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Biological availability of minerals from organic and inorganic sources for the chick Aw-yong, Lai Mon 1980

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BIOLOGICAL AVAILABILITY OF MINERALS FROM ORGANIC AND INORGANIC SOURCES FOR THE CHICK?/ M by v ^ / L a i ' M o n Aw-Yong B.Sc. (Hons.), M c G i l l U n i v e r s i t y , 1972 ,Sc., U n i v e r s i t y of B r i t i s h Columbia, 1974 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n THE DEPARTMENT OF POULTRY 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 (6) L a i Mon Aw-Yong J u l y 22, 1980 In p r e s e n t i n g t h i s t h e s i s in p a r t i a l f u l f i l m e n t o f the r e q u i r e m e n t s f o r an advanced degree at the U n i v e r s i t y o f B r i t i s h Co lumb ia , I a g ree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s tudy . I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y purposes may be g r a n t e d by the Head o f my Department or by h i s r e p r e s e n t a t i v e s . It i s u n d e r s t o o d that c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i thout my w r i t t e n p e r m i s s i o n . Department o f The U n i v e r s i t y o f B r i t i s h Co lumbia .2075 Wesbrook P l a c e . Vancouver, Canada V6T 1W5 Date . '9&* i i ABSTRACT A v a i l a b i l i t y of s i x minerals (Ca, P, Mg, Mn, Zn, and Cu) i n commercial wheat, t r i t i c a l e , corn and b a r l e y samples was estimated wit h three-week o l d growing c h i c k s . E f f e c t s of soybean meal and wheat fed at d i f f e r e n t d i e t a r y c oncentration on a v a i l a b i l i t y of these minerals were s t u d i e d . The a v a i l a b i l i t y of minerals from s p e c i f i c i n o r g a n i c sources were a l s o evaluated. A v a i l a b i l i t y value was determined by a balance procedure c o r r e c t e d f o r endogenous minerals. Results i n d i c a t e d t h a t the a v a i l a b i l i t y o f calcium, phosphorus, magnesium, manganese, z i n c , and copper was 71.0, 67.4, 53.5, 48.4, 49.6 and 78.5%, r e s p e c t i v e l y f o r the wheat and t r i t i c a l e samples. Copper a v a i l a b i l i t y was the highest i n corn (87.2%), followed by calcium (70.0%), phosphorus (60.9%), manganese (60.0%), z i n c (57.5%) and magnesium (51.0%). The a v a i l a b i l i t y of Ca, P, Mg, Mn, Zn and Cu i n b a r l e y was 68.9, 68.8, 54.9, 54.9, 49.1 and 77.5%, r e s p e c t i v e l y . S i g n i f i c a n t v a r i a t i o n (P < 0.05) e x i s t s among the c e r e a l grains t e s t e d . Results i n d i c a t e t h a t mineral a v a i l a b i l i t y i s i n f l u e n c e d by the o r i g i n of the samples obtained. A v a i l a b i l i t y of minerals i s a f f e c t e d by the c o n c e n t r a t i o n o f i n g r e d i e n t s i n the t e s t d i e t . 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 a v a i l a b i l i t y f o r a l l the minerals t e s t e d when soybean meal and wheat were su p p l i e d i n the t e s t mixture at f i v e l e v e l s . Calcium and phosphorus from calcium phosphate were h i g h l y a v a i l a b l e to growing c h i c k s . However, the a v a i l a b i l i t y decreased i i i r a p i d l y when the mineral l e v e l was i n excess of the d i e t a r y requirement. S i x l e v e l s of magnesium (150, 300, 450, 600, 750, and 900 ppm) from magnesium carbonate were evaluated. Results showed that magnesium was h i g h l y a v a i l a b l e to growing c h i c k s . The values ranged from 82.3 to 61.9%. Excess amounts of magnesium i n the d i e t tended t o reduce the a v a i l a b i l i t y value. Various l e v e l s (25, 50, 75, 100 and 125 ppm) of manganese from manganese s u l f a t e were t e s t e d . Manganese appeared to be po o r l y a v a i l a b l e f o r the l e v e l s t e s t e d . Zinc a v a i l a b i l i t y from z i n c oxide was h i g h l y a v a i l a b l e f o r the ch i c k . The a v a i l a b i l i t y values/ranged from 84.4 to 93% f o r a l l the d i e t s c o n t a i n i n g 25 to 125 ppm of z i n c . The a v a i l a b i l i t y of copper from copper s u l f a t e was moderate to high (72.1-80.2%) f o r the low d i e t a r y copper concentrations (2-32 ppm). However, the copper a v a i l a b i l i t y values (61.8-63.6%) tended to decrease at higher d i e t a r y c o n c e n t r a t i o n (50-250 ppm). XV TABLE OF CONTENTS Page ABSTRACT . 1 1 TABLE OF CONTENTS i v LIST OF TABLES v i i LIST OF APPENDIX TABLES x ACKNOWLEDGEMENTS x l INTRODUCTION 1 LITERATURE REVIEW 4 I. Methods and Techniques f o r Est i m a t i n g M i n e r a l A v a i l a b i l i t y 4 1. Chemical Balance Method 4 a. Apparent d i g e s t i b i l i t y 4 b. True d i g e s t i b i l i t y 5 c. Carcass a n a l y s i s technique 5 d. Radioisotope techniques 6 2. B i o l o g i c a l Assay Techniques 8 a. Bone ash method 9 b. Toe ash method 10 c. Body weight method H d. Other miscellaneous methods 11 3. In Vitro Assay Procedure H I I . A v a i l a b i l i t y of Minerals i n Feed Ingredients from Vegetable .Sources I 2 I I I . A v a i l a b i l i t y o f Min e r a l s i n Inorganic Sources f o r Livest o c k 15 1. Calcium 1 6 2. Phosphate 1 7 3. Magnesium 19 4. Manganese, Zinc and Copper 20 IV. Factors A f f e c t i n g M i n e r a l A v a i l a b i l i t y 21 1. P h y t i c A c i d 22 2. F i b e r 23 3. O x a l i c A c i d 24 V Page 4. Ethylene-Diamine-Tetraaccate (EDTS) 25 5. P r o t e i n and Amino Acids 26 6. Lactose. . . , 27 7. Vitamins 28 8. A n t i b i o t i c s 29 9. Species D i f f e r e n c e 29 10. M i n e r a l I n t e r a c t i o n 30 11. Feed Processing 3 2 12. Endocrine Influence 3 3 13. Miscellaneous Factors 33 MATERIALS AND METHODS 3 5 T r i a l 1: M i n e r a l A v a i l a b i l i t y from Wheat and T r i t i c a l e 3 6 T r i a l 2: M i n e r a l A v a i l a b i l i t y from Corn 4 2 T r i a l 3: M i n e r a l A v a i l a b i l i t y from Barley 4 2 T r i a l 4: A v a i l a b i l i t y of M i n e r a l s i n Diets Containing D i f f e r e n t Levels of Soybean Meal 47 T r i a l 5: A v a i l a b i l i t y of M i n e r a l s i n D i e t s Containing D i f f e r e n t Levels of Wheat 4 7 T r i a l 6; A v a i l a b i l i t y o f Calcium and Phosphorus from Calcium Phosphate (Dibasic) 52 T r i a l 7: A v a i l a b i l i t y o f Magnesium from Magnesium Carbonate 54 T r i a l 8: A v a i l a b i l i t y of Manganese from Manganese S u l f a t e . . . . 56 T r i a l 9: . A v a i l a b i t i t y o f Zinc from Zinc Oxide 56 T r i a l s 10 and 11: A v a i l a b i l i t y o f Copper from Copper S u l f a t e , 5 8 RESULTS AND DISCUSSION 62 T r i a l 1: 6 2 (a) Calcium 6 4 (b) Phosphorus 65 (c) Magnesium 67 (d) Manganese..., 68 (e) Zinc , 69 (f) Copper 69 , T r i a l 2 7 0 (a) Calcium 7 2 (b) Phosphorus.., 7 3 (c) Magnesium 7 4 (d) Manganese • 7 5 (e) '.': Zinc 7 6 ( f ) Copper. 7 7 T r i a l 3: 7 7 (a) Calcium, . . . , , 7 ^ (b) Phosphorus 7 ^ (c) Magnesium, 8 ^ (d) Manganese, . 80 (e) Zinc , , 81 (f) Copper 81 Page General D i s c u s s i o n of T r i a l s 1, 2 and 3 8 2 T r i a l 4. , 87 (a) Calcium. 89 (b) Phosphorus , 89 (c) Magnesium, 90 (d) Manganese. 90 (e) Zinc 9 1 ( f ) Copper , 9 1 T r i a l 5; , 9 2 (a) Calcium , , 9 2 (b) Phosphorus • • • • 9 ^ (c) Magnesium. 