BFM BCM BFM 8918 BCM CCM BCM 8920 CCM BFM CCM JCFM = steam-r o l l e d c o r n - f i s h meal, CCM = steam-- r o l l e d c o r n - c a n o l a meal, BFM = steam-- r o l l e d b a r l e y - f i s h meal, BCM = steam-- r o l l e d b a r l e y - c a n o l a meal. (4 t r e a t m e n t s - c o m p l e t e d e s i g n w i t h b l o c k s d i s r e g a r d e d - Lucas, 1956) 2Cows # 8707, 8802, 8810 and 8821 were used f o r m e t a b o l i s m s t u d y . 3Cow # 8913 = removed from t r i a l a f t e r s p r a y i n g h i n d l e g s . 198 

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