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Nutritive evaluation of low=quality forages supplemented with different nitrogen sources in ruminant… Adeleye, Isaac Omotosho Adewale 1972

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I 0 I Y 7 NUTRITIVE EVALUATION OF LOW-QUALITY FORAGES SUPPLEMENTED WITH DIFFERENT NITROGEN SOURCES IN RUMINANT FEEDS by ISAAC OMOTOSHO ADEWALE ADELEYE B . S c , U n i v e r s i t y of Ibadan, N i g e r i a , 1966 M.Sc , M c G i l l U n i v e r s i t y , 1969 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n the Department of ANIMAL SCIENCE We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA May, 1972 In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y available for reference and study. I further agree that permission for extensive copying of t h i s thesis for scholarly purposes may be granted by the Head of my Department or by h i s representatives. It i s understood that copying or publication of t h i s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. I.O.A. ADELEYE Department of Animal Science The University of B r i t i s h Columbia Vancouver 8, Canada Date May £ b , 1972 I l l Chairman: P r o f . W.D. K i t t s ABSTRACT The u t i l i z a t i o n o f l o w - q u a l i t y forages i n the feeds of ruminant animals takes on s p e c i a l importance because of the abundance o f these m a t e r i a l s and t h e i r p o t e n t i a l v a l u e i f supplemented wi t h p r o t e i n . The e f f e c t of the use of three d i f f e r e n t n i t r o g e n sources, urea, b i u r e t and p o u l t r y wastes, to r e p l a c e a p o r t i o n of soybean meal n i t r o g e n i n h i g h roughage-r a t i o n s o f sheep was i n v e s t i g a t e d u s i n g i n v i v o and i_n v i t r o t e c h niques. The chemical composition of p o u l t r y waste was determined to study the f e a s i b i l i t y of u s i n g i t as a n i t r o g e n source. There was a c o n s i d e r a b l e v a r i a t i o n i n the chemical composition of p o u l t r y l i t t e r (bedding m a t e r i a l p l u s droppings) as compared with the cage droppings. The l i t t e r c o n t a i n e d 21.5 to 30.4% p r o t e i n e q u i v a l e n t , approximately o n e - t h i r d o f which was i n form ' of u r i c a c i d n i t r o g e n . The cage droppings c o n t a i n e d 26.3 to 35.4% p r o t e i n e q u i v a l e n t and about t w o - f i f t h s of t h i s was i n the form of u r i c a c i d n i t r o g e n . Before f e e d i n g t r i a l s were undertaken, attempts were made to reduce the number of pathogenic b a c t e r i a t h a t might be pr e s e n t i n the p o u l t r y wastes by heat treatment. Though a u t o c l a v i n g or steaming had no s i g n i f i c a n t e f f e c t on the t o t a l n i t r o g e n or u r i c a c i d n i t r o g e n , these heat treatments however, were s u f f i -c i e n t t o d e s t r o y a l l the m i c r o f l o r a i n the wastes. i v No s i g n i f i c a n t d i f f e r e n c e s were observed i n the d i g e s t i b i l i t y c o e f f i c i e n t s o f dry matter, crude p r o t e i n , crude f i b e r or gross energy when approximately 50% o f the soybean meal (SBM) n i t r o g e n of the c o n t r o l r a t i o n was r e p l a c e d by urea, b i u r e t or p o u l t r y droppings i n the r a t i o n s o f f a t t e n i n g lambs f e d i n the u n p e l l e t e d form. However, s i m i l a r replacement of 50% of the SBM n i t r o g e n of the c o n t r o l r a t i o n by p o u l t r y l i t t e r , r e s u l t e d i n s i g n i f i -c a n t l y lower n u t r i e n t d i g e s t i b i l i t y c o e f f i c i e n t s of t h i s r a t i o n when compared wi t h the c o n t r o l . I t might t h e r e f o r e by concluded • t h a t the presence o f bedding m a t e r i a l i n the p o u l t r y l i t t e r hampered the a v a i l a b i l i t y o f n i t r o g e n from t h i s source when fed to lambs. However, when the r a t i o n s were o f f e r e d i n the p e l l e t e d form, the d i f f e r e n c e s i n n u t r i e n t d i g e s t i b i l i t y c o e f f i c i e n t s , p a r t i c -u l a r l y between the c o n t r o l and the l i t t e r supplemented r a t i o n s , were no Monger s i g n i f i c a n t . P e l l e t i n g was found to i n c r e a s e the v o l u n t a r y i n t a k e o f the r a t i o n s r e g a r d l e s s o f the source o f n i t r o g e n supplementation. Although a l l animals were i n p o s i t i v e n i t r o g e n b alance, those f ed the urea and p o u l t r y l i t t e r supplemented r a t i o n s had s i g n i f i c a n t l y lower n i t r o g e n r e t e n t i o n than those f ed the soybean, b i u r e t and p o u l t r y droppings supplemented r a t i o n s . T h i s obser-v a t i o n was a l s o r e f l e c t e d i n the lower body weight gains and feed e f f i c i e n c y o f the animals f ed the urea and l i t t e r c o n t a i n i n g d i e t s . V In experiments designed to determine the maximum l e v e l o f p o u l t r y droppings t h a t c o u l d be s a f e l y i n c o r p o r a t e d as an NPN source i n hig h roughage r a t i o n s , i t was found t h a t a t l e v e l s o f 18.7, 50.2 and 64.2% of the t o t a l n i t r o g e n i n the r a t i o n s , there was no s i g n i f i c a n t d i f f e r e n c e i n the v o l u n t a r y i n t a k e . This i n d i c a t e d t h a t as a source o f NPN, p o u l t r y droppings had an e q u a l l y e f f e c t i v e replacement value a t a l l the three l e v e l s s t u d i e d . In v i t r o t e s t s were employed t o determine the e f f e c t of a l k a l i treatment on the n u t r i t i v e v alue of l o w - q u a l i t y f o r a g e s . Treatment wi t h NaOH o r NH^OH s i g n i f i c a n t l y i n c r e a s e d c e l l u l o s e d i g e s t i b i l i t y . The type o f n i t r o g e n source (urea, b i u r e t or u r i c acid) used i n the b a s a l medium d i d a f f e c t the c e l l u l o s e d i g e s t i b i l i t y . There appeared to be a p o s i t i v e r e l a t i o n s h i p between the s o l u b i l i t y of the n i t r o g e n source and c e l l u l o s e d i g e s t i b i l i t y i n v i t r o . v i ACKNOWLEDGEMENTS I wish t o thank Dr. W.D. K i t t s , P r o f e s s o r and Head, Department of Animal S c i e n c e , under whose s u p e r v i s i o n t h i s study was undertaken and f o r h i s guidance and t e c h n i c a l suggestions i n the p r e p a r a t i o n of t h i s t h e s i s . S i n c e r e a p p r e c i a t i o n i s extended, f o r i n d i v i d u a l and c o l l e c t i v e advice and the review o f t h i s t h e s i s , to Dr. R.M. T a i t , Dr. C.R. Kri s h n a m u r t i and Dr. R.M. Beames, a l l o f the Department of Animal S c i e n c e , U n i v e r s i t y o f B r i t i s h Columbia. I a l s o wish to thank Mr. J.C. MacGregor and h i s s t a f f f o r t h e i r a c t i v e involvement i n the p r e p a r a t i o n o f the experimental r a t i o n s and h a n d l i n g of the animals. I wish to express my s i n c e r e g r a t i t u d e to the Canadian Commonwealth S c h o l a r s h i p and F e l l o w s h i p A d m i n i s t r a t i o n f o r the p e r m i s s i o n t o extend my v i s a to cover the p e r i o d o f t h i s study. F i n a l l y , I wish to thank my w i f e , Modupe, f o r her encourage-ment throughout the p e r i o d o f t h i s study and f o r her p a t i e n c e i n t y p i n g the many d r a f t s o f t h i s t h e s i s . Dedicated to my son, Adebowale Adeleke A d e t o l a v i i i LIST OF TABLES Page. 1 THE CHEMICAL COMPOSITION OF BROILER LITTER AS AFFECTED BY LENGTH OF TIME BIRDS WERE KEPT ON THE LITTER 36 2 THE CHEMICAL COMPOSITION OF HEN DROPPINGS AS AFFECTED BY LENGTH OF TIME THE DROPPINGS WERE ALLOWED TO ACCUMULATE 37 3 THE EFFECT OF HEAT TREATMENTS ON THE BACTERIAL GROWTH IN POULTRY WASTES 44 4 RESULTS OF BACTERIOLOGICAL ANALYSIS OF FORTY-FOUR SAMPLES OF POULTRY LITTER 4 5 5 TOTAL NITROGEN AND URIC ACID NITROGEN CONTENT OF UNTREATED AND HEAT TREATED POULTRY DROPPINGS AND LITTER 47 6 MEAN CHEMICAL COMPOSITION OF WOOD-SHAVINGS BROILER LITTER AND CAGED LAYERS' DROPPINGS USED IN FEEDING TRIAL I 57 7 COMPOSITION OF RATIONS TRIAL I 5 8 8 AVERAGE CHEMICAL ANALYSIS OF THE RATIONS FED TO LAMBS IN FEEDING TRIAL I 70 9 THE PERCENTAGE OF TOTAL NITROGEN ATTRIBUTABLE TO NON-PROTEIN NITROGEN (NPN) SUPPLEMENTS IN THE RATIONS FED TO LAMBS IN FEEDING TRIAL I 71 10 AVERAGE FEED INTAKE AND APPARENT DIGESTIBILITY BY SHEEP OF THE EXPERIMENTAL RATIONS 74 11 AVERAGE NITROGEN BALANCE OF LAMBS FED THE EXPERIMENTAL RATIONS 85 12 AVERAGE BODY WEIGHT GAINS AND FEED EFFICIENCY OF LAMBS FED THE EXPERIMENTAL RATIONS 90 13 AVERAGE CHEMICAL ANALYSIS OF RATIONS FED TO LAMBS 96 i x Page 14 AVERAGE FEED INTAKE AND APPARENT DIGESTIBILITY BY SHEEP OF EXPERIMENTAL RATIONS 9 8 15 AVERAGE NITROGEN BALANCE OF LAMBS FED THE EXPER-IMENTAL RATIONS '"' 99 16 COMPOSITION OF RATIONS FED TO THE LAMBS IN THE FEEDING TRIAL III. 106 17 AVERAGE CHEMICAL ANALYSIS OF RATIONS FED TO LAMBS IN FEEDING TRIAL I I I 111 18 AVERAGE FEED INTAKE AND APPARENT DIGESTIBILITY BY LAMBS OF POULTRY DROPPINGS SUPPLEMENTED RATIONS 114 19 AVERAGE NITROGEN BALANCE OF LAMBS FED POULTRY DROPPINGS SUPPLEMENTED RATIONS — TRIAL I I I 120 20 COMPOSITION OF IN VITRO BASAL MEDIUM AND INOCULUM 133 21 THE EFFECT OF NaOH and NH OH TREATMENT ON THE IN". VITRO CELLULOSE DIGESTION OF GAT STRAW AND POPLAR WOOD 139 22 THE EFFECT OF NITROGEN SOURCE ON THE IN VITRO CELLULOSE DIGESTION OF UNTREATED AND ALKALI TREATED OAT STRAW AND POPLAR WOOD 142 23 IN VIVO AND IN VITRO CELLULOSE DIGESTION OF THE RATIONS FED TO LAMBS IN TRIALS I AND I I I 144 X TABLE OF CONTENTS TITLE PAGE ABSTRACT ACKNOWLEDGEMENTS LIST OF TABLES— I. INTRODUCTION 1 I I . LITERATURE REVIEW 5 A. Importance of forages i n l i v e s t o c k p r o d u c t i o n 5 B. N u t r i t i v e e v a l u a t i o n of forages 6 1. Chemical composition 7 2. D i g e s t i b i l i t y (or a v a i l a b i l i t y ) o f forage n u t r i e n t s 9 3. V o l u n t a r y feed i n t a k e 10 4. A v a i l a b l e energy 11 C. Low-quality forages - t h e i r f u t u r e i n ruminant f e e d i n g 12 D. Improvement of l o w - q u a l i t y forages 16 1. P h y s i c a l Treatments 17 (a) Steaming 17 (b) G r i n d i n g 17 (c) I r r a d i a t i o n 18 2. Chemical Treatments 19 (a) Sodium hydroxide (NaOH) 19 3. Supplementation o f l o w - q u a l i t y forages 20 (a) R e a d i l y d i g e s t i b l e carbohydrates 20 (b) N i t r o g e n supplementation 22 Page i n v i v i i i x i Page I I I . OBJECT OF THE RESEARCH 27 IV. EXPERIMENTAL 29 (I.) Chemical and B i o l o g i c a l Examinations of P o u l t r y Wastes 30 A. Chemical a n a l y s i s o f p o u l t r y wastes 32 1. I n t r o d u c t i o n 32 2. Experimental methods 32 3. R e s u l t s and D i s c u s s i o n 34 B. E f f e c t of heat treatments on the chemical composition and b a c t e r i a l f l o r a of p o u l t r y 41 wastes 1. I n t r o d u c t i o n 41 2. Experimental Methods 42 3. R e s u l t s and D i s c u s s i o n 46 4. Summary and C o n c l u s i o n 49 (II.) Animal Feeding T r i a l s 51 A. T r i a l I. Supplementation of high-roughage r a t i o n s with v a r i o u s n i t r o g e n sources ( u n p e l l e t e d r a t i o n s ) . 52 1. I n t r o d u c t i o n 52 2. Design of Experiment 5 3 3. P r e p a r a t i o n of r a t i o n components 53 (a) G r i n d i n g of oat straw 53 (b) P r e p a r a t i o n o f the p o u l t r y wastes- 54 (c) Mixing o f experimental r a t i o n s 56 (d) Animal p r e p a r a t i o n and f e e d i n g 60 (e) Metabolism s t u d i e s 61 (i) V o l u n t a r y feed i n t a k e d e t e r m i n a t i o n 61 ( i i ) D i g e s t i b i l i t y and n i t r o g e n balance determinations 62 Page ( i i i ) Sampling o f experimental r a t i o n s 6 3 (iv) Urine c o l l e c t i o n 63 (v) Chemical a n a l y s i s o f feeds, feces and u r i n e samples 64 (f) C a l c u l a t i o n s 65 (i) Apparent d i g e s t i b i l i t y c o e f f i c i e n t s 65 ( i i ) N i trogen balance 66 ( i i i ) R e l a t i v e Intake (RI) : 67 (iv) N u t r i t i v e Value Index (NVI) 67 (v) D i g e s t i b l e Energy (DE) I n t a k e — 67 (vi) S t a t i s t i c a l procedures 68 4. Resu l t s and d i s c u s s i o n 69 (a) Chemical composition o f experimental r a t i o n s 69 (b) Dry matter d i g e s t i b i l i t y 73 (c) Gross energy d i g e s t i b i l i t y 76 (d) Crude f i b e r and c e l l u l o s e d i g e s t i b i l i t y 78 (e) Crude p r o t e i n d i g e s t i b i l i t y 79 (f) R e l a t i v e Intake 81 (g) N u t r i t i v e Value Index (NVI) 83 (h) D i g e s t i b l e Energy (DE) Intake p o t e n t i a l 84 (i) N i t r o g e n balance 84 (j) Body weight g a i n and feed e f f i c i e n c y - 88 5. Summary and Conclus i o n s 91 T r i a l I I . Supplementation o f hig h roughage r a t i o n s with v a r i o u s n i t r o g e n sources ( P e l l e t e d r a t i o n s 94 1. Experimental methods 94 2. R e s u l t s and d i s c u s s i o n 95 3. N i t r o g e n balance 100 4. Summary and c o n c l u s i o n s 102 T r i a l I I I . Supplementation o f d i f f e r e n t low-q u a l i t y forages with p o u l t r y droppings ( p e l l e t e d r a t i o n s ) . 104 1. I n t r o d u c t i o n 104 x i i i Page 2. P r e p a r a t i o n o f r a t i o n components 104 (a) Mixing and p e l l e t i n g o f e x p e r i -mental r a t i o n s 10 5 3. Metabolism s t u d i e s 10 8 4. Chemical analyses o f feeds, feces and u r i n e samples 109 5. C a l c u l a t i o n s 109 6. Re s u l t s and d i s c u s s i o n 110 Apparent d i g e s t i b i l i t y c o e f f i c i e n t s (a) Dry matter 113 (b) Gross energy 113 (c) Crude f i b e r 115 (d) Crude p r o t e i n 116 (e) R e l a t i v e Intake (RI) 117 (f) N u t r i t i v e Value Index (NVI) 118 (g) D i g e s t i b l e energy (DE) i n t a k e p o t e n t i a l 119 (h) N i t r o g e n balance determinations 119 7. Summary and Conclusions 123 (III) In v i t r o c e l l u l o s e d i g e s t i o n o f a l k a l i t r e a t e d and u n t r e a t e d l o w - q u a l i t y roughages (oat straw and p o p l a r wood) . 125 1. I n t r o d u c t i o n 125 2. Experimental methods 127 (a) In v i t r o systems and s u b s t r a t e s 128 (b) P r e p a r a t i o n of inoculum (Phosphate B u f f e r E x t r a c t ) 131 (c) P r e p a r a t i o n and d i s p e n s a t i o n o f b a s a l medium 132 (d) I n i t i a t i o n and t e r m i n a t i o n o f the ferm e n t a t i o n run 134 (e) C e l l u l o s e a n a l y s i s 134 (i) A c i d d i g e s t i o n 135 ( i i ) F i l t r a t i o n 135 ( i i i ) Drying and ash i n g 136 (iv) C a l c u l a t i o n o f c e l l u l o s e con-t e n t 136 (v) C a l c u l a t i o n o f c e l l u l o s e d i g e s t i b i l i t y i n v i t r o 137 XX V 3. Resu l t s and d i s c u s s i o n 138 V. SUMMARY AND CONCLUSION 14 7 VI. BIBLIOGRAPHY 150 NUTRITIVE EVALUATION OF LOW-QUALITY FORAGES SUPPLEMENTED WITH DIFFERENT NITROGEN SOURCES IN RUMINANT FEEDS I INTRODUCTION I t i s d i f f i c u l t t o a n t i c i p a t e the steps which w i l l be taken d u r i n g the next few decades to cope wi t h the problem of p r o v i d i n g adequate food f o r the e v e r - i n c r e a s i n g world p o p u l a t i o n . Curbs on p o p u l a t i o n growth brought about by war and by c o n t r a c e p t i o n may p l a y a p a r t i n e k i n g out the world resources but the extent o f t h i s c o n t r i b u t i o n i s impossible t o p r e d i c t . In any event, the n u t r i t i o n i s t i s not concerned with t h i s aspect but onl y w i t h e n s u r i n g t h a t the b e s t use i s made of the a v a i l a b l e f o o d s t u f f s . Most w r i t e r s on the s u b j e c t o f the world's food s u p p l i e s c o n f i n e themselves to c a l c u l a t i n g man's t o t a l c a l o r i c requirements and the c a p a b i l i t y of a g r i c u l t u r e t o meet these demands. T h i s appears to be an o v e r s i m p l i f i c a t i o n o f the problem of food shortage, i f one c o n s i d e r s the f a c t t h a t , d e s p i t e the impressive s c i e n t i f i c and t e c h n i c a l progress we have made, mankind has f a i l e d i n i t s e f f o r t s t o feed the b i l l i o n s o f people now l i v i n g on e a r t h i n terms o f a balanced d i e t c o n t a i n i n g adequate energy, p r o t e i n , m i n e r a l s and v i t a m i n s . Although o p i n i o n s vary about the extent o f m a l n u t r i t i o n and 2 of a c t u a l hunger, there i s g e n e r a l r e c o g n i t i o n t h a t there i s food shortage and t h a t the most s e r i o u s problem i s l a c k o f p r o t e i n . Many suggestions have been put forward as to how the world's resources can be b e t t e r u t i l i z e d t o produce more p r o t e i n . Such p o s s i b i l i t i e s i n c l u d e s y n t h e s i s o f p r o t e i n from b a c t e r i a s u b s i s t i n g on petroleum by-products; p r o d u c t i o n of e d i b l e algae; b e t t e r e x p l o i t a t i o n o f the animal resources of the sea; and i n a d d i t i o n , the i n c r e a s i n g of l a n d produc-t i v i t y by c l e a r i n g , drainage and i r r i g a t i o n . But, perhaps one o f the most important sources o f food energy and thus p o t e n t i a l animal p r o t e i n i s t h a t c o n t a i n e d i n the world's g r a s s l a n d s . The importance of forage-producing lands i s emphasized because o f t h e i r abundance and because t h e i r crops can form a major p o r t i o n o f the r a t i o n o f many of man's food-producing animals. The ruminant s p e c i e s are predominant among the world's food producing animals. Ruminants have evolved through many m i l l i o n s o f years i n t o the a©mesticated s p e c i e s which today c o n s t i t u t e one of the most important components of animal a g r i c u l t u r e . T h e i r s p e c i a l i z a t i o n as forage consumers i s dependent on the capacious nature of a p o r t i o n of t h e i r d i g e s t i v e t r a c t , ( r u m e n ) , and the microorganisms l i v i n g i n a symbiotic r e l a t i o n s h i p w i t h i n t h i s organ. I t i s these 3 m i c r o f l o r a and microfauna which are the a c t u a l c o n v e r t e r s of the c e l l u l o s i c forage components i n t o n u t r i e n t s which can be absorbed and u t i l i z e d by the host animal. These are among the c h a r a c t e r i s t i c s which have enabled these s p e c i e s t o p l a y a dominant r o l e i n the p r o d u c t i o n of human food from pasture m a t e r i a l which would otherwise be of l i t t l e n u t r i t i o n a l v alue as a d i r e c t food f o r humans. Modern-day c o m m e r c i a l i z a t i o n of animal husbandry has r e s u l t e d i n an i n t e n s i v e e f f o r t t o i n c r e a s e the e f f i c i e n c y of meat, milk and wool p r o d u c t i o n , an important m a n i f e s t a t i o n of which i s the f e e d i n g of r a t i o n s which most economically can r e s u l t i n high l e v e l s of p r o d u c t i o n . Although ruminants may not be as e f f i c i e n t as o t h e r c l a s s e s of l i v e s t o c k i n terms of u n i t s of feed needed to produce a g i v e n u n i t of product, they compare more f a v o u r a b l y when r a t i o n s used t o feed the v a r i o u s c l a s s e s of l i v e s t o c k are examined q u a l i t a t i v e l y . For while s p e c i e s such as swine and p o u l t r y r e q u i r e h i g h energy co n c e n t r a t e feeds to ma i n t a i n l e v e l s of e f f i c i e n t p r o d u c t i o n , ruminants have the a b i l i t y t o u t i l i z e r e l a t i v e l y low-energy and low-cost f i b r o u s feeds. These c a p a c i t i e s are not being f u l l y e x p l o i t e d when, as a t pre s e n t , h a l f the world's g r a i n crop i s being f e d to both ruminants and non-ruminants and a l a r g e p a r t of the p o t e n t i a l a r a b l e land i n many p a r t s of the world i s devoted to the p r o d u c t i o n of fodder. 4 In those p a r t s of the world, p a r t i c u l a r l y i n the t r o p i c a l r e g i o n s , where the c l i m a t i c c o n d i t i o n s are conducive to r a p i d p l a n t growth and subsequent o v e r m a t u r i t y , an abundance of matured and h i g h l y l i g n i f i e d forages i s a v a i l a b l e . These forages are o f t e n of such poor q u a l i t y t h a t the ruminant animal i s unable to consume the forages i n amounts t h a t would meet i t s maintenance energy requirements. However, the u t i l i z a t i o n of such l o w - q u a l i t y forages takes on s p e c i a l importance because of the abundance of these forages and because of t h e i r p o t e n t i a l v alue i f supplemented with p r o t e i n s , m i n e r a l s and v i t a m i n s . 5 II LITERATURE REVIEW A. Importance of forages i n l i v e s t o c k p r o d u c t i o n In most c o u n t r i e s i n A f r i c a where c a t t l e and o t h e r h e r b i v o r o u s animals are r a i s e d , forages c o n s t i t u t e the major p o r t i o n o f , and i n some cases, the e n t i r e d i e t f o r these animals. In North America, as w e l l as most temperate r e g i o n s , forage i n one form or another c o n s t i t u t e s some 65% of the feed of beef c a t t l e , 55% of d a i r y c a t t l e and about 90%.of sheep (Crampton e t a l . , 1960). In d e v e l o p i n g c o u n t r i e s , forage i s even.;more important i n regions where grain-growing i s uneconomic of the g r a i n which i s produced i s used f o r human consumption, and c a t t l e p r o d u c t i o n i s becoming i n c r e a s -i n g l y dependent on g r a s s l a n d farming. A fundamental m a t e r i a l i n the s t r u c t u r e of p l a n t c e l l w a l l s i s c e l l u l o s e . Notwithstanding i t s abundant d i s t r i b u t i o n i n nature, only the her b i v o r o u s animals among the h i g h e r animals can u t i l i z e i t as t h e i r primary source of energy. I t has long been known th a t the d i g e s t e d p o r t i o n o f crude f i b e r c o n s i s t s mainly of c e l l u l o s e (Armsby, 1896), which has the same n u t r i t i v e v alue as s t a r c h once d i g e s t e d . The s i t e 6 of c e l l u l o s e d e g r a d a t i o n i s the rumen, and t h i s d e g r a d a t i o n (fermentation) i s brought about by microorganisms p r e s e n t i n t h i s organ. The a c t u a l s i g n i f i c a n c e of c e l l u l o s e breakdown to v o l a t i l e f a t t y a c i d s was not f u l l y a p p r e c i a t e d u n t i l r e p o r t s d e a l i n g w i t h v o l a t i l e f a t t y a c i d (VFA) matabolism were p u b l i s h e d . Among the f i r s t of these was t h a t of P h i l l i p s o n (1947) who estimated t h a t VFAs are produced i n the rumen i n q u a n t i t i e s t h a t c o u l d supply up to 40% of the f a s t i n g energy requirements of the animal. Thus, apart from the supply of other n u t r i e n t s by the forage the c e l l u l o s e component makes a s i g n i f i c a n t c o n t r i b u t i o n to the energy requirements of the animals. B. N u t r i t i v e e v a l u a t i o n of forages The search f o r a meaningful q u a n t i t a t i v e d e s c r i p t i o n of the " o v e r - a l l " n u t r i t i v e value of feeds has r e s u l t e d i n i n t e n s i v e b i o l o g i c a l and chemical r e s e a r c h . N u t r i t i v e e v a l u -a t i o n of forages has come i n t o new prominence i n the p a s t decade as evidenced by the i n c r e a s i n g amount of p u b l i s h e d i n f o r m a t i o n r e l a t i n g to the development of v a l i d i n v i v o , i n v i t r o and chemical techniques used i n measuring forage q u a l i t y . 7 1. Chemical composition N u t r i e n t a v a i l a b i l i t y of a feed i s l i m i t e d by chemical composition. L i m i t s imposed by composition c o n s i s t of two k i n d s : the q u a n t i t y of t o t a l l y u n a v a i l a b l e substances and the f a c t o r s which i n f l u e n c e the r a t e of d i g e s t i o n (Van Soest, 1968). Crampton (1957) s t a t e d t h a t chemical composition data of forages are u s e f u l i n determining the r e l a t i v e amount of each c o n s t i t u e n t , but are not c o n s i s t e n t l y c o r r e l a t e d w i t h animal performance c r i t e r i a . The p a r t i t i o n i n g of f e e d s t u f f s i n t o t h e i r chemical components - moisture, ether e x t r a c t , crude p r o t e i n , crude f i b e r , ash and n i t r o g e n - f r e e e x t r a c t - owed i t s o r i g i n to the work of two German s c i e n t i s t s (Henneberg and Stohmann, 1864). The crude f i b e r and NFE r e p r e s e n t the carbohydrate p o r t i o n of the feed; the crude f i b e r was designated as the p o r t i o n t h a t i s r e l a t i v e l y i n d i -g e s t i b l e w h ile the NFE c o n t a i n s the r e l a t i v e l y s o l u b l e carbohydrates. Many workers have c r i t i c i z e d t h i s d i v i s i o n of carbohydrates (Norman, 193 5; Crampton and Maynard, 19 38; Ferguson, 1942; E l l i s e t a l . , 1946; Moxon and B e n t l e y , 1953; and E l y e t a l . , 1953), e s p e c i a l l y i n the case of roughages where the crude f i b e r c o u l d be as w e l l or b e t t e r d i g e s t e d than the NFE f r a c t i o n . 8 The l i g n i n content of the forage has g e n e r a l l y been a s s o c i a t e d w i t h poor d i g e s t i b i l i t y of the forage. S i g n i f i c a n t n e g a tive c o r r e l a t i o n s have been demonstrated (Kamstra e t a l . , 1958; D e h o r i t y and Johnson, 1961) between l i g n i n content and the dry matter d i g e s t i b i l i t y of v a r i o u s forages grazed by or cut and fed green to s t e e r s and wethers (Forbes and G a r r i g u s , 1948, 1950). L a t e r r e p o r t s by some workers i n c l u d i n g S t a l l c u p (1957) and D e h o r i t y e t a l . (1960) have shown t h a t the observed r e d u c t i o n i n c e l l u l o s e d i g e s t i o n of l i g n i f i e d mature forages i s due to the " i n c r u s t i n g " e f f e c t of l i g n i n r a t h e r than i t s t o t a l c o n c e n t r a t i o n . Quicke and B e n t l e y (19 59) from t h e i r study of l i g n i n content i n hays a t d i f f e r e n t stages of m a t u r i t y concluded t h a t l i g n i n content per se may not be the s o l e f a c t o r r e s p o n s i b l e f o r the d i f f e r e n c e s i n c e l l u l o s e d i g e s t i b i l i t y . The crude p r o t e i n content of forages has been g e n e r a l l y r e l a t e d t o the f e e d i n g q u a l i t y . The f a c t t h a t the b i o l o g i c a l a v a i l a b i l i t y o f crude p r o t e i n to the animal i s v a r i a b l e , puts a l i m i t t o the use of t h i s c o n s t i t u e n t as a measure of n u t r i t i v e q u a l i t y of f o r a g e s . 9 2. D i g e s t i b i l i t y (or a v a i l a b i l i t y ) o f forage n u t r i e n t s Much of the e a r l i e r work on the n u t r i t i v e value of herbage expressed n u t r i t i v e q u a l i t y i n terms of t o t a l d i g e s t i b l e n u t r i e n t s (TDN), s t a r c h e q u i v a l e n t £E) o r net energy (NE). Now, however, there i s i n c r e a s i n g r e a l i z a t i o n t h a t i n p r a c t i c e , animal p r o d u c t i o n from herbage depends on the l e v e l of n u t r i e n t i n t a k e , t h a t i s , on the product o f the weight o f food i n t a k e and the n u t r i t i v e value of the food per u n i t weight (Crampton e t a l . , 1960). N u t r i e n t i n t a k e i s a f f e c t e d by three major f a c t o r s , namely, food i n t a k e , d i g e s t i b i l i t y and u t i l i z a t i o n o f absorbed n u t r i e n t s . D i g e s t i b i l i t y i s an important component o f a l l three parameters, as i t i s now known t h a t h i g h d i g e s t i b i l i t y i s necessary f o r both high i n t a k e and f o r e f f i c i e n t u t i l i z a t i o n o f m e t a b o l i z a b l e energy. During the e x e c u t i o n o f many i n v i v o experiments on the d i g e s t i b i l i t y of herbage, chemical analyses o f the fodder have been c a r r i e d out i n an attempt to develop a mathematical r e l a t i o n s h i p between d i g e s t i b i l i t y and i t s contents of crude f i b e r ( G a i l l a r d , 1962; Wilson e t a l . , 1966), l i g n i n (Dehority and Johnson, 1961; B l a x t e r , 1964; Armstrong e t a l . . 