9 ^ (d) Manganese. , , - 9 ^ (ej. Zinc 9 6 Q7 (f) Copper , T r i a l 6 9 8 (a) Calcium , 9 8 (b) Phosphorus , 101 T r i a l 7 , 1 0 2 T r i a l 8 1 ° 4 T r i a l 9 , . .. , 1 0 7 T r i a l s 10 and 11.. , 107 SUMMARY AND CONCLUSION 113 REFERENCE l i 6 APPENDIX TABLES. • 1 4 2 v i i LIST OF TABLES TABLE PAGE 1 Composition o f S y n t h e t i c Diet used Throughout the Experimental T r i a l s 38 2 Chemical A n a l y s i s of the Eleven Wheat and One T r i t i c a l e Samples (dry matter ba s i s ) 40 3 M i n e r a l Content o f Eleven Wheat and a T r i t i c a l e Sample (dry matter ba s i s ) 41 4 Chemical A n a l y s i s o f the Ten Corn Samples (dry matter b a s i s ) 43 5 M i n e r a l Content of Ten Corn Samples (dry matter b a s i s ) 44 6 Chemical A n a l y s i s of Three Bar l e y Samples from D i f f e r e n t Sources (dry matter ba s i s ) 45 7 The M i n e r a l Content of Three Bar l e y Samples from D i f f e r e n t Sources (dry matter ba s i s ) 46 8 Proximate A n a l y s i s of Diets i n T r i a l • 4 (dry matter b a s i s ) 48 9 M i n e r a l Content o f Diets i n ' T r i a l 4 (dry matter b a s i s ) 49 10 Proximate A n a l y s i s of Diets ""in T r i a l 5 (dry matter ba s i s ) 50 11 Mi n e r a l Content of Diets i n T r i a l 5. (dry matter b a s i s ) 51 v i i i TABLE PAGE 12 O u t l i n e o f D i e t a r y Treatments i n T r i a l 6 53 13 O u t l i n e o f D i e t a r y Treatments i n T r i a l 7 55 14 O u t l i n e of D i e t a r y Treatments i n T r i a l 8 57 15 O u t l i n e o f D i e t a r y Treatments i n T r i a l 9 59 16 O u t l i n e o f D i e t a r y Treatments i n T r i a l 10 60 17 O u t l i n e o f D i e t a r y Treatments i n T r i a l 11 61 18 Percent A v a i l a b i l i t y of M i n e r a l s i n Wheat and T r i t i c a l e Samples 63 19 A v a i l a b i l i t y of M i n e r a l s from Ten Corn Samples 71 20 A v a i l a b i l i t y o f M i n e r a l s i n Three Bar l e y Samples C o l l e c t e d from D i f f e r e n t Places 78 21 Summary of M i n e r a l A v a i l a b i l i t y ftom Wheat, Com and B a r l e y 83 22 A v a i l a b i l i t y o f M i n e r a l s i n Die t s Containing D i f f e r e n t Levels of Soybean Meal 88 23 A v a i l a b i l i t y o f M i n e r a l s i n Die t s Containing D i f f e r e n t Levels of Wheat • 94 24 A v a i l a b i l i t y o f Calcium and Phosphorus from Calcium Phosphate i n the Growing Chicks 99 25 * A v a i l a b i l i t y o f Magnesium from Magnesium Carbonate i n the Growing Chicks •' .....103 26 A v a i l a b i l i t y o f Manganese from Manganese S u l f a t e i n the Growing Chicks 106 27 A v a i l a b i l i t y of Zinc from Zinc Oxide i n the Growing i x TABLE PAGE 28 A v a i l a b i l i t y of Copper from Low D i e t a r y Levels of Copper' S u l f a t e i n the Growing Chicks 110 29 A v a i l a b i l i t y of Copper from High' D i e t a r y Levels of Copper S u l f a t e i n the Growing Chicks I l l X LIST OF APPENDIX TABLES  APPENDIX PAGE 1 A n a l y s i s o f Variance f o r M i n e r a l A v a i l a b i l i t y from Wheat and T r i t i c a l e 142 2 A n a l y s i s o f Variance f o r M i n e r a l A v a i l a b i l i t y from Corn 143 3 A n a l y s i s of Variance f o r M i n e r a l A v a i l a b i l i t y from Barley 144 4 A n a l y s i s of Variance f o r M i n e r a l . A v a i l a b i l i t y i n D i e t s Containing D i f f e r e n t Levels of Soybean Meal-. 145 5 A n a l y s i s of Variance f o r M i n e r a l A v a i l a b i l i t y i n D i e t s Containing D i f f e r e n t Levels of Wheat 146 6 A n a l y s i s o f Variance f o r the A v a i l a b i l i t y of Calcium. and Phosphorus from Calcium Phosphate 147 7 A n a l y s i s of Variance f o r the A v a i l a b i l i t y of Magnesium from Magnesium Carbonate 148 8 A n a l y s i s o f Variance f o r the A v a i l a b i l i t y from Manganese S u l f a t e , Zinc Oxide and Copper S u l f a t e . . . 149 x i ACKNOWLEDGEMENT The author wishes to express h i s s i n c e r e g r a t i t u d e to h i s research s u p e r v i s o r , Dr. D. B. Bragg, Professor and Head of the P o u l t r y Science Department, f o r h i s i n v a l u a b l e guidance, constant encouragement and c o n s t r u c t i v e c r i t i s i c m throughout the course of t h i s study and the p r e p a r a t i o n of the manuscript. Sincere a p p r e c i a t i o n i s a l s o extended to the members of my t h e s i s committee: Profess o r B. E. March, Department of P o u l t r y Science; Dr. Fitzsimmons, A s s o c i a t e P r o f e s s o r , Department of P o u l t r y Science; and Dr. R. M. Beames, As s o c i a t e P r o f e s s o r , Department of Animal Science f o r t h e i r advice and encouragement during the p r e p a r a t i o n and w r i t i n g of t h i s t h e s i s . The t e c h n i c a l a s s i s t a n c e given by Mr. R. Soong, Mr. M. Hudson and other l a b o r a t o r y and farm personnel was g r e a t l y appreciated. The f i n a n c i a l support by Na t i o n a l Research C o u n c i l , Canada f o r t h i s study i s a l s o g r a t e f u l l y acknowledged. I t i s the author's wish to dedicate t h i s t h e s i s to h i s w i f e , Boh-Sing and h i s parents, Mr. and Mrs. Y. Aw-Yong. 1 INTRODUCTION The concept of n u t r i e n t a v a i l a b i l i t y o f f e e d s t u f f has become very important f o r the modern l i v e s t o c k and feed i n d u s t r i e s . I t i s a current p r a c t i c e to formulate feed f o r l i v e s t o c k based on the content of v a r i o u s n u t r i e n t s i n the feed i n g r e d i e n t s . The n u t r i t i v e value of a f e e d s t u f f r i s -determined. by -the content.of the a v a i l a b l e -nutrients i n the feed. In the study of n u t r i e n t metabolism, i t i s g e n e r a l l y recognized that the t o t a l content of a n u t r i e n t i n a p a r t i c u l a r feed-s t u f f used i n a complete d i e t has l i t t l e s i g n i f i c a n c e unless i t i s q u a l i f i e d by a f a c t o r i n d i c a t i n g the b i o l o g i c a l a v a i l a b i l i t y of the n u t r i e n t s to animals. For an example, amino a c i d or mineral content i n the.feedstuff does not i n d i c a t e the degree i n which the n u t r i e n t i s u t i l i z e d when consumed by an animal. No element i s completely absorbed and u t i l i z e d . At the best, part of the element i s l o s t i n normal d i g e s t i v e and metabolic processes. Recent research has i n d i c a t e d that there i s a s i g n i f i c a n t d i f f e r e n c e between t o t a l content of n u t r i e n t s and q u a n t i t i e s a v a i l a b l e . P u b l i c a t i o n s by the Nutrition;CoMiitfeee of the .National ' Research Council on Nutrient'.Requirements- f o r L i v e s t o c k have been determined with the d i e t formulated by t o t a l n u t r i e n t content on the assumption that the n u t r i e n t i n f e e d s t u f f i s h i g h l y a v a i l a b l e . More p r e c i s e recommendations have not been p o s s i b l e due to the shortage of n u t r i e n t a v a i l a b i l i t y i n f o r m a t i o n f o r most feed i n g r e d i e n t s . P r e c i s e a v a i l a b i l i t y measurements f o r feed i n g r e d i e n t s become 2 i n c r e a s i n g l y urgent f o r economical d i e t a r y f o r m u l a t i o n due to soari n g feed costs at present and inS-the foreseeable f u t u r e . I t i s th e r e f o r e necessary to evaluate how much of the t o t a l n u t r i e n t content i s a c t u a l l y a v a i l a b l e t o animals r e l a t i v e t o meeting requirements f o r maintenance., and productive f u n c t i o n (growth and r e p r o d u c t i o n ) . Cereal g r a i n s (wheat, corn and barley) are the most common feed grains u t i l i z e d i n the l i v e s t o c k i n d u s t r y . These c e r e a l s are used mainly as energy and p r o t e i n sources f o r animal production. However, the mineral c o n t r i b u t i o n o f these c e r e a l s has always been overlooked during feed f o r m u l a t i o n . Many minerals i n c e r e a l g r a i n s are present i n low concentrations. Thus, there has been ' l i t t l e " ' i n t e r e s t • i n s t u d i e s on mi n e r a l a v a i l a b i l i t y of these f e e d s t u f f s . Although s e v e r a l s t u d i e s have reported low a v a i l a b i l i t y o f phosphorus i n vegetables to monogastric animals, c o n f l i c t i n g f i n d i n g s have been reported i n the l i t e r a t u r e . The discrepancy may be due to the various methods used f o r a v a i l a b i l i t y e s t i m a t i o n i n d i f f e r e n t l a b o r a t o r i e s as w e l l as v a r i a b i l i t y among samples. Most st u d i e s on mineral a v a i l a b i l i t y were determined on r e l a t i v e b i o a v a i l a b i l i t y assuming 100% mineral a v a i l a b l e i n an i n o r g a n i c s a l t i n s t e a d o f tr u e a v a i l a b i l i t y measurements. The breakthrough o f the t r u e a v a i l a b i l i t y e s t i m a t i o n method by Nwokolo et at. (1976) has st i m u l a t e d enthusiasm f o r studying other f e e d s t u f f s . In a d d i t i o n , increasing- feed costs,.....-• have, also : ;encouraged m i n e r a l n u t r i t i o n a n d - a v a i l a b i l i t y ^studies in-general f e e d s t u f f s . 3 The o b j e c t i v e s of t h i s study were to evaluate the a v a i l a b i l i t y of minerals (calcium, phosphorus, magnesium, manganese, z i n c and copper) from c e r e a l grain's (wheat, corn, b a r l e y and t r i t i c a l e ) and ino r g a n i c mineral s a l t s . Comparison was a l s o made on v a r i a t i o n - i n a v a i l a b i l i t y i t * d i f f e r e n t shipments o f gra i n s from commercial sources. The e f f e c t of d i f f e r e n t l e v e l s of f e e d s t u f f i n the t e s t mixture on a v a i l a b i l i t y was a l s o s t u d i e d . I t has been assumed i n most cases that i n o r g a n i c minerals are t o t a l l y a v a i l a b l e to the animal when conducting the r e l a t i v e a v a i l a b i l i t y study o f the f e e d s t u f f s . Very l i m i t e d i n f o r m a t i o n i s a v a i l a b l e to demonstrate the true a v a i l a b i l i t y o f i n o r g a n i c mineral sources to animals. Therefore, the f i n a l phase of t h i s study was focused on the t r u e a v a i l a b i l i t y of minerals from i n o r g a n i c sources and the e f f e c t of i n o r g a n i c mineral l e v e l s (Ca, P, Mg, Mn, Zn and Cu) on a v a i l a b i l i t y from v a r i o u s mineral s a l t s . 4 LITERATURE REVIEW I. Methods and Techniques for Estimating Mineral A v a i l a b i l i t y Methods commonly employed to study the a v a i l a b i l i t y or u t i l i z a t i o n of mineral f o r various species of animals, may be d i v i d e d i n t o three c a t e g o r i e s : (1) Chemical Balance Method; (2) B i o l o g i c a l Assay Procedures; and (3) In-vitro Assay Procedures. (1) Chemical Balance Method (a) Apparent digestibility According to M i t c h e l l (1964), apparent d i g e s t i b i l i t y . i s one of the most common methods used i n determining a v a i l a b i l i t y . This method i s simple, r e q u i r e s only a knowledge of the intake and t o t a l f e c a l e x c r e t i o n o f the t e s t minerals. However, t h i s i s an : u n s a t i s f a c t o r y a n e t h o d because i t does not' take metabolic fecal.:-V; * and endogenous u r i n a r y losses i n t o account. As a consequence, there i s a tendency to underestimate u t i l i z a t i o n of t e s t minerals. Ammerman et at.' (1957)^employed the'procedure to-study . ' " • the b i o - a v a i l a b i l i t y of various i n o r g a n i c phosphate sources.: f o r sheep. Rock and Campling (1962) pointed out that most in f o r m a t i o n on u t i l i z a t i o n i n ruminants i s c a l c u l a t e d on t h i s b a s i s . Calcium u t i l i z a t i o n i s a l s o commonly estimated by t h i s method. I t i s obvious that "the- balance technique u s i n g only- apparent ; 3 i : g e s t i b i r i f y ; " r e s U l t s are not i n d i c a t i v e o f the a v a i l a b i l i t y of minerals to l i v e s t o c k . M o d i f i c a t i o n of the method i s needed to ob t a i n the true 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 of mineral f o r animals. 5 (b) True digestibility The a v a i l a b i l i t y o f mineral estimated by tr u e d i g e s t i b i l i t y account f o r the metabolic f e c a l and:endogenous mineral .loss which' i s not of feed o r i g i n present i n the f e c a l and u r i n a r y e x c r e t i o n . . Although the estimate of a v a i l a b i l i t y f o r mineral by t h i s method i s f a r more accurate, the procedure employed to estimate the endogenous l o s s of f e c a l and u r i n a r y mineral i s u s u a l l y tedious and laborous. Nwokolo et al. (1976), r e c e n t l y developed a method to estimate endogenous mineral e x c r e t i o n i n .the*.chick. .";Th'e '-procedure i n v o l v e s the use of p u r i f i e d mineral f r e e d i e t s which are formulated so as to exclude minerals being t e s t e d . The endogenous mineral e x c r e t i o n i s determined w i t h c h i c k s fed the p u r i f i e d d i e t . The advantage of t h i s procedure i s the short p e r i o d o f time r e q u i r e d f o r the whole experiment, so that the d e l i c a t e mineral e q u i l i b r i u m of the animals i s not d i s t u r b e d s u b s t a n t i a l l y . As a r e s u l t , a more r e a l i s t i c estimate o f mineral a v a i l a b i l i t y i s obtained. (c) Carcass analysis technique Fincke and Sherman (1935) were the f i r s t to determine calcium r e t e n t i o n of the animal by carcass a n a l y s i s . The technique i n v o l v e s the use of l i t t e r mates, some of which are slaughtered at the beginning of the experiment to determine the content of the t e s t m i n e r a l . The other members o f the l i t t e r are fed a c o n t r o l l e d d i e t i n which the t e s t i n g r e d i e n t i s the only source of the mineral under study. Amount of feed i n t a k e i s recorded during 6 the experimental-.period' so that the t o t a l mineral i n t a k e can be c a l c u l a t e d . The t e s t animals are slaughtered when the experiment i s terminated. The animals are ashed and mineral content i s determined. The a v a i l a b i l i t y can be estimated from the mineral r e t a i n e d expressed as a f r a c t i o n of mineral i n t a k e . The carcass a n a l y s i s method apparently gives reasonable estimates o n . a v a i l a b i l i t y . Armstrong and Thomas (1952). observed no s i g n i f i c a n t d i f f e r e n c e s between calcium a v a i l a b i l i t y r e s u l t s obtained by other methods compared to the carcass a n a l y s i s method. The l i m i t a t i o n of the method i s thatf i t i s l a b o r i o u s p a r t i c u l a r l y when dealing-'with • l a r g e •  animals. Homogenous carcass samples must be taken f o r the a n a l y s i s . (d) Radioisotope technique Radioisotopes have been employed to estimate mineral a v a i l a b i l i t y f o r a number of years. Two techniques have commonly been used, isotope d i l u t i o n technique and comparative balance technique w i t h r a d i o i s o t o p e . Isotope d i l u t i o n technique i n v o l v e s a s i n g l e i n j e c t i o n i n t r a v e n o u s l y (Hansard et at., 1952; 1954), i n t r a m u s c u l a r l y (Evans et al., 197.9), or m u l t i p l e doses of r a d i o i s o t o p e of the t e s t element (Visek et al., 1953). I f there i s no endogenous e x c r e t i o n of m i n e r a l , the s p e c i f i c a c t i v i t i e s of the isotopes i n the feces and plasma should be i d e n t i c a l at e q u i l i b r i u m . Therefore, the d i l u t i o n of the t o t a l element i n the feces by endogenous e x c r e t i o n can be measured by d i f f e r e n c e i n the plasma and f e c a l s p e c i f i c a c t i v i t i e s . 