1964) and a c i d d e t e r g e n t f i b e r (Van Soest; 1963). Butterworth (1963) has shown t h a t the r e l a t i o n s h i p between d i g e s t i b i l i t y and crude f i b e r content of t r o p i c a l forages d i f f e r markedly from those found f o r correspond-i n g forages of temperate zones, so t h a t data d e r i v e d i n temperate regions should not be a p p l i e d to t r o p i c a l c o n d i t i o n s . The most pro m i s i n g approach to the 10 e s t i m a t i o n of forage d i g e s t i b i l i t y i n the l a b o r a t o r y has been the attempt to simulate i n v i t r o the b i o l o g i c a l processes of rumen d i g e s t i o n and c o r r e l a t e the r e s u l t s so obt a i n e d with those achieved i n v i v o (Donefer e t a l . , 1960). 3. V o l u n t a r y feed i n t a k e V o l u n t a r y i n t a k e as a measure o f the f e e d i n g value o f a forage has long been r e c o g n i z e d (Armsby, 1896). V o l u n t a r y i n t a k e may be d e f i n e d as the maximum consumption of a feed under ad l i b i t u m f e e d i n g c o n d i t i o n s . I t i s g e n e r a l l y agreed t h a t v o l u n t a r y i n t a k e o f roughage by ruminant animals i s d i r e c t l y r e l a t e d to i t s d i g e s t i b i l i t y and t h a t t h i s i s the rev e r s e o f what normally occurs i n monogastrics or ruminants e a t i n g non-roughage d i e t s ( B l a x t e r e t a l . , 1961). The problem of poor q u a l i t y roughages i s t h a t t h e i r r a t e of d i g e s t i o n i s so slow t h a t s u f f i c i e n t q u a n t i t i e s of undigested r e s i d u e s remain i n the rumen to l i m i t f u r t h e r consumption o f the feed. When feed components are examined f o r t h e i r a v a i l a b i l i t y and the r a t e a t which they are d i g e s t e d , the c e l l - w a l l f r a c t i o n s , i n c l u d i n g h e m i c e l l u l o s e , c e l l u l o s e and l i g n i n stand out as the slowly fermenting f r a c t i o n . The sugars, s t a r c h e s , p r o t e i n s and other substances ferment much f a s t e r than c e l l u l o s e and h e m i - c e l l u l o s e and do not c o n t r i b u t e to the f i l l - p a s s a g e problem (Van Soest, 1968) . 11 I t i s known t h a t forage q u a l i t y , i n t a k e l e v e l and ; p r o d u c t i o n are c l o s e l y r e l a t e d . A c c o r d i n g to the c l a s s i f i c a t i o n scheme f o r forages proposed by Cramptom (19 56), average d a i l y v o l u n t a r y i n t a k e was d i r e c t l y p r o p o r t i o n a l to the a v a i l a b l e energy content of the forage p r o v i d i n g p r o t e i n i s adequate. I t was f u r t h e r shown (Crampton, 19 57) t h a t the f e e d i n g v a l u e of a forage depends on i t s c o n t r i b u t i o n towards the energy requirement of the animal, and tha&' d i f f e r e n c e s between forages are almost completely a consequence of the r e l a t i v e amounts i n which they are v o l u n t a r i l y consumed. V o l u n t a r y i n t a k e of timothy hay has been shown to decrease with advancing m a t u r i t y ( J e f f e r s , 1960) w h i l e Smith (1958) and Beacom (1959) found s i g n i f i c a n t c o r r e l a t i o n s between v o l u n t a r y i n t a k e and l i v e w e i g h t g a i n s . F a c t o r s a f f e c t i n g the v o l u n t a r y i n t a k e of forages by ruminants have been reviewed by a number o f authors i n c l u d i n g Campling (1964), Van Soest (1965), Conrad (1966) and Baumgardt (1970). 4. A v a i l a b l e energy I t has been demonstrated by many workers i n c l u d i n g Reid e t a l . (19 59) t h a t the primary purpose served by forages i n the d i e t of ruminants i s the p r o v i s i o n of energy. B l a x t e r (1956) i n h i s review of the n u t r i t i v e v alue of feeds as sources 12 of energy concluded t h a t , the primary c o n s i d e r a t i o n i n the f e e d i n g of the i n d i v i d u a l animal i s the adequacy of energy supply. B l a x t e r (1956) f u r t h e r e l a b o r a t e d t h a t shortages of d i e t a r y energy are u s u a l l y f a r more important causes of low p r o d u c t i v i t y i n farm animals, than are d i e t a r y d e f i c i e n c i e s of v i t a m i n s , minerals or p r o t e i n . Crampton (19 57) p o i n t e d out t h a t a v a i l a b l e energy r a t h e r than some s p e c i f i c n u t r i e n t i s the fundamental l i m i t i n g f a c t o r i n the n u t r i t i v e v a l u e of f o r a g e s , because i f a forage i s consumed i n amounts s u f f i c i e n t to meet the energy requirements, i t w i l l most l i k e l y meet the animal's needs with r e s p e c t to p r o t e i n , c a l c i u m and phosphorus. S w i f t (1957) showed t h a t much more n u t r i e n t i s r e q u i r e d to m a i n t a i n normal energy metabolism than a l l other purposes combined. C. Low-quality forages - t h e i r f u t u r e i n ruminant f e e d i n g Examples of l o w - q u a l i t y forages are i l l u s t r a t e d by m a t e r i a l such as straw, g r a i n h u l l s , corn cobs, sugarcane bagasse, sawdust, wood shavings, e t c . The common charac-t e r i s t i c shared by these types of m a t e r i a l s i s the f a c t t h a t they are extremely low i n p r o t e i n and d i g e s t i b l e energy but are r a t h e r h i g h i n crude f i b e r and l i g n i n . Low-quality forages, p a r t i c u l a r l y mature g r a s s e s , are abundant a l l over the world 13 but much more so i n the t r o p i c a l r e g i o ns where the e f f e c t s of high a i r temperature and heavy r a i n f a l l are conducive t o r a p i d p l a n t growth and subsequent o v e r - m a t u r i t y . The grasses mature very r a p i d l y such t h a t d u r i n g the dry season l a r g e q u a n t i t i e s o f dry m a t e r i a l s are a v a i l a b l e but are g e n e r a l l y of such poor q u a l i t y t h a t g r a z i n g animals l o s e weight and some even d i e of s t a r v a t i o n even though app a r e n t l y i n the midst of p l e n t y . Whereas the gross energy of l e s s mature forage p l a n t s can be u t i l i z e d (digested) t o the extent of 50-70%, i n c r e a s e d l i g n i f i c a t i o n w i t h advancing p l a n t m a t u r i t y can r e s u l t i n only 20-50% of the p o t e n t i a l energy being made a v a i l a b l e to the animal (Donefer e t a l . , 19 69). E q u a l l y , or of more importance than the e f f e c t o f l i g n i f i c a t i o n i n d e c r e a s i n g d i g e s t i b i l i t y i s the marked r e d u c t i o n i n v o l u n t a r y i n t a k e by ruminants of p l a n t m a t e r i a l o f advanced m a t u r i t y . As a r e s u l t o f both these e f f e c t s , the ruminant animal i s unable i n many cases to o b t a i n i t s maintenance energy requirements when fed h i g h l y l i g n i f i e d forage p l a n t s . That c e l l u l o s e i s a p o t e n t i a l energy source f o r ruminants has been known f o r y e a r s . But the a v a i l a b i l i t y 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 of l o w - q u a l i t y roughages i s hampered by the e f f e c t o f l i g n i n . L i g n i n i s not a w e l l - d e f i n e d chemical 14 e n t i t y , but i t s i n c r e a s e d a s s o c i a t i o n with c e l l u l o s e and h e m i - c e l l u l o s e s i n p l a n t m a t e r i a l s as the p l a n t matures i s w e l l known (Dehority and Johnson, 1960). Crampton and Maynard (19 38) found t h a t l i g n i n occurs i n p l a n t as l i g n o -c e l l u l o s e . These workers were of the o p i n i o n t h a t substances of the g lucosanxylan s e r i e s are the f o r e r u n n e r s of l i g n i n , but t h a t n e i t h e r i t s exact chemical s t r u c t u r e nor the manner i n which i t i s combined with c e l l u l o s e i s f u l l y understood. They concluded t h a t i t s behaviour i n n u t r i t i o n i s l i k e w i s e u n s e t t l e d , w i t h d i f f e r e n t f e e d i n g t e s t s y i e l d i n g c o n f l i c t i n g r e s u l t s . Woodman and Stewart (1932) were o f the o p i n i o n t h a t l i g n o c e l l u l o s e i s e n t i r e l y i n d i g e s t i b l e and thus the d i g e s t i -b i l i t y of the crude f i b e r f r a c t i o n i s i n v e r s e l y p r o p o r t i o n a l to the content o f l i g n o c e l l u l o s e . Crampton and Maynard (1938), Gray (19 47) and many others have a l s o r e p o r t e d t h a t l i g n i n i s p r a c t i c a l l y n o n - d i g e s t i b l e . However, S u l l i v a n (1955) noted t h a t the d i g e s t i b i l i t y of l i g n i n c o u l d exceed 10% i n some cases. Nehring and Laube (1955) a l s o r e p o r t e d t h a t i n the case o f straw, l i g n i n d i g e s t i b i l i t y c o u l d be as h i g h as 20%. Balch e t a l . (1954) were of the o p i n i o n t h a t the d i f f e r e n t chemical methods used f o r the d e t e r m i n a t i o n of l i g n i n c o u l d be r e s p o n s i b l e f o r the i n c o n s i s t e n t d i g e s t i b i l i t y r e s u l t s r e p o r t e d by most workers. Most r e p o r t s i n d i c a t e t h a t the a s s o c i a t i o n between l i g n i n and c e l l u l o s e i s a p h y s i c a l one ( C l a r k e , 1938; Kamstra 15 e t a l . , 1958; Freudenberg, 1965). D e h o r i t y e t a l . (1960) showed t h a t the e f f e c t of l i g n i n i n d e c r e a s i n g c e l l u l o s e d i g e s -t i o n was most probably due to i t s i n c r u s t i n g e f f e c t r a t h e r than i t s t o t a l c o n c e n t r a t i o n . A s i m i l a r o b s e r v a t i o n was made by S t a l l c u p (19 57) when he added commercially p u r i f i e d l i g n i n to i n v i t r o f l a s k s a t fou r d i f f e r e n t l e v e l s , w i t h no s i g n i f i c a n t d i f f e r e n c e i n c e l l u l o s e d i g e s t i o n i n any of the f l a s k s . He then suggested t h a t the r e d u c t i o n i n c e l l u l o s e d i g e s t i b i l i t y u s u a l l y a s s o c i a t e d with i n c r e a s i n g l i g n i f i c a t i o n might be due t o i t s r o l e i n the p h y s i c a l s t r u c t u r e of the p l a n t , r a t h e r than i t s dhemical c o n c e n t r a t i o n . Because of the importance o f c e l l u l o s e as a source o f energy to ruminants and the abundance of t h i s p l a n t c o n s t i -tuent i n l i g n i f i e d roughages, e f f o r t s have been d i r e c t e d towards the d i s s o c i a t i o n of the p h y s i c a l bond between l i g n i n and c e l l u l o s e which would no doubt r e s u l t i n improved c e l l u l o s e d i g e s t i b i l i t y of roughages. In many areas, p a r t i c u l a r l y i n the t r o p i c s , h i g h l y l i g n i f i e d p l a n t by-products such as straws, although a v a i l a b l e i n l a r g e supply, are not e f f i c i e n t l y u t i l i z e d and i n many cases are completely wasted. The u t i l i z a t i o n of l o w - q u a l i t y roughages has become a necessary step i n the pr e s e n t attempts to i n c r e a s e world food s u p p l i e s , because one of the major f a c t o r s l i m i t i n g the p r o d u c t i o n o f h i g h - q u a l i t y p r o t e i n s through animal a g r i c u l t u r e i s the shortage o f s u i t a b l e f e e d s t u f f s f o r these animals. 16 D. Improvement of l o w - q u a l i t y forages The l i g n o c e l l u l o s e complex accounts f o r most of the o r g a n i c matter and hence, gross energy of common forages and wood. The ruminant animal can r e a d i l y and e f f i c i e n t l y e x t r a c t most of the energy from the l i g n o c e l l u l o s e of immature p l a n t m a t e r i a l s , but i s p o o r l y equipped to remove i t from mature forage p l a n t s and wood. The problem r e s o l v e s i t s e l f i n t o three components: (1) b r e a k i n g down the c e l l w a l l m a t e r i a l i n t o p a r t i c l e s i z e s which f a c i l i t a t e b a c t e r i a l a t t a c k and allow the feed to move through the a l i m e n t a r y t r a c t e f f i c i e n t l y ; (2) improving the a v a i l a b i l i t y of the energy i n the l i g n o -c e l l u l o s e f r a c t i o n ; and (3) p r o v i d i n g adequate n u t r i e n t s f o r the rumen m i c r o f l o r a to u t i l i z e the a v a i l a b l e energy. N u t r i t i o n a l l y , the gross energy of forages and wood c o n s i s t s o f an u n a v a i l a b l e f r a c t i o n i n c l u d i n g compounds such as l i g n i n which f o r p r a c t i c a l purposes i s not degraded by rumen micro-f l o r a , the d i g e s t i b l e energy (DE) f r a c t i o n r e p r e s e n t i n g the carbohydrates which are normally a v a i l a b l e f o r ' b a c t e r i a l d e g r a d a t i o n , and the p o t e n t i a l l y d i g e s t i b l e energy (PDE) f r a c t i o n which i n c l u d e s the carbohydrates not normally a v a i l a b l e to rumen m i c r o f l o r a because of chemical and or p h y s i c a l a s s o c i a t i o n s w i t h i n the l i g n o c e l l u l o s e complex, but which can be made a v a i l a b l e by a p p r o p r i a t e treatment and supplementation (Pigden and Hearney, 1969). The d i f f e r e n t 17 treatments of l i g n o c e l l u l o s i c m a t e r i a l s can be d i v i d e d i n t o two major c l a s s e s ; p h y s i c a l ( i n c l u d i n g steaming, g r i n d i n g and i r r a d i a t i o n ) and chemical ( p a r t i c u l a r l y the use o f a l k a l i s ) . 1. P h y s i c a l Treatments (a) Steaming Very few i n v e s t i g a t i o n s have been conducted u s i n g t h i s approach to d e l i g n i f y f o r a g e s . The reason i s probably due to the f a c t t h a t the r e s u l t s obtained were not encouraging and the method i t s e l f appears to have very l i t t l e t o o f f e r i n commercial animal p r o d u c t i o n . Honcamp (19 32) and Kormanov-skaya (1956) s t u d i e d the decomposition of straw by steaming. The method was shown t o r e s u l t i n a l o s s of the crude p r o t e i n and an i n c r e a s e i n the s t a r c h e q u i v a l e n t v a l u e . (b) G r i n d i n g The r e s u l t s o b t a i n e d by D e h o r i t y and Johnson((1960) from t h e i r i n v i t r o s t u d i e s o f forages cut a t d i f f e r e n t stages of m a t u r i t y i n d i c a t e d t h a t the extent of l i g n i n d e p o s i t i o n around the c e l l u l o s e f i b e r (forming a p h y s i c a l b a r r i e r r a t h e r 18 than i t s t o t a l c o n c e n t r a t i o n ) i s r e s p o n s i b l e f o r the decreased d i g e s t i b i l i t y of mature f o r a g e s . These workers a l s o r e p o r t e d t h a t b a l l - m i l l i n g of bromegrass and orchardgrass f o r 72 hours 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 c e l l u l o s e d i g e s t i b i l i t y e s p e c i a l l y i n the more mature samples. Rony (1964) s i m i l a r l y r e p o r t e d h i g h e r i n v i t r o c e l l u l o s e d i g e s t i o n at a l l stages of growth when the forage was ground i n a b a l l - m i l l . In v i v o s t u d i e s r e p o r t e d by L l o y d e t a l . (19 60) i n d i c a t e d t h a t g r i n d i n g of a forage ( e a r l y or l a t e cut) i n a hammermill caused s l i g h t r e d u c t i o n i n apparent d i g e s t i b i l i t y of the gross energy, although marked i n c r e a s e s were observed f o r i n t a k e and n u t r i -t i v e value index as a r e s u l t of g r i n d i n g . This o b s e r v a t i o n appears to suggest t h a t the i n c r e a s e d c e l l u l o s e d i g e s t i o n i n v i t r o as a r e s u l t of f i n e g r i n d i n g has not been demonstrated i n v i v o . (c) I r r a d i a t i o n g Gamma i r r a d i a t i o n of wheat straw a t l e v e l s of 1 x 10 g and 2.5 x 10 rads had been shown to i n c r e a s e the dry matter d i g e s t i b i l i t y i n v i t r o from 40% to approximately 70% ( P r i t c h a r d e t a l . , 1962). The r e s u l t s obtained by K i t t s e t a l . (1969) a l s o showed t h a t i n v i t r o c e l l u l o s e d i g e s t i o n and dry matter-, disappearance of hemlock sawdust i n c r e a s e d with i n c r e a s i n g 19 i r r a d i a t i o n dosage. The i n c r e a s e d v o l a t i l e f a t t y a c i d (VFA) pr o d u c t i o n d u r i n g the i n v i t r o f e rmentation i n d i c a t e d t h a t the breakdown products o f the i r r a d i a t i o n were l a r g e l y a v a i l -a b l e to rumen microorganisms. N e v e r t h e l e s s , the l e v e l s o f gamma i r r a d i a t i o n necessary t o r e l e a s e the n u t r i e n t s e ncrusted with l i g n i n , are w e l l above what are eco n o m i c a l l y f e a s i b l e f o r commercial feed p r o c e s s i n g . 2. Chemical Treatments (a) Sodium hydroxide (NaOH) The use o f chemical procedures to e f f e c t d e l i g n i f i c a t i o n have been e l a b o r a t e d p a r t i c u l a r l y through the e f f o r t s of the pulp and paper i n d u s t r y . E f f o r t s to i n c r e a s e the n u t r i t i v e value o f l o w - q u a l i t y forages such as straw date back to the beginn i n g of t h i s century ( K e l l n e r and Kohler, 1900) and were h i g h - l i g h t e d by the procedure r e p o r t e d by Beckmann (1921). The Beckmann procedure c o n s i s t s of s t e e p i n g chopped straw i n 8 times i t s weight o f 1.5% NaOH s o l u t i o n f o r 4 t o 8 hours at atmospheric temperature and p r e s s u r e . The t r e a t e d straw i s then washed f r e e of a l k a l i and can be fed to animals as such, s t o r e d i n s i l o s or d r i e d . While the Beckmann process has proved popular i n s m a l l - s c a l e farm o p e r a t i o n s , w i d e - s c a l e 20 use has been l i m i t e d owing to the l a r g e volume of d i l u t e NaOH s o l u t i o n s r e q u i r e d , the tedious washing o p e r a t i o n s to remove excess a l k a l i and the l o s s e s of s o l u b l e n u t r i e n t s caused by washing. In an attempt to minimize the amount of water used i n washing, a number of workers i n c l u d i n g W i l l i a m s o n (1941), Godden (1942), A r r a z o l a (1950), L u c i f e r o (1958)and Homb (1958), have used more concentrated a l k a l i than the c o n c e n t r a t i o n used i n the Beckmann procedures. However, the process o f washing was not completely e l i m i n a t e d . In order to overcome the need f o r washing, Wilson and Pigden (19 64) developed the "dry" process of a l k a l i treatment, i n which excess a l k a l i was n e u t r a l i z e d with a c e t i c a c i d . The newer methods which tend to overcome the use of excess a l k a l i (Singh and Jackson, 1971; and Chandra and Jackson, 1971) thereby e l i m i n a t i n g washing or n e u t r a l i z a t i o n with a c i d , have been demonstrated to be as e f f e c t i v e i n i n c r e a s i n g d i g e s t i b i l i t y as the o l d e r procedures. 3. Supplementation of l o w - q u a l i t y forages (a) R e a d i l y d i g e s t i b l e carbohydrates Not only have i n v i t r o and i n v i v o s t u d i e s helped our understanding o f the n u t r i e n t requirement and u t i l i z a t i o n by 21 ruminant animals, these techniques have a l s o p o i n t e d t o new areas o f r e s e a r c h and improved f e e d i n g p r a c t i c e s . The bene-f i c i a l e f f e c t s o f s o l u b l e carbohydrates on the s y n t h e s i s o f b a c t e r i a l p r o t e i n from n o n - p r o t e i n n i t r o g e n sources have been demonstrated ( M i l l s , 1942; Pearson and Smith, 1943; Smith and Baker, 1944). These e a r l y r e p o r t s i n d i c a t e d t h a t there i s a requirement f o r a s m a l l amount of r e a d i l y fermentable c a r -bohydrate to s t i m u l a t e f e r m e n t a t i o n o f the l i g n o c e l l u l o s e complex. Burroughs e t a l . (19 50) showed t h a t , the requirement i s of the order o f 5-10% o f the r a t i o n . Larger amounts of r e a d i l y fermentable m a t e r i a l f r e q u e n t l y have a d e p r e s s i n g e f f e c t on l i g n o c e l l u l o s e u t i l i z a t i o n . This i n h i b i t i o n i s b e l i e v e d to be p r i m a r i l y caused by c o m p e t i t i o n between c e l l u -l o l y t i c and a m y l o l y t i c groups of b a c t e r i a ( E l - S h a z l y , e t al.,1961). L o o s l i (1963) has confirmed E l - S h a z l y ' s o b s e r v a t i o n by demon-s t r a t i n g t h a t l a r g e i n t a k e o f molasses reduced c e l l u l o s e d i g e s t i o n i n sheep and c a t t l e p a r t i c u l a r l y when p r o t e i n was low or m a r g i n a l . Other i n v e s t i g a t o r s have suggested d i f f e r e n t reasons f o r the de p r e s s i o n o f c e l l u l o s e d i g e s t i o n when r e a d i l y fermentable carbohydrates were added to l o w - q u a l i t y roughage. Hamilton (1942) was of the o p i n i o n t h a t rumen microorganisms p r e f e r e n -t i a l l y a t t a c k the s o l u b l e carbohydrates, w h i l e Zafren (1960) a t t r i b u t e d the r e d u c t i o n i n c e l l u l o s e d i g e s t i o n to the f a c t t h a t the microorganisms are unable t o cope with the i n c r e a s e d a c i d p r o d u c t i o n r e s u l t i n g from the fer m e n t a t i o n o f the s o l u b l e 22 carbohydrates. Coombe and T r i b e (1962) compared s t a r c h and molasses and concluded t h a t s t a r c h was of low p a l a t a b i l i t y compared wi t h molasses and t h e r e f o r e u n s a t i s f a c t o r y as a carbo-hydrate supplement. (b) N i t r o g e n supplementation Whereas d e l i g n i f i c a t i o n procedures, e s p e c i a l l y NaOH' treatment, r e s u l t i n l a r g e i n c r e a s e s i n c e l l u l o s e d i g e s t i b i l i t y , no e f f e c t on v o l u n t a r y i n t a k e i s achieved (Donefer e t a l . , 1969) . I t has been suggested and shown e x p e r i m e n t a l l y t h a t the major f a c t o r l i m i t i n g the i n t a k e o f d e l i g n i f i e d l o w - q u a l i t y forages i s the low p r o t e i n content ( E l - S h a z l y , 1961; L o o s l i , 1963). Zafren (1960) used ammonium hydroxide (NH^OH) as the treatment a l k a l i and concluded t h a t the ammonium ac e t a t e r e s u l t i n g from the n e u t r a l i z a t i o n of excess NH^OH with a c e t i c a c i d c o u l d supply up to 25% of the supplemental n i t r o g e n . One o f the most important advances t h a t have been made i n r e s p e c t of ruminant n u t r i t i o n has been r e l a t e d to the r o l e of rumen microorganisms as s y n t h e s i z e r s o f p r o t e i n from low-c o s t n o n - p r o t e i n n i t r o g e n sources (Johnson et a l . , 1944; Bela s c o , 1954; O l t j e n , 1967). Studi e s d e a l i n g with NPN i n ruminant r a t i o n s have i n d i c a t e d t h a t a c o n s i d e r a b l e p r o p o r t i o n 23 of the p r o t e i n u l t i m a t e l y u t i l i z e d by the ruminant i s b a c t e r i a l p r o t e i n , r e g a r d l e s s of the nature of the n i t r o g e n contained i n the r a t i o n . S e v e r a l e x c e l l e n t reviews ori the v a r i o u s aspects of NPN u t i l i z a t i o n by ruminants have been w r i t t e n r e c e n t l y (Hungate, 1966; McLaren, 1966; B r i g g s , 1967; Chalupa, 1970) . Urea i s c u r r e n t l y the most widely used NPN source. Growth, r e p r o d u c t i o n and l a c t a t i o n on p r o t e i n - f r e e d i e t s c o n t a i n i n g excess of 97% of the n i t r o g e n from urea has been demonstrated ( V i r t a n e n , 1966; O l t j e n , 1969). In s p i t e of the tremendous r e s e a r c h e f f o r t , problems s t i l l e x i s t i n the u t i l i z a t i o n o f urea (Chalupa, 1968). S u b s t i t u t i o n of urea f o r p r o t e i n has been shown to cause feed i n t a k e d e p r e s s i o n s . Huber and Cook (1969) have suggested t h a t the i n t a k e d p e r e s s i o n on high urea d i e t s was due to the u n d e s i r a b l e t a s t e o f urea and not to ruminal or p o s t - r u m i n a l e f f e c t s . Using two c h o i c e p r e f e r e n c e t e s t s w i t h sheep, Goatcher and Ch;urch (1970) r e p o r t e d t h a t c o n s i s t e n t r e j e c t i o n of urea s o l u t i o n s d i d not occur u n t i l c o n c e n t r a t i o n s o f 2.5 and 5% were reached. At the h i g h e r c o n c e n t r a t i o n , s u f f i c i e n t urea was i n g e s t e d to cause i l l n e s s and death. With l o w - q u a l i t y f o r a g e s , a d d i t i o n of n i t r o g e n has o f t e n l e d to g r e a t e r v o l u n t a r y consumption (Chalupa, 1968, and Donefer e t a l . , 1969). The e f f e c t of d i e t a r y n i t r o g e n upon i n t a k e l e v e l i s a t t r i b u t e d to i n c r e a s e s 24 i n f ermentation and r a t e o f passage ( E l l i o t and Topps, 1963). Urea can be used s a f e l y and eco n o m i c a l l y as a s u b s t i t u t e f o r p r o t e i n p r o v i d e d the b i o c h e m i c a l and p h y s i o l o g i c a l aspects of urea metabolism are understood and advantage i s taken o f t h i s knowledge. In g e n e r a l , the rumen ferme n t a t i o n system must be s u p p l i e d w i t h m a t e r i a l s which w i l l a llow f o r maximum and continuous r a t e s o f fe r m e n t a t i o n . In p r a c t i c e , t h i s r e q u i r e s the supply of the needed types and amounts of carbohydrates, minerals and oth e r growth f a c t o r s (Beames, 1959, 1960 ; Coombe and T r i b e , 1962; Coombe e t a l . , 1971). The f i e l d o f no n - p r o t e i n n i t r o g e n supplements f o r ruminants continues t o be an a c t i v e one i n an e f f o r t to f i n d m a t e r i a l s o f h i g h e r replacement value than urea. B i u r e t i s one such m a t e r i a l . I t has been shown t h a t b i u r e t i s l e s s t o x i c than urea f o r p r o t e i n replacement i n ruminant d i e t s (Meiske e t a l . , 1955; Repp e t a l . , 1955; Berry e t a l . , 1956; H a t f i e l d e t a l . , 1959 and I o s e t , 1969) . E a r l y r e p o r t s on the u t i l i z a t i o n o f b i u r e t - N were c o n f l i c t i n g . Belasco (1954) r e p o r t e d a r e d u c t i o n i n c e l l u l o s e d i g e s t i o n by rumen' b a c t e r i a i n i n v i t r o s t u d i e s when b i u r e t r e p l a c e d urea as a source o f n i t r o g e n . However, l a t e r r e p o r t s (Gaither e t a l . , 1955; Ewan e t a l . , 1958; Campbell e t a l . , 1960; O l t j e n , 1968 and Schroder and G i l c h r i s t , 1969) i n d i c a t e comparable u t i l i z a t i o n of b i u r e t and urea by ruminants as sources o f supplemental n i t r o g e n 25 p r o v i d e d t h a t animals f e d b i u r e t supplemented d i e t s were allowed t o adapt t o b i u r e t u t i l i z a t i o n . Most r e p o r t s i n d i c a t e t h a t ruminants r e q u i r e a longer p e r i o d f o r a d a p t a t i o n to b i u r e t than to urea (Repp e t a l . , 1955 and O l t j e n , 1968). Another m a t e r i a l which has found a l t e r n a t i v e use i n ruminant f e e d i n g i s o r g a n i c wastes ( p a r t i c u l a r l y from p o u l t r y o p e r a t i o n s ) . P o u l t r y manure i s used p r i m a r i l y as a f e r t i l i z e r f o r crops but re c e n t r e p o r t s (El-Sabban e t a l . , 1970; Lowman and Knight, 1970) have i n d i c a t e d t h a t i t c o u l d be su c c e s s -f u l l y used as a n i t r o g e n supplement i n ruminant d i e t s . D e t a i l e d chemical analyses have r e v e a l e d t h a t p o u l t r y waste cont a i n s a c o n s i d e r a b l e amount of n u t r i e n t s , p a r t i c u l a r l y n i t r o g e n (Bhattacharya and Fontenot, 1966; L e i b h o l z , 1969). Approximately, 30 t o 45% of t h i s n i t r o g e n i s u r i c a c i d n i t r o g e n ( L e i b h o l z , 1969; Lowman and Knight, 1970). In v i t r o s t u d i e s have shown t h a t rumen microorganisms can u t i l i z e u r i c a c i d as a source o f n i t r o g e n f o r p r o t e i n s y n t h e s i s (Belasco, 1954; Jurtshuk e t a l . , 1955). Noland e t a l . (1955) found t h a t n i t r o g e n from p o u l t r y l i t t e r was e q u i v a l e n t to th a t from soybean meal f o r g e s t a t i n g - l a c t a t i n g ewes, w h i l e Fontenot e t a l . (1963) showed t h a t p o u l t r y l i t t e r w i t h a peanut h u l l or corn cob base c o u l d be used f o r f a t t e n i n g and w i n t e r i n g s t e e r s . Bhattacharya and Fontenot (1965) found t h a t there was no r e d u c t i o n i n the d i g e s t i b i l i t y o f n i t r o g e n 26 i n sheep when p o u l t r y manure s u p p l i e d up to 50% of the n i t r o g e n i n the d i e t . P o u l t r y l i t t e r , i n a d d i t i o n to s u p p l y i n g n i t r o -gen, c o u l d supply a s u b s t a n t i a l amount o f energy f o r ruminants (Bhattacharya and Fontenot, 1966; Lowman and Knight, 1970). In the comparison of urea, b i u r e t , u r i c a c i d and urea phosphate as NPN sources i n p u r i f i e d d i e t s f e d to c a t t l e ( O l t j e n , 1967), the i n v i t r o r e s u l t s i n d i c a t e d t h a t the ruminal microorganisms must be adapted to u r i c a c i d and b i u r e t b e f o r e ruminal d e g r a d a t i o n o f these compounds to ammonia occurs to any extent. Even a f t e r a 21-day a d a p t a t i o n , the ruminal ammonia c o n c e n t r a t i o n s o f c a t t l e f e d b i u r e t were much lower than those of c a t t l e f e d the other NPN sources. Metabolism r e s u l t s o f the same study i n d i c a t e d t h a t the apparent d i g e s -t i b i l i t y o f dry matter and gross energy were s i g n i f i c a n t l y g r e a t e r with u r i c a c i d than with b i u r e t . A l s o , n i t r o g e n r e t e n t i o n was g r e a t e s t w i t h u r i c a c i d , f o l l o w e d by urea, b i u r e t and urea phosphate i n descending o r d e r . 