7 The comparative balance technique i n v o l v e s p a i r s of animals. One animal, i s dosed o r a l l y while the other i s i n j e c t e d i n t r a v e n o u s l y w i t h a r a d i o i s o t o p e of the t e s t element. I t i s assumed that the element from d i e t a r y sources becomes completely l a b e l l e d by the o r a l l y administered r a d i o i s o t o p e element. Endogenous e x c r e t i o n i s estimated from an i n t r a v e n o u s l y i n j e c t e d animal. . This procedure was modified by Aubert et at. (1963) who proposed the use of two d i f f e r e n t isotopes w i t h the same animal. This e l i m i n a t e s the use of p a i r e d animals. The main assumption i n the comparative balance procedure i s based on the d i e t a r y source becoming f u l l y l a b e l l e d by the oral!.dose of r a d i o i s o t o p e . This assumption was questioned by s e v e r a l researchers (Tillman and Brethone, 1958; F i e l d , 1961). The above assumption i s el i m i n a t e d when the d i e t a r y source i s p r e - l a b e l l e d as c a r r i e d out by Ammerman et at. (1963), i n which the u n i f o r m i t y of l a b e l l i n g was confirmed. Guenter and S e l l (1974) have proposed a method to determine the " t r u e " a v a i l a b i l i t y of mineral w i t h a r a d i o i s o t o p e . The procedure i n v o l v e s combining the comparative balance and isotope d i l u t i o n technique f o r segregating the mineral i n i n g e s t a or feces according to d i e t a r y or endogenous o r i g i n . Most r e c e n t l y , Evans and Johnson (1977) have e s t a b l i s h e d the use of the e x t r i n s i c l a b e l technique to determine z i n c a v a i l a b i l i t y i n food. These workers were able to demonstrate that endogenous z i n c and exogenous ^ Z n enter a common pool p r i o r to being 8 absorbed from the i n t e s t i n e . Since e x t r i n s i c Zn enters a common pool w i t h i n t r i n s i c z i n c , whole body absorption of e x t r i n s i c ^ Z n was used to o b t a i n an accurate estimate of a v a i l a b i l i t y of z i n c i n food. The formula employed f o r the c a l c u l a t i o n i s percent ^ Z n absorbed cpm i n carcass, blood, u r i n e = : c j ~ • . ' • " ~ X 100 cpm m carcass, blood, g a s t r o m t e s t m e t r a c t x feces (2) B i o l o g i c a l Assay Techniques (a) Bone ash method The balance s t u d i e s i n general are more tedious and l a b o r i o u s . I t has l e d many workers to consider methods which give at l e a s t a comparative measure of the degree .of u t i l i z a t i o n of minerals i n d i e t a r y sources. The most simple way to evaluate b i o l o g i c a l a v a i l a b i l i t y of m i n e r a l i s to compare growth r a t e and bone ash content of chicks fed t e s t m a t e r i a l to those fed the standard i n o r g a n i c source. Baruah et al. (1960) and H i j i k u r o et al. (1967) showed the r e l a t i v e response of c h i c k s on the t e s t m a t e r i a l by an index t a k i n g the resonse of the chicks on the standard as 100. G i l l i s et al. (1954)' were the f i r s t to attempt the deter-mination q u a n t i t a t i v e l y of phosphorus a v a i l a b i l i t y by measuring bone ash content of t e s t animals. The assay i n v o l v e d the establishment of a standard response curve u s i n g a s e m i - p u r i f i e d b a s a l d i e t and graded l e v e l s of an i n o r g a n i c phosphate source i n which a v a i l a b i l i t y was assumed or known to be 100% at low d i e t a r y l e v e l . The t e s t i n g r e d i e n t 9 was s u b s t i t u t e d f o r a s m a l l • f r a c t i o n of the basal d i e t . A s t r a i g h t l i n e curve was obtained by p l o t t i n g the percentage of bone ash of solvent e x t r a c t e d l e f t chick t i b i a against the logarithm of the percentage d i e t a r y m i n e r a l . B i o l o g i c a l a v a i l a b i l i t y was defined as the r a t i o , expressed as a percentage of the amount of the i n o r g a n i c s a l t to the amount of t e s t i n g r e d i e n t which produced the same bone ash when.each was added to the basal d i e t . Percentage bone ash i s the most commonly used t e s t f o r e s t i m a t i n g mineral a v a i l a b i l i t y i n feed. Nelson (1967) noted that bone ash content i s one of the most s e n s i t i v e , p r a c t i c a l c r i t e r i a f o r e v a l u a t i n g the a v a i l a b i l i t y of d i e t a r y phosphorus. I t i s more accurate than body weight (Nelson and Walker, 1964; D i l w o r t h and Day, 1964), and i s l i t t l e a f f e c t e d by other d i e t a r y v a r i a b l e s . Calcium and phosphate r e t e n t i o n has f r e q u e n t l y been assessed by measuring the incremental r e t e n t i o n i n a s e l e c t e d bone caused by a known amount of d i e t a r y element (Ammerman et at., 1960). This technique, however, can only be used with young growing animals. Lengemann (1959) and P a t r i c k 45 and Bacon (1957) have used the Ca content of r a t t i b i a or femurs to assess u t i l i z a t i o n of d i e t a r y sources l a b e l l e d by an o r a l dose of r a d i o i s o t o p e . (b) Toe ash method Yoshida and H o s h i i (1977)' have deyeloped a toe-ash method to estimate 'pfro'spfiexus •  ayaMabi£ity;.,fp.rl.'th.e;;growing- c h i c k . • I t was observed that there was a l i n e a r r e l a t i o n s h i p between d i e t a r y phosphorus and toe ash content w i t h i n the range of added 10 phosphorus from 0 to 0.3%. The a v a i l a b i l i t y of phosphorus can th e r e f o r e be determined by a slope r a t i o assay o f the l i n e a r r e g r e s s i o n l i n e s between added phosphorus and toe ash content. A ten day feeding p e r i o d i s r e q u i r e d f o r t h i s assay. The authors i n d i c a t e d that the toe ash content method was more s u p e r i o r than t i b i a ash content method i n measuring a v a i l a b i l i t y . The r e s u l t obtained bv toe ash content was i n agreement with the carcass a n a l y s i s method (Ho s h i i and Yoshida, 1978b):, (a) Body weight method Long et al. (1956) used body weight as a c r i t e r i o n to assess phosphorus supplement f o r c a t t l e by adding i t to a low phosphorus d i e t . O'Dell et al. (1972) used body weight i n "' "•• esti m a t i n g m i n e r a l a v a i l a b i l i t y to chic k . The technique i n v o l v e s e s t a b l i s h i n g standard curves by supplementing basal d i e t s w i t h graded l e v e l s of the t e s t element o f an i n o r g a n i c form which i s assumed to be 100% a v a i l a b l e . A l i n e a r response can be obtained by p l o t t i n g weight or weight gain versus the logarithm of the supplement at lower l e v e l s of supplementation. The t e s t i n g r e d i e n t s are subsequently s u b s t i t u t e d f o r carbohydrate i n the basal d i e t at low l e v e l . The q u a n t i t y of b i o l o g i c a l l y a v a i l a b l e mineral i s e s t i -mated from the standard curve and d i v i d e d by the content of t e s t mineral i n the: i n g r e d i e n t . This method was, however, c r i t i c i z e d by Nelson (1967), to be inaccurate i n measuring a v a i l a b l e phosphorus and y i e l d i n g m isleading conclusions. 