27 I I I OBJECT OF THE RESEARCH The improvement of the n u t r i t i v e value of l o w - q u a l i t y forages by p h y s i c a l and chemical treatments i s w e l l e s t a b l i s h e d . Although such treatments r e s u l t i n s i g n i f i c a n t i n c r e a s e s i n n u t r i e n t d i g e s t i b i l i t y o f the roughage, no e f f e c t on i n c r e a s i n g v o l u n t a r y feed i n t a k e has been demonstrated. I t appears t h e r e f o r e , t h a t the r a t e of m i c r o b i a l d e g r a d a t i o n of the f i b r o u s c o n s t i t u e n t s o f the roughage i s l i m i t e d not only by over-m a t u r i t y and l i g n i f i c a t i o n o f the roughage but a l s o by d e f i -c i e n c i e s i n a v a i l a b l e n i t r o g e n , m i n e r a l s and v i t a m i n s . The r e s e a r c h work r e p o r t e d i n t h i s t h e s i s was under-taken to i n v e s t i g a t e the i n t e r a c t i o n between p h y s i c a l t r e a t -ment and n i t r o g e n supplementation of high-roughage r a t i o n s . The s t u d i e s were d i v i d e d i n t o three p a r t s . The f i r s t p a r t d e a l t with the chemical and b i o l o g i c a l examination of p o u l t r y wastes i n an attempt to develop a p r o c e s s i n g method t h a t w i l r e s u l t i n the p r o d u c t i o n o f p o u l t r y droppings and l i t t e r t h a t are p r a c t i c a l l y f r e e o f pathogenic b a c t e r i a and a t the same time r e t a i n t h e i r n u t r i t i v e value as a n i t r o g e n supplement. 28 The second p a r t i n v o l v e d the animal f e e d i n g t r i a l s to determine which no n - p r o t e i n n i t r o g e n source can be used to r e p l a c e more than o n e - t h i r d o f the t o t a l r a t i o n n i t r o g e n as i s p r e s e n t l y recommended f o r urea n i t r o g e n . The n u t r i t i v e value o f the high-roughage r a t i o n s supplemented with v a r i o u s n i t r o g e n sources was e v a l u a t e d on the b a s i s of n u t r i e n t d i g e s t i b i l i t y , n i t r o g e n balance and v o l u n t a r y consumption of the experimental d i e t s by sheep. The t h i r d p a r t was concerned with the d e t e r m i n a t i o n of c e l l u l o s e d i g e s t i b i l i t y i n v i t r o of samples of the a l k a l i t r e a t e d oat straw and p o p l a r wood ( l o w - q u a l i t y - forages)-v Samples of the r a t i o n s fed to sheep i n the f e e d i n g t r i a l s were a l s o i n c l u d e d as s u b s t r a t e s i n the f e r m e n t a t i o n t e s t s so t h a t com-p a r i s o n between i n v i v o and i n v i t r o c e l l u l o s e d i g e s t i b i l i t i e s c o u l d be made. IV EXPERIMENTAL SECTION I CHEMICAL AND BIOLOGICAL EXAMINATIONS OF POULTRY WASTES 30 CHEMICAL AND BIOLOGICAL EXAMINATION OF POULTRY WASTES  I n t r o d u c t i o n G e n e r a l l y the u t i l i z a t i o n o f by-products o r waste m a t e r i a l s i n animal f e e d i n g i s s t i m u l a t e d by 3 main i n t e r e s t s : (1) d i s p o s i n g o f these wastes by b e n e f i c i a l and economical means (2) redu c i n g the c o n t r i b u t i o n of these wastes to e n v i r o n -mental p o l l u t i o n and (3) s p a r i n g the land used i n the p r o d u c t i o n of l i v e s t o c k feeds f o r crops which can be used d i r e c t l y f o r human consumption. As a g r i c u l t u r a l s p e c i a l i z a t i o n and p r o d u c t i v i t y become i n t e n s i f i e d , problems a s s o c i a t e d with the d i s p o s a l o f l i q u i d , s o l i d and gaseous waste products have g r e a t l y i n c r e a s e d . In a d d i t i o n to the c o n f l i c t s of i n t e r e s t over the environmental q u a l i t y i s the mammoth problem o f d i s p o s a l o f s o l i d wastes which are not only extremely o f f e n s i v e but have the p o t e n t i a l to p o l l u t e both a i r , s u r f a c e and sub-surface waters. A f t e r h a r v e s t i n g seed c r o p s , farmers are u s u a l l y faced with the problem of d i s p o s i n g the remainder of the p l a n t . In many areas, the p r a c t i c e has been t o burn the p l a n t r e s i d u e s i n the f i e l d c a u s i n g great p a l l s o f smoke s e v e r a l weeks each year. Farmers are now f i n d i n g t h a t enforcement of a i r p o l l u -t i o n laws makes i t impe r a t i v e to change c u r r e n t d i s p o s a l p r a c t i c e s . 31 The problems o f animal wastes d i s p o s a l are more complex. They i n c l u d e not only the e n g i n e e r i n g but a l s o the s o c i a l , l e g a l and economic as p e c t s . I t i s now a b s o l u t e l y e s s e n t i a l t h a t the c o s t of a l i v e s t o c k o p e r a t i o n must i n c l u d e the waste h a n d l i n g and d i s p o s a l a c t i v i t y as a t o t a l p a r t o f the management system. A g r e a t d e a l o f i n v e s t i g a t i o n i s being conducted i n many i n s t i t u t i o n s i n d i s p o s a l systems, p r e v e n t i o n of water and a i r p o l l u t i o n , r e u t i l i z a t i o n of animal wastes e i t h e r as f e r t i l i z e r s o r f e e d s t u f f s . With the development o f any e c o n o m i c a l l y f e a s i b l e method o f p r o c e s s i n g and r e c y c l i n g these wastes, i t may be p o s s i b l e to reduce a i r and water p o l l u t i o n , the c o s t of animal p r o d u c t i o n and a t the same time r e l i e v e p o u l t r y farmers o f the problem o f d i s p o s a l o f manure from p o u l t r y houses. A l s o , s i n c e many of the forages and waste product f e e d s t u f f s are very low i n n i t r o g e n , r e s e a r c h i s needed i n which NPN i s used to supply c o n s i d e r a b l y more than o n e - t h i r d of the t o t a l n i t r o g e n i n the d i e t . 32 A. CHEMICAL ANALYSIS OF POULTRY WASTES 1. I n t r o d u c t i o n There are two d i s t i n c t types of p o u l t r y wastes: P o u l t r y droppings with l i t t e r ; p o u l t r y droppings without l i t t e r . The l i t t e r may be d e s c r i b e d as a by-product c o n t a i n i n g a bedding m a t e r i a l , u s u a l l y wood shavings, saw-dust, peanut h u l l s , c e r e a l h u l l s , or any other f i b r o u s p l a n t by-product. P o u l t r y l i t t e r v a r i e s c o n s i d e r a b l y i n chemical composition depending on such f a c t o r s as type of b i r d s from which i t comes, the age of the l i t t e r , type of bedding m a t e r i a l used, management of the l i t t e r , and the number of b i r d s kept on the bedding m a t e r i a l . 2. Experimental Methods Samples of p o u l t r y l i t t e r were c o l l e c t e d from a b r o i l e r house on 3 occasions -- 2, 4 and 6 weeks f o l l o w i n g the date the b i r d s were put on the bedding m a t e r i a l . Chemical analyses data o f the samples are presented i n t a b l e 1. The l i t t e r c o n s i s t e d o f bedding m a t e r i a l , droppings, some f e a t h e r s and wasted feed. No attempt was made to make the l i t t e r completely f r e e o f these extraneous m a t e r i a l s . However, l a r g e f e a t h e r s 33 and p i e c e s of stones were hand-picked b e f o r e the chemical a n a l y s i s was done. At each sampling date, the samples were taken from d i f f e r e n t spots and a t d i f f e r e n t l e v e l s i n order to o b t a i n f a i r l y r e p r e s e n t a t i v e samples. Moisture and n i t r o g e n contents were determined on the wet f r e s h m a t e r i a l . N i t r o g e n d e t e r -m i n a t i o n was done on the wet sample u s i n g the macro-Kjeldahl procedure (A.O.A.C. 1960). T h e r e a f t e r , the remaining samples were d r i e d i n a f o r c e d - a i r oven a t 85°C f o r 24 hours. The d r i e d m a t e r i a l was ground to pass a 20-mesh screen and analyzed f o r o ther proximate components. U r i c a c i d n i t r o g e n was d e t e r -mined on the d r i e d samples by the s p e c t r o p h o t o m e t r y procedure as r e p o r t e d by Buys and P o t g i e t e r (19 59). The u r i c a c i d n i t r o g e n content was a l s o expressed as percent o f the t o t a l n i t r o g e n o f the l i t t e r . P o u l t r y droppings were s i m i l a r l y taken from the caged b i r d l a y e r s ' house on three o c c a s i o n s f o l l o w i n g the p e r i o d i c c l e a n i n g of the house. Samples were taken a t 1, 2 and 4 weeks f o l l o w i n g the c l e a n i n g of the p r e v i o u s l y accumulated droppings. Chemical analyses .. procedures on the droppings were the same as t h a t f o r the l i t t e r . The droppings c o n s i s t e d p r i m a r i l y of pure cage droppings, wasted feeds, f e a t h e r s , broken eggs and a l a r g e p o p u l a t i o n of h o u s e f l y l a r v a e and 34 and pupae. I n f e s t a t i o n o f h o u s e f l y was high at the time o f sampling as i t was summer time. S e p a r a t i o n o f the pure cage droppings was not attempted and the a n a l y s i s data i n Table 2 re p r e s e n t the composition of the droppings as c o l l e c t e d from the l a y e r s ' house, each v a l u e r e p r e s e n t i n g the mean of 5 de t e r m i n a t i o n s . 3. R e s u l t s and D i s c u s s i o n The chemical composition data r e p o r t e d i n Tables 1 and 2 c o n f i r m the g e n e r a l o p i n i o n as regards the c o n s i d e r a b l e v a r i a t i o n i n the chemical composition of p o u l t r y wastes (Brugman et a l . , 1964; Mowat, 1965; El-Sabban e t a l . , 1970). Greater v a r i a t i o n i n chemical composition i n p o u l t r y wastes was observed between sampling dates than w i t h i n samples taken on the same day. P o u l t r y droppings contained a h i g h e r moisture content at any sampling date than the b r o i l e r l i t t e r . The h i g h e r moisture content i n the droppings c o u l d be e x p l a i n e d by the f a c t t h a t the dry wood-shaving bedding m a t e r i a l has the tendency to d i l u t e the chemical composition o f the e x c r e t a mixed with i t . M o i sture content of both the droppings and l i t t e r i n c r e a s e d p r o g r e s s i v e l y w i t h l e n g t h of accumulation, t h i s i n c r e a s e b e i n g 35 more n o t i c e a b l e i n the l i t t e r . The reason f o r t h i s i n c r e a s e i n moisture content can be a t t r i b u t e d t o many f a c t o r s . The i n f e s t a t i o n of h o u s e f l y T the presence o f the h o u s e f l y d e v e l -opmental stages — l a r v a e and pupae — produce a moist environment. The decomposition of o r g a n i c matter i n the l i t t e r o r droppings by the s a p r o p h y t i c group o f b a c t e r i a (Alexander e t a l . , 1968) would r e s u l t i n the accumulation of wet m a t e r i a l e s p e c i a l l y i n the lower p o r t i o n . Wasted feed and water tend to i n c r e a s e the moisture content and a l s o s i n c e the p r o d u c t i o n of e x c r e t a i s l i k e l y to be a t a f a s t e r r a t e than the d r y i n g , accumulation of e x c r e t a would favour the p r o d u c t i o n of wet l i t t e r or droppings. The mean crude protein.: content o f the droppings tended to be uniform over the sampling dates, but a g r e a t v a r i a t i o n i n the mean crude p r o t e i n content was observed i n the l i t t e r . T h i s i s expected s i n c e the d i s t r i b u t i o n of e x c r e t a on the bedding m a t e r i a l was uneven. The crude p r o t e i n content of p o u l t r y l i t t e r or droppings i s i n f l u e n c e d by many f a c t o r s , the most important of which i s the decomposition of urea and u r i c a c i d by the s a p r o p h y t i c groups of b a c t e r i a and subsequent l o s s of n i t r o g e n as ammonia. Other f a c t o r s i n c l u d e the amount o f wasted feed, shed f e a t h e r s , broken eggs and the presence of h o u s e f l y l a r v a e and pupae ( M i l l e r , 1970) . 36 TABLE I The Chemical Composition of B r o i l e r Litter"*" as A f f e c t e d by Length o f Time B i r d s Were Kept on the L i t t e r Age of L i t t e r (weeks) Composition 2 4 6 Dry Matter (%) 80. 1 ±3. 5 74.2 ±5 .1 66.6 ±7. 4 Other components (DM b a s i s ) Crude P r o t e i n (%) 16. 3 ±1. 9 22.7 ±2 .3 26.4 ±4. 2 Eth e r E x t r a c t (%) 1. 93 ±0. 6 2.14 ±0 .8 2.61 ±0. 5 Crude f i b e r (%) 26 . 1 ±3. 4 18.6 ±2 .9 16.6 ±2. 3 Ash (%) 10. 7 ±1. 8 18.9 ±4 .7 24 .2 ±6. 4 NFE (%) 45. 0 ±3. 2 37.7 ±5 .8 30.2 ±6. 1 L i g n i n (%) 6. 8 ±1. 1 6.1 ±0 .8 5.2 ±1. 2 Gross Energy (kcal/g) 3. 88 ±0. 7 3.36 ±0 .4 3.05 ±0. 4 U r i c A c i d - N (mg/g) 8. 7 ±1. 2 12.7 ±1 .4 14.4 ±1. 3 U r i c A c i d - N as % o f t o t a l N 33. 3 35.0 34.1 Each value i s a mean of 5 d e t e r m i n a t i o n s . 37 TABLE 2 The Chemical Composition of Hen D r o p p i n g s 1 as A f f e c t e d by Length of Time the Droppings Were Allowed to Accumulate Age of Droppings (weeks) Composition 1 2 4 Dry Matter (%) 61 .7 ±2 .7 56.2 ±3 .1 50 . 5 ±3 .6 Other components (DM b a s i s ) Crude P r o t e i n (%) 34 .2 ±1 .1 32.6 ±0 .9 31. 8 ±0 .9 Ether E x t r a c t (%) 1 .21 ±0 .6 0.97 ±0 .3 0. 76 ±0 .4 Crude f i b e r (%) 10 .1 ±0 .4 9.6 ±0 .6 9. 1 ±0 .6 Ash (.%) 24 .5 ±2 .6 26.9 ±2 .4 28. 9 ±3 .1 NFE (%) 30 .0 ±1 .1 29 .9 ±2 .7 29. 4 ±2 .4 L i g n i n (%) 3 .6 ±0 .9 3.1 ±0 .6 . 2. 8 ±0 .7 Gross Energy (kcal/g) 2 .87 ±0 . 3 2.84 ±» .2 2. 82 ±0 .2 U r i c Acid-N (mg/g) 22 .9 ±0 .6 22.5 ±0 .5 21. 4 ±0 .6 U r i c Acid-N as % of t o t a l N 41 .9 43.1 42. 0 Each value i s a mean of 5 d e t e r m i n a t i o n s . 38 U r i c a c i d n i t r o g e n c o n s t i t u t e d approximately o n e - t h i r d of the t o t a l n i t r o g e n i n the l i t t e r (33.3 to 35.0%), and between 41.9 and 4 3.1% of the t o t a l n i t r o g e n i n the droppings. These values are i n c l o s e agreement with those r e p o r t e d by a number o f workers i n c l u d i n g Fontenot e t a l . (19 66) 30%, L e i b h o l z (1969) 38.7% and Lowman and Knight (1970) 43%. The mean ash content o f the l i t t e r i n c r e a s e d r a p i d l y from the time b i r d s were put on the new wood shaving bedding m a t e r i a l . T h i s i n c r e a s e i n the ash content r e s u l t e d from an i n c r e a s e i n the r a t i o o f droppings to woodshaving. The mean ash content o f the droppings was more o r l e s s c onstant over the sampling p e r i o d . However, th e r e was a tendency f o r s l i g h t i n c r e a s e s i n the ash content as accumulation of droppings p r o g r e s s e d . Although complete m i n e r a l a n a l y s i s of the ash was not c a r r i e d out, the r e s u l t s o b t a i n e d by P e r k i n s and Parker (1971) showed t h a t c a l cium c o n s t i t u t e s the major macro-element ranging between 2.0 and 4.8% of the hen droppings and between 1.2 and 3.8% of b r o i l e r l i t t e r . Other macro- and micro-elements are p r e s e n t i n the droppings, but none i s p r e s e n t i n amounts t h a t can l e a d to n u t r i t i o n a l problems when used as a n i t r o g e n supplement i n ruminant r a t i o n s . 39 The crude f i b e r content o f b r o i l e r l i t t e r decreased p r o g r e s s i v e l y over the 6-week sampling p e r i o d . T h i s decrease i s expected as the r a t i o of e x c r e t a t o wood shaving bedding m a t e r i a l i n c r e a s e d w i t h accumulation o f droppings on the l i t t e r . Wasted feed accounted f o r a major p o r t i o n o f crude f i b e r and l i g n i n p r e s e n t i n the pure droppings. U s u a l l y p o u l t r y droppings are q u i t e low i n crude f i b e r and l i g n i n ( L e i b h o l z , 1969). The l i t t e r had a h i g h e r e t h e r e x t r a c t than the droppings a t a l l sampling dates. The mean ether e x t r a c t of the l i t t e r i n c r e a s e d s l i g h t l y over the sampling p e r i o d w h i l e t h a t o f the droppings decreased. However, the mean eth e r e x t r a c t values obtained f o r the l i t t e r a t the end of s i x weeks (2.6%) agree w e l l with those r e p o r t e d by Fontenot e t a l . (1966) 2.8%, Mowat (1965) 2.5% and Brugman et a l . (19 64) 2.53%. I t does appear t h a t the h i g h e r e t h e r e x t r a c t value i n the l i t t e r as compared with the droppings i s i n f l u e n c e d by the presence o f the bedding m a t e r i a l i n the l i t t e r . The mean gross energy content (kcal/g) o f the b r o i l e r l i t t e r was h i g h e r than t h a t of the droppings i r r e s p e c t i v e of sampling dates. This d i f f e r e n c e i n energy content c o u l d be e x p l a i n e d by the f a c t t h a t the l i t t e r i s h i g h e r i n crude f i b e r , e t h e r e x t r a c t and lower i n ash contents than the 40 droppings. The gross energy content of the l i t t e r was observed to decrease with l e n g t h of time o f accumulation of e x c r e t a on the l i t t e r . The d e c r e a s i n g energy content of the l i t t e r can thus be a t t r i b u t e d to the i n c r e a s i n g r a t i o of droppings to the bedding m a t e r i a l and thus an i n c r e a s e i n the ash content which has no energy v a l u e . 41 B. EFFECT OF HEAT TREATMENTS ON THE CHEMICAL COMPOSITION  AND BACTERIAL FLORA OF POULTRY WASTES. 1. I n t r o d u c t i o n In the development o f a s u i t a b l e procedure f o r h a n d l i n g p o u l t r y wastes f o r ruminant f e e d i n g , the p h y s i c a l , chemical and m i c r o b i o l o g i c a l p r o p e r t i e s o f the wastes should be con-s i d e r e d . P o u l t r y waste has been shown to be q u i t e high i n b a c t e r i a , moulds and ye a s t s (Halbrook e t a l . , 1951; Brugman e t a l . , 1964; S c h e f f e r l e , 1965; Alexander e t a l . , 1968). The m a j o r i t y o f the m i c r o f l o r a i n the waste are normal i n h a b i t a n t s o f the i n t e s t i n a l t r a c t o f ruminants and t h e r e f o r e not pathogenic t o l i v e s t o c k (Ivos e t a l . , 1966; S c h e f f e r l e , 1966). N e v e r t h e l e s s , the presence o f c e r t a i n pathogenic b a c t e r i a i n the p o u l t r y wastes i s of extreme concern when the wastes are used i n ruminant f e e d i n g (Alexander e t a l . , 196 8). I t i s not c e r t a i n whether a p p l i c a t i o n of heat t r e a t -ments can a f f e c t the value o f p o u l t r y waste as a feed supple-ment f o r ruminants. On the oth e r hand, the presence o f di s e a s e c a u s i n g b a c t e r i a c o u l d c o n s t i t u t e a p o t e n t i a l h e a l t h hazard t o l i v e s t o c k and man. 42 2. Experimental Methods A t o t a l o f 12 samples c o n s i s t i n g o f 6 samples each of b r o i l e r l i t t e r and cage droppings were taken from the bulk of wastes c o l l e c t e d to be used f o r the animal f e e d i n g t r i a l s . The 6 samples of each type of p o u l t r y waste were composited, mixed thoroughly and sub-sampled f o r m i c r o b i o l o g i c a l t e s t s f o l l o w i n g the procedure r e p o r t e d by Alexander e t a l . (1968) as o u t l i n e d below. A lOg p o r t i o n o f each specimen;:, was suspended i n 100 ml. o f phosphate b u f f e r e d s a l i n e a t pH 7.2 i n a 250 ml. Erlenmeyer f l a s k . The f l a s k s were w e l l stoppered and put on an automatic a g i t a t o r f o r 30 minutes. A f t e r t h i s , the suspension was passed through a B e r k e f e l d f i l t e r c y l i n d e r without a f i l t e r paper, to separate the l a r g e p a r t i c l e s . The suspensions were allowed to s e t t l e f o r 30 minutes and the supernatant poured i n t o d i l u t i o n b o t t l e s . D i f f e r e n t d i l u t i o n s o f t h i s supernant were prepared and used as the inoculum. P r i o r to the p r e p a r a t i o n of the inoculum, the c u l t u r e media t o be used i n the s t u d i e s were s t e r i l i z e d i n an autoclave a t 1.06 kg/sq. cm p r e s s u r e and 121°C f o r 30 minutes. The specimens were i n o c u l a t e d u s i n g a 2 mm. wire loop onto b o r i c a c i d sheep b l o o d agar (6.5 ml of 4% b o r i c a c i d 43 s o l u t i o n i n 250 ml. o f 5% sheep blo o d a g a r ) , MacConkey agar (Difco) and b r i l l i a n t green agar (Difco) "*". Tubes of beef i n f u s i o n b r o t h were i n o c u l a t e d with 1 ml. of the supernatant and incubated a t 37°C f o r 4 hours p r i o r to i n o c u l a t i n g tubes of s e l e n i t e - F b r o t h (Difco)"'" with 3 ml. of t h i s growth. The s e l i n i t e - F b r o t h was incubated f o r 24 h r s . b e f o r e b e i n g s u b c u l t u r e d to b r i l l i a n t green agar. A l l the i n o c u l a t e d c u l t u r e media were incubated at 37°C and i n s p e c t e d d a i l y f o r 6 days f o r b a c t e r i a l growth. The remaining l i t t e r and cage droppings were s u b j e c t e d to three d i f f e r e n t heat treatments to produce oven-dried, a u t o c l a v e d and cooked p o u l t r y wastes (El-Sabban e t a l . , 1970). Autoclaved p o u l t r y waste (APW) was t r e a t e d by steam a t 1.06 kg/ sq.cm. pr e s s u r e and 121°C f o r 30 minutes. Cooked p o u l t r y waste (CPW) was prepared by f i r s t wrapping the f r e s h p o u l t r y waste i n aluminium f o i l and steaming a t atmospheric p r e s s u r e f o r 30 minutes. D r i e d p o u l t r y waste (DPW) was prepared by spreading the m a t e r i a l very t h i n l y on aluminium f o i l and d r y i n g i n a f o r c e d - a i r oven at 37.5°C f o r 72 hours. Both the processed and unprocessed p o u l t r y wastes were d r i e d i n the oven, ground i n the l a b o r a t o r y hammermill to pass the 20 mm. s c r e e n and analyzed f o r n i t r o g e n (A.O.A.C., 1960) and u r i c a c i d (Buys and P o t g i e t e r , 1959). The processed D i f c o L a b o r a t o r i e s Inc., D e t r o i t , Michigan, U.S.A. 44 TABLE 3 The E f f e c t of Heat Treatments on the B a c t e r i a l Growth i n P o u l t r y Wastes Media Blood agar Type of Product Untreated ++ APW CPW DPW MacConkey agar B r i l l i a n t green agar ( S e l i n i t e - F broth) ++ APW = a u t o c l a v e d p o u l t r y waste CPW = cooked p o u l t r y waste DPW = d r i e d p o u l t r y waste ++ = 50 or more c o l o n i e s of b a c t e r i a observed + = 10 or l e s s c o l o n i e s o f b a c t e r i a observed media overgrown w i t h moulds. 45 TABLE 4 RESULTS OF BACTERIOLOGICAL ANALYSIS OF FORTY-FOUR SAMPLES OF POULTRY LITTER 1 Types i s o l a t e d Number I s o l a t e d C l o s t r i d i u m p e r f r i n g e n s 8 C l o s t r i d i u m chauvoei 1 C l o s t r i d i u m n o v y i 8 C l o s t r i d i u m s o r d e l l i c 1 C l o s t r i d i u m butyricum 2 C l o s t r i d i u m cochlearium 1 C l o s t r i d i u m multifermentans 1 C l o s t r i d i u m c a r n i s 1 C l o s t r i d i u m tetanomorphum 1 C l o s t r i d i u m h i s t o l y t i c u m 1 Corynebacterium pyogenes 1 Corynebacterium equi 2 Salmonella b l o c k l e y 1 Salmonella s a i n t - p a u l 1 Salmonella typhimurium v a r . Copenhagen 1 A c t i n o b a c i l l u s spp. 1 Yeast 1 Mycobacterium spp. 2 E n t e r o b a c t e r i a c e a e (other than Salmonella) A l l samples B a c i l l u s spp. A l l samples Staphylococcus spp. A l l samples Streptococcus spp. A l l samples Alexander, D.C., J.A.J. C a r r i e r e and K.A. McKay. Can. Vet. J . 9:127 (1968) 46 m a t e r i a l s (APW, CPW and DPW) were c u l t u r e d u s i n g the same procedure r e p o r t e d e a r l i e r . 3. R e s u l t s and D i s c u s s i o n The e f f e c t o f heat treatments o f p o u l t r y waste on the b a c t e r i a l growth i s shown i n t a b l e 3. A l a r g e number o f b a c t e r i a l c o l o n i e s was observed i n the media i n o c u l a t e d with the untreated p o u l t r y waste. A few c o l o n i e s were a l s o observed i n the media i n o c u l a t e d with the d r i e d p o u l t r y waste. No c o l o n i e s were observed i n e i t h e r the au t o c l a v e d o r cooked p o u l t r y waste i n d i c a t i n g t h a t the microorganisms i n the waste were destroyed by the heat treatments. The d i f f e r e n t i a l media ( b r i l l i a n t green agar and s e l e n i t e - F broth) used f o r the i s o l a t i o n o f Salmonella spp d i d not show any growth. The b i r d s from which the wastes were c o l l e c t e d were fed a n t i b i o t i c -supplemented feeds. I d e n t i f i c a t i o n o f the types of b a c t e r i a observed i n the media i n o c u l a t e d with the un t r e a t e d p o u l t r y waste was not c a r r i e d out. However, t a b l e 4 shows the types of b a c t e r i a which were i s o l a t e d from a t o t a l o f 44 f i e l d samples of p o u l t r y waste ob t a i n e d from s i x p r o v i n c e s i n Canada (Alexander e t a l . , 1968). The 44 samples were made up of 27 b r o i l e r , 15 hen and 2 turkey l i t t e r samples. Salmonella spp were i s o l a t e d from on l y three samples. T h i r t e e n o f the 44 47 TABLE 5 TOTAL NITROGEN AND URIC ACID NITROGEN CONTENT OF UNTREATED AND HEAT TREATED POULTRY DROPPINGS AND LITTER (a) P o u l t r y droppings Type of Product Component T o t a l N (%) U r i c a c i d N (mg/g) U r i c a c i d as % of t o t a l N (b) P o u l t r y l i t t e r T o t a l N (%) U r i c a c i d N (mg/g) U r i c a c i d as % of t o t a l N Untreated 5.09 21.4 42.0 4.22 14.4 34.1 APW 4.97 20 .3 41.3 CPW 4.86 19 .7 40.1 4.06 13.9 33.4 3.98 13.4 33.1 DPW 4.30 18.8 43.7 3.55 12.5 35.2 APW = aut o c l a v e d p o u l t r y waste CPW = cooked p o u l t r y waste DPW = d r i e d p o u l t r y waste 48 samples were negative f o r pathogenic b a c t e r i a . Most o f the b a c t e r i a i s o l a t e d by these workers are normal i n h a b i t a n t s of the i n t e s t i n a l t r a c t of ruminants. I t was observed t h a t storage o f l i t t e r f o r one or two months was probably s u f f i c i e n t to d e s t r o y s a l m o n e l l a p r e s e n t i n the l i t t e r . The a l k a l i n i t y of p o u l t r y wastes has been shown to i n c r e a s e with storage (Halbrook e t a l . , 1951). Increased a l k a l i n i t y t h e r e f o r e may be one of the f a c t o r s a f f e c t i n g v i a b i l i t y o f b a c t e r i a i n aged p o u l t r y wastes (Tucker, 1967; C a r r i e r e e t a l . , 1968). The t o t a l n i t r o g e n and u r i c a c i d n i t r o g e n content of the u n t r e a t e d and t r e a t e d p o u l t r y droppings and l i t t e r are presented i n t a b l e 5. The data i n d i c a t e d t h a t steaming of p o u l t r y waste under p r e s s u r e (APW) or at atmospheric p r e s s u r e (CPW) had l i t t l e e f f e c t on the t o t a l n i t r o g e n and u r i c a c i d n i t r o g e n content of the wastes. However, s l i g h t decreases i n the content of these components were observed. Drying o f the f r e s h p o u l t r y wastes r e s u l t e d i n g r e a t e r decrease i n the t o t a l and u r i c a c i d n i t r o g e n content when compared with the heat t r e a t e d samples. I t appeared t h a t a i r - d r y i n g o f p o u l t r y wastes without f i r s t a r r e s t i n g the process of decomposition by heat treatment i n c r e a s e d the n i t r o g e n l o s s most probably by way of ammonia. 49 4. Summary and C o n c l u s i o n Analyses o f b r o i l e r l i t t e r and hen droppings i n d i c a t e t h a t these wastes c o n t a i n v a l u a b l e n u t r i e n t s , p a r t i c u l a r l y n i t r o g e n , and thus c o u l d be used t o r e p l a c e p a r t o f the n i t r o g e n i n the r a t i o n o f ruminant animals. B r o i l e r l i t t e r as removed from the house c o n t a i n e d between 31.8 and 41.6% moisture. \ On an oven-dry b a s i s , i t contained between 3.2 and 4.8% N, 21.8 and 25.7% ash and a v a r i a b l e p e r c e n t of crude f i b e r depending on the r a t i o o f the droppings t o the bedding m a t e r i a l . Cage droppings c o n t a i n e d h i g h e r moisture content on the average than b r o i l e r l i t t e r . As c o l l e c t e d from the house, p o u l t r y droppings c o n t a i n e d between 41.9 and 54.3% moisture. On dry b a s i s , i t co n t a i n e d between 4.1 and 5.8% N, and 26.2 and 33.1% ash. Approximately o n e - t h i r d of the t o t a l N i n p o u l t r y l i t t e r i s u r i c acid-N, w h i l e p o u l t r y droppings c o n t a i n e d s l i g h t l y h i g h e r v a l u e s . Minor v a r i a t i o n s e x i s t e d i n the chemical a n a l y s i s o f p o u l t r y wastes c o l l e c t e d i n the same house a t any sampling date as compared wi t h samples c o l l e c t e d on d i f f e r e n t dates. A p p l i c a t i o n o f heat treatments ( a u t o c l a v i n g and steaming) had l i t t l e e f f e c t on the t o t a l and u r i c a c i d n i t r o g e n o f the wastes. Higher n i t r o g e n l o s s was observed i n the d r i e d samples as compared wi t h the heat t r e a t e d samples. The reason f o r t h i s 50 d i f f e r e n c e i s most l i k e l y due to the f a c t t h a t the process o f decomposition by the s a p r o p h y t i c groups of b a c t e r i a was a r r e s t e d by the heat treatments. The heat treatments were s u f f i c i e n t to destroy a l l m i c r o f l o r a p r e s e n t i n the wastes. The d r y i n g process r e s u l t e d i n the p r o d u c t i o n o f m a t e r i a l t h a t s t i l l c o n t a i n e d some microorganisms, p a r t i c u l a r l y moulds and y e a s t s . Salmonella spp was not i s o l a t e d i n the p o u l t r y wastes t e s t e d . A number o f f a c t o r s have been r e p o r t e d to c o n t r i b u t e to decreased v i a b i l i t y o f pathogenic b a c t e r i a i n p o u l t r y wastes. Among these f a c t o r s are the storage o r accumulation p e r i o d , a l k a l i n i t y o f the wastes, hi g h p o p u l a t i o n of competing and s a p r o p h y t i c groups o f b a c t e r i a . Water and type o f feed are among the major f a c t o r s which a f f e c t the m i c r o f l o r a o f the i n t e s t i n a l t r a c t of c h i c k e n s , and s i n c e most p o u l t r y producers are now u s i n g a n t i b i o t i c - s u p p l e m e n t e d r a t i o n s , the i n c i d e n c e of pathogenic b a c t e r i a i n the feces o f chickens i s much l e s s . Heat treatment of the wastes b e f o r e b e i n g i n c o r p o r a t e d i n t o ruminant d i e t w i l l f u r t h e r ensure t h a t the waste i s f r e e o f pathogenic b a c t e r i a . SECTION I I ANIMAL FEEDING TRIALS 52 A * TRIAL I. Supplementation of High-roughage r a t i o n s with v a r i o u s N i t r o g e n sources ( u n p e l l e t e d r a t i o n s ) . D i g e s t i b i l i t y and N i t r o g e n Balance S t u d i e s 1. I n t r o d u c t i o n A review of the l i t e r a t u r e shows t h a t l o w - q u a l i t y forages can serve as a p o t e n t i a l energy source f o r ruminants i f the e f f e c t of l i g n i n , which reduces both n u t r i e n t a v a i l -a b i l i t y and v o l u n t a r y consumption can be circumvented. V a r i o u s p h y s i c a l and chemical treatments have been used to e f f e c t d e l i g n i f i c a t i o n and thus i n c r e a s e the energy d i g e s t i b i l i t y . However, i t has been observed by many authors t h a t the d e l i g n i f i e d m a t e r i a l i s i n most cases not consumed by ruminant animals i n amounts to meet the energy requirement. I t has t h e r e f o r e been found necessary to accompany d e l i g n i f i c a t i o n procedures w i t h energy and/or n i t r o g e n supplementation i n order to i n c r e a s e both the n u t r i e n t d i g e s t i b i l i t y and v o l u n t a r y consumption of l o w - q u a l i t y forages by ruminants. In most cases, n i t r o g e n supplementation alone has been found to be more b e n e f i c i a l as regards n u t r i e n t d i g e s t i b i l i t y and consumption of roughages by animals. The animal f e e d i n g t r i a l and n i t r o g e n balance s t u d i e s to be r e p o r t e d were designed to e v a l u a t e the n u t r i t i v e value 53 of a l o w - q u a l i t y forage (Oat straw) when supplemented with f i v e d i f f e r e n t n i t r o g e n sources u s i n g soybean meal n i t r o g e n as the r e f e r e n c e n i t r o g e n . 2. Design of Experiment A randomized b l o c k design was used with the 4 NPN sources (urea, b i u r e t , p o u l t r y droppings and b r o i l e r l i t t e r ) and the r e f e r e n c e n i t r o g e n source (soybean meal) c o n s t i t u t i n g the treatments. E i g h t lambs were assigned t o each experimental r a t i o n . The male animals i n each experimental group were to be used f o r d i g e s t i b i l i t y and n i t r o g e n balance s t u d i e s w h i l e the female animals were to be group-fed t o determine the r e l a t i v e f e e d i n g value of the experimental r a t i o n s , u s i n g changes i n body weight as the b a s i s f o r comparison. 3. P r e p a r a t i o n of r a t i o n components (a\ G r i n d i n g o f Oat straw Baled oat straw which was ha r v e s t e d i n 1969 was used as the l o w - q u a l i t y roughage. The straw was prepared f o r f e e d i n g by f i r s t chopping i n a Haybuster model B No. 162 1, and "'"J.&J. Manufacturing Company, Minot, North Dakota, 5 8701, U.S.A. 54 then g r i n d i n g i n a Massey H a r r i s l a b o r a t o r y hammermill. The average length of the r e s u l t a n t ground straw was about 0.35 cm. (fc^ P r e p a r a t i o n of the p o u l t r y wastes P o u l t r y droppings were c o l l e c t e d from a caged l a y e r s ' house. The droppings had accumulated f o r approximately 4 weeks f o l l o w i n g the l a s t day of c l e a n i n g the house. Wood-shaving-base l i t t e r was c o l l e c t e d from a b r o i l e r house. The l i t t e r had been used f o r about 6 weeks s t a r t i n g from the date the b i r d s were f i r s t put on the new bedding. Samples were taken from the bulk of p o u l t r y droppings and l i t t e r and analyzed f o r chemical c o n s t i t u e n t s as r e p o r t e d e a r l i e r . The l i t t e r c o n s i s t e d p r i m a r i l y o f wood-shavings and c h i c k e n droppings but mixed with o t h e r extraneous m a t e r i a l s such as shed f e a t h e r s , wasted feed, h o u s e f l y l a r v a e and pupae. The cage; droppings were mixed with shed f e a t h e r s , wasted feed, h o u s e f l y l a r v a e and pupae and some broken eggs. No attempts were made to remove these extraneous m a t e r i a l s . The l i t t e r and droppings thus c o l l e c t e d t o be used f o r the f e e d i n g t r i a l were a i r - d r i e d , heated and ground b e f o r e being mixed with the oth e r i n g r e d i e n t s i n the experimental 55 r a t i o n . T h i s procedure was deemed s u f f i c i e n t t o e l i m i n a t e pathogenic b a c t e r i a , i f any, and s t i l l m a i n t a i n a h i g h n u t r i t i v e value of the l i t t e r and droppings. Furthermore, the procedure i s most l i k e l y to be more a p p l i c a b l e and economical on s m a l l to medium-scale farms, than a u t o c l a v i n g . The l i t t e r and droppings were prepared f o r a i r - d r y i n g by spreading very t h i n l y ( 3 - 6 cm. deep) on p o l y e t h y l e n e p l a s t i c sheets on concrete f l o o r s . Drying was i n an open space f o r the f i r s t 2 weeks i n order to a c c e l e r a t e the process of d r y i n g . The m a t e r i a l s were turned o c c a s i o n a l l y with a wooden rake i n order to expose the lower p o r t i o n to the e f f e c t s of sunshine and a i r . E x t r a p l a s t i c sheets were kept f o r p r o t e c t i o n i n case of r a i n . A f t e r 2 weeks, the d r y i n g continued indoors and i n f r a - r e d l i g h t bulbs were used to hasten d r y i n g . Drying was completed i n approximately a week f o l l o w i n g the indoor d r y i n g . The a i r - d r i e d l i t t e r and droppings were put i n separate j u t e sacks and exposed to h i g h temperatures of between 50-65.5°C f o r 4 8 hours. A f t e r t h i s , the m a t e r i a l s were passed through the hammermill i n order to break up the lumps and f a c i l i t a t e proper mixing with other r a t i o n components. Before g r i n d i n g however, p i e c e s of stone, l a r g e f e a t h e r s and other n o t i c e a b l e extraneous matters were removed. The r e s u l t a n t ground m a t e r i a l was a f r e e - f l o w i n g powdery substance, which was dark-brown i n c o l o u r . 56 Samples were taken from the processed l i t t e r and droppings and analyzed f o r chemical components. S i m i l a r b a c t e r i o l o g i c a l s t u d i e s r e p o r t e d e a r l i e r were c a r r i e d out on the samples. The ground l i t t e r and droppings were s t o r e d i n p l a s t i c bags u n t i l used, and r e q u i r e d no f u r t h e r p r o c e s s i n g b e f o r e being i n c o r p o r a t e d i n t o experimental r a t i o n s . The average chemical composition of the processed l i t t e r and droppings i s shown i n Table 6. (c) M i x i n g of Experimental Rations The p e r c e n t composition of the experimental r a t i o n s i s g i v e n i n Table 7. Soybean meal was used as the c o n t r o l n i t r o g e n source i n r a t i o n 1. In r a t i o n s 2 and 3, 50 percent of the soybean meal n i t r o g e n of r a t i o n 1 was r e p l a c e d with urea and b i u r e t r e s p e c t i v e l y . Urea was i n c o r p o r a t e d a t a l e v e l of 2% and b i u r e t a t a l e v e l of 2.3% of the t o t a l r a t i o n . Feed grade urea (262 p e r c e n t p r o t e i n e q u i v a l e n t ) and b i u r e t o b t ained from Dow Chemical Company, Canada, as "Keldor 2 30" feed compound (230 p e r c e n t p r o t e i n e q u i v a l e n t ) were used. P o u l t r y droppings and b r o i l e r l i t t e r processed as d e s c r i b e d above were i n c o r p o r a t e d i n t o r a t i o n s 4 and 5 respec-t i v e l y a t l e v e l s high enough to r e p l a c e approximately 50 57 TABLE 6 MEAN CHEMICAL COMPOSITION OF WOOD-SHAVINGS BROILER LITTER AND CAGED LAYERS' DROPPINGS USED IN FEEDING TRIAL I Composition (%) on P.M. basis Mean Standard Deviation Range Broiler l i t t e r : Dry Matter Crude Protein Ether Extract Crude fiber Ash NFE Lignin Gross Energy (kcal/g) Uric Acid-N (mg/g) 62.6 26.4 2.6 16.6 24.2 30.2 5.1 3.048 14.4 ±3.93 ±3.54 ±1.12 ±2.66 ±1.67 ±2.54 ±0.66 ±0.14 ±0.96 58.4 — 21.5 — 1.5 -13.6 — 21.8 — 26.9 -4.3 -2.871-68.2 30.4 4.1 20.1 25.7 33.6 5.8 3.212 13.0 — 15.4 Cage Droppings: Dry Matter Crude Protein Ether Extract Crude Fiber Ash NFE Lignin Gross Energy (kcal/g) Uric Acid-N (mg/g) 50.5 31.8 0.76 9.1 28.9 29.4 2.8 2.821 21.4 ±4.82 45.7 — 58.1 ±3.84 26.3 — 35.4 ±0.25 0.49 — 1.12 ±1.12 7.4 — 10.2 ±2.69 26.2 — 33.1 ±2.36 27.4 — 33.4 ±0.44 2.4 — 3.4 ±0.11 2.661— 2.956 ±1.96 19.8 — 24.8 Hfean of analyses of 5 samples, 58 TABLE 7 COMPOSITION OF RATIONS TRIAL I Supplemental nitrogen sources Soybean meal Urea Biuret Poultry droppings Poultry l i t t e r Ingredients (%) (1) (2) (3) (4) (5) Oat straw 45.0 45.0 45.0 30.0 30.0 Urea 2.0 Biuret 2.3 Poultry droppings 20.0 Poultry l i t t e r 25.0 Soybean meal 20.0 10.0 10.0 10.0 10.0 Ground barley 23.0 31.0 30.7 29.0 24.0 Cane molasses (dehydrated) 10.0 10.0 10.0 10.0 10.0 Dicalcium phosphate 1.5 1.5 1.5 Sodium tripolyphosphate 0.5 0.5 Cobalt iodized s a l t 0.5 0.5 0.5 0.5 0.5 Vitamin premix 1 + + + + + "Vitamin premix containing: Vitamin A 2,000 IUAg feed Vitamin D 200 IUAg feed Vitamin E 20 IUAg feed 59 percent of the soybean meal n i t r o g e n of the c o n t r o l r a t i o n ( r a t i o n 1). The r e s u l t o b t a i n e d by Mclnnes e t a l . (196 8) , when they fed mixtures- o f l i t t e r and wheat to weaner sheep showed t h a t p o u l t r y waste i s h i g h l y u n p a l a t a b l e p a r t i c u l a r l y when fed with l o w - q u a l i t y roughage. Since urea and l o w - q u a l i t y roughages are themselves u n p a l a t a b l e , dehydrated cane molasses was added to a l l r a t i o n s a t a l e v e l of 10 p e r c e n t of the t o t a l r a t i o n i n order to reduce any problems a s s o c i a t e d with unfav-ourable p a l a t a b i l i t y . Chemical analyses of p o u l t r y l i t t e r and droppings (Brugman e t a l . , 1964; P e r k i n s and Parker, 1971) have shown t h a t p o u l t r y wastes are h i g h i n c a l c i u m and r e a l t i v e l y low i n phosphorus. In an attempt to narrow the Ca:P r a t i o t h e r e f o r e , sodium t r i p o l y p h o s p h a t e (Na^-P^O^g) was added to r a t i o n s c o n t a i n i n g p o u l t r y droppings and l i t t e r ( r a t i o n s 4 and 5). D i c a l c i u m phosphate was added to r a t i o n s 1, 2 and 3 a t a l e v e l of 1.5 p e r c e n t of the t o t a l r a t i o n i n order to b r i n g the Ca and P contents o f these r a t i o n s to a s i m i l a r l e v e l as those f o r r a t i o n s 4 and 5. C o b a l t i o d i z e d s a l t was added to a l l r a t i o n s at 0.5 p e r c e n t l e v e l . Ground straw was used a t a l e v e l of 45 percent of the t o t a l r a t i o n i n r a t i o n s 1, 2 and 3 and a t 30 p e r c e n t i n r a t i o n s 4 and 5 r e s p e c t i v e l y . The remaining r a t i o n was made up of ground b a r l e y as t h i s i s one of the most common c e r e a l g r a i n s used i n ruminant f e e d i n g . V i t a m i n premix was added to a l l 6Q r a t i o n s to supply approximately 2,000 I.U. v i t a m i n A, 200 I.U. v i t a m i n D and 20 I.U. v i t a m i n E per k i l o g r a m feed. M i x i n g of r a t i o n s was done u s i n g a David Bradley v e r t i c a l mixer. (d) Animal p r e p a r a t i o n and f e e d i n g F o r t y lambs of the Dorset Horn breed c o n s i s t i n g of 15 males and 25 females ranging i n age from 5-6 months and weighing between 23.6 and 39.1 kg. were used f o r : t h i s study. The animals were d i v i d e d randomly on weight and sex b a s i s i n t o f i v e groups each of 8 (3 males and 5 females). Each group of lambs were put i n separate pens and f e d approx-imat e l y 1 kg r o l l e d b a r l e y per head d a i l y and f r e e c h o ice grass hay, pending the i n t r o d u c t i o n of the experimental r a t i o n s . The f i v e groups of 8 lambs were randomly assigned to the experimental r a t i o n s . To commence the f e e d i n g of the r a t i o n s , each group r e c e i v e d a mixture of t h e i r r e s p e c t i v e experimental r a t i o n and r o l l e d b a r l e y . T h e r e a f t e r on each of the f o l l o w i n g days, the amount of the r o l l e d b a r l e y was p r o g r e s s i v e l y decreased w h i l e t h a t of the experimental r a t i o n was i n c r e a s e d , so t h a t by the f i f t h day, a l l animals were on t h e i r r e s p e c t i v e experimental r a t i o n s with no mixture of r o l l e d b a r l e y . The animals were group-fed twice d a i l y a t approximately 61 1 kg per head per day. Fresh tap water was a v a i l a b l e i n auto-matic d r i n k i n g troughs a t a l l times. A l l animals were weighed a t weekly i n t e r v a l s throughout the experimental p e r i o d . (e) Metabolism Studies Only the male lambs i n each group were used f o r metabolism s t u d i e s i n order to allow f o r an easy q u a n t i t a t i v e s e p a r a t i o n o f feces and u r i n e . These animals were c o n f i n e d i n i n d i v i d u a l d i g e s t i o n cages designed to enable t o t a l c o l l e c t i o n o f feces and u r i n e . Since the animals had been i n t r o d u c e d to the experimental r a t i o n i n the pens and had been on t h e i r r e s p e c t i v e r a t i o n s f o r about 3 weeks p r i o r to b e i n g put i n the d i g e s t i o n cages, 10 days were allowed f o r adjustment to the cages. A 10-day p r e l i m i n a r y p e r i o d has been r e p o r t e d to be q u i t e adequate i n the d e t e r m i n a t i o n o f n u t r i e n t d i g e s t i b i l i t i e s and v o l u n t a r y consumption of penned sheep (Lloyd e t a l . , 1956; L i s t e r , 1957). (i) V o l u n t a r y feed i n t a k e d e t e r m i n a t i o n In determining v o l u n t a r y feed i n t a k e , the animals were fe d ad l i b i t u m by o f f e r i n g each animal a known weight of the 62 experimental r a t i o n t o i n s u r e an excess o f at l e a s t 10% over the p r e v i o u s day's consumption. On the f o l l o w i n g morning, the feed l e f t unconsumed was weighed and s u b t r a c t e d from the feed o f f e r e d t o o b t a i n the a c t u a l consumption. Fresh tap water was a v a i l a b l e to i n d i v i d u a l caged animals a t a l l times. ( i i ) D i g e s t i b i b i l i t y and N i t r o g e n Balance Determinations The 3 male animals i n each experimental group were used f o r the d i g e s t i b i l i t y o f r a t i o n n u t r i e n t s and n i t r o g e n balance d eterminations because of the ease of q u a n t i t a t i v e s e p a r a t i o n of feces and u r i n e . One male lamb from each group c o n s t i t u t e d a run or r e p l i c a t e . The animals were weighed p r i o r t o being put i n the d i g e s t i o n cages and a l s o immediately a f t e r the c o n c l u s i o n of a run. T o t a l f e c a l c o l l e c t i o n was made d u r i n g the l a s t 7 days of each run which was preceeded by a 10-day adjustment p e r i o d . C o l l e c t i o n of feces was done each morning b e f o r e f e e d i n g . The t o t a l f e c a l output was weighed mixed thoroughly w i t h a wooden s p a t u l a and a r e p r e s e n t a t i v e a l i q u o t sample (approximately 10% by weight of the t o t a l feces) was taken and put i n p l a s t i c bags. Sub-samples o f these were weighed i n t o p e t r i p l a t e s and d r i e d i n a f o r c e d - a i r oven a t 85°C f o r 48 hours. At the completion of a run, the d r i e d f e c a l samples f o r each animal over the 7-day c o l l e c t i o n p e r i o d were 63 composited, ground t o pass the 20-mm screen mesh and s t o r e d i n t i g h t - f i t t i n g g l a s s j a r s f o r subsequent chemical a n a l y s i s . ( i i i ) Sampling o f Experimental Rations Samples o f the experimental r a t i o n s were taken d a i l y f o r 7 days s t a r t i n g a day prev i o u s to the begin n i n g of f e c a l c o l l e c t i o n . This was done i n or d e r to o b t a i n a more represen-t a t i v e sample of the r a t i o n the animals were consuming d u r i n g the c o l l e c t i o n p e r i o d . At the end o f the 7 days, samples from each r a t i o n were composited and d r i e d i n the oven a t 85°C f o r 24 hours. The d r i e d samples were ground i n a hammermill to pass the 20-mm mesh screen and s t o r e d i n screw-capped b o t t l e s f o r chemical a n a l y s i s . (iv) U r i n e C o l l e c t i o n As i n the case o f f e c a l c o l l e c t i o n , t o t a l u r i n a r y c o l l e c t i o n was made d u r i n g the l a s t 7 days of each run. U r i n e was c o l l e c t e d i n narrow-necked p l a s t i c b o t t l e s i n order t o reduce the s u r f a c e area o f the u r i n e exposed to the atmosphere. A l s o , to prevent decomposition and l o s s o f n i t r o g e n i n the form o f ammonia, approximately 2 ml. toluene and 2 ml. 64 c o n c e n t r a t e d I^SO^ were put i n the r e c e i v i n g b o t t l e s a f t e r emptying the previous day's u r i n e . The volume of d a i l y output of u r i n e was measured and a sample o f the u r i n e taken. Samples were r e f r i g e r a t e d at 4°C d u r i n g the c o l l e c t i o n p e r i o d . At the end of each run, u r i n a r y samples from each animal were composited and f r o z e n u n t i l analyzed f o r t o t a l n i t r o g e n . . (v) Chemical a n a l y s i s of feeds, feces and u r i n e samples A l l chemical analyses were by A.O.A.C. (1960) methods where a p p l i c a b l e and a l l r e s u l t s were expressed on Dry Matter (DM) b a s i s , except f o r u r i n e . Gross energy determinations were done on feed and feces samples o n l y , u s i n g the Gallenkamp A d i a b a t i c Bomb Calorimeter''" and e x p r e s s i n g the r e s u l t s (kcal/g) on DM b a s i s . C e l l u l o s e content i n the feed and feces samples were determined u s i n g the Crampton and Maynard (19 38) procedure, s l i g h t l y m o d i f i e d as r e p o r t e d by Donefer e t a l . (1960). A c i d -detergent f i b e r (ADF) and l i g n i n contents were determined i n feed and feces samples a c c o r d i n g to the procedure o f Van Soest (1963) and Van Soest and Wine (1968) . A Gallenkamp & Co. L t d . , C h r i s t o p h e r S t r e e t , London, E.C. 2. England. 65 Nit r o g e n d e t e r m i n a t i o n s were made on feed, feces and u r i n e samples u s i n g the A.O.A.C. (1960) macro-Kjeldahl method. N i t r o g e n content was converted to crude p r o t e i n by m u l t i p l y i n g the percent n i t r o g e n by the f a c t o r 6.25 and e x p r e s s i n g the r e s u l t on DM b a s i s . ( f ) C a l c u l a t i o n s (i) Apparent D i g e s t i b i l i t y C o e f f i c i e n t s The apparent d i g e s t i b i l i t y c o e f f i c i e n t s o f the dry matter (DM), gross energy (G.E.), c e l l u l o s e , crude p r o t e i n , ether e x t r a c t , c r u d e f i b e r and n i t r o g e n - f r e e e x t r a c t (NFE) were c a l c u l a t e d as the d i f f e r e n c e between the n u t r i e n t i n t a k e and e x c r e t i o n i n the feces expressed as a perc e n t o f n u t r i e n t i n t a k e . Since no c o r r e c t i o n s were made f o r f e c a l components of endogenous o r i g i n , i t was assumed t h a t the feces represented r e s i d u e s o f d i e t a r y o r i g i n o n l y , and thus, the term apparent d i g e s t i b i l i t y would d e s c r i b e a l l such c o e f f i c i e n t s c a l c u l a t e d i n t h i s manner. The f o l l o w i n g formula was used to c a l c u l a t e d i g e s t i b i l i t y . 66 D i g e s t i b i l i t y (%) (F. x A ) - (F x A ) x 100 o o e e (F x A ) o o where F = g feed consumed, o ^ A q = percent n u t r i e n t (DM, energy, p r o t e i n etc.) content i n the feed. F = g feces e x c r e t e d , e ^ A G = per cent n u t r i e n t (DM, energy, p r o t e i n etc.) content i n the f e c e s . ( A l l v alues are on dry matter b a s i s . ) ( i i ) N i t r o g e n Balance T o t a l d a i l y n i t r o g e n i n t a k e per animal was c a l c u l a t e d from the d a i l y v o l u n t a r y consumption of the feed and the n i t r o g e n content of the r a t i o n . N i t r o g e n e x c r e t i o n was determined both i n the feces and i n the u r i n e . A l l values were expressed on 0 7 5 the m e t a b o l i c s i z e (Wj^ >.._) o f the animal i n order to e l i m i n a t e d i f f e r e n c e s due to body weight of the animals. N i t r o g e n r e t e n -t i o n was c a l c u l a t e d as the d i f f e r e n c e between n i t r o g e n i n t a k e and e x c r e t i o n ( f e c a l p l u s u r i n a r y ) and was expressed both as per cent o f n i t r o g e n i n t a k e and absorbed (or digested) n i t r o g e n . 67 ( i i i ) R e l a t i v e Intake (RI) R e l a t i v e Intake (RI) was c a l c u l a t e d from the average d a i l y v o l u n t a r y consumption o f the experimental r a t i o n s and 0 75 ex p r e s s i n g t h i s r e l a t i v e t o 80g/W ' a c c o r d i n g t o the method Kg of Crampton e t a l . (19 60) u s i n g the formula: RI = 100 (Voluntary Intake) sow?• 7 5 kg (iv) N u t r i t i v e Value Index (NVI) The N u t r i t i v e Value I n d i c e s (NVI) were c a l c u l a t e d by m u l t i p l y i n g the gross energy per cent d i g e s t i b i l i t y by the RI value (Crampton e t a l . , 1960) . Per cent gross energy d i g e s t i b i l i t y x RI = NVI (v) D i g e s t i b l e Energy (DE) Intake The d i g e s t i b l e energy intake p o t e n t i a l was calculated either d i r e c t l y as kcaL of di g e s t i b l e energy per kg metabolic 0 75 size of the animal (Real. DE/W * ) or i n d i r e c t l y by multiplying Kg 68 the NVI of the r a t i o n by i t s gross energy content (Iccal/g) and d i v i d i n g by the f a c t o r 1.25 (Crampton e t a l . , 1962). (vi) S t a t i s t i c a l Procedures A l l data were s u b j e c t e d t o s t a t i s t i c a l a n a l y s i s u s i n g the a n a l y s i s of v a r i a n c e procedure (Snedecor and Cochran, 196 8). S t a t i s t i c a l s i g n i f i c a n c e between treatment means was determined u s i n g Duncan's (1955) M u l t i p l e Range T e s t . 69 RESULTS AND DISCUSSION a. Chemical Composition of Experimental Rations Chemical analyses data of the experimental r a t i o n s are presented i n Table 8. The crude p r o t e i n content- of a l l r a t i o n s are i n the range recommended f o r f a t t e n i n g lambs of s i m i l a r age and weight (NRC, 1968). I t c o u l d however be observed t h a t the crude p r o t e i n content of the p o u l t r y l i t t e r supplemented r a t i o n ( r a t i o n 5) was s l i g h t l y lower than t h a t f o r the o t h e r r a t i o n s . In a s e r i e s o f p a i r e d f e e d i n g experiments w i t h growing lambs, Hamilton e t a l . (1948) showed t h a t the t o t a l r a t i o n p r o t e i n e q u i v a l e n t should be about 12% and t h a t a t l e a s t 25% of the r a t i o n n i t r o g e n should be p r o v i d e d as p r o t e i n n i t r o g e n f o r the most e f f i c i e n t u t i l i z a t i o n o f urea or other NPN. In t h i s t r i a l , the t o t a l crude p r o t e i n o f a l l the experimental r a t i o n s was h i g h e r than 12% and more than 25% of the r a t i o n n i t r o g e n was p r o v i d e d as p r o t e i n n i t r o g e n (Table 9). The per cent of t o t a l r a t i o n n i t r o g e n f u r n i s h e d by NPN source i n the urea and b i u r e t supplemented r a t i o n s ( r a t i o n s 2 and 3 r e s p e c t i v e l y ) was i n the range of 33% to 50% suggested as o p t i m a l by a number o f workers i n c l u d i n g Perham e t a l . (1955) , Brown et a l . (1956) and Davis e t a l . (1957). The crude f i b e r content of r a t i o n s 1, 2 and 3 i n which oat straw was used a t a l e v e l o f 45% of the t o t a l r a t i o n , was 70 TABLE 8 AVERAGE CHEMICAL ANALYSIS OF THE RATIONS FED TO LAMBS IN FEEDING TRIAL I Supplemental Nitrogen Source Soybean meal Urea Biuret Poultry droppings Poultry l i t t e r Composition 1 (1) (2) (3) (4) (5) Crude Protein (%) 14.90 15.10 15.50 14.90 13.70 Crude fiber (%) 25.90 27.70 26.70 23.00 27.60 Ether Extract (%) 0.79 0.64 0;63 2.33 (2.10 £sh (%) 7.50 6.80 6.70 9.40 12.30 NFE (%) 50.91 49.76 50.47 50.37 44.30 Gross Energy (kcal/g) 4.20 4.18 4.20 4.08 3.96 Acid-detergent fiber (%) 29.80 32.20 30.80 25.90 32.00 Lignin (%) 4.00 4.50 4.70 460 9.90 Cellulose (%) 25.80 27.70 26.10 21.30 22.10 A l l values are expressed on dry matter basis. 