11 (d) Other miscellaneous methods Other b i o l o g i c a l assay techniques are being employed i n estim a t i n g mineral a v a i l a b i l i t y . Wilder e t al. (1933) s t u d i e d the a v a i l a b i l i t y of va r i o u s forms of i o d i n e ( d r i e d k e l p , i o d i z e d l i n s e e d meal and potassium iodide) to. the l a y i n g hen by observing t h e i r e f f e c t s upon the i o d i n e content of the egg. M i t t l e r and Banhan "(1954) used the enlargement of the t h y r o i d gland as a c r i t e r i o n to study the n u t r i t i o n a l a v a i l a b i l i t y of s e v e r a l i o d i d e compounds to a l b i n o r a t . Very extensive s t u d i e s have been made on the blood as a measure of mi n e r a l a v a i l a b i l i t y , p a r t i c u l a r l y of i r o n and magnesium. Thompson and Raven (1959) measured the u t i l i z a t i o n of i r o n from a number of herbage species by means of r e l a t i v e r a t e s of haemoglobin regeneration i n r a t s rendered anaemic by p r i o r feeding on an i r o n d e f i c i e n t d i e t . The haemoglobin r e p l e t i o n method was al s o employed by P l a and F r i t z (1971) studying a v a i l a b i l i t y of supplemental i r o n from s e v e r a l sources to chi c k s and r a t s . The r e s u l t s have been s a t i s f a c t o r y and the method was proposed to be adopted by A.O.A.C. (3) In -Vitro Assay Procedure Anderson et al. (1956) have devised a r a p i d in vitro method of e v a l u a t i n g phosphorus suuplements f o r ruminants by measuring the decomposition of c e l l u l o s e i n an a r t i f i c a l rumen when the supplement 12 was the s o l e source of phosphate f o r the microorganism. Value's obtained were i n reasonable agreement with those found by animal experiment. II. Availability of Mineral in Feed Ingredients -from Vegetable Bourses R e l a t i v e l y l i t t l e i n f o r m a t i o n has been developed on 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 minerals from d i f f e r e n t p l a n t sources f o r l i v e s t o c k , e s p e c i a l l y f o r non-ruminant. Most of the work on mineral studies has been devoted to calcium and phosphorus, p a r t i c u l a r l y phytate phosphate.• A s i g n i f i c a n t p o r t i o n of the t o t a l phosphate of p l a n t o r i g i n i s present i n t h i s form. Armstrong and Thomas (1952) reported that calcium a v a i l a b i l i t y of lucerne, red c l o v e r and w i l d white c l o v e r were 84.89, 83.11 and 79.95%, r e s p e c t i v e l y . f o r r a t s . i n the f o l l o w i n g year the a v a i l a b i l i t y of calcium i n three herbs of grassland (burnet, c h i c o r y and narrow leaved p l a n t a i n ) were estimated to be 80.38, 87.73 and 95.28%, respectively.(Armstrong et al., 1953). Another r e p o r t by Armstrong et al. (1957) showed that the calcium a v a i l a b i l i t y of three erasses, timothy, p e r e n n i a l rye grasses and cocksfoot were 78.99, 76.53 and 69.02%. r e s p e c t i v e l y . The a v a i l a b i l i t y of calcium i n amaranthus, sesbania g r a n d i f l o r a and moringa o l e i f e r a were estimated by Devadatta and Appana (1954), to be 74-78, 85 and 69%, r e s p e c t i v e l y . As e a r l y as 1939. Common reported that the phosphorus i n p l a n t s passed through the hen unhydrolyzed. G i l l i s et al. (1953) l a t e r observed that phosphorus from i s o l a t e d calcium phytate was 13 l e s s than 50% as b i o l o g i c a l l y a v a i l a b l e as that from d i c a l c i u m or d e f l o u r i n a t e d phosphate and 10% phosphorus a v a i l a b i l i t y was reported from phytate phosphate. Ashton et al. (1960) showed that approximately 20% of the phytate phosphorus was r e t a i n e d by four-week o l d c h i c k s while six-week o l d c h i c k s r e t a i n e d 36 to 49% of phytate phosphorus. However, Temperton and Cassidy (1964) observed that c h i c k s u t i l i z e d approximately 60.7% non-phytate phosphorus. Salman and McGinnis (1968), u s i n g l a y i n g hens, reported that phosphorus u t i l i z a t i o n i n r a t i o n s contains, ing 0.3% p l a n t phosphorus was i n s i g n i f i c a n t l y d i f f e r e n t from i t s u t i l i z a t i o n i n r a t i o n c o n t a i n i n g either- 0.6% p l a n t phosphorus or 0.3% p l a n t phosphorus plus 0.3% i n o r g a n i c phosphorus. Nwokolo et al. (1976) observed t h a t the a v a i l a b i l i t y of phosphorus from soybean meal, rapeseed meal, cottonseed and palm k e r n e l meal to four-week o l d c h i c k s was 89.3, 74.8, 76.9 and 70.8%,: r e s p e c t i v e l y . A v a i l a b i l i t y o f the m i n e r a l was estimated by the percentage of the mineral r e t a i n e d i n the chick u s i n g a c o r r e c t i o n f o r endogenous f e c a l mineral excreted. Most r e c e n t l y H o s h i i and Yoshida (1978a)„ using toe ash content technique reported that phosphorus i n wheat, wheat bran and b a r l e y has a v a i l a b i l i t y higher than 60%.. A s i g n i f i c a n t s t r a i n d i f f e r e n c e i n phosphorus a v a i l a b i l i t y was observed between two s t r a i n s of wheat. The authors also observed that the phosphorus i n feed i n g r e d i e n t s of animal o r i g i n (e.g. f i s h meals and meat and bone meals) was h i g h l y a v a i l a b l e w h ile a v a i l a b i l i t y of phosphorus i n plant sources (e.g. p l a n t o i l cake, yellow corn and milo) was very low. 14 Woodman and Evans (1948) showed that 30 to 40% of the phosphorus i n barley-wheat bran w i t h no added i n o r g a n i c source was absorbed by pigs r a i s e d from 50 to 90 kg of weight. Besecker et al. (1967) obtained an apparent phosphorus d i g e s t i b i l i t y value i n b a r l e y o f 17.7% when i t was fed to 45 kg pigs i n a d i e t c o n t a i n i n g a 0.3% t o t a l phosphorus. Tonroy et al. (1973) reported apparent phosphorus d i g e s t i b i l i t y values of 4.5 and 63.7% f o r sorghum g r a i n and d i c a l c i u m phosphate, r e s p e c t i v e l y . Bayley and Thomson (1969) s t a t e d that 27 kg pigs were able to absorb 19% of the phosphorus contained i n a corn-soybean meal d i e t c o n t a i n i n g 0.9% ; Ca and 0.35% t o t a l phosphorus when fed i n meal form, whereas 3% phosphate a b s o r b a b i l i t y value was reported by Bayley et al. (1975) f o r a corn-soybean meal d i e t to 25 kg p i g s . Most r e c e n t l y , M i r a c l e et al. (1977) observed that the phosphorus a v a i l a b i l i t y i n corn,.wheat and soybean f o r pigs i s 16, 51 and 18%, r e s p e c t i v e l y . P i e r c e et al. (1977) a l s o showed that the apparent d i g e s t i b i l i t y o f phosphorus i n wheat was no b e t t e r than i n corn and that the phytate from calcium phytate was e s s e n t i a l l y u n a v a i l a b l e f o r growing pigs (11-45 kg). The l i t e r a t u r e i n d i c a t e s that there are tremendous d i f f e r e n c e s regarding phosphorus a v a i l a b i l i t y from various sources. The d i f f e r e n c e s may be due to the source of m a t e r i a l s t e s t e d , methods used, species and age d i f f e r e n c e s . The N a t i o n a l Research Council (NRC, 1969) suggested that approximately 20 to 50% of phosphorus i n p l a n t m a t e r i a l s may be u t i l i z e d by non-ruminants. Peer (1972) i n a review of the l i t e r a t u r e i n d i c a t e d that the a v a i l a b i l i t y of magnesium i n forages ranges from 10 to 25% with a 15 mean of approximately 20%. A v a i l a b i l i t y from grains and concentrations ranges from 30 to 40% f o r ruminants. Very l i m i t e d i n f o r m a t i o n on magnesium, z i n c , manganese and copper a v a i l a b i l i t y has been published f o r p o u l t r y . Guenter and S e l l (1974), u s i n g intramuscular i n j e c t i o n of r a d i o a c t i v e Mg-28, reported that the a v a i l a b i l i t y of magnesium f o r wheat, corn, b a r l e y , oat, r i c e and soybean meal was-48. l'i 47.5, 54.2, 82.9, 42.2 and 60.4%, r e s p e c t i v e l y , f o r the mature male chicken. Recently Nwokolo et al. (1976) reported that a v a i l a b i l i t y o f magnesium i n soybean, rapeseed, cottonseed and palm kernel meal was 77.4, 61.1, 74.6 and 56.4%, r e s p e c t i v e l y . O'Dell et at. (1972) usi n g growth response of chicks observed that the a v a i l a b i l i t y o f z i n c i n sesame meal, soybean meal and f i s h meal was 57, 67 and 75%, r e s p e c t i v e l y . Zinc a v a i l a b i l i t y of raw corn endosperm f l o u r was reported to be 51% f o r r