71 TABLE 9 THE PERCENTAGE OF TOTAL NITROGEN ATTRIBUTABLE TO NON-PROTEIN NITROGEN (NPN) SUPPLEMENTS IN THE RATIONS FED TO LAMBS IN FEEDING TRIAL I Crit e r i a Supplemental Nitrogen Source Soybean meal (1) Urea Biuret (2) (3) Poultry droppings (4) Poultry l i t t e r (5) Percent supplementation with NPN source Total ration N (%) NPN (%) NPN as % of total N (control) 2.36 2.0 2.42 0.83 34.3 2.3 2.46 0.81 32.9 20.0 2.36 1.02 43.2 25.0 2.19 1.05 47.9 72 about the same (25.9, 27.7 and 26.7% r e s p e c t i v e l y ) . The crude f i b e r content of the p o u l t r y dropping-supplemented r a t i o n ( r a t i o n 4) i n which oat straw was used a t a l e v e l o f 30% was lower than those f o r other r a t i o n s . The crude f i b e r content o f the l i t t e r supplemented r a t i o n ( r a t i o n 5) was about the same as those f o r r a t i o n s 1, 2 and 3, d e s p i t e the f a c t t h a t o at straw was used at a l e v e l o f 30% as i n r a t i o n 4. The h i g h e r crude f i b e r content i n r a t i o n 5 as compared to r a t i o n 4 c o u l d be e x p l a i n e d by the f a c t t h a t the l i t t e r c o n t a i n e d a wood-shaving base which would no doubt c o n t r i b u t e to a h i g h e r crude f i b e r content. The a c i d detergent f i b e r (ADF) and c e l l u l o s e contents of the r a t i o n s f o l l o w e d a s i m i l a r p a t t e r n as t h a t f o r the crude f i b e r content and c o u l d t h e r e f o r e be e x p l a i n e d i n the same manner. The e t h e r e x t r a c t i v e s (EE) i n r a t i o n s 4 and 5, i n which p o u l t r y droppings and l i t t e r were used as supplemental n i t r o g e n source r e s p e c t i v e l y , were c o n s i d e r a b l y h i g h e r than the EE contents o f r a t i o n s 1, 2 and 3 where p o u l t r y wastes were not i n c l u d e d . This shows t h a t the p o u l t r y wastes c o n t r i b u t e d a h i g h e r EE i n r a t i o n s 4 and 5. S i m i l a r l y , the ash contents of the p o u l t r y droppings and l i t t e r supplemented r a t i o n s (4 and 5) were h i g h e r than those f o r ..the o t h e r r a t i o n s . T h i s c o u l d be e x p l a i n e d on the b a s i s of the h i g h ash content i n p o u l t r y wastes (Brugman e t a l . , 1964; Fontenot e t a l . , 1966; L e i b h o l z , 1969; Perkins and Parker, 1971). As a r e s u l t o f the h i g h e r ash 73 content of the p o u l t r y droppings and l i t t e r supplemented r a t i o n s (4 and 5) the gross energy (kcal/g) of these same r a t i o n s were s l i g h t l y lower than those f o r r a t i o n s 1, 2 and 3. The NFE values f o r a l l the r a t i o n s were about equal w i t h the e x c e p t i o n of the l i t t e r supplemented r a t i o n (5) which had a s l i g h t l y lower v a l u e . A l s o to be noted was the l i g n i n content o f the l i t t e r supplemented r a t i o n which was more than double the l i g n i n content of any of the ot h e r r a t i o n s . T h i s was most l i k e l y due to the presence of wood i n the l i t t e r and agrees w e l l w i t h the o b s e r v a t i o n s of Brugman e t a l . (1964). b. Dry Matter D i g e s t i b i l i t y Data on average dry matter (DM) i n t a k e s and apparent d i g e s t i b i l i t y c o e f f i c i e n t s are presented i n Table 10. Each value r e p r e s e n t s the mean of 3 i n d i v i d u a l sheep d e t e r m i n a t i o n s . A h i g h l y s i g n i f i c a n t (P c 0.01) decrease i n DM d i g e s t i b i l i t y was observed i n animals f e d the p o u l t r y l i t t e r supplemented r a t i o n ( r a t i o n 5). The reason f o r t h i s s i g n i f i c a n t decrease i n DM d i g e s t i b i l i t y o f the r a t i o n i n which p o u l t r y l i t t e r r e p l a c e d p a r t o f the n i t r o g e n , c o u l d be e x p l a i n e d on the b a s i s of the r e s u l t s o b t a i n e d by L e i b h o l z (1969). A l l of L e i b h o l z ' s d i e t s i n which 40- 47% of the meat meal n i t r o g e n was r e p l a c e d TABLE 10 AVERAGE FEED INTAKE AND APPARENT DIGESTIBILITY BY SHEEP OF THE EXPERIMENTAL RATIONS Supplemental n i t r o g e n sources Soybean mna\ Urea B i u r e t P o u l t r y droppings Poult: l i t t e : C r i t e r i a (1) (2) (3) (4) (5) ^ " D i g e s t i b i l i t y c o e f f i c i e n t s (%) Dry Matter 60 .6 C 58.1 C 59.9 C 61. 2° 42.3 d Crude P r o t e i n 71.5 C 73.5 C 67.6 C 68.9 C 56.4 d C e l l u l o s e 49.1 C 45.9 C 4 8.1° 46.3 C 24.3 d Gross Energy 61.7 C 59 .2° 59.5 C 62.3 C 43.8 d Crude F i b e r 43.5 C 40 .2° 44.1° 42.0 C 13. 4 d R e l a t i v e Intake (%) 73.8 a 66. l b 79.3 a 80.0 a 87. 0 a N u t r i t i v e Value Index (NVI) 45.4 39.6 47.3 49 .7 38.1 D i g e s t i b l e Energy Intake P o t e n t i a l 152.4 132.4 158.9 162.3 120.8 Represents the average of 3 d i g e s t i b i l i t y t r i a l s u s i n g 3 male lambs per treatment. Means on the same l i n e b e a r i n g d i f f e r e n t s u p e r s c r i p t l e t t e r s d i f f e r s i g n i f i c a n t l y : a, b (P < 0.05) c, d (P < 0.01) 75 with p o u l t r y droppings r e s u l t e d i n comparable n u t r i e n t d i g e s -t i b i l i t y to the c o n t r o l r a t i o n . However, a d d i t i o n of sawdust at a l e v e l of 15 and 30% i n a d d i t i o n to the wheat straw used as the l o w - q u a l i t y roughage, 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 the o v e r a l l d i g e s t i b i l i t y of the n u t r i e n t s . T h i s i s probably a r e f l e c t i o n o f the low d i g e s t i b i l i t y o f the f i b e r i n the added sawdust. Although a s l i g h t d i f f e r e n c e e x i s t e d i n the average DM d i g e s t i b i l i t y c o e f f i c i e n t s f o r the o t h e r r a t i o n s these 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 4. 0.05). I t i s i n t e r e s t i n g to note t h a t the average DM d i g e s t i b i l i t y c o e f f i c i e n t of the p o u l t r y droppings supplemented r a t i o n (4) was s l i g h t l y h i g h e r than t h a t of the c o n t r o l r a t i o n (1). S i m i l a r r e s u l t s have been r e p o r t e d by other workers i n c l u d i n g El-Sabban e t a l . (1970) when they obtained an average of 76.27% DM d i g e s t i b i l i t y f o r sheep f e d a r a t i o n t h a t was supplemented with p o u l t r y waste as compared with 75.3% f o r sheep on the c o n t r o l r a t i o n i n which soybean meal was used as the n i t r o g e n source. The r e s u l t s o b t a i n e d by Fontenot e t a l . (19 66) s i m i l a r l y f a i l e d to show s i g n i f i c a n t d i f f e r e n c e i n the DM d i g e s t i b i l i t y c o e f f i c i e n t s when 25 and 50% of the soybean meal n i t r o g e n of the c o n t r o l r a t i o n was r e p l a c e d with a u t o c l a v e d p e a n u t - h u l l b r o i l e r l i t t e r . However, 100% replacement of the soybean meal 76 n i t r o g e n o f the c o n t r o l r a t i o n w i t h l i t t e r r e s u l t e d i n s i g n i f i -cant decreases i n DM d i g e s t i b i l i t y c o e f f i c i e n t s . Both the urea and b i u r e t supplemented r a t i o n s (2 and 3 r e s p e c t i v e l y ) had DM d i g e s t i b i l i t y c o e f f i c i e n t s which were s l i g h t l y lower than t h a t o f the c o n t r o l , but showed no s i g n i f -i c a n t d i f f e r e n c e s . The DM d i g e s t i b i l i t y c o e f f i c i e n t s of the urea and b i u r e t supplemented r a t i o n s were about equal, i n d i c a t i n g t h a t these two n i t r o g e n sources are e q u a l l y w e l l u t i l i z e d by ruminants i f a s u f f i c i e n t a d a p t a t i o n p e r i o d was allowed ( H a t f i e l d e t a l . , 1955; Ewan e t a l . , 1958 and O l t j e n e t a l . , 1968). This probably e x p l a i n s the l a c k o f s i g n i f i c a n t d i f f e r e n c e s between the DM d i g e s t i b i l i t i e s of the urea and b i u r e t supplemented r a t i o n s i n t h i s t r i a l . c. Gross Energy D i g e s t i b i l i t y The average gross energy d i g e s t i b i l i t y c o e f f i c i e n t s are presented i n Table 10. I t i s i n t e r e s t i n g t o note t h a t the p a t t e r n of the r e s u l t s o b t a i n e d f o r the DM d i g e s t i b i l i t y d i s -cussed e a r l i e r i s s i m i l a r t o t h a t o b t a i n e d f o r the gross energy d i g e s t i b i l i t y . v However> t h e . c o e f f i c i e n t o f gross energy d i g e s t i b i l i t y values are s l i g h t l y h i g h e r than those f o r the DM d i g e s t i b i l i t y . T h i s s i m i l a r i t y c o u l d be e x p l a i n e d by the f a c t t h a t the dry matter f r a c t i o n ( e x c l u d i n g the ash) i s predominantly a source o f energy. 77 A h i g h l y s i g n i f i c a n t (P <. 0.01) decrease i n gross energy d i g e s t i b i l i t y was obtained as a r e s u l t of the p a r t i a l replacement o f the soybean meal n i t r o g e n o f the c o n t r o l r a t i o n with p o u l t r y l i t t e r i n r a t i o n 5. The replacement o f a p p r o x i -mately 50% of the soybean meal n i t r o g e n of the c o n t r o l r a t i o n (1) with e i t h e r urea, b i u r e t or p o u l t r y droppings ( r a t i o n s 2, 3 and 4 r e s p e c t i v e l y ) d i d not r e s u l t i n any s i g n i f i c a n t (P < 0.05) d i f f e r e n c e s i n the gross energy d i g e s t i b i l i t i e s when compared to the c o n t r o l r a t i o n . The h i g h l y s i g n i f i c a n t decrease i n the gross energy d i g e s t i b i l i t y o f the p o u l t r y l i t t e r supplemented r a t i o n i s probably due to the low d i g e s t i b i l i t y o f the f i b r e of the wood shavings present i n the l i t t e r . When p o u l t r y droppings alone were used as i n r a t i o n 4, the gross energy d i g e s t i b i l i t y was q u i t e comparable to t h a t obtained f o r the c o n t r o l r a t i o n . The gross energy d i g e s t i b i l i t y c o e f f i c i e n t s o b tained f o r the urea and b i u r e t supplemented r a t i o n s (2 and 3) were s l i g h t l y but not s i g n i f i c a n t l y lower than those f o r the c o n t r o l and p o u l t r y droppings supplemented r a t i o n s . (1 and 4). However, the gross energy d i g e s t i b i l i t y c o e f f i c i e n t s f o r the urea and b i u r e t supplemented r a t i o n s were about e q u a l . Many authors i n c l u d i n g H a t f i e l d e t a l . (1955), Meiske e t a l . (1955) , H a t f i e l d e t a l . (1959), Karr e t a l . (1963) and O l t j e n e t a l . (1968)have r e p o r t e d on comparable u t i l i z a t i o n o f urea and b i u r e t n i t r o g e n 78 e s p e c i a l l y when s u f f i c i e n t time i s allowed f o r the a d a p t a t i o n of the animals to b i u r e t . d. Crude F i b e r and C e l l u l o s e D i g e s t i b i l i t y The mean crude f i b e r and c e l l u l o s e d i g e s t i b i l i t y c o e f f i c i e n t s are presented i n Table 10. A s i g n i f i c a n t l y (P < 0.01) lower crude f i b e r d i g e s t i b i l i t y was observed i n the p o u l t r y l i t t e r supplemented r a t i o n . Although s l i g h t d i f f e r e n c e s were n o t i c e d i n the crude f i b e r d i g e s t i b i l i t y of the oth e r r a t i o n s , these 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). The s i g n i -f i c a n t l y lower crude f i b e r d i g e s t i b i l i t y o f the p o u l t r y l i t t e r supplemented r a t i o n i s probably due to the low d i g e s t i b l i t y of the f i b e r i n the l i t t e r ( L e i b h o l z , 1969). Bhattacharya and Fontenot (1966) i n t h e i r s t u d i e s on the u t i l i z a t i o n o f d i f f e r e n t l e v e l s o f p o u l t r y l i t t e r n i t r o g e n by sheep a l s o r e p o r t e d t h a t crude f i b e r d i g e s t i b i l i t y was s i g n i f i c a n t l y depressed when the l e v e l of l i t t e r was i n c r e a s e d from 25 to 50%. The c o e f f i c i e n t s o f c e l l u l o s e d i g e s t i b l i t y were s i m i l a r to those of f i b e r , but the c o e f f i c i e n t s f o r the crude f i b e r d i g e s t i b i l i t y were lower than those f o r c e l l u l o s e d i g e s t i b i l i t y . 79 e. Crude P r o t e i n D i g e s t i b i l i t y The mean crude p r o t e i n d i g e s t i b i l i t y c o e f f i c i e n t s are presented i n Table 10. The p o u l t r y l i t t e r supplemented r a t i o n (5) had a s i g n i f i c a n t l y (P £ 0.01) lower crude p r o t e i n d i g e s t i -b i l i t y v a lue than the other r a t i o n s . The depressed d i g e s t i b i l i t y c o e f f i c i e n t s o f a l l n u t r i e n t s i n the p o u l t r y l i t t e r supplemented r a t i o n c o u l d be a t t r i b u t e d to the unfavourable i n f l u e n c e of the wood-shavings l i t t e r base. This h y p o t h e s i s i s j u s t i f i e d when one compares the n u t r i e n t d i g e s t i b i l i t y c o e f f i c i e n t s o f the p o u l t r y droppings supplemented r a t i o n (4) w i t h those o f the c o n t r o l r a t i o n i n which 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 . Although- many workers have r e p o r t e d on the comparable u t i l i z a t i o n of p o u l t r y l i t t e r n i t r o g e n as compared to soybean meal and oth e r c o n v e n t i o n a l p r o t e i n supplements (Noland e t a l . , 1955; Fontenot et a l . , 1964; Mowat, 1965; Bhattachary.a and Fontenot, 1966; Fontenot e t a l . , 1966; Mclnnes e t a l . , 1968 and Lowman and Knight, 1970), d i f f e r e n c e s i n the l i t t e r composition, e s p e c i a l l y the bedding (or base) m a t e r i a l s c o u l d i n f l u e n c e the u t i l i z a t i o n of the l i t t e r by ruminants. Fontenot e t a l . (19 64) found t h a t feed e f f i c i e n c y and c a r c a s s grades o f s t e e r s fed the peanut h u l l p o u l t r y l i t t e r were h i g h e r than those f ed the wood-shavings p o u l t r y l i t t e r . I t appears t h a t the i n c l u s i o n o f wood-shavings p o u l t r y l i t t e r t o d i e t s a l r e a d y h i g h i n l o w - q u a l i t y roughage depresses the c o e f f i c i e n t s o f n u t r i e n t d i g e s t i b i l i t y . T h i s 80 o b s e r v a t i o n was a l s o r e p o r t e d by L e i b h o l z (1969) who found t h a t the a d d i t i o n o f sawdust at or above 30% l e v e l to the wheat straw used as the l o w - q u a l i t y forage, depressed n u t r i e n t d i g e s -t i b i l i t y and body weight gains i n sheep. I t c o u l d be concluded t h e r e f o r e , t h a t p o u l t r y l i t t e r should be used with .high energy d i e t s as was r e p o r t e d i n the s t u d i e s conducted by Mclnnes et a l . (1968) who observed s a t i s f a c t o r y performance of weaner sheep when p o u l t r y l i t t e r was used along w i t h h i g h energy d i e t s -- mixtures of p o u l t r y l i t t e r and wheat (1:1 r a t i o n ) . Mowat (1965) a l s o r e p o r t e d weight gains o f 2.6 to 2.8 l b s . (1.18 to 1.27 kg) per day when 3 p a r t s h i g h energy feed and 1 p a r t p o u l t r y l i t t e r were fed to f a t t e n i n g s t e e r s . Crude p r o t e i n d i g e s t i b i l i t y c o e f f i c i e n t s of urea, b i u r e t , and p o u l t r y droppings supplemented r a t i o n s (2, 3 and 4 r e s p e c t i v e l y ) were not s i g n i f i c a n t l y d i f f e r e n t from t h a t o f the c o n t r o l r a t i o n . The crude p r o t e i n d i g e s t i b i l i t y c o e f f i c i e n t fee the urea supplemented r a t i o n was h i g h e s t . T h i s probably shows t h a t urea i s r a p i d l y and completely h y d r o l y z e d i n the rumen, thus accounting f o r very s m a l l f e c a l n i t r o g e n and h i g h d i g e s t i b i l i t y . The crude p r o t e i n d i g e s t i b i l i t y c o e f f i c i e n t of the b i u r e t supplemented r a t i o n was s l i g h t l y , but not s i g n i f i c a n t l y , lower than t h a t f o r the urea supplemented r a t i o n . S i m i l a r r e s u l t s were r e p o r t e d by H a t f i e l d e t a l . (19 59) when they found t h a t s t e e r s f e d e i t h e r the soybean meal o r urea 81 supplemented r a t i o n s had a b e t t e r n i t r o g e n d i g e s t i b i l i t y and u t i l i z a t i o n than the s t e e r s fed the b i u r e t supplemented r a t i o n . Welch e t al.(1956) a l s o r e p o r t e d depressed apparent n i t r o g e n d i g e s t i b i l i t y w i t h crude b i u r e t when compared to urea. Most of the d i f f e r e n c e s observed i n the n i t r o g e n u t i l i z a t i o n o f urea and b i u r e t supplemented r a t i o n s c o u l d be e x p l a i n e d on the b a s i s of a d a p t a t i o n of the ruminant animals to urea and b i u r e t . Welch e t a l . (1956), Berry J r . eit a l . (1956), Repp e t a l . (1955), Ewan e t a l . (1958), Schroder and G i l c h r i s t (1969) and many others have shown t h a t b i u r e t n i t r o g e n i s as w e l l u t i l i z e d by ruminants as urea n i t r o g e n but t h a t animals r e q u i r e a longer p e r i o d of a d a p t a t i o n when f e d b i u r e t supplemented r a t i o n s . f. R e l a t i v e Intake The v o l u n t a r y consumption of the experimental r a t i o n s were expressed r e l a t i v e to the v o l u n t a r y i n t a k e of good q u a l i t y hay (Crampton e t a l . , 1960), assuming t h a t sheep w i l l v o l u n t a r i l y consume about 80g of good q u a l i t y hay per u n i t of m e t a b o l i c s i z e . In o r d e r to demonstrate the o v e r a l l n u t r i t i v e v a l u e of the t e s t r a t i o n s , the v o l u n t a r y consumption of the experimental r a t i o n s was r e l a t e d to the observed R e l a t i v e Intake (RI) r e p o r t e d by Crampton e t a l . (1960). A summary of the RI data i s shown i n Table 10, i n which each value r e p r e s e n t s the mean of 3 animal d e t e r m i n a t i o n s . 82 The RI value f o r the urea supplemented r a t i o n (2) was s i g n i f i c a n t l y (P ^- 0.05) lower than the RI values f o r the o t h e r r a t i o n s . T h i s might have been due to the poor p a l a t a -b i l i t y of urea which has been r e p o r t e d by a number o f workers i n c l u d i n g Anderson (1967) and I o s e t (1969). D i f f e r e n c e s i n the RI values of the other r a t i o n s were not s i g n i f i c a n t . The p o u l t r y droppings and l i t t e r supplemented r a t i o n s (4 and 5 r e s p e c t i v e l y ) showed the h i g h e s t RI v a l u e s . I t i s d i f f i c u l t to e x p l a i n why there was a h i g h e r RI value f o r the l i t t e r supplemented r a t i o n as compared with the o t h e r r a t i o n s . I t appeared t h a t i n t a k e of the l i t t e r supplemented r a t i o n was i n c r e a s e d to compensate f o r the lower n u t r i e n t d i g e s t i b i l i t y of t h i s r a t i o n . T h i s o b s e r v a t i o n i s c o n t r a r y to what normally occurs i n ruminants fed l o w - q u a l i t y forage. Baumgardt (19 70) showed t h a t a t low n u t r i t i v e v a l u e , i n t a k e i s l i m i t e d by the gut f i l l and thus feed (dry matter) i n t a k e i s p o s i t i v e l y r e l a t e d to d i g e s t i b i l i t y . Since the l i t t e r supplemented r a t i o n had a dry matter d i g e s t i -b i l i t y value (42.3%) lower than t h a t of any o f the o t h e r r a t i o n s , i t s i n t a k e was expected to be lower than the i n t a k e o f any of the other r a t i o n s . However:, i t c o u l d be mentioned t h a t n u t r i e n t a v a i l a b i l i t y i s only one of the many f a c t o r s i n v o l v e d i n feed i n t a k e r e g u l a t i o n i n ruminants. The c o n t r o l of feed i n t a k e by an animal i s a r e s u l t of mechanisms which work to m a i n t a i n a d e s i r a b l e constancy o f the i n t e r n a l environment or homeostatis of the animal. The p r e c i s e i n t e r a c t i o n of these mechanisms i s s t i l l not f u l l y understood (Baumgardt, 1970) . 83 g. N u t r i t i v e Value Index (NVI). The NVI i s a numerical d e s c r i p t i o n o f the " o v e r a l l " n u t r i t i v e value o f a forage and i t i s c a l c u l a t e d as the product of gross energy d i g e s t i b i l i t y c o e f f i c i e n t and the RI (Crampton e t al.1960). The summary of the n u t r i t i v e value i n d i c e s f o r the experimental r a t i o n s i s presented i n Table 10. Although no s i g n i f i c a n t (P 0.05) d i f f e r e n c e s were observed i n the NVI values f o r a l l r a t i o n s , the valu e s f o r the urea and p o u l t r y l i t t e r supplemented r a t i o n s (2 and 5 r e s p e c t i v e l y ) tended to be lower than the value f o r the c o n t r o l r a t i o n . B i u r e t and p o u l t r y droppings supplemented r a t i o n (3 and 4) had NVI values s l i g h t l y h i g h e r than the c o n t r o l . Lack of s i g n i f i c a n t d i f f e r e n c e s i n the i n d i c e s c o u l d be e x p l a i n e d i f the two f a c t o r s i n v o l v e d i n the c a l c u l a t i o n o f NVI are examined. Of the two f a c t o r s i n v o l v e d (per cent energy d i g e s t i l i b i t y and RI) the RI accounts f o r the l a r g e r c o n t r i b u t i o n t o the NVI (Crampton e t a l . , 1960). This i s c l e a r l y shown i n the p o u l t r y l i t t e r supplemented r a t i o n (5) i n which the hig h RI r e s u l t e d i n NVI t h a t was no longer s i g n i f i c a n t l y (P < 0.05) d i f f e r e n t from the oth e r r a t i o n s d e s p i t e the s i g n i f i c a n t l y (P < 0.01) lower energy d i g e s t i b i l i t y f o r t h i s r a t i o n . Using the same e x p l a n a t i o n , the NVI value f o r the urea supplemented r a t i o n (2) was lower than t h a t f o r the c o n t r o l r a t i o n as a r e s u l t o f the s i g n i f i c a n t l y (P < 0.05) lower RI f o r t h i s r a t i o n . «4 h. D i g e s t i b l e Energy (DE) Intake P o t e n t i a l The DE i n t a k e P o t e n t i a l ( k c a l DE / w j ^ 7 5 ) o f the experimental r a t i o n s were c a l c u l a t e d by m u l t i p l y i n g the NVI values o f the r a t i o n s by t h e i r r e s p e c t i v e gross energy content (kcal/g) and d i v i d i n g the product by the f a c t o r 1.25 (Crampton e t a l . 1962) . A summary o f the DE intake values i s presented i n Table 10. As would be expected, s t a t i s t i c a l a n a l y s i s f a i l e d to i n d i c a t e any s i g n i f i c a n t d i f f e r e n c e s i n the DE i n t a k e values of a l l r a t i o n s . T h i s l a c k o f s i g n i f i c a n t d i f f e r e n c e i s mainly due t o the f a c t t h a t the DE i n t a k e values were c a l c u l a t e d u s i n g the NVI v a l u e s , which were themselves not s i g n i f i c a n t l y d i f f e r e n t from one another. The t r e n d i n magnitude o f the DE i n t a k e values i s s i m i l a r to t h a t f o r the NVI v a l u e s . I t i s however worthy of note t h a t NPN supplementation of the hig h roughage r a t i o n s r e s u l t e d i n DE in t a k e s equal t o t h a t expected f o r h i g h - q u a l i t y forages such as legume hay. i . N i t r o g e n Balance The mean n i t r o g e n balance data are presented i n Table 11. There was no s i g n i f i c a n t d i f f e r e n c e (P 0.05) i n the observed t o t a l d a i l y n i t r o g e n i n t a k e by sheep on a l l experimental r a t i o n s . But i t c o u l d be seen t h a t n i t r o g e n i n t a k e by animals fed the urea supplemented r a t i o n (2) tended to be s l i g h t l y lower than f o r the o t h e r r a t i o n s . T h i s i s a r e f l e c t i o n of the marked decrease i n v o l u n t a r y consumption of r a t i o n 2 as compared with the o t h e r TABLE I I AVERAGE NITROGEN BALANCE OF LAMBS FED THE EXPERIMENTAL RATIONS Supplemental n i t r o g e n source C r i t e r i a No. o f animals N Intake (g/W^ 7 5/day) N e x c r e t i o n : f e c a l (g/W°g 7 5/day) U r i n a r y (g/W^ 7 5/day) N r e t e n t i o n (g/W^"7^/day) N r e t e n t i o n as % of N i n t a k e N r e t e n t i o n as % of absorbed N Soybean meal Urea B i u r e t P o u l t r y droppings P o u l t r y l i t t e r (1) (2) (3) (4) (5) 3 3 3 3 3 1.49 1.29 1.59 1.53 1.51 0.42 0.34 0.51 0.47 0.66 0.62 0. 80 0.59 0.57 0.74 0.45 a 0.15 b 0.47 a 0.49 a o . n b 20.2 a 11. 6 b 29.9 a 32.0 a 7.3 b 4 2 . l a 15. 8 b 44 .3 a 46.2 a 12. 9 b ''"Represents the mean o f 3 determinations using 3 male lambs per treatment. Means on the same l i n e b e a r i n g d i f f e r e n t s u p e r s c r i p t l e t t e r s d i f f e r s i g n i f i c a n t l y a, b (P <~ 0.05) . 86 r a t i o n s ^ as d i s c u s s e d e a r l i e r . The h i g h e s t f e c a l n i t r o g e n l o s s was observed i n the animals fed the p o u l t r y l i t t e r supplemented r a t i o n (5). T h i s o b s e r v a t i o n agrees with the r e s u l t s o b t a i n e d by Fontenot e t a l . (1966) who r e p o r t e d h i g h l y s i g n i f i c a n t i n c r e a s e i n f e c a l n i t r o g e n when l i t t e r s u p p l i e d 100% of the n i t r o g e n i n the sheep r a t i o n . The h i g h f e c a l n i t r o g e n observed i n animals f e d r a t i o n 5 was a c o n f i r m a t i o n of the lov/er crude p r o t e i n d i g e s t i b i l i t y o f t h i s r a t i o n . F e c a l n i t r o g e n o f the b i u r e t and p o u l t r y droppings supplemented r a t i o n s (3 and 4 r e s p e c t i v e l y ) were s l i g h t l y h i g h e r than t h a t f o r the c o n t r o l . El-Sabban e t a l . (1970) r e p o r t e d s i m i l a r r e s u l t s . However the f e c a l n i t r o g e n content of the urea supplemented r a t i o n was lower than t h a t f o r the c o n t r o l . D i f f e r e n c e s i n the f e c a l n i t r o g e n content o f urea and b i u r e t supplemented r a t i o n s are most probably due to the f a c t t h a t h y d r o l y s i s o f urea i n the rumen i s r a p i d (Schwartz, 1967) w h ile t h a t of b i u r e t i s slow (I o s e t , 1969). Schroder (1970) a l s o showed t h a t the breakdown o f b i u r e t i n the lower gut of sheep was very s m a l l . T h i s probably means t h a t any b i u r e t t h a t passes i n t o the lower gut from the rumen w i l l be e x c r e t e d i n the f e c e s . The r a p i d h y d r o l y s i s of urea i n t o ammonia which i n t u r n i s absorbed i n t o the b l o o d stream probably accounts f o r 87 the lower f e c a l n i t r o g e n l o s s i n the urea supplemented r a t i o n as compared wit h the c o n t r o l r a t i o n . Highest u r i n a r y n i t r o g e n l o s s e s were observed i n animals fed the urea and o p o u l t r y l i t t e r supplemented r a t i o n s . The h i g h u r i n a r y n i t r o g e n l o s s i n animals f ed the urea supplemented r a t i o n c o u l d be e x p l a i n e d on the b a s i s o f r a p i d h y d r o l y s i s o f d i e t a r y urea i n the rumen. Since the u t i l i z a t i o n o f ammonia by the rumen microorganisms f o r p r o t e i n s y n t h e s i s i s slower than the r e l e a s e , p a r t of the ammonia n i t r o g e n i s absorbed i n t o the b l o o d stream, which w i l l cause a r a p i d e l i m i n a t i o n of urea by the kidney (Lewis 1-957) . I t i s d i f f i c u l t to e x p l a i n what c o n t r i b u t e d to the h i g h u r i n a r y n i t r o g e n l o s s i n the animals fed the p o u l t r y l i t t e r supplemented r a t i o n . However i t c o u l d be t h e o r i z e d t h a t s i n c e the l i t t e r supplemented r a t i o n had the lowest DE i n t a k e v a l u e , n i t r o g e n e x c r e t i o n i n the u r i n e might be i n c r e a s e d due to deamination of feed p r o t e i n ,, as an energy source. N i t r o g e n balance was c a l c u l a t e d as the d i f f e r e n c e between n i t r o g e n i n t a k e and e x c r e t i o n . E x p r e s s i n g n i t r o g e n r e t e n t i o n as per cent o f n i t r o g e n i n t a k e and absorbed n i t r o g e n show s i m i l a r t r e n d . Although a l l animals were i n p o s i t i v e n i t r o g e n balance, the high f e c a l and u r i n a r y n i t r o g e n l o s s e s observed i n animals f ed the l i t t e r supplemented r a t i o n and the 88 high u r i n a r y n i t r o g e n l o s s i n animals f ed the urea supplemented r a t i o n , r e s u l t e d i n s i g n i f i c a n t l y (P *£. 