a t s (Evans iarid;:Johnson, 1977) . Nwokolo et al. (1976) evaluated a v a i l a b i l i t y of s e v e r a l minerals i n p l a n t p r o t e i n sources and reported that z i n c a v a i l a b i l i t y i n soybean, rapeseed, cottonseed and palm k e r n e l meals were 66.5, 44.0, 38.0 and 13.5%, r e s p e c t i v e l y . The manganese a v a i l a b i l i t y was 76:1, 56.7, 76.3 and 45.7%, r e s p e c t i v e l y . The copper a v a i l a b i l i t y was 51.0, 62.2, 42.3 and 44.7%, r e s p e c t i v e l y f o r four-week o l d b r o i l e r c h i c k s . III. Availability of Minerals in Inorganic Sources for Livestock M i n e r a l s of p l a n t o r i g i n are not adequate to meet the mineral requirement f o r l i v e s t o c k production. Therefore, p r a c t i c a l 16 feed f o r m u l a t i o n u t i l i z e s i n o r g a n i c mineral supplements to o b t a i n the optimum d i e t a r y concentration. Hence the b i o a v a i l a b i l i t y of i n o r g a n i c minerals have been of i n t e r e s t to many research workers. (1) Calcium R e l a t i v e l y l i t t l e i n f o r m a t i o n has been developed on comparative b i o l o g i c a l a v a i l a b i l i t y of calcium from d i f f e r e n t feed sources f o r animals. There i s considerably more research on the comparative value of calcium source reported f o r p o u l t r y than f o r other species. According to the r e s u l t s o f some studies on various calcium sources i n c l u d i n g calcium carbonate, calcium s u l f a t e , oyster s h e l l , limestone, various calcium phosphates, calcium gluconate and f i s h meal (Bethke et al., 1929; Deobald et al., 1936; Waldroup et al., 1964; Sandorf and M u l l a r , 1965; HurwitZ; and Rand, 1965), there are no d i f f e r e n c e s i n b i o l o g i c a l a v a i l a -b i l i t y among d i f f e r e n t calcium sources using bone ash and weight gain i n chicks as the c r i t e r i a of response. In contrast to these r e p o r t s , however, a number of researchers have reported d i f f e r e n c e s i n b i o l o g i c a l a v a i l a b i l i t y between v a r i o u s calcium c a r r i e r s f o r young c h i c k s . Motzok et al. (1965) observed t h a t the calcium i n s o f t phosphate was 70% as a v a i l a b l e as that i n calcium carbonate (100%) and d i c a l c i u m phosphate (100%). In these s t u d i e s , the e f f e c t i v e n e s s of calcium was found to be s e n s i t i v e to the Ca:P r a t i o . Hurwitz and Rand (1965) reported that the calcium i n gypsum was 90% as a v a i l a b l e as limestone when feed i n t a k e was e q u i l i z e d . Calcium a v a i l a b i l i t y of s e v e r a l feed grade calcium phosphates has ; been measured usi n g bone ash as the c r i t e r i o n of response. D i l w o r t h et al. (1964) observed that the 17 r e l a t i v e , calcium a v a i l a b i l i t y i n the sources ranged from 68 to 95% as compared to calcium carbonate. B l a i r et al. (1965) reported 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 a v a i l a b i l i t y of calcium carbonate and v a r i o u s phosphate s a l t s . The calcium i n d o l o m i t i c limestone was from 64 to 68% as a v a i l a b l e as that i n pure calcium carbonate i n which average a v a i l a b i l i t y was 66% ( S t i l l m a k and Sunde, 1971). A recent study by Reid and Weber (1976) on calcium a v a i l a b i l i t y of f i v e ground limestone.samples with l a y i n g hens showed that the ground limestone samples v a r i e d from 82.4 to 98.4% calcium a v a i l a b i l i t y when apparent calcium r e t e n t i o n and egg s h e l l t hickness were employed as the t e s t c r i t e r i a . In other r e p o r t s , d i f f e r e n c e s i n calcium a v a i l a b i l i t y were observed when hydrated and anhydrous d i c a l c i u m phosphate were compared (Rucker et al., 1968). Buckner et al. (1929) showed that calcium carbonate was s u p e r i o r to a number o f calcium s a l t s f o r egg production as judged by eggs s h e l l weight. Balloun and Marion (1962) demonstrated the d i f f e r e n c e s i n r e l a t i v e e f f i c i e n c y of calcium l a c t a t e and calcium carbonate i n the production of egg s h e l l . However, most l a b o r a t o r i e s have been unable to demonstrate 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 b i o a v a i l a b i l i t y of a number of calcium sources u s i n g egg production, egg s h e l l q u a l i t y and bone ash values as c r i t e r i a (Hurwitz and Rand, 1965; Heywang and Lowe, 1962). (2) Phosphate A large number of s t u d i e s have been conducted to determine the r e l a t i v e b i o l o g i c a l value of the various i n o r g a n i c phosphate sources f o r 18 the-chick.. • G i l 3 i s et 'eel- •(1954), w e r e ' t h e - f i r s t to.---quantitate the a v a i l a b i l i t y i n va r i o u s phosphate compounds f o r the c h i c k . Assuming beta-t r i c a l c i u m phosphate to be 100% a v a i l a b l e , , the r e l a t i v e values f o r monocalcium phosphate, d i c a l c i u m phosphate, d e f l u o r i n a t e d phosphate and!.low f l u o r i n a t e d phosphate were 113, 98, 98 and 87%, r e s p e c t i v e l y . S i m i l a r r e s u l t s were obtained by Nelson and Walker (1964), but with- a lower value i n low f l u o r i d e rock (68%). Peeler (1972) made the comparison of b i o a v a i l a b i l i t y of v a r i o u s phosphorus sources n o t i n g that ;the. r e s u l t s obtained from d i f f e r e n t l a b o r a t o r i e s ( G i l l i s et al., 1954; Nelson.'and Pe e l e r , 1961; Nelson and Walker,\ 1964; Di l w o r t h and Day, 1964), were apparently i n good agreement. Numerous studies have/demonstrated that the l e v e l o f calcium i n the d i e t has a considerable i n f l u e n c e on the response of chi c k s to c e r t a i n phosphate sources. A s e r i e s of st u d i e s on the comparative a v a i l a b i l i t y of i n o r g a n i c phosphate f o r l a y i n g hen was reported by Singsen et al. (1969a). On the b a s i s o f a l l performance c h a r a c t e r i s t i c s observed, the s o f t phosphate a v a i l a b i l i t y has a s l i g h t l y higher a v a i l a b i l i t y value than low f l u o r i n e rock phosphate and e s s e n t i a l l y equal a v a i l a b i l i t y to d e f l u o r i n a t e d and d i c a l c i u m phosphate. A f u r t h e r experiment by Singsen et al. (1969b) i n d i c a t e d 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 of low f l u o r i n e rock phosphate was 25% f o r the l a y i n g hen. In s t u d i e s w i t h i n o r g a n i c sources, Wilcox and Asso c i a t e s (1954, 1955) found wide d i f f e r e n c e s i n the -avaii-abi-rit.^ of ^y^ymgv. turkeys', to u t i l i z e v a r i o u s phosphates. A v a i l a b i l i t y values ranged from low to very h i g h , based on growth r a t e and bone ash observations. 19 G i l l i s et al. (1962) and Scott et al. (1962) reported.that f o r the turkey p o u l t the primary calcium phosphate s a l t i s most b i o l o g i c a l l y a v a i l a b l e f o l l o w e d by the secondary s a l t w i t h the t e r t i a r y s a l t o r t r i c a l c i u m phosphate having the l e a s t b i o l o g i c a l a v a i l a b i l i t y of the three. Therefore i t i s noted that hydrated d i c a l c i u m phosphate (CaHPO^'H^O) i s an e x c e l l e n t source of phosphate, whereas the anhydrous form o f d i c a l c i u m phosphate (CaHPO^) i s very p o o r l y u t i l i z e d by turkey ( G i l l i s et al., 1962; Scott et al., 1962; Rucker et al., 1968). S u l l i v a n (1966) reported that r e l a t i v e a v a i l a b i l i t y of d i c a l c i u m phosphate, d e f l u o r i n a t e d phosphate and low f l u o r i n a t e d rock phosphate f o r the turkey was 98.4V. 82.6 and 91.2%, r e s p e c t i v e l y i n which monocalcium phosphate was assumed to be 100% a v a i l a b i l i t y . (3) Magnesium Ammerman and Assoc i a t e s (1972)compared the a v a i l a b i l i t y of se v e r a l magnesium s a l t s f o r sheep and reported that b i o l o g i c a l a v a i l a b i l i t y values f o r MgCO^, MgO and MgSO^ were 43.77, 50.87 and 57.63%, r e s p e c t i v e l y . When reagent grade magnesium oxide was assigned a value: of 100, the r e l a t i v e value of MgSO^ was 113% and reagent grade MgCO^ was 86%. Cook (1973) used balance s t u d i e s to evaluate v a r i o u s i n o r g a n i c magnesium s a l t s and reported that magnesium carbonate was the most a v a i l a b l e form. Magnesium c h l o r i d e was as a v a i l a b l e as carbonate form. The oxide, phosphate, s u l f a t e and s i l i c a t e s a l t s were s l i g h t l y lower compared to magnesium carbonate. 20 Limited i n f o r m a t i o n has been reported f o r a v a i l a b i l i t y o f inor g a n i c magnesium source to p o u l t r y . Guenter and S e l l (1974) usi n g r a d i o i s o t o p e technique showed that the a v a i l a b i l i t y of magnesium from M gSO^H 0 was 57.4%. (4) Manganese3 Zine and Copper L i t t l e work has been conducted on the b i o a v a i l a b i l i t y of : • ino r g a n i c sources of manganese, z i n c and copper. Most of the data reported were q u a l i t a t i v e r a t h e r than q u a n t i t a t i v e . Schaible and Bandemer (1942) reported that manganese oxide, manganese carbonate, manganese s u l f a t e , manganese c h l o r i d e (with widely v a r y i n g s o l u b i l i t y ) are e q u a l l y v a l u a b l e as sources of manganese i n p o u l t r y r a t i o n s and presumable, t h e r e f o r e , are e q u a l l y w e l l absorbed. However, Henning et at. 54 -(1967) observed that r a d i o a c t i v i t y as MnCl^ was incorporated, i n t o the 54 body o f chic k s to a greater extent than that s u p p l i e d as MnSO^ or 54 MnO^. Recent research i n d i c a t e d that d i f f e r e n c e s i n the a v a i l a b i l i t y of manganese from d i f f e r e n t sources e x i s t (Watson et at., 1970). Using b i o l o g i c a l assay, Watson et al. (1971) showed that the a v a i l a b i l i t y was d i f f e r e n t between the carbonate and oxide forms of manganese. However/ no q u a n t i t a t i v e data were reported.. Edwards (1959) observed that z i n c i n the forms of zine s u l f a t e , w i l l e m i t e , z i n c carbonate, z i n c metal, z i n c oxide ( t e c h n i c a l grade) and zi n c oxide (A.R. grade) i s r e l a t i v e l y a v a i l a b l e to the young growing chicken whereas, z i n c i n s p h a l e r i t e (mostly z i n c s u l f i d e ) and i n f r a n k l i n i t e (oxides of Zn, Fe and Mn) i s l a r e g l y u n a v a i l a b l e . K r a t z e r 21 and Vohra (1966) a l s o showed that z i n c i s l e s s a v a i l a b l e from z i n c orthophosphate, z i n c t r i p o l y p h o s p h a t e , z i n c hexametaphosphate, z i n c pyrophosphate and z i n c phytate than from oxide. Anemic r a t s were shown to be unable to use the copper of copper s u l f i d e or copper por p h y r i n , whereas the oxide, hydroxide and pyrophosphate were r e a d i l y u t i l i z e d (Schultze et al., 1936). Pigs a l s o absorb the copper of c u p r i c s u l f i d e much l e s s e f f i c i e n t l y than that of c u p r i c s u l f a t e (Bowland et al., 1961). IV. Factors Affecting Mineral Availability Several f a c t o r s i n f l u e n c e the b i o a v a i l a b i l i t y of mineral elements. One of the most s i g n i f i c a n t f a c t o r s i s the p h y t i c a c i d ( i n o s i t o l hexaphosphoric acid) which chelates mineral elements reducing the a v a i l a b i l i t y to the animals (Nelson et al., 1968; Davies and N i g h t i n g a l e , 1975). These workers suggest that phytate probably chelates part of a l l the c a t i o n r e q u i r e d by animals. Phytate has a l s o been shown to form s t a b l e complexes in vitro w i t h Cu, Zn, Co, Mn, Fe and Ca (Oberleas, 1973). Some other recognized f a c t o r s a f f e c t i n g mineral a v a i l a b i l i t y are crude f i b r e , o x a l a t e , ethylenediaminetetraacetate (EDTA), p r o t e i n and amino a c i d s , v i t a m i n s , a n t i b i o t i c s and i n t e r a c t i o n between mineral elements. 22 (1) Phytic Aoid An e a r l i e r r eport by Bruce and Callow (1934) suggested that p h y t i c a c i d would render calcium u n a v a i l a b l e f o r absorption by the formation of i n s o l u b l e calcium phytate. They al s o showed that phosphorus from c e r e a l sources was l e s s e f f e c t i v e than i n o r g a n i c phytate phosphorus i n he a l i n g r i c k e t s and suggested that phosphorus as phytate was p o o r l y absorbed from the i n t e s t i n a l t r a c t . The poor u t i l i z a t i o n of phytate phosphorus by various p o u l t r y species has been reported by many researchers (e.g. Lower et al., 1939; G i l l i s et at., 1957) and i n a review o f Nelson (1967). In c o n t r a s t t o t h i s , the a d d i t i o n of phytate as bran (Roberts and Yudkin, 1961) or as a mixture .of pentacalcium phytate and sodium phytate (Hoff-Jorgensen, 1946) was reported to increase a v a i l a b i l i t y of phosphorus, on c e r e a l -based d i e t s . I t i s apparent that observed values f o r the a b i l i t y of chickens to u t i l i z e phytate phosphorus may be d i f f e r e n t due to c r i t e r i a and m a t e r i a l used i n the assay. Methods to improve phosphorus a v a i l a b i l i t y have been i n d i c a t e d by se v e r a l workers (Anderson, 1915; Singsen, 1948; Summer et at., 1967). P h y t i c a c i d a l s o reduces a v a i l a b i l i t y of i r o n (McCance et at., 1943; Davies and N i g h t i n g a l e , 1975), .magnesium (Roberts and Yudkin, 1961; L i k u s k i and Forbes, 1965), z i n c (O'Dell and Savage, I960; Oberleas et at., 1960, Davies and N i g h t i n g a l e , 1975; Davies and Reid, 1979), manganese and copper (Davies and N i g h t i n g a l e , 1975). Byrd and Matrone (1965) and Oberleas et al. (1966) have suggested that the i n t e r f e r e n c e i n z i n c absorption by p h y t i c a c i d was due to z i n c combining 23 with phytate and calcium to form an i n s o l u b l e Zn-Ca-phytate complex. This was confirmed by Oberleas (1973), Davies and N i g h t i n g a l e (1975) and Davies and Reid (1979). Nwokolo and Bragg (1977) reported that p h y t i c a c i d content of soybean, rapeseed, cotton seed and palm k e r n e l meals s i g n i f i c a n t l y a f f e c t e d a v a i l a b i l i t y o f phosphorus, calcium, z i n c and magnesium but not manganese and copper. I t i s evident that p h y t i c a c i d i s a f a c t o r i n f l u e n c i n g the a v a i l a b i l i t y of mine r a l s . (2) Fiber Armstrong et oil. (1953), i n the study on the a v a i l a b i l i t y of calcium i n three herbs of grassland, reported an inverse r e l a t i o n s h i p between calcium a v a i l a b i l i t y and crude f i b e r content. Smith (1961) demonstrated that net absorption of calcium and magnesium decreased i n m i l k fed calves i n g e s t i n g a high l e v e l of f i b e r as wood shavings.' Reinhold (1975) reported t h a t crude f i b e r caused the decreased a v a i l a b i l i t y of z i n c f o r i n t e s t i n a l a bsorption. Nwokolo and Bragg (1977) reported that crude f i b e r content of soybean, rapeseed, cottonseed- ~ and palm k e r n e l meals s i g n i f i c a n t l y depressed a v a i l a b i l i t y of calcium, phosphorus, magnesium, manganese, z i n c and copper i n growing c h i c k s . Reinhold et al. (1975, 1976) a l s o observed that f i b e r was a determinant of a v a i l a b i l i t y of calcium, z i n c and i r o n i