0.05) lower n i t r o g e n r e t e n t i o n f o r these two r a t i o n s when compared with the other r a t i o n s . The h i g h e r n i t r o g e n r e t e n t i o n by animals f ed the p o u l t r y droppings supplemented r a t i o n compared with the p o u l t r y l i t t e r r a t i o n i n d i c a t e s t h a t p o u l t r y feces per se i s an e x c e l l e n t source of NPN f o r ruminants and t h a t the a v a i l a b i l i t y of n i t r o g e n from t h i s source i s hampered by the presence o f wood-shavings as i n the l i t t e r . Numerous workers i n c l u d i n g Meiske e t a l . (19 55) , Repp e t a l . (1955), G a i t h e r e t a l . (1955), Ewan e t a l . (1958), and H a t f i e l d e t a l . (1959) have shown by means of balance s t u d i e s t h a t b i u r e t n i t r o g e n i s r e t a i n e d by lambs as w e l l as urea n i t r o g e n i f an adequate a d a p t a t i o n p e r i o d i s allowed. The s i g n i f i c a n t l y (P 0.05) lower n i t r o g e n r e t e n t i o n observed i n lambs fed the urea supplemented r a t i o n as compared wi t h t h a t f o r the b i u r e t supplemented r a t i o n c o u l d be due to the v a r i a b i l i t y i n response of lambs fed u r e a - c o n t a i n i n g r a t i o n s (Anderson, 1967). j . Body Weight Gain and Feed E f f i c i e n c y The summary of data on body weight changes and feed e f f i c i e n c y o f lambs f e d the experimental r a t i o n s i s pre s e n t e d 89 i n Table 12. The weights o f male lambs used f o r the balance s t u d i e s were not i n c l u d e d i n the c a l c u l a t i o n s because the s t r e s s of confinement i n the d i g e s t i o n cages was not conducive to normal weight g a i n . Although a l l r a t i o n s produced p o s i t i v e average weight changes, urea and p o u l t r y l i t t e r supplemented r a t i o n s (2 and 5 r e s p e c t i v e l y ) had s i g n i f i c a n t l y ( P^. 0.05) lower weight gains compared w i t h the o t h e r r a t i o n . The marked decreases i n n i t r o g e n r e t e n t i o n by animals fed r a t i o n s 2 and 5 as compared with the other r a t i o n s , have most probably c o n t r i b u t e d to the observed s i g n i f i c a n t d e p r e s s i o n i n average weight g a i n . Group mean values of e f f i c i e n c y o f feed u t i l i z a t i o n i n d i c a t e d t h a t the p o u l t r y l i t t e r supplemented r a t i o n had a lower feed e f f i c i e n c y value than the c o n t r o l . Both the urea and b i u r e t supplemented r a t i o n s tended to produce feed e f f i c i e n c y values t h a t were i n t e r m e d i a t e between the c o n t r o l and t h a t f o r r a t i o n 5. P o u l t r y droppings supplemented r a t i o n had a value comparable to t h a t f o r the c o n t r o l . TABLE 12 AVERAGE BODY WEIGHT GAINS AND FEED EFFICIENCY OF LAMBS FED THE EXPERIMENTAL RATIONS Supplemental n i t r o g e n sources Soybean meal Urea B i u r e t P o u l t r y droppings P o u l t r y l i t t e r C r i t e r i a (1) (2) (3) (4) (5) No. o f animals'*" 5 5 5 5 5 Av. i n i t i a l weight (kg.) 30.7 30.6 30 .6 30.7 30.6 Av. f i n a l weight (kg.) 34.9 33.8 34.7 36.2 33.6 Av. weight change (%) 13.7* 10. 4fc 13.4* a 17.9 9 .8 b 2 Av. d a i l y feed consumption (g) 830 770 900 970 1010 Av. d a i l y weight g a i n (g) 110 70 90 130 70 Feed e f f i c i e n c y (g feed/g weight gain) 7.55 11.00 10.00 7.46 14.43 ~Only female animals used f o r the determination The animals were on the t e s t r a t i o n s f o r 4 2 days. Means on the same l i n e b e a r i n g d i f f e r e n t s u p e r s c r i p t l e t t e r s d i f f e r s i g n i f i c a n t l y : a, b (P < 0.05). 91 Summary and Conclusions-; The r e s u l t s of t h i s study have shown t h a t f a t t e n i n g lambs can make l i v e - w e i g h t gains when fed high-roughage r a t i o n s i n which up to 50% of the t o t a l n i t r o g e n i s r e p l a c e d by urea, b i u r e t o r p o u l t r y wastes. However, the use o f p o u l t r y wastes as supplemental n i t r o g e n source must be c o n s i d e r e d not only w i t h r e s p e c t to i t s p h y s i c a l and chemical composition but a l s o on the type o f bedding m a t e r i a l used i n the l i t t e r . The r e s u l t s of the animal f e e d i n g t r i a l j u s t r e p o r t e d i n d i c a t e t h a t the r a t i o n c o n t a i n i n g wood-shaving p o u l t r y l i t t e r was i n f e r i o r i n a l l a t t r i b u t e s to t h a t c o n t a i n i n g cage droppings o n l y . The dry matter (DM) d i g e s t i b i l i t y c o e f f i c i e n t s f o r the r a t i o n s i n which urea, b i u r e t and cage droppings were used as the supplemental n i t r o g e n sources (58.1, 59.9 and 61.2% r e s p e c t i v e l y ) d i d not d i f f e r s i g n i f i c a n t l y from t h a t o f the c o n t r o l r a t i o n (60.6%) i n which soybean meal was used as the n i t r o g e n source. N e v e r t h e l e s s , the wood-shaving p o u l t r y l i t t e r supplemented r a t i o n had a s i g n i f i c a n t l y lower DM d i g e s t i b i l i t y c o e f f i c i e n t (42.3%) as compared with the c o n t r o l r a t i o n . T h i s s i g n i f i c a n t decrease i n DM and oth e r n u t r i e n t d i g e s t i b i l i t y c o e f f i c i e n t s was due to the i n c r e a s e i n the crude f i b e r content as a r e s u l t of the a d d i t i o n o f p o u l t r y l i t t e r which contained wood-shavings as the bedding m a t e r i a l . I t can thus be concluded 92 t h a t p o u l t r y l i t t e r should be used as a n i t r o g e n supplement i n h i g h energy d i e t s r a t h e r than i n high-roughage r a t i o n s . Supplementation o f the hig h roughage r a t i o n s with b i u r e t , p o u l t r y droppings and l i t t e r d i d not a f f e c t the v o l u n t a r y consumption o f the d i e t s by sheep when compared w i t h the soybean meal supplemented c o n t r o l r a t i o n . However, a s i g n i f i c a n t decrease i n v o l u n t a r y feed consumption was observed i n animals fed the urea supplemented ration.. T h i s might be due to uneven mixing o f urea with the r a t i o n , because a d d i t i o n of urea a t low l e v e l s t o l o w - p r o t e i n roughages has o f t e n l e d to g r e a t e r v o l u n t a r y feed consumption. The n u t r i t i v e v alue index (NVI) data i n d i c a t e d some d i f f e r e n c e s , however, these d i f f e r e n c e s were not s i g n i f i c a n t . The h i g h v o l u n t a r y feed consumption observed i n animals f ed the l i t t e r supplemented r a t i o n compensated f o r the s i g n i f i c a n t decrease i n gross energy d i g e s t i b i l i t y o f t h i s r a t i o n , thus making the NVI comparable t o those o f the other r a t i o n s . The 0 75 amount of d i g e s t i b l e energy (DE) i n t a k e ( k c a l DE/W * ) f o r k g a l l the r a t i o n s , showed no s i g n i f i c a n t d i f f e r e n c e s . N i t r o g e n d i g e s t i b i l i t y c o e f f i c i e n t s f o r the urea, b i u r e t and p o u l t r y droppings supplemented r a t i o n s (73.5, 6 7.6 and 68.9% r e s p e c t i v e l y ) d i d not d i f f e r s i g n i f i c a n t l y from t h a t 93 f o r the c o n t r o l (71.5%). However, the c o e f f i c i e n t f o r the p o u l t r y l i t t e r supplemented r a t i o n (56.4%) was s i g n i f i c a n t l y lower than t h a t f o r the c o n t r o l . Although a l l animals were i n p o s i t i v e n i t r o g e n balance, those fed the urea and p o u l t r y l i t t e r d i e t s had s i g n i f i c a n t l y lower n i t r o g e n r e t e n t i o n than those animals on the c o n t r o l d i e t . The s i g n i f i c a n t d e c r e a s e s i n n i t r o g e n r e t e n t i o n most probably c o n t r i b u t e d to lower body weight gains of the animals f e d the urea and l i t t e r c o n t a i n i n g d i e t s when compared with the weight gains o f animals on the other r a t i o n s . The e f f i c i e n c y o f feed u t i l i z a t i o n by animals f e d the p o u l t r y droppings supplemented r a t i o n (4) was comparable to t h a t by animals fed the c o n t r o l r a t i o n . Feed e f f i c i e n c y by the animals fed the l i t t e r supplemented r a t i o n (5) was lowest, while those of animals fed the urea and b i u r e t s upple-mented r a t i o n s ( r a t i o n s 2 and 3 r e s p e c t i v e l y ) were i n t e r m e d i a t e . 94 B. TRIAL I I . Supplementation o f High roughage Rations w i t h v a r i o u s N i t r o g e n sources. ( P e l l e t e d r a t i o n s ) . D i g e s t i b i l i t y and N i t r o g e n Balance Studies 1. Experimental Methods A second t r i a l was c a r r i e d out u s i n g the same r a t i o n i n g r e d i e n t s as were used i n t r i a l I. The r a t i o n s were p e l l e t e d b e f o r e being f e d to the lambs. F i f t e e n male lambs c o n s i s t i n g of Dorset Horn, B l a c k -face and White face breeds with body weights ranging between 2 8.6 and 4 8.5 kg were randomly d i v i d e d on weight b a s i s i n t o f i v e groups of three lambs. Each group was assigned to an experimental r a t i o n . The animals were fed t h e i r r e s p e c t i v e r a t i o n s f o r approximately three weeks i n the pens b e f o r e being put i n metabolism cages. T h i s p e r i o d of time was deemed s u f f i c i e n t f o r a d a p t a t i o n of the animals to NPN u t i l i z a t i o n , p a r t i c u l a r l y b i u r e t and p o u l t r y wastes. T o t a l f e c a l and u r i n a r y c o l l e c t i o n s were made f o r a 10^ day p e r i o d which was preceded by a 4-day adjustment p e r i o d to the cages. The animals were fed ad l i b i t u m i n o r d e r to allow f o r v o l u n t a r y i n t a k e d e t e r m i n a t i o n s . Samples of feed, feces 95 and u r i n e ".obtained d u r i n g the 10-day c o l l e c t i o n p e r i o d were composited f o r each lamb and s e p a r a t e l y prepared f o r chemical a n a l y s i s . Chemical analyses of the feeds and feces f o r dry matter, crude p r o t e i n , e ther e x t r a c t and ash were done u s i n g the A.O.A.C. (1960) methods. A c i d - d e t e r g e n t f i b e r (ADF) and l i g n i n were determined u s i n g Van Soest (1968) procedure. C e l l u l o s e was determined u s i n g Crampton and Maynard (19 38) methods, m o d i f i e d by Donefer e t a l (1960). U r i n a r y n i t r o g e n was determined by the macro K j e l d a h l method. A l l other c a l c u l a -t i o n s were as r e p o r t e d i n the f e e d i n g t r i a l I. 2. R e s u l t s and D i s c u s s i o n The average chemical composition of the experimental r a t i o n s i s presented i n Table 13. The crude p r o t e i n content of the r a t i o n s v a r i e d between 14.84 and 15.80%. These amounts are w i t h i n the requirements recommended f o r sheep of s i m i l a r age and weight (NRC, 196 8). However, i t must be mentioned t h a t sheep do not e f f i c i e n t l y d i g e s t the crude p r o t e i n i n poor-q u a l i t y , mature and weathered roughages. The crude f i b e r content of the l i t t e r supplemented r a t i o n was h i g h e s t w h i l e t h a t of the cage dropping r a t i o n was l e a s t . T h i s was probably due to the presence of wood-shavings i n the l i t t e r which con-t r i b u t e d to the crude f i b e r . The gross energy content of the TABLE 13 AVERAGE CHEMICAL ANALYSIS OF RATIONS FED TO LAMBS Supplemental n i t r o g e n sources Soybean meal Urea B i u r e t P o u l t r y droppings P o u l t r y l i t t e r Prosimate composition"'" (1) (2) (3) (4) (5) Crude p r o t e i n (%) 15.48 15.68 15.80 14.84 15.22 Crude f i b e r (%) 25.10 26.20 26.10 23.60 27.50 Ether e x t r a c t (%) 0.69 0.61 0.63 2.27 2.01 Ash (%) 6.93 7.25 7.18 12.00 7.78 N i t r o g e n - f r e e e x t r a c t (%) 51.80 50 .26 50.29 47.29 47.49 Gross energy (kcal/g) 4.22 4.20 4.21 3.98 4.07 Ac i d - d e t e r g e n t f i b e r (%) 27.10 29.63 28.86 27.52 30 .01 L i g n i n (%) 4.29 3.56 3.72 3.59 4.04 C e l l u l o s e (%) 22.81 26.07 25.14 23.93 25.97 A l l values are expressed on dry matter b a s i s . 97 cage dropping r a t i o n was s l i g h t l y lower than those of the o t h e r r a t i o n s , and t h i s i s e x p l a i n e d by the hicjrer ash content of t h i s r a t i o n (12.00%) as compared with t h a t (6.93%) f o r the c o n t r o l r a t i o n . Data on average feed i n t a k e s and apparent n u t r i e n t d i g e s t i b i l i t i e s are presented i n Table 14. The c o e f f i c i e n t s o f n u t r i e n t d i g e s t i b i l i t y f o r dry matter (DM) showed s m a l l d i f -f erences among r a t i o n s , but these d i f f e r e n c e s were not s i g n i f i c a n t . The p o u l t r y l i t t e r supplemented r a t i o n had the lowest DM d i g e s t i b i l i t y c o e f f i c i e n t (61.9%) as compared with t h a t f o r the c o n t r o l r a t i o n (66.5%). The c o e f f i c i e n t s f o r gross energy d i g e s t i b i l i t y were s i m i l a r to those of DM d i g e s t i b i l i t y , i n d i c a t i n g t h a t a major p o r t i o n of the dry matter ( e x c l u d i n g ash) i s p r i m a r i l y a source o f energy. Crude p r o t e i n d i g e s t i b i l i t y c o e f f i c i e n t s a l s o d i d not show s i g n i f i c a n t d i f f e r e n c e s among r a t i o n s . However, the h i g h e s t value was observed i n animals fed the urea-supplemented r a t i o n s . This c o u l d be e x p l a i n e d by the f a c t t h a t , urea i s r a p i d l y and completely h y d r o l y z e d i n the rumen r e s u l t i n g i n very small f e c a l n i t r o g e n and thus h i g h d i g e s t i b i l i t y . The mean crude f i b e r and c e l l u l o s e d i g e s t i b i l i t y c o e f f i c i e n t s d i d not show s i g n i f i c a n t d i f f e r e n c e s . I t c o u l d however, be observed t h a t the c o e f f i c i e n t s of crude f i b e r and c e l l u l o s e d i g e s t i b i l i t y are h i g h e s t i n the p o u l t r y dropping r a t i o n and lowest i n the l i t t e r supplemented r a t i o n . TABLE 14 AVERAGE FEED INTAKE AND APPARENT DIGESTIBILITY BY SHEEP OF EXPERIMENTAL RATIONS Supplemental n i t r o g e n source Soybean meal Urea B i u r e t P o u l t r y droppings P o u l t r y l i t t e r C r i t e r i a (1) (2) (3) (4) (5) D i g e s t i b i l i t y c o e f f i c i e n t s (%): Dry matter 66.5 65.2 63.8 64 .1 61.9 Crude p r o t e i n 71.4 72.3 71.9 68.7 70.7 C e l l u l o s e 47.2 50.2 45.5 53.6 47.3 Gross energy 67.2 65.7 64.3 64.8 62.9 Crude f i b e r 44 .1 44.8 40.2 46.4 39.3 R e l a t i v e Intake (%) 120 .1 111.0 105.0 135.2 127.5 N u t r i t i v e Value Index (NVI) 80.7 72.8 67.1 87.6 79.8 D i g e s t i b l e Energy (DE) i n t a k e 272.4 244.7 226.1 278.8 259.7 TABLE 15 AVERAGE NITROGEN BALANCE OF LAMBS FED THE EXPERIMENTAL RATIONS Supplemental n i t r o g e n source Soybean P o u l t r y P o u l t r y Mgal Urea B i u r e t droppings l i t t e r (1) (2) (3) (4) (5) C r i t e r i a  No. o f animals 3 N i n t a k e 2.38 N e x c r e t i o n : F e c a l 0.61 U r i n a r y 1.0 3 N r e t e n t i o n 0.74 a N r e t a i n e d as % o f N i n t a k e 3 1 . l a N r e t a i n e d as % o f N absorbed 41.8 3 3 3 3 2.23 2.12 2.57 2.48 0.47 0 .57 0.60 0.93 1.44 0 .92 1.12 1.21 0.32 b 0.63 a 0.85 a 0 .34 b 14. 3 b 29.7 a 3 3 . l a 13. 7 b 18.2 b 40.6 a 4 3 . l a 21.9 b Means on the same l i n e b e a r i n g d i f f e r e n t s u p e r s c r i p t l e t t e r s d i f f e r s i g n i f i c a n t l y (P ^  0.05) 100 In order to be a b l e to demonstrate the o v e r a l l n u t r i t i v e v alue of the r a t i o n s , the mean v o l u n t a r y consumption of the t e s t r a t i o n s was expressed r e l a t i v e to v o l u n t a r y consumption by sheep o f good q u a l i t y hay (Crampton e t a l . , 1960). The r e l a t i v e i n t a k e (RI) values i n d i c a t e d t h a t the p o u l t r y l i t t e r and dropping supplemented r a t i o n s were as w e l l consumed as the soybean meal supplemented c o n t r o l r a t i o n . The urea and b i u r e t c o n t a i n i n g r a t i o n s had lower RI values fhan the c o n t r o l r a t i o n but the d i f f e r e n c e s were not s i g n i f i c a n t . S i m i l a r l y , the n u t r i t i v e value index (NVI) values c a l c u l a t e d from the gross energy d i g e s t i b i l i t y and RI data d i d not show s i g n i f i c a n t d i f f e r e n c e s . However, the urea and b i u r e t r a t i o n s had lower NVI values than the c o n t r o l r a t i o n . The d i g e s t i b l e energy (DE) i n t a k e values c a l c u l a t e d from the NVI data a l s o f a i l e d t o show any s i g n i f i c a n t d i f f e r e n c e s . 3. N i t r o g e n Balance The average balance data o f the animals are presented i n Table 15. There was no s i g n i f i c a n t d i f f e r e n c e i n the t o t a l d a i l y n i t r o g e n i n t a k e f o r a l l r a t i o n s . The minor d i f f e r e n c e observed i n the n i t r o g e n i n t a k e between groups was due to d i f f e r e n c e s i n feed i n t a k e . F e c a l n i t r o g e n l o s s e s were g r e a t e s t i n animals fed the p o u l t r y l i t t e r supplemented r a t i o n 101 w h i le h i g h e s t u r i n a r y n i t r o g e n l o s s e s were observed i n animals f e d the urea supplemented r a t i o n . These h i g h e r n i t r o g e n l o s s e s ( f e c a l or u r i n a r y ) r e s u l t e d i n a s i g n i f i c a n t l y (P 4. 0.05) lower n i t r o g e n r e t e n t i o n f o r animals fed the urea or p o u l t r y l i t t e r supplemented r a t i o n s as compared with the c o n t r o l r a t i o n . The animals fed the b i u r e t and p o u l t r y dropping supplemented r a t i o n s had n i t r o g e n r e t e n t i o n v a l u e s which were not s i g n i f i c a n t l y d i f f e r e n t from t h a t f o r the soybean meal supplemented r a t i o n ( c o n t r o l d i e t ) . These o b s e r v a t i o n s are s i m i l a r to those r e p o r t e d f o r the ground u n p e l l e t e d r a t i o n s used i n t r i a l I. 102 Summary and Conclus i o n s The r e s u l t s o f t h i s t r i a l have indicated t h a t sheep can perform w e l l on hig h roughage r a t i o n s supplemented with urea, b i u r e t , p o u l t r y droppings or l i t t e r . In the presen t t r i a l , the i n c r e a s e s i n the apparent n u t r i e n t d i g e s t i b i l i t y c o e f f i c i e n t s of the r a t i o n s as a r e s u l t o f p e l l e t i n g i s of p a r t i c u l a r i n t e r e s t e s p e c i a l l y with the p o u l t r y l i t t e r supplemented d i e t ( r a t i o n 5). T h i s o b s e r v a t i o n has confirmed the widely h e l d view t h a t the b e s t e f f e c t s on animal performance of p e l l e t e d as compared to u n p e l l e t e d feeds are observed with roughages of r e l a t i v e l y h i g h f i b e r content (Davidson and Hoodham, 1966) . In f e e d i n g t r i a l I, n u t r i e n t d i g e s t i b i l i t y o f the p o u l t r y l i t t e r supplemented r a t i o n was s i g n i f i c a n t l y i n f e r i o r t o those of the oth e r r a t i o n s , but i n t r i a l I I , n u t r i e n t d i g e s t i b i l i t y among r a t i o n s f a i l e d to show any s i g n i f i c a n t d i f f e r e n c e s . T h i s o b s e r v a t i o n appears to be j u s t i f i e d by the s u g g e s t i o n o f Cate e t a l . , (1955) t h a t , as the q u a l i t y of the r a t i o n decreased the 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 feed u t i l i z a t i o n between animals given the p e l l e t e d and those g i v e n the u n p e l l e t e d d i e t s pro-g r e s s i v e l y i n c r e a s e d . The h i g h e r n u t r i e n t d i g e s t i b i l i t i e s o f the l i t t e r supplemented r a t i o n used i n the second t r i a l as compared to those o f t r i a l I c o u l d be due i n p a r t o t the s l i g h t d i f f e r e n c e s i n the chemical composition o f these r a t i o n s . The l i t t e r supplemented r a t i o n o f t r i a l I I contained h i g h e r n i t r o g e n and NFE content and l e s s l i g n i n and ash than the same r a t i o n i n t r i a l I. 103 The e f f e c t o f p e l l e t i n g was p a r t i c u l a r l y n o t i c e a b l e on the v o l u n t a r y consumption of the high-roughage r a t i o n (Table 13). R e l a t i v e i n t a k e s (RI) o f the same r a t i o n s i n the ground form v a r i e d between 6 6.1 and 87.0% while the RIs of the p e l l e t e d r a t i o n s v a r i e d between 105.0 and 135.2%. S i m i l a r l y , the amount o f DE i n t a k e a v a i l a b l e to the lambs from the p e l l e t e d r a t i o n s was about twice t h a t from the same r a t i o n i n the ground form. Often, o p i n i o n i s d i v i d e d on the whole q u e s t i o n of p e l l e t i n g , e s p e c i a l l y of g o o d - q u a l i t y feeds, and whatever b e n e f i t the process has f o r the animals, i t s c o s t s always have to be s e t a g a i n s t any savings made by i n c r e a s e d e f f i c i e n c y o f u t i l i z a t i o n o f the feed. 104 C. TRIAL I I I . Supplementation of D i f f e r e n t Low-quality Forages with P o u l t r y Droppings ( P e l l e t e d r a t i o n s ) . 1. I n t r o d u c t i o n The r e s u l t s o b t a i n e d i n T r i a l 1 have shown t h a t p o u l t r y droppings can be used as the main supplementry sources o f n i t r o g e n when sheep are f e d l o w - p r o t e i n p o o r - q u a l i t y roughage r a t i o n s . In the p r e s e n t t r i a l t h e r e f o r e , i t i s intended to i n v e s t i g a t e the f e e d i n g value o f p o u l t r y droppings when i t c o n s t i t u t e s the main supplementary source of n i t r o g e n i n the d i e t s of sheep h i g h i n l o w - q u a l i t y roughage. 2. P r e p a r a t i o n of r a t i o n components Oat straw h a r v e s t e d i n 1970 was prepared as was r e p o r t e d i n the f e e d i n g t r i a l 1. Extruded wood was used as the o t h e r low*-; q u a l i t y roughage. Grass hay which was ground i n a s i m i l a r manner as the straw was used as the c o n t r o l forage. P o u l t r y droppings were c o l l e c t e d from a caged l a y e r s ' house at the U n i v e r s i t y p o u l t r y farm. The droppings had accumulated f o r a t l e a s t 6 weeks b e f o r e the c o l l e c t i o n . Wasted feed, shed f e a t h e r s , broken eggs and a l a r g e p o p u l a t i o n o f 105 h o u s e f l y l a r v a e and pupae were found mixed w i t h the droppings. No attempts were made to remove these extraneous m a t e r i a l s . The droppings were spread very t h i n l y on p l a s t i c sheet indoors and i n f r a - r e d l i g h t bulbs used to hasten the d r y i n g p r o c e s s . A i r - d r y i n g of the p o u l t r y droppings was completed i n about 2 weeks. The d r i e d p o u l t r y droppings were not s t e r i l i z e d as the d i s e a s e s of p o u l t r y , apart from s a l m o n e l l o s i s , V a r e not thought to be o f major importance i n the f e e d i n g o f ruminants (Alexander e t a l . , 1968) . Brugman e t a l . (1967) have r e p o r t e d t h a t s t e r i l -i z a t i o n of p o u l t r y l i t t e r reduced i t s d i g e s t i b i l i t y and o v e r a l l n u t r i t i v e v a l u e . The a i r - d r i e d p o u l t r y droppings were t h e r e f o r e i n c o r p o r a t e d i n t o the experimental r a t i o n s without f u r t h e r p r o c e s s i n g . a. Mixing and p e l l e t i n g o f experimental r a t i o n s The composition o f the experimental r a t i o n s i s shown i n Table 16 and the average chemical a n a l y s i s i n Table 17. Good-quality grass hay was used as the c o n t r o l forage i n r a t i o n 1 a t a l e v e l o f 40 p e r c e n t of the t o t a l r a t i o n (DM b a s i s ) . Ground oat straw was used as the l o w - q u a l i t y roughage i n r a t i o n 2 at a l e v e l of 40 p e r c e n t of the t o t a l r a t i o n (DM b a s i s ) ; w h i l e extruded wood was used as the l o w - q u a l i t y roughage i n r a t i o n 3 at a l e v e l of 35% o f the t o t a l r a t i o n (DM b a s i s ) . 106 TABLE 16 COMPOSITION OF RATIONS FED TO THE LAMBS IN THE FEEDING TRIAL ]\[ Rations I n g r e d i e n t s Grass hay 40.0 Oat straw -- 4 0.0 Extruded wood -- — 35.0 Ground b a r l e y 54.0 45.0 40.0 P o u l t r y droppings 6.0 15.0 20.0 Corn o i l — — 5.0 107 Ground b a r l e y was used as the r e a d i l y a v a i l a b l e energy source i n a l l r a t i o n s and was used a t a l e v e l of 54, 45 and 40 percent of the t o t a l r a t i o n (DM b a s i s ) i n r a t i o n s 1, 2 and 3 r e s p e c t i v e l y . A i r - d r i e d p o u l t r y droppings were i n c o r p o r a t e d i n t o the r a t i o n s i n o r d e r to b r i n g the crude p r o t e i n content of the r a t i o n s to a l e v e l t h a t i s adequate f o r f a t t e n i n g lambs. Corn o i l was added to the r a t i o n c o n t a i n i n g extruded wood ( r a t i o n 3) at 5 p e r c e n t l e v e l i n o r d e r to enhance p e l l e t i n g and to i n c r e a s e the d i g e s t i b l e energy. Mixing of the r a t i o n s was done i n a David Bradley v e r t i c a l mixer. Adequate time f o r mixing was allowed i n order to break up the lumps i n the d r i e d p o u l t r y droppings to ensure uniform d i s t r i b u t i o n i n the r a t i o n . Immediately f o l l o w i n g mixing, the r a t i o n s were p e l l e t e d u s i n g the 1 cm d i e . During p e l l e t i n g , a l o t of heat was generated by the p e l l e t i n g machine and t h i s heat was assumed s u f f i c i e n t to d e s t r o y and pathogenic organisms t h a t might s t i l l be p r e s e n t i n the a i r - d r i e d p o u l t r y droppings. The hot p e l l e t s were spread on c o n c r e t e f l o o r s to c o o l b e f o r e b e i n g put i n p l a s t i c buckets. Samples of the p e l l e t e d r a t i o n s were taken and t e s t e d m i c r o b i o l o g i c a l l y f o r pathogenic b a c t e r i a f o l l o w i n g the procedure d e s c r i b e d e a r l i e r . No pathogenic b a c t e r i a were i s o l a t e d . 108 3. Metabolism s t u d i e s Twelve male lambs, c o n s i s t i n g of a mixture of B l a c k -face and Dorset Horn breeds, approximately 6 months of age and with i n i t i a l body weight ranging from 23.1 to 31.3 kg., were d i v i d e d i n t o 3 groups of 4 lambs on weight b a s i s and were randomly a l l o t e d t o the experimental r a t i o n s . The lambs were group-fed i n the pens f o r approximately two weeks befo r e the metabolism s t u d i e s s t a r t e d . While i n the pens, the lambs were fed approximately 1 kg. feed per head d a i l y . Two metabolism t r i a l s were c a r r i e d out u s i n g 2 lambs from each group at each t r i a l . The lambs were c o n f i n e d i n t o d i g e s t i o n cages designed to enable t o t a l c o l l e c t i o n o f feces and u r i n e . The lambs having been fed the experimented r a t i o n s i n the pens f o r about 2 weeks were allowed another 10 days f o r adjustment to the cages and f o r s t a b i l i z i n g i n t a k e at about 1 kg. feed per head d a i l y . The 10-day adjustment p e r i o d was f o l l o w e d by 8-day c o l l e c t i o n p e r i o d . While i n the d i g e s t i o n cages, the lambs were i n d i v i d u a l l y f ed t h e i r r e s p e c t i v e experimental r a t i o n s . E x a c t l y 1 kg. o f feed was o f f e r e d to each animal per day, which was f e d i n two batches of 500g i n the morning and a f t e r n o o n . Unconsumed feed was weighed back the f o l l o w i n g morning and deducted from the o f f e r e d feed i n o r d e r to determine a c t u a l consumption. 109 T o t a l f e c a l c o l l e c t i o n was made d u r i n g the l a s t 8 days of each t r i a l . C o l l e c t i o n o f feces was done each morning bef o r e the morning f e e d i n g . The t o t a l f e c a l output was weighed, mixed thoroughly and sampled. S i m i l a r l y t o t a l u r i n a r y c o l l e c t i o n was made. The volume of d a i l y output of u r i n e was recorded and a l i q u o t samples taken f o r a n a l y s i s . A l l lambs were weighed p r i o r to being put i n the d i g e s t i o n cages and a l s o immediately a f t e r the c o n c l u s i o n of the t r i a l . T his was necessary i n order to be able to c a l c u l a t e the R e l a t i v e Intake of the r a t i o n s . 