n b r e a d s t u f f f o r man. Eastwood (1973) suggested that vegetable f i b r e c o n s i s t s o f a heterogeneous complex of polysaccharides and l i g n i n capable of sequestering water, c a t i o n or anion depending on the chemistry of the c o n s t i t u e n t macromolecules. Oberleas and Hardland (1977) i n d i c a t e d that f i b e r may a f f e c t mineral 24 a v a i l a b i l i t y by any or a l l of the f o l l o w i n g mechanisms: a c t i n g as a c a t i o n exchanger, d i l u t i n g the i n t e s t i n a l contents, a l t e r i n g t r a n s i t time or changing the o x i d a t i o n - r e d u c t i o n p o t e n t i a l of the g a s t r o i n t e s t i n a l t r a c t . McConnell et al. (1974) suggested that the -COOH groups of f i b e r polysaccharides are r e s p o n s i b l e f o r the apparent c a t i o n exchange c a p a c i t y . However, -OH,-PO(OH)2 and -SO^ are al s o able to re v e r s a b l y exchange organic r a d i c a l s f o r c a t i o n s i n the surrounding environment (Oberleas and Hardland, 1977). I t appears that f i b e r i s i m p l i c a t e d as a causative agent i n re d u c t i o n of mineral b i o a v a i l a b i l i t y . (3) Oxalic Acid High c o n c e n t r a t i o n of o x a l i c a c i d i n food can impair the a v a i l a b i l i t y o f minerals by forming a p o o r l y absorbable mineral oxalate ( M i t c h e l l , 1939; 1942). Skorkowska-Zieleniewska et al. (1974) showed that d i e t s c o n t a i n i n g o x a l i c a c i d reduced calcium, magnesium and i r o n absorption. S i m i l a r r e s u l t s were observed f o r calcium ( M u r i l l o et al. (1973) and phosphorus (Compere, 1966). However, Brune and Bredehorn (1962) demonstrated.that-pigs-apparently u t i l i z e d calcium oxalate as e f f e c t i v e l y as other calcium sources. P a t e l et al. (1967) reported that most concentrates and vegetable leaves had p r a c t i c a l l y no oxa l a t e s . Fasett (1966) who c r i t i c a l l y evaluated the l i t e r a t u r e p e r t a i n i n g to p o s s i b l e oxalate i n t e r f e r e n c e with calcium metabolism concluded that there was very l i t t l e danger associated with i n g e s t i n g oxalate c o n t a i n i n g p l a n t s . 25 (4) Ethylene-Diamine-Tetraacoate (EDTA) The r o l e o f mineral i o n c h e l a t i o n has been discussed by Scott et al. (1969). They p o i n t out that organic chelates may be the most important f a c t o r governing the absorption of mineral elements, e.g. asc o r b i c a c i d and amino a c i d s . There are some chelates which can decrease the a v a i l a b i l i t y of one or more mineral elements and simultaneously improve the a v a i l a b i l i t y o f other minerals. K r a t z e r et al. (1959) observed that the a v a i l a b i l i t y of z i n c f o r chicks on a p u r i f i e d d i e t c o n t a i n i n g soybean p r o t e i n was g r e a t l y enhanced by the a d d i t i o n of EDTA. S i m i l a r r e s u l t s were reported on chi c k s fed p u r i f i e d d i e t s and EDTA by other workers (Davis et al.., 1962; L i k u s k i n and Forbes, 1964; O'Dell et al. 1964). Kratzer and Starcher (1963) i n d i c a t e d that EDTA not only improved the a v a i l a b i l i t y of z i n c already present i n the d i e t but al s o made added z i n c more e f f e c t i v e f o r use by p o u l t s . S i m i l a r evidence was reported i n r a t s (Oberleas et al., 1966). EDTA improved u t i l i z a t o n of manganese and copper i n chickens r e c e i v i n g a d i e t c o n t a i n i n g i s o l a t e d soybean p r o t e i n (Scott et al., 1969). EDTA decreased i r o n a v a i l a b i l i t y to r a t s (Larsen et al., 1960) and chi c k s ( F r i t z et al., 1971). A study was reported by Suso and Edwards (1960) concerning the i n f l u e n c e of various c h e l a t i n g agents on absorption of ^ C o , "^Fe, *^Mn and ^ Z n i n the chicken. Results showed a s i g n i f i c a n t increase i n ^ Z n absorption 54 but a n o n - s i g n i f i c a n t increase i n Mn absorption with i n c r e a s i n g l e v e l s of EDTA. D i e t a r y of EDTA decreased absorption of *^Fe and ^ C o ( F r i t z et al., 1971) f o r c h i c k s ; These r e s u l t s demonstrated that EDTA bound i r o n and manganese very t i g h t l y making "these elements l e s s a v a i l a b l e f o r u t i l i z a t i o n . The f r e e a c i d form of EDTA was more 26 d e t r i m e n t a l than was calcium disodium EDTA or disodium EDTA. A d d i t i o n at c r i t i c a l l e v e l s of any form of EDTA to the d i e t reduced the hemoglobin l e v e l s i n the chi c k s i n d i c a t i n g the EDTA i n t e r f e r e n c e w i t h i r o n u t i l i z a t o n . Also the incidence of p e r o s i s increased i n d i c a t i n g that EDTA i n t e r f e r e d w i t h manganese u t i l i z a t i o n . (5) Protein and Amino Acids Various p r o t e i n sources have been reported to i n t e r f e r e w i t h the a v a i l a b i l i t y of minerals i n the d i e t s . These i n c l u d e peas.(Kienholz et al., 1959; Kienholz et al., 1962) i s o l a t e d soybean p r o t e i n (O'Dell and Savage, 1960), sesame meal (Lease et al., 1960), s a f f l o w e r , cottonseed, soybean meals (Lease and W i l l i a m s , 1976a,b), f r e e amino a c i d and ca s e i n d i e t s ( L i k u s k i and Fores, 1964). I s o l a t e d soybean p r o t e i n reduced the a v a i l a b i l i t y of molybdenum (Reid et al., 1956), z i n c (O'Dell and Savage, 1960) and manganese and copper (Davis et al., 1962). Copper can form i n s o l u b l e complexes with p r o t e i n which are u n a v a i l a b l e f o r absorption (Underwood, 1977). The same mechanism would l i k e l y apply to other minerals l i s t e d above. Wasserman et al. (1956) reported that s e v e r a l amino acids promoted calcium absorption andvtHat l y s i n e and a r g i n i n e were the most e f f e c t i v e . Amino a c i d s , e s p e c i a l l y c y s t e i n e and h i s t i d i n e , are a l s o e f f e c t i v e metal b i n d i n g agents. Van Campen and Gross (1969) reported 59 that h i s t i d i n e increased . . Fe uptake from i s o l a t e d segments of r a t duodenum. Van Campen ' (1973) a l s o observed enhancement of i r o n absorption from 'a I-|gat-.ed j.g'egine'nt-idfa^s^»tes.tine?-by- h i s t i d i n e . , 27 c y s t i n e and l y s i n e . Cysteine and h i s t i d i n e were shown to have a b e n e f i c i a l e f f e c t on the z i n c d e f i c i e n c y syndrome (N i e l s e n et al., 1966a; 1966b). Zinc d e f i c i e n t c h i c k s fed i s o l a t e d soybean p r o t e i n and a supple-ment of 1,0 and 2.0% h i s t i d i n e showed a l l e v i a t i o n of l e g d i s o r d e r s ( N i e l s e n , 1966a). A supplement of 0.5% c y s t e i n e a l l e v i a t e d a l l signs of z i n c d e f i c i e n c y (Nielsen et al., 1966a). I t was noted that supplementation of c y s t e i n e improved the body weight g a i n , f e a t h e r i n g and t i b i a z i n c c o n c e n t r a t i o n , p o s s i b l y due to improved z i n c a v a i l a b i l i t y i n the d i e t . However, supplementation of h i s t i d i n e d i d not give the same response. Coleman et al. (1969) showed th a t a supplementation of 2.0% a r g i n i n e hydrochloride i n a z i n c d e f i c i e n t d i e t of chicks aggravated both the l e g abnormality and f e a t h e r defects and tended to depress growth. I t seems, t h e r e f o r e , that c y s t e i n e , h i s t i d i n e and a r g i n i n e are p o s s i b l e antagonists of z i n c i n some aspects of the c h i c k metabolism. M i s k i and K r a t z e r (1977) observed that p r o t e i n d e f i c i e n c y lowers the e f f i c i e n c y of i r o n u t i l i z a t i o n w h i l e g l y c i n e and tryptophan supplementation enhance i