4. Chemical Analyses of feeds, feces and u r i n e samples Samples were prepared f o r chemical a n a l y s i s and c h e m i c a l l y analyzed as r e p o r t e d e a r l i e r . 5. C a l c u l a t i o n s Apparent d i g e s t i b i l i t y c o e f f i c i e n t s f o r dry matter, gross energy, crude f i b e r , c e l l u l o s e , and crude p r o t e i n were c a l c u l a t e d as r e p o r t e d e a r l i e r . A l l o t h e r c a l c u l a t i o n s were the same as those r e p o r t e d i n t r i a l I. 110 RESULTS AND DISCUSSION The chemical composition data of the experimental r a t i o n s are presented i n Table 17. The crude p r o t e i n contents were about equal i n the three r a t i o n s . However the per c e n t of the t o t a l r a t i o n n i t r o g e n s u p p l i e d by p o u l t r y dropping n i t r o g e n were 18.7, 50.2 and 64.2 per c e n t f o r r a t i o n s l l , 2 and 3 r e s p e c t i v e l y . The remaining r a t i o n n i t r o g e n was c o n t r i b u t e d by grass hay and b a r l e y i n r a t i o n 1, straw and b a r l e y i n r a t i o n 2 and b a r l e y i n r a t i o n s 3. The crude f i b e r content of the hay r a t i o n was c o n s i d e r a b l y lower than those f o r the straw and wood r a t i o n s . Although grass hay and oat straw were each used a t 40 percent of the t o t a l r a t i o n i n r a t i o n s 1 and 2 r e s p e c t i v e l y , the crude f i b e r i n the hay r a t i o n was lower than t h a t f o r the straw r a t i o n . This i s because the straw i s a by-product of c e r e a l which i s c h a r a c t e r i z e d by high f i b e r content. Extruded wood i s ' s i m i l a r l y high i n crude f i b e r and d e s p i t e i t s being used a t a l e v e l o f 35 percent of r a t i o n 3, the crude f i b e r content of the wood r a t i o n was s l i g h t l y h i g h e r than t h a t f o r the straw r a t i o n . The ADF and c e l l u l o s e contents of a l l r a t i o n s f o l l o w e d a s i m i l a r p a t t e r n as t h a t f o r the crude f i b e r content. The l i g n i n content f o r the r a t i o n s were 3.55, 6.64 and 9.0 6 percent f o r the hay, straw and wood I l l TABLE 17 AVERAGE CHEMICAL ANALYSIS OF RATIONS FED TO LAMBS IN FEEDING TRIAL I I I Rations Composition''' Crude protein (%) Crude fiber (%) Ether extract (%) Ash (%) Nitrogen-free extract (%) Gross Energy (kcal/g) 11.74 18.50 2.20 6.05 61.51 4.22 10.95 24.80 1.70 6.51 56.04 4.13 r;3 11.53 25.50 5.80 8.01 49.16 4.05 Acid-detergent fiber (%) Lignin (%) Cellulose (%) 19.9 3.55 16.35 28.3 6.64 21.66 29.2 9.06 20.14 A l l values are expressed on dry matter basis. 112 r a t i o n s r e s p e c t i v e l y . This i s i n d i c a t i v e o f the e f f e c t of l i g n i f i c a t i o n as m a t u r i t y of p l a n t s p r o g r e s s e d . The e t h e r e x t r a c t i v e s (EE) of the wood r a t i o n (5.8%) was high e r than those f o r the other r a t i o n s . T h i s was because corn o i l was used i n the wood r a t i o n a t a l e v e l of 5% of the t o t a l r a t i o n i n order to enhance p e l l e t i n g . The EE content f o r the hay r a t i o n was s l i g h t l y h i g h e r than t h a t f o r the straw r a t i o n . The reason f o r t h i s v a l u e might be due t o the e x t r a c t i o n of a g r e a t e r amount of n o n - l i p i d m a t e r i a l s from the hay. The extruded wood r a t i o n had a h i g h e r ash content than the other r a t i o n s . The lower ash content i n the hay r a t i o n c o u l d be due to the f a c t t h a t p o u l t r y droppings were used a t a lower percent of the t o t a l r a t i o n as compared to the straw and wood r a t i o n s . The gross energy content (kcal/g) o f the hay r a t i o n was h i g h e r than f o r the other r a t i o n s most l i k e l y as a r e s u l t of the lower ash content of the hay r a t i o n . The corn o i l used i n the wood r a t i o n might have i n c r e a s e d the gross energy content of t h i s r a t i o n s l i g h t l y . Nontheless, the gross energy content o f the wood r a t i o n was s t i l l s l i g h t l y lower than t h a t f o r the straw r a t i o n . 113 6. Apparent D i g e s t i b i l i t y C o e f f i c i e n t s : a. Dry Matter Data on average feed i n t a k e s and apparent n u t r i e n t d i g e s t i b i l i t i e s are presented i n Table 18. A h i g h l y s i g n i f -i c a n t (P 0.01) decrease i n dry matter d i g e s t i b i l i t y was observed i n animals f ed the extruded wood r a t i o n as compared with the hay or straw r a t i o n . The reason f o r t h i s s i g n i f i -cant decrease i n dry matter d i g e s t i b i l i t y of the wood r a t i o n might be due to lower f i b e r d i g e s t i b i l i t y of the wood (L e i b h o l z , 1969; Fontenot e t a l . 1966). The dry matter d i g e s t i b i l i t y of the straw r a t i o n was s i g n i f i c a n t l y (P 4. 0.05) lower than t h a t f o r the hay r a t i o n . T h i s would be expected s i n c e straw, a l o w - q u a l i t y forage, i s not degraded to the same extent as good q u a l i t y forage such as hay. b. Gross Energy The average gross energy d i g e s t i b i l i t y c o e f f i c i e n t s are presented i n Table 18. As would be expected, the p a t t e r n of the r e s u l t s o b t ained f o r the gross energy d i g e s t i b i l i t y c o e f f i c i e n t s was q u i t e s i m i l a r to those f o r the dry matter d i g e s t i b i l i t y . However the c o e f f i c i e n t s of gross energy 1 M TABLE 18 AVERAGE FEED INTAKE AND APPARENT DIGESTIBILITY BY LAMBS OF POULTRY DROPPINGS SUPPLEMENTED RATIONS Rations Cri t e r i a 1 2 3 Digestibility coefficients (%): Dry Matter 64.6 a C 56.8 b c 49.4d Crude Protein 62.2 56.1 62.6 Cellulose 38.1C 37.5C 13.7d Gross Energy 66.0 a c 57.6 b c 45.3d Crude Fiber 42. l c 35.7C 17.3d Ether Extract 82.0 79.7 86.4 Relative Intake (%) 93.7 82.7 89.7 Nutritive Value Index (NVI) 61.9a 47.6b 40. d° Digestible Energy Intake Potential 209.0a 157.2b 132.0b Means on the same line having different superscript letters d i f f e r significantly: a, b (P 0.05) c, d (P 0.01) 115 d i g e s t i b i l i t y were s l i g h t l y h i g h e r than those f o r the dry matter d i g e s t i b i l i t y p a r t i c u l a r l y i n the hay and straw r a t i o n s . A h i g h l y s i g n i f i c a n t (P^. 0.01) lower gross energy d i g e s t i b i l i t y was o b t a i n e d i n the wood r a t i o n as compared with the hay or straw r a t i o n . This lower gross energy d i g e s -t i b i l i t y was most probably as a r e s u l t o f low d i g e s t i b i l i t y of wood. A l s o , the gross energy d i g e s t i b i l i t y of the straw r a t i o n was s i g n i f i c a n t l y (P < 0.05) lower than t h a t f o r the hay r a t i o n . The lower gross energy d i g e s t i b i l i t y o f the straw r a t i o n c o u l d be a t t r i b u t e d t o reduced d i g e s t i b i l i t y of straw as a r e s u l t of advanced m a t u r i t y and l i g n i f i c a t i o n . c. Crude F i b e r The average crude f i b e r and c e l l u l o s e d i g e s t i b i l i t y c o e f f i c i e n t s are presented i n Table 18. A h i g h l y s i g n i f i c a n t (P < 0.01) lower crude f i b e r and c e l l u l o s e d i g e s t i b i l i t y was ob t a i n e d i n the extruded wood r a t i o n . This o b s e r v a t i o n confirmed the r e s u l t s o b t ained by Fontenot e t a l . (19 66) when they r e p o r t e d t h a t crude f i b e r d i g e s t i b i l i t y of wood-shaving p o u l t r y l i t t e r r a t i o n was depressed when the l e v e l of l i t t e r i n c r e a s e d from 25 to 50 p e r c e n t . L e i b h o l z (1969) noted a s i m i l a r r e d u c t i o n i n crude f i b e r d i g e s t i b i l i t y when sawdust was i n c l u d e d i n the r a t i o n f o r sheep at a l e v e l 116 above 15 per c e n t of the t o t a l r a t i o n . Although no s i g n i f i c a n t d i f f e r e n c e (P 0.05) was observed i n the crude f i b e r d i g e s t i b i l i t y c o e f f i c i e n t between the hay and straw r a t i o n s , the c o e f f i c i e n t s f o r the hay r a t i o n were h i g h e r than those f o r the straw r a t i o n ; i n d i c a t i n g t h a t the crude f i b e r o f straw was degraded t o a l e s s e r e x t e n t as a r e s u l t o f advanced m a t u r i t y of the straw as compared wi t h the hay (Reid e t a l . , 1959; D e h o r i t y and Johnson, 1960: Wilson e t a l . , 1966). The c o e f f i c i e n t s f o r the 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 m i l a r t o those of crude f i b e r . Since a high p r o p o r t i o n o f the crude f i b e r i s c e l l u l o s e , d i f f e r e n c e s i n c e l l u l o s e d i g e s t i b i l i t y between r a t i o n s c o u l d be e x p l a i n e d i n s i m i l a r f a s h i o n as those between crude f i b e r d i g e s t i b i l i t y . d. Crude P r o t e i n The mean crude p r o t e i n d i g e s t i b i l i t y c o e f f i c i e n t s are presented i n Table 18. Although 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 observed i n the average crude p r o t e i n d i g e s -t i b i l i t y between r a t i o n s , the crude p r o t e i n d i g e s t i b i l i t y c o e f f i c i e n t f o r the straw r a t i o n was s l i g h t l y lower than t h a t ' f o r the hay or wood r a t i o n . T h i s s l i g h t decrease might be due to the f a c t t h a t crude p r o t e i n i n the straw i s r e l a t i v e l y u n a v a i l a b l e f o r m i c r o b i a l d e g r a d a t i o n (Crampton and Maynard, 1938;Dehority and Johnson, 1960). The l a c k o f a s i g n i f i c a n t (P ^ . 0.05) d i f f e r e n c e i n the crude p r o t e i n d i g e s t i b i l i t y between r a t i o n s c o u l d be a t t r i b u t e d t o the 117 l a r g e v a r i a t i o n observed between animals i n the same group. Despite the f a c t t h a t p o u l t r y droppings were used a t very wide l e v e l s (6, 15 and 20 p e r c e n t of the t o t a l r a t i o n ) the o v e r a l l crude p r o t e i n d i g e s t i b i l i t y d i d not r e v e a l any s i g n i f i c a n t d i f f e r e n c e s between r a t i o n s . e. R e l a t i v e Intake (RI) The feed consumption of the lambs were expressed r e l a t i v e to the v o l u n t a r y consumption o f good q u a l i t y hay assuming t h a t sheep w i l l v o l u n t a r i l y consume about 80g good q u a l i t y hay per u n i t of m e t a b o l i c s i z e (Crampton e t a l . , 1960). In t h i s t r i a l however, the lambs were not fed ad l i b i t u m ; each animal was o f f e r e d lOOOg feed d a i l y . A c t u a l v o l u n t a r y consumption was t h e r e f o r e d i f f i c u l t t o determine s i n c e some of the animals ate a l l the feed, i n d i c a t i n g t h a t these animals had not reached t h e i r maximum v o l u n t a r y consumption. I t was n e v e r t h e l e s s necessary to c a l c u l a t e the R e l a t i v e Intake (RI) i n order to be able to compare the r e l a t i v e f e e d i n g value of the t e s t r a t i o n s with c o n v e n t i o n a l good q u a l i t y f e e d s t u f f s . The c a l c u l a t e d RI's f o r a l l r a t i o n s (Table 18) f a i l e d to show any s i g n i f i c a n t (P Z. 0.05) d i f f e r e n c e . However, the mean RI value f o r the hay r a t i o n tended to be s l i g h t l y h i g h e r than f o r the o t h e r r a t i o n s . The l a c k of s i g n i f i c a n t 118 d i f f e r e n c e c o u l d be a t t r i b u t e d to the f a c t t h a t a few of the animals, p a r t i c u l a r l y those on hay r a t i o n , d i d not reach t h e i r maximum v o l u n t a r y consumption. f. N u t r i t i v e Value Index (NVI) The summary of the n u t r i t i v e v alue i n d i c e s f o r a l l given (or shown) r a t i o n s i s / i n Table 18. The hay had a s i g n i f i c a n t l y (P *L 0.05) h i g h e r NVI value than the other r a t i o n s . Although no s i g n i f -i c a n t d i f f e r e n c e s were observed between the NVI values f o r the straw and wood r a t i o n s , the value f o r the straw r a t i o n was s l i g h t l y h i g h e r than t h a t f o r the wood r a t i o n . I t i s i n t e r e s t i n g to note t h a t the NVI values f o r the straw and wood r a t i o n s (47.6 and 40.8 r e s p e c t i v e l y ) were q u i t e comparable to the NVI values obtained i n t r i a l I f o r the p o u l t r y droppings and l i t t e r supplemented r a t i o n s (49.7 and 38.1 r e s p e c t i v e l y ) . The g r e a t e r p r o p o r t i o n of the d i f f e r e n c e s i n the observed NVI values i n t h i s t r i a l c o u l d be accounted f o r by the d i f f e r e n c e s i n gross energy d i g e s t i b i l i t y , as there appeared t o be very l i t t l e d i f f e r e n c e i n the r e l a t i v e i n t a k e v a l u e s . 119 g. D i g e s t i b l e Energy (DE) Intake P o t e n t i a l The DE i n t a k e was c a l c u l a t e d from the NVI valu e s and the gross energy content of the r a t i o n s a c c o r d i n g to the method o f Crampton e-t a l . (1962) . A summary of the DE-'; intake values i s presented i n Table 18. The hay r a t i o n had a s i g n i f i c a n t l y (P 0.05) h i g h e r DE i n t a k e value than the other r a t i o n s . The tr e n d i n magnitude of the DE i n t a k e values among r a t i o n s was very s i m i l a r t o t h a t f o r the NVI v a l u e s . This i s so because the DE i n t a k e values were c a l c u l a t e d u s i n g the NVI v a l u e s . No s i g n i f i c a n t d i f f e r e n c e s were observed between the DE i n t a k e values f o r the straw and wood r a t i o n s , however, the values f o r the straw r a t i o n appeared to be s l i g h t l y h i g h e r than t h a t f o r the wood r a t i o n . h. N i t r o g e n Balance Determinations T o t a l d a i l y n i t r o g e n i n t a k e was c a l c u l a t e d from the feed i n t a k e and the percentage n i t r o g e n i n the r a t i o n . In an attempt to e l i m i n a t e d i f f e r e n c e s due to l i v e w e i g h t , the n i t r o g e n i n t a k e , e x c r e t i o n and r e t e n t i o n were expressed on the m e t a b o l i c s i z e o f each animal. N i t r o g e n i n t a k e by the lambs fed the hay r a t i o n was h i g h e r than those f e d e i t h e r the straw o r wood r a t i o n . N i t r o g e n i n t a k e by the lambs fed the 120 TABLE 19 AVERAGE NITROGEN BALANCE OF LAMBS FED POULTRY DROPPINGS L SUPPLEMENTED RATIONS — TRIAL I] [I Rations Cri t e r i a 1 2 3 Number of animals 4 4 4 N Intake (G/W^75/day) 1.42 1.17 1.31 N excretion: Fecal (g/w|^75/day) 0.54 0.51 0.49 Urinary (g/WJJg75/day) 0.47 0.54 0.41 N Retention (g/W°'75/day) Kg 0.41C 0.12d 0.41C N Retention as % of N Intake 28.7C 9.2d 31.1° N Retention as % of digested N 46.3° 15. l d 49.6C Means on the same line having different superscript letters d i f f e r significantly: c, d (P^.0.01). 121 straw r a t i o n was lowest. This might have been due to low n i t r o g e n content o f the straw r a t i o n as compared with the other r a t i o n s and a l s o t o the s l i g h t r e d u c t i o n i n feed -consumption. Ni t r o g e n e x c r e t i o n i n the feces and u r i n e were determined as p r e v i o u s l y r e p o r t e d . F e c a l n i t r o g e n l o s s i n a l l lambs appeared t o be q u i t e comparable, however, lambs on the hay r a t i o n had s l i g h t l y h i g h e r f e c a l n i t r o g e n l o s s than those on straw or wood r a t i o n . The mean u r i n a r y n i t r o g e n l o s s i n lambs fed the straw r a t i o n was hi g h e r than those f o r the hay and wood r a t i o n s . I t i s important t o r e p o r t t h a t one lamb i n the group fed the straw r a t i o n was i n neg a t i v e n i t r o g e n ba lance. As a r e s u l t o f t h i s , the group mean was g r e a t l y reduced and t h i s might have accounted f o r the h i g h l y s i g n i f i c a n t (P<C 0.01) d i f f e r e n c e i n n i t r o g e n r e t e n t i o n (Table 18). The negative n i t r o g e n balance observed i n the lamb on the straw r a t i o n c o u l d be a t t r i b u t e d to e i t h e r the e f f e c t o f reduced feed consumption which might have r e s u l t e d i n decreased n i t r o g e n i n t a k e , high u r i n a r y n i t r o g e n l o s s probably as a r e s u l t o f t i s s u e m o b i l i z a t i o n f o r energy purposes or the presence o f worms i n the feces which might have e l e v a t e d the f e c a l n i t r o g e n c o n t e n t . By e l i m i n a t i n g the data on t h i s p a r t i c u l a r sheep, mean n i t r o g e n r e t e n t i o n f o r a l l groups became q u i t e comparable. E x p r e s s i n g n i t r o g e n r e t e n t i o n as p e r c e n t o f n i t r o g e n i n t a k e and d i g e s t e d showed a s i m i l a r t r e n d . 122 Weight g a i n and feed e f f i c i e n c y f o r the lambs were not c a l c u l a t e d because l i v e w e i g h t gains o r l o s s e s cannot be co n s i d e r e d an important c r i t e r i o n i n e v a l u a t i n g the n u t r i t i v e value o f the experimental r a t i o n s i n t h i s t r i a l because; the s t r e s s of confinement i n the d i g e s t i o n cages i s not conducive to normal weight g a i n . A l s o , each experimental d i e t was o f f e r e d t o the lambs f o r a s h o r t p e r i o d o f time to permit r e l i a b l e weight changes v a l u e s . Furthermore, the experimental d i e t s were p o s s i b l y s t i l l d e f i c i e n t i n other n u t r i e n t s -v i t a m i n s and minerals - which are e s s e n t i a l f o r proper phys-i o l o g i c a l f u n c t i o n s . But because of the s h o r t - t e r m nature o f the experiment, supplementation was l i m i t e d to energy and p r o t e i n . 123 Summary and Conclus i o n s The r e s u l t s of t h i s f e e d i n g t r i a l had c l e a r l y shown t h a t p o u l t r y droppings c o u l d be used as the main supplementary n i t r o g e n source f o r sheep f e d l o w - q u a l i t y roughage r a t i o n s . The r e p o r t s of Parham e t a l . (1955), Brown e t a l . (1956), and Davis e t a l . (1956) i n d i c a t e t h a t urea can s a t i s f a c t o r i l y r e p l a c e n a t u r a l p r o t e i n i n ruminant feeds without a f f e c t i n g the growth gains or m i l k y i e l d s , p r o v i d e d the p r o t e i n r e p l a c e -ment with urea does not exceed o n e - t h i r d of the t o t a l p r o t e i n i n the r a t i o n . In the f e e d i n g t r i a l j u s t r e p o r t e d , d e s p i t e the f a c t t h a t complete supplementation of the roughage r a t i o n s was not e f f e c t e d with regards t o vitamins and m i n e r a l s , the i n c l u s i o n o f a i r - d r i e d p o u l t r y droppings to supply a p p r o x i -mately 50.2 and 64.2 per c e n t of the t o t a l crude p r o t e i n i n the straw and wood r a t i o n s r e s p e c t i v e l y has r e s u l t e d i n v o l u n t a r y consumption and d i g e s t i b l e energy i n t a k e t h a t would be expected f o r high q u a l i t y forages such as grass hay. 124 SECTION I I I IN VITRO CELLULOSE DIGESTION OF CHEMICALLY TREATED LOW-QUALITY ROUGHAGES. THE EFFECT OF SUPPLEMENTAL NITROGEN SOURCE ON THE IN VITRO CELLULOSE DIGESTION OF RATIONS FED TO LAMBS IN SECTION I I . 125 IN VITRO CELLULOSE DIGESTION OF ALKALI TREATED AND UNTREATED LOW-QUALITY ROUGHAGES (Oat straw and P o p l a r wood). 1. I n t r o d u c t i o n W i t h i n the p a s t decade, n u t r i t i v e e v a l u a t i o n of forages has come i n t o new prominence as evidenced by the number of s t u d i e s d e a l i n g with the development of v a l i d i n v i v o and i n  v i t r o techniques to be used i n forage e v a l u a t i o n programs. S e v e r a l workers i n c l u d i n g B a r n e t t (1957), Quicke e t a l . (1958) and Hershberger e t a l . (1959) have demonstrated a h i g h c o r r e l a -t i o n between i n v i v o and i n v i t r o d i g e s t i b i l i t y of forage c e l l u l o s e . In v i t r o dry matter and c e l l u l o s e d i g e s t i o n have a l s o been shown to be h i g h l y c o r r e l a t e d w i t h i n v i v o c r i t e r i a of a v a i l a b l e energy, such as the d i g e s t i b i l i t y of dry matter and gross energy (Donefer e t a l . , 1960) . The N u t r i t i v e Value Index (NVI) proposed by Crampton e t a l . (1960) , pr o v i d e s a complete d e s c r i p t i o n of the f e e d i n g value of a forage, because i t measures both the v o l u n t a r y i n t a k e and energy d i g e s t i b i l i t y of the f o r a g e . S t u d i e s with a number of forages have i n d i c a t e d t h a t the NVI c o u l d be p r e d i c t e d by means of an i n v i t r o rumen fermentation method (Donefer e t a l . , 1960; 1962). A c o m p l i c a t i o n i n a s s e s i n g the v a l i d i t y of the various i n v i t r o techniques i s the d i f f e r e n c e of o p i n i o n as to what i n v i v o c r i t e r i a are most meaningful i n the e v a l u a t i o n 126 of f o r a g e s . The reason being t h a t any i n v i t r o procedure, no matter how p r e c i s e , can o n l y be as accurate as the i n v i v o measure of n u t r i t i v e value i t attempts to p r e d i c t . Neverthe-l e s s , the high c o r r e l a t i o n t h a t e x i s t s between i n v i v o and i n v i t r o techniques has r a i s e d the q u e s t i o n as to whether the c o s t l y and time-consuming i n v i v o t r i a l s c o u l d be r e p l a c e d by the i n v i t r o techniques i n e s t i m a t i n g the n u t r i t i v e value of f o r a g e s . The c h i e f advantages of the a r t i f i c i a l rumen appear to be the speed with which determinations can be c a r r i e d out i n the l a b o r a t o r y , the p r e c i s i o n and c o n t r o l which can be e x e r c i s e d over v a r i o u s c o n d i t i o n s i n the l a b o r a t o r y as opposed to the i n t a c t animal, and the g r e a t r e d u c t i o n i n the expense of experimentation, not only of c a r i n g f o r animals but a l s o i n the amount of d i f f e r e n t feed i n g r e d i e n t s needed. However, the above advantages should not be over-emphasized s i n c e the a r t i f i c i a l rumen i s only an approximation o f the n a t u r a l con-d i t i o n i n the i n t a c t animal. There i s always doubt whether the i n v i t r o set-up i s t r u l y r e p r e s e n t a t i v e o f the n a t u r a l c o n d i t i o n s i n the l i v e animals. The types of microorganisms which develop i n the a r t i f i c i a l rumen might be d i f f e r e n t from the f l o r a maintained i n a rumen proper. The above l i m i t a t i o n s are d o u b t l e s s l y incomplete and any i n t e r p r e t a t i o n p l a c e d upon r e s u l t s o b t a i n e d by i n v i t r o methods must be tempered 127 w i t h r e s e r v a t i o n s embodying such l i m i t a t i o n s . N e v e r t h e l e s s , there i s c o n s i d e r a b l e evidence i n d i c a t i n g t h a t these l i m i t a t i o n s are of minor importance and t h a t the approximations made to rumen c o n d i t i o n s i n the l a b o r a t o r y f l a s k are, f o r the most p a r t , s a t i s f a c t o r y . Perhaps the s t r o n g e s t evidence to date s u p p o r t i n g t h i s c o n t e n t i o n i s the a b i l i t y to m a i n t a i n over long p e r i o d s o f time h i g h degrees o f c e l l u l o s e d i g e s t i o n i n a r t i f i c i a l rumens which compare f a v o u r a b l y w i t h the degree of c e l l u l o s e d i g e s t i o n which occurs i n l i v e ruminants. I t would seem t h a t the a r t i f i c i a l rumen can b e s t be used as a s c r e e n i n g d e v i c e i n s t u d y i n g i n f l u e n t i a l f a c t o r s of feeds i n rumen p h y s i o l o g y , from which the most promising r e s u l t s must be u l t i m a t e l y t e s t e d i n animal e x p e r i m e n t a t i o n . 2. Experimental methods. The procedure adopted f o r a l l the fermentation runs was t h a t r e p o r t e d by Donefer e t a l . (1960) with very s i g h t m o d i f i c a t i o n s , and i s o u t l i n e d below. 128 a. In v i t r o systems and s u b s t r a t e s The i n v i t r o systems c o n s i s t e d o f 36 fermentation tubes (90 ml. Pyrex No. 8260), each f i t t e d w i t h a 1-hole rubber stopper (No. 6) through which was i n s e r t e d a g l a s s d e l i v e r y tube attached by means o f rubber t u b i n g t o a gas ma n i f o l d with 36 o u t l e t s . Flow of gas i n t o the fermentation tubes was c o n t r o l l e d by means of c l i p v a l v e s , at approximately 160 bubbles per minute (unused o u t l e t s were completely c l o s e d ) . The gas m a n i f o l d was connected to a l a r g e (50 l b . c a p a c i t y ) tank o f CC>2 f i t t e d with a pressure r e g u l a t o r . The d e l i v e r y tube was ad j u s t e d so t h a t i t s t i p was approximately 40 mm. from the bottom of the ferme n t a t i o n tube, and t h i s t o gether with the r e l a t i v e l y slow gasing r a t e enabled the s u b s t r a t e s to s e t t l e t o the bottom of the tube d u r i n g f e r m e n t a t i o n . Gas was exhausted by way of c l e a r a n c e between the p o u r i n g l i p o f the tube and the rubber stopper. Fermentation was maintained at a temperature o f approximately 40°C±0.5°C i n a water-bath. T o t a l l i q u i d volume i n each tube was 50 ml. with 200 to 700 mg. of s u b s t r a t e s and standards s u p p l y i n g approximately 200 mg. c e l l u l o s e . S u b s t r a t e samples from the r a t i o n s used f o r animal f e e d i n g i n t r i a l s I and I I I were i n c l u d e d i n the fermentation 129 run. Samples o f the c h e m i c a l l y t r e a t e d o a t straw and p o p l a r wood were a l s o i n c l u d e d . Chemical treatment o f the o a t straw and p o p l a r wood and p r e p a r a t i o n f o r i n v i t r o f ermentation run was as f o l l o w s : oat straw and p o p l a r wood ground to pass the 20 mm. screen mesh were s e p a r a t e l y t r e a t e d with NaOH and NH^OH s o l u t i o n s . E x a c t l y 60 ml. of 13.3% s o l u t i o n s of NaOH were used to t r e a t 100 g of e i t h e r straw or wood; wh i l e 24 ml. of 12.5% NH^OH s o l u t i o n were used to t r e a t separate batches of 100 g of straw and wood. The d e c i s i o n to use the above c o n c e n t r a t i o n s and d i l u t i o n s was based on the r e s u l t s o b t a i n e d by Donefer e t a l . (1969) and Za f r e n (1960). The ground oat straw or p o p l a r wood was t r e a t e d i n 100 g batches i n 500 ml. Erlenmeyer f l a s k s . A f t e r thorough mixing w i t h the a p p r o p r i a t e a l k a l i , the f l a s k s were covered with aluminium f o i l and the chemical r e a c t i o n allowed to continue f o r 24 h r s . A f t e r t h i s , a c e t i c a c i d (50% v/v.') was added'to the t r e a t e d samples to ad j u s t the pH to n e u t r a l i t y . The t r e a t e d m a t e r i a l was then allowed to dry i n open dishes b e f o r e b e i n g weighed i n t o the fermentation tubes f o r i n v i t r o c e l l u l o s e d i g e s t i o n . The e f f e c t o f n i t r o g e n source on c e l l u l o s e d i g e s t i o n i n v i t r o was i n v e s t i g a t e d on the un t r e a t e d and a l k a l i t r e a t e d straw and wood. Ni t r o g e n sources used were urea, b i u r e t and u r i c a c i d . The reason f o r u s i n g u r i c a c i d was t h a t t h i s compound c o n s t i t u t e s between 30 and 40% of the t o t a l n i t r o g e n 130 i n p o u l t r y e x c r e t a (Fontenot e t a l . , 1966; L e i b h o l z , 1969) and rumen microorganisms had been shown to u t i l i z e i t f o r t h e i r body p r o t e i n (Belasco, 1954; Jurtshuk e t a l . , 1955). The l e v e l of n i t r o g e n supplementation i n the f e r m e n t a t i o n s u b s t r a t e s were 2.0, 2.3 and 2.5 p e r c e n t f o r urea, b i u r e t and u r i c a c i d r e s p e c t i v e l y , i n order to supply e q u i v a l e n t amounts of n i t r o g e n i n the fermentation medium. Standard s u b s t r a t e s were i n c l u d e d i n each run i n order to t e s t the r e p e a t a b i l i t y of r e s u l t s between runs. These 1 1 standards c o n s i s t e d of a l f a l f a , Solka f l o e and A v i c e l . A l l s u b s t r a t e s to be t e s t e d were prepared f o r i n v i t r o f e r m e n t a t i o n by g r i n d i n g i n the hammermill f i t t e d w i t h the 20 mm. s c r e e n mesh. Samples c o n t a i n i n g between 26 and 34% c e l l u l o s e were used a t a s u b s t r a t e l e v e l o f 700 mg. per tube thus s u p p l y i n g a c e l l u l o s e l e v e l o f approximately 200 mg. Samples c o n t a i n i n g l e s s than 26% or more than 34% c e l l u l o s e were used a t a l e v e l of 800 mg. or or 600 mg. r e s p e c t i v e l y to m a i n t a i n the same approximate l e v e l of c e l l u l o s e (200 mg.) i n a l l tubes. In r e l a t i o n to s u b s t r a t e l e v e l , Quicke e t a l . (19 59a) had demonstrated t h a t v a r y i n g forage l e v e l s from 0.6 to 1.3 gm. per tube had no e f f e c t on p e r c e n t c e l l u l o s e d i g e s t i b i l i t y . p u r i f i e d c e l l u l o s e source. 131 b. P r e p a r a t i o n o f inoculum (Phosphate B u f f e r E x t r a c t ) Rumen i n g e s t a was c o l l e c t e d from a H e r e f o r d s t e e r f i t t e d with a permanent rumen f i s t u l a . The s t e e r was maintained on an a l l a l f a l f a hay d i e t , supplemented with t r a c e m i n e r a l i z e d s a l t . Feed was not a v a i l a b l e to the animal f o r about 12 hours p r i o r to sampling. A p o l y e t h y l e n e bucket l i n e d w i t h 2 l a y e r s o f c h e e s e c l o t h was used to c o l l e c t a sample o f approximately 6 l i t e r s of rumen i n g e s t a . The i n g e s t a was pressed and the l i q u i d d i s c a r d e d . Approximately 41b. o f the r e s u l t a n t s o l i d m a t e r i a l was mixed with 1500 ml. o f phosphate b u f f e r s o l u t i o n (pH 7) a c c o r d i n g to the method d e s c r i b e d by Johnson e t a l . (19 58). P r i o r to making the e x t r a c t , the phosphate b u f f e r s o l u t i o n (1.059 g Na2HPC>4 + 0.436 g KH 2P0 4 per l i t e r ) was preheated to 45°C (to compensate f o r drop of temperature to approximately 40°C d u r i n g e x t r a c t i n g procedures) and 25 ml. s a t u r a t e d Na2CC>3 s o l u t i o n added to i t and CC>2 bubbled through the mixture u n t i l the pH was 7. A f t e r moderate a g i t a t i o n o f the i n g e s t a with the phosphate b u f f e r s o l u t i o n , the mixture was pressed again and the r e s u l t a n t l i q u i d which c o n s t i t u t e d the inoculum and d e s i g n a t e d as phosphate b u f f e r e x t r a c t (PBE) was f i l t e r e d through 4 l a y e r s o f c h e e s e c l o t h i n t o preheated thermos c o n t a i n e r s f o r t r a n s p o r t a t i o n to the l a b o r a t o r y . 132 c. P r e p a r a t i o n and d i s p e n s a t i o n o f b a s a l medium A l l the b a s a l medium (Table 20) except i r o n and c a l c i u m were premixed i n a 2 - l i t e r Erlenmeyer f l a s k i n q u a n t i t i e s s u f f i c i e n t f o r the i n o c u l a t i o n o f 40 fermentation tubes. The mixture was heated to 40°C, s a t u r a t e d with CO^ and the pH adju s t e d to 7. F o l l o w i n g t h i s , 800 ml. of the inoculum (PBE) and 20 ml. of F e r r i c c h l o r i d e and Calcium c h l o r i d e mixture were added to the f l a s k c o n t a i n i n g the b a s a l medium and the t o t a l mixture a d j u s t e d with d i s t i l l e d water to 2 l i t e r s . The mixture was then poured i n t o the New Z i p p e t t 1 f l a s k , p l a c e d on a magnetic s t i r e r and 50 ml. o f the mixture were manually dispensed i n t o each o f the f e r m e n t a t i o n tubes i n t o which the s u b s t r a t e s had been preweighed. Urea and glucose were omitted from the b a s a l medium used f o r the p r e p a r a t i o n of the inoculum used f o r s u b s t r a t e s c o n t a i n i n g samples of the r a t i o n s fed to lambs i n t r i a l s I and I I I . The reason f o r t h i s was t h a t the r a t i o n s c o n t a i n e d adequate crude p r o t e i n and an e a s i l y a v a i l a b l e source of energy i n the form of molasses. Urea was s i m i l a r l y omitted from the inoculum used f o r some of the a l k a l i t r e a t e d oat straw and p o p l a r wood i n which the e f f e c t of n i t r o g e n source on c e l l u l o s e d i g e s t i o n i n v i t r o was b e i n g s t u d i e d . Manufactured by Jencons ( S c i e n t i f i c ) L t d . , Mark Road, Hemel Hempstead, H e r t f o r d s h i r e , England. 133 TABLE 20 COMPOSITION OF IN VITRO BASAL MEDIUM AND INOCULUM Solution Mineral mixture Iron and Calcium chloride Glucose (100 mg./ml.)* Urea (126 mg./ml.)* Biotin (10 mg./ml.) PABA (100 mg./ml.) n-Valeric acid (5.mg. /ml.)* c Casein hydrolysate-enzymatic (20 mg./ml.)* Sodium carbonate (200 mg./ml.) cl Phosphate buffer * extract (inoculum) Volume used per tube (ml.) 10.0 0.5 0.5 0.5 1.0 0.25 3.0 2.5 1.5 20.0 Amount used per tube (mg.) (see a) 4.845 50 63 10 25 15 50 300 (see d) aNa 2HP0 4 5.65 g.; NaH2P04H2@ 6.27 g.; KC1 2.15 g.; NaCl 2.15g.; MgS047H20 0.582 g.; and Na 2S0 4 0.75 g. per l i t e r . bFeCl 36H 20 4.4 mg./ml.; CaCl 22H 20 5.29 mg./ml. °Nutritional Biochemicals Corp. dNa 2HP0 4 1.059 g. and KH2P04 0.436 g. per l i t e r . *Prepared prior to each fermentation run. 134 d. I n i t i a t i o n and t e r m i n a t i o n o f the f e r m e n t a t i o n run The a d d i t i o n o f the inoculum and the b a s a l medium to the s u b s t r a t e s marked the b e g i n n i n g o f the f e r m e n t a t i o n run. Two drops of m i n e r a l o i l were added to each tube i n order to prevent foaming, a f t e r which the tubes were connected to the CC>2 gas supply and p l a c e d i n the water bath. The tubes were shaken h o u r l y f o r the f i r s t 5 hours o f f e r m e n t a t i o n to e f f e c t adequate mixing of the s u b s t r a t e and inoculum. At the end o f 2 4 hours, the tubes were removed from the water bath, s u b s t r a t e m a t e r i a l s a t the s i d e s of the tubes were washed down with d i s t i l l e d water and the tubes were immediately c e n t r i f u g e d a t 2200 r.p.m. f o r 8 minutes. The supernatant was d i s c a r d e d and the r e s i d u e was immediately analyzed f o r c e l l u l o s e or r e f r i g e r a t e d f o r subsequent c e l l u l o s e a n a l y s i s . e. C e l l u l o s e a n a l y s i s The procedure used f o r the c e l l u l o s e a n a l y s i s of the o r i g i n a l s u b s t r a t e samples and the r e s i d u e s from the i n v i t r o f e r m e n t a t i o n , was t h a t r e p o r t e d by Crampton and Maynard (19 38) s l i g h t l y m o d i f i e d by Donefer e t a l . (1960), and i s o u t l i n e d below. 135 (i) A c i d d i g e s t i o n The a c i d d i g e s t i o n mixture was prepared by mixing 650 ml. a c e t i c a c i d (99.7% v / v ) , 80 ml. con c e n t r a t e d n i t r i c a c i d , and 150 ml. d i s t i l l e d water. Approximately 25 ml. o f the a c i d d i g e s t i o n mixture was dispensed i n t o each f e r m e n t a t i o n tube. A g l a s s s t i r r i n g rod was i n s e r t e d i n each tube and the contents w e l l mixed, wi t h the s t i r r i n g rod l e f t i n the fermen-t a t i o n tube d u r i n g the e n t i r e d i g e s t i o n p e r i o d . The tubes were p l a c e d i n a s t e e l wire basket and immersed i n a b o i l i n g water bath f o r 30 minutes. Contents of the tubes were mixed every ten minutes with the s t i r r i n g rod. At the end o f the d i g e s t i o n p e r i o d , the tubes were removed from the b o i l i n g water bath and allowed to c o o l f o r about 5 minutes. ( i i ) F i l t r a t i o n A f t e r c o o l i n g f o r 5 minutes, 25 ml. of 95% et h a n o l were added t o each tube mixing the contents w i t h the s t i r r i n g rod. The contents were immediately t r a n s f e r r e d q u a n t i t a t i v e l y i n t o f i l t e r i n g c r u c i b l e s (Selas - coarse p o r o s i t y ) , u s i n g a p o l y e t h y l e n e wash b o t t l e c o n t a i n i n g 95% e t h a n o l t o wash down the s i d e s o f the tubes. F i l t r a t i o n was a i d e d by a p p l y i n g s u c t i o n . The p r e c i p i t a t e i n the c r u c i b l e was then washed wi t h 136 approximately 10 ml. each of acetone and ethyl e t h e r i n suc-c e s s i o n . ( i i i ) D r y ing and ashing The c r u c i b l e s t ogether w i t h t h e i r contents were d r i e d i n an oven a t approximately 100 C f o r 12 hours, a f t e r which they were co o l e d i n a d e s i c a t o r and weighed. The c r u c i b l e s with t h e i r contents were then ashed i n the m u f f l e furnace (600°C) f o r 8 hours, c o o l e d i n the d e s i c a t o r and weighed. (iv) C a l c u l a t i o n o f c e l l u l o s e content C e l l u l o s e content of the o r i g i n a l s u b s t r a t e or of the fermentation r e s i d u e was c a l c u l a t e d as the l o s s i n weight on ashing the oven-dried a c i d d i g e s t e d m a t e r i a l u s i n g the f o l l o w i n g formula: C e l l u l o s e content (g) = Weight (g) dry c r u c i b l e and contents minus, weight (g) ashed c r u c i b l e and c o n t e n t s . C e l l u l o s e (.%) Weight (g) c e l l u l o s e x 100 Weight (g) of s u b s t r a t e 1 137 (v) C a l c u l a t i o n of c e l l u l o s e d i g e s t i b i l i t y i n v i t r o . C e l l u l o s e d i g e s t i b i l i t y i n v i t r o was c a l c u l a t e d as the d i f f e r e n c e between i n i t i a l c e l l u l o s e content o f the s u b s t r a t e and the c e l l u l o s e content o f the ferm e n t a t i o n r e s i d u e , e x p r e s s i n g t h i s as a per cent of the i n i t i a l c e l l u l o s e content. The f o l l o w i n g formula was used: W - W C e l l u l o s e d i g e s t i b i l i t y (%) = o f 100 W X 1 o Weight of c e l l u l o s e (g) i n the s u b s t r a t e Weight of c e l l u l o s e (g) i n the ferm e n t a t i o n r e s i d u e . where W = o 138 RESULTS AND DISCUSSION Data presented i n Table 21 show the c e l l u l o s e content and i n v i t r o c e l l u l o s e d i g e s t i o n o f ground u n t r e a t e d and a l k a l i t r e a t e d o a t straw and p o p l a r wood. There was a g r e a t e r decrease i n the c e l l u l o s e content of the NaOH t r e a t e d straw and wood than the NH^OH t r e a t e d samples. S i m i l a r r e d u c t i o n i n the c e l l u l o s e content o f NaOH t r e a t e d oat straw was r e p o r t e d by Adeleye (1969). The e x p l a n a t i o n f o r t h i s apparent r e d u c t i o n i n the c e l l u l o s e content c o u l d be a t t r i b u t e d to the d i l u t i n g e f f e c t of the sodium hydroxide. The ash content o f the NaOH t r e a t e d straw i n c r e a s e d from an i n i t i a l v a lue of 5.21% to 14.10% a f t e r NaOH treatment and a c i d n e u t r a l i z a t i o n , with the decreased c e l l u l o s e content d i r e c t l y a t t r i b u t a b l e to the i n c r e a s e d ash content. When NH^OH was used, very s l i g h t decrease i n c e l l u l o s e content was observed. T h i s might be e x p l a i n e d by the f a c t t h a t HN^OH i s v o l a t i l e so t h a t a f t e r d r y i n g o f the NH^OH t r e a t e d m a t e r i a l s , very l i t t l e d i f f e r e n c e i n c e l l u l o s e content was observed between the t r e a t e d and untr e a t e d samples. The i n v i t r o c e l l u l o s e d i g e s t i o n o f the un t r e a t e d o at straw (41.3%) was s i g n i f i c a n t l y (P 4- 0.01) lower than those f o r the NaOH and NH^OH t r e a t e d straw samples — 78.7 and 66.5% r e s p e c t i v e l y . The almost t w o - f o l d i n c r e a s e i n c e l l u l o s e 139 TABLE 21 THE EFFECT OF NaOH AND NH.OH TREATMENT ON THE IN VITRO CELLULOSE 4 DIGESTION OF OAT STRAW AND POPLAR WOOD. Sample Chemical treatment Cellulose content (%) a In vitro cellulose d i g e s t i b i l i t y (%) Oat straw None NaOH NH.OH 4 40.06 34.77 39.04 41.3 78.7 66.5 Poplar wood None NaOH NHjOH 53.36 46.26 52.55 16.4 71.4 57.6 each value i s a mean of 3 determinations each value i s a mean of 4 determinations 140 d i g e s t i b i l i t y observed f o r the NaOH t r e a t e d straw (78.7%) as compared wi t h the unt r e a t e d straw (41.3%) was expected s i n c e the NaOH treatment acted to s o l u b u l i z e l i g n i n , thereby exposing c e l l n u t r i e n t s p a r t i c u l a r l y c e l l u l o s e , t o the a c t i o n of m i c r o b i a l d e g r a d a t i o n . C e l l u l o s e d i g e s t i b i l i t y o f the NaOH t r e a t e d straw was s i g n i f i c a n t l y (P *~ 0.05) g r e a t e r than the NH^OH t r e a t e d straw. I t i s d i f f i c u l t to e x p l a i n why t h i s s i g n i f i c a n t d i f f e r e n c e i n c e l l u l o s e d i g e s t i o n o c c u r r e d . However, i t might be suggested t h a t the h i g h e r c e l l u l o s e d i g e s t i o n o f the NaOH t r e a t e d straw was most probably due to the f a c t t h a t d i f f e r e n t volumes of a l k a l i were used to t r e a t equal weights o f m a t e r i a l - 60 ml. of NaOH as a g a i n s t 24 ml. of NH^OH. The e f f e c t o f t h i s i s t h a t more uniform mixing of straw with NaOH was achieved and thus the r e a c t i o n would be more complete. Furthermore, l e s s complete chemical r e a c t i o n might be obtained with the NH^OH treatment due to the v o l a t i l i t y o f ammonia. S i m i l a r r e s u l t s as those f o r straw were ob t a i n e d with p o p l a r wood. However p o p l a r wood appeared to be more re s p o n s i v e to a l k a l i treatment than was o a t straw. The i n v i t r o c e l l u l o s e d i g e s t i o n o f the u n t r e a t e d wood was i n c r e a s e d s i g n i f i c a n t l y (P ^ - 0.01) from a mean value o f 16.4% to 71.4% wit h NaOH treatment and 57.6% with NH^OH treatment. S i m i l a r o b s e r v a t i o n s were made by Huffman (1970) i n h i s study o f the e f f e c t o f NaOH treatment on the i n v i t r o c e l l u l o s e d i g e s t i o n o f fou r wood types. 141 The e f f e c t o f n i t r o g e n source on the i n v i t r o c e l l u l o s e d i g e s t i o n of unt r e a t e d and a l k a l i (NaOH o r NH^OH) t r e a t e d straw and p o p l a r wood i s shown i n Table 22. Urea s o l u t i o n was omitted from the b a s a l medium used f o r the p r e p a r a t i o n o f the inoculum, i n order to e l i m i n a t e i t s e f f e c t on the other sources o f n i t r o g e n used as the supplement to the untr e a t e d and t r e a t e d m a t e r i a l . With the unt r e a t e d oat straw, the source o f n i t r o g e n had no s i g n i f i c a n t e f f e c t on the i n v i t r o c e l l u l o s e d i g e s t i o n . However, c e l l u l o s e d i g e s t i o n values o b t a i n e d when b i u r e t and u r i c a c i d were used as the n i t r o g e n source, were s l i g h t l y lower than when urea was used. NaOH or NH^OH treatment o f the straw s i g n i f i c a n t l y (P < 0.01) i n c r e a s e d c e l l u l o s e d i g e s t i o n , and d i g e s t i b i l i t y v a l u e s o b t a i n e d were comparable to those observed with the u s u a l medium, r e g a r d l e s s of n i t r o g e n source used. With the p o p l a r wood, supplementation o f the un t r e a t e d m a t e r i a l with n i t r o g e n from urea, b i u r e t or u r i c a c i d r e s u l t e d i n i n v i t r o c e l l u l o s e d i g e s t i o n values t h a t were not s i g n i f i -c a n t l y (P 0.05) d i f f e r e n t from one another and from the value obtained when the us u a l medium was used. A l k a l i t r e a t e d p o p l a r wood had s i m i l a r c e l l u l o s e d i g e s t i b i l i t y v a l u e s as those observed when the usual medium was used. However, there was a tendency f o r s l i g h t decreases i n the c e l l u l o s e d i g e s t i o n o f both u n t r e a t e d and a l k a l i t r e a t e d oat straw and 142 TABLE 2 2 THE EFFECT OF NITROGEN SOURCE ON THE IN VITRO CELLULOSE DIGESTION OF UNTREATED AND ALKALI TREATED OAT STRAW AND POPLAR WOOD Sample Chemical Cellulose content Nitrogen /ova. treatment source In vitro cellulose d i g e s t i b i l i t y (%) Oat straw None None None NaOH NaOH NaOH NH4OH NH.OH 4 NHjOH 40.06 40.06 40.06 34.77 34.77 34.77 39.04 39.04 39.04 Urea Biuret Uric acid Urea Biuret Uric Acid Urea Biuret Uric acid 40.5 38.4 37.8 77.9 69.6 71.3 63.1 60.3 60.7 Poplar wood None None None NaOH NaOH NaOH NH^ OH NH.OH 4 NH4OH 53.36 53.36 53.36 46.26 46.26 46; 26 52.55 52.55 52.55 Urea Biuret Uric acid Urea Biuret Uric acid Urea Biuret Uric acid 14.7 12.8 13.2 73.5 69.4 68.6 54.9 54.1 51.8 each value represents the mean of 3 determinations each value represents the mean of 4 determinations 143 p o p l a r wood when b i u r e t or u r i c a c i d was used as the n i t r o g e n source. I t i s d i f f i c u l t to suggest the a c t u a l reason f o r t h i s o b s e r v a t i o n , but i t can be p o s t u l a t e d t h a t the s o l u b i l i t y o f the n i t r o g e n compound used w i l l a f f e c t i t s u t i l i z a t i o n by the rumen microorganisms. N e v e r t h e l e s s , the data i n d i c a t e t h a t i n v i t r o c e l l u l o s e d i g e s t i o n of oat straw and p o p l a r wood was l i t t l e a f f e c t e d by the source of n i t r o g e n when urea, b i u r e t or u r i c a c i d was used as n i t r o g e n supplement. Data presented i n Table 23 shows the c e l l u l o s e content, the i n v i v o and i n v i t r o c e l l u l o s e d i g e s t i b i l i t y values f o r the r a t i o n s used i n the animal f e e d i n g t r i a l s I and I I I . C e l l u l o s e content of the r a t i o n s of t r i a l I ranged between 21.3 and 27.7%. The i n v i v o c e l l u l o s e d i g e s t i b i l i t y values showed t h a t r a t i o n 5 ( p o u l t r y l i t t e r supplemented) had a s i g n i f i c a n t l y (P -C 0.01) lower c e l l u l o s e d i g e s t i o n v a l u e . The s i g n i f i c a n t l y lower c e l l u l o s e d i g e s t i b i l i t y observed i n t h i s r a t i o n c o u l d be a t t r i b u t e d to the low d i g e s t i b i l i t y o f crude f i b e r of wood which was used as the base m a t e r i a l f o r the l i t t e r (Bhattacharya and Fontenot, 1966; L e i b h o l z , 1969). The i n v i t r o c e l l u l o s e d i g e s t i b i l i t y values f o r these r a t i o n s were s i g n i f i c a n t l y (P < 0.01) h i g h e r than the i n v i v o v a l u e s . The reason f o r t h i s i s most l i k e l y due to the g r e a t e r c o n t r o l and p r e c i s i o n which c o u l d be e x e r c i s e d over the v a r i o u s c o n d i t i o n s of the i n v i t r o systems as compared with s t u d i e s 144 TABLE 23 IN VIVO AND IN VITRO CELLULOSE DIGESTION OF THE RATIONS FED TO feeding t r i a l T r i a l I ration 1 2 3 4 LAMBS IN TRIALS I AND I I I Description of Cellulose ration content (%) control (Soybean meal) urea supplement biuret " poultry droppings 5 poultry l i t t e r 25.8 27.7 26.1 21.3 22.1 di g e s t i b i l i t y d i g e s t i b i l i t y .a In vivo cellulose iti : (%)' 49.1 45.9 48.1 46.3 24.3 In v i t r o cellulose 3 ] (%) 58.2 56.7 57.4 52.1 32.8 TriaP III ration 1 grass hay 16.35 2 oat straw 21.66 3 extrduded wood 20.14 38.1 37.5 13.7 62.1 53.6 21.5 each vlaue represents the mean of 3 lambs determinations each value represents the mean of 4 determinations. 145 d e a l i n g with l i v e animals. Another p o s s i b l e reason might be due t o the d i f f e r e n c e s i n s u b s t r a t e p a r t i c l e s used i n the i n v i v o and i n v i t r o systems. The use of f i n e r p a r t i c l e s f o r the i n v i t r o would no doubt r e s u l t i n g r e a t e r s u r f a c e area exposed to the a c t i o n o f microorganisms. A c o r r e l a t i o n of 0.985 was observed between the i n v i v o and the i n v i t r o c e l l u l o s e d i g e s t i o n o f the t r i a l I r a t i o n s . C e l l u l o s e content of the r a t i o n s used i n the f e e d i n g t r i a l I I I v a r i e d between 16.35 and 21.66%. The i n v i v o c e l l u l o s e d i g e s t i b i l i t y value (13.7%) o f r a t i o n 3, i n which extruded wood was used as the roughage, was s i g n i f i c a n t l y (P *L 0.01) lower than those f o r r a t i o n s 1 and 2 i n which grass hay and oat straw were used as the roughage source r e s p e c t i v e l y . The s i g n i f i c a n t l y lower c e l l u l o s e d i g e s t i b i l i t y of the r a t i o n i n which extruded wood was used as the roughage source might suggest t h a t the f u l l p o t e n t i a l of wood and woody by-products i s not r e a l i z e d u nless the m a t e r i a l i s s u b j e c t e d to chemical treatment. T h i s statement might be j u s t i f i e d by the data presented by K i t t s e t a l . (1969) i n t h e i r study of the e f f e c t of the i n c o r p o r a t i o n of a l d e r sawdust i n beef c a t t l e r a t i o n s . These workers r e p o r t e d a s m a l l degree o f a c t u a l u t i l i z a t i o n of the a l d e r sawdust by the animals as i n d i c a t e d by the per cent dry matter d i g e s t i b i l i t y o f the r a t i o n s c o n t a i n i n g 13.3% sawdust. However, they suggested t h a t the b e n e f i c i a l e f f e c t s 146 of i n c o r p o r a t i o n of sawdust i n the r a t i o n o f ruminants are p o s s i b l y the s t i m u l a t i o n of rumination and support o f a more s u s t a i n e d f e r m e n t a t i o n i n the rumen thereby c a u s i n g a more e f f i c i e n t u t i l i z a t i o n o f ot h e r d i g e s t i b l e n u t r i e n t s o f the r a t i o n . The i n v i t r o c e l l u l o s e d i g e s t i b i l i t y values f o r the 3 r a t i o n s used i n f e e d i n g t r i a l I I I were s i g n i f i c a n t l y (P 0.01) h i g h e r than the i n v i v o v a l u e s . C e l l u l o s e d i g e s t i b i l i t y values between r a t i o n s were s i g n i f i c a n t l y d i f f e r e n t , with the grass hay e x h i b i t i n g the h i g h e s t i n v i t r o c e l l u l o s e d i g e s t i b i l i t y f o l l o w e d by oat straw and extruded wood i n descending o r d e r . A h i g h l y s i g n i f i c a n t p o s i t i v e c o r r e l a t i o n (r=0.974) was observed between the i n v i v o and i n v i t r o c e l l u l o s e d i g e s t i b i l i t i e s . 147 V SUMMARY AND CONCLUSIONS The u t i l i z a t i o n of three n i t r o g e n sources, urea, b i u r e t and p o u l t r y wastes, t o r e p l a c e a p o r t i o n of a c o n v e n t i o n a l p r o t e i n supplement (soybean meal) i n hig h roughage r a t i o n s f o r sheep was i n v e s t i g a t e d . Chemical a n a l y s i s showed t h a t p o u l t r y wastes are q u i t e v a r i a b l e i n composition. Greater v a r i a t i o n e x i s t e d i n the chemical composition o f p o u l t r y l i t t e r (bedding m a t e r i a l p l u s droppings) than i n t h a t o f cage droppings alone. I t i s p o s s i b l e t h a t the bedding m a t e r i a l i n the l i t t e r must have been r e s p o n s i b l e f o r the d i l u t i o n o f chemical components i n t h i s m a t e r i a l . P o u l t r y l i t t e r c o n tained 21.5 to 30.4% p r o t e i n e q u i v a l e n t w h i l e the cage droppings co n t a i n e d 26.3 to 35.4% p r o t e i n e q u i v a l e n t . Approximately 33% of the p o u l t r y l i t t e r n i t r o g e n and 40% o f the p o u l t r y droppings n i t r o g e n was i n the form o f u r i c a c i d n i t r o g e n . The t o t a l n i t r o g e n o r the u r i c a c i d n i t r o g e n of p o u l t r y droppings o r l i t t e r was not s i g n i f i c a n t l y a f f e c t e d by auto-c l a v i n g o r steaming. These heat treatments however were s u f f i c i e n t t o de s t r o y a l l the m i c r o f l o r a i n the wastes. No s i g n i f i c a n t d i f f e r e n c e s were observed i n the d i g e s t i b i l i t y c o e f f i c i e n t s o f dry matter, crude p r o t e i n , crude f i b e r or gross energy when approximately 50% o f the soybean meal (SBM) n i t r o g e n of the c o n t r o l r a t i o n was r e p l a c e d by urea, b i u r e t or p o u l t r y droppings i n the r a t i o n s o f f a t t e n i n g lambs f e d i n the u n p e l l e t e d 148 form. However, s i m i l a r replacement of 50% o f the SBM n i t r o g e n of the c o n t r o l r a t i o n by p o u l t r y l i t t e r r e s u l t e d i n s i g n i f i c a n t l y lower n u t r i e n t d i g e s t i b i l i t y c o e f f i c i e n t s o f t h i s r a t i o n when compared with the c o n t r o l . I t appeared t h a t the presence o f bedding m a t e r i a l as i n the l i t t e r hampered the a v a i l a b i l i t y of n i t r o g e n from t h i s source. A s i g n i f i c a n t l y lower v o l u n t a r y i n t a k e was observed i n animals fed the urea supplemented r a t i o n when compared wi t h the animals fed the soybean meal c o n t a i n i n g r a t i o n . T h i s apparent d e p r e s s i o n i n i n t a k e c o u l d not however be e x p l a i n e d o n l y by the e f f e c t o f reduced p a l a t a b i l i t y . The data o b t a i n e d i n d i c a t e d t h a t p a l a t a b i l i t y probably p l a y e d o n l y a minor r o l e i n determining v o l u n t a r y i n t a k e o f the t e s t r a t i o n s as evidenced by the presence of oth e r supposedly u n p a l a t a b l e substances ( b i u r e t , p o u l t r y wastes and straw) i n the r a t i o n s . When the r a t i o n s were o f f e r e d i n the p e l l e t e d form, the d i f f e r e n c e s i n n u t r i e n t d i g e s t i b i l i t y c o e f f i c i e n t s p a r t i c u l a r l y between the c o n t r o l and the l i t t e r supplemented r a t i o n s were no l o n g e r s i g n i f i c a n t . P e l l e t i n g was a l s o found t o i n c r e a s e the v o l u n t a r y consumption of the r a t i o n s i r r e s p e c t i v e o f the source o f n i t r o g e n supplementation. Although a l l animals were i n p o s i t i v e n i t r o g e n balance, those f e d the urea and p o u l t r y l i t t e r supplemented r a t i o n s had s i g n i f i c a n t l y lower n i t r o g e n r e t e n t i o n than those f e d soybean meal, b i u r e t o r p o u l t r y droppings supplemented r a t i o n s . This 149 o b s e r v a t i o n was a l s o r e f l e c t e d i n the lower body weight gains and feed e f f i c i e n c y o f the animals f ed the urea and l i t t e r c o n t a i n i n g d i e t s . Reduced feed i n t a k e and high u r i n a r y n i t r o g e n l o s s o f animals f ed the urea supplemented r a t i o n s and the hig h f e c a l n i t r o g e n l o s s o f animals f ed the l i t t e r supplemented r a t i o n s might have been r e s p o n s i b l e f o r the lower n i t r o g e n r e t e n t i o n observed i n these animals. When p o u l t r y droppings were i n c o r p o r a t e d i n t o high-roughage r a t i o n s to supply approximately 18.7, 50.2 and 64.2% of the t o t a l n i t r o g e n i n r a t i o n s i n which grass hay ( c o n t r o l ) , oat straw and extruded wood were used as the roughage sources r e s p e c t i v e l y , no s i g n i f i c a n t d i f f e r e n c e s were observed i n the v o l u n t a r y consumption o f the r a t i o n s . This i n d i c a t e d t h a t , as a source o f NPN, p o u l t r y droppings had an e q u a l l y e f f e c t i v e replacement value at a l l the three l e v e l s s t u d i e d . A l k a l i (NaOH o r NH^OH) treatment o f oat straw and p o p l a r wood s i g n i f i c a n t l y i n c r e a s e c e l l u l o s e d i g e s t i b i l i t y i n v i t r o . C e l l u l o s e d i g e s t i b i l i t y was s l i g h t l y , but no s i g n i f i c a n t l y , a f f e c t e d by the type of n i t r o g e n source used i n the in. v i t r o b a s a l medium. The maximum c e l l u l o s e d i g e s t i b i l i t y , i n v i t r o was o b t a i n e d with the urea n i t r o g e n , f o l l o w e d by b i u r e t and u r i c a c i d n i t r o g e n i n descending o r d e r . 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( I n c r e a s i n g the n u t r i t i v e value of straw and a t the same time adding d i g e s t i b l e n i t r o g e n ) . Nutr. Abs. Rev. 30:252 ( A b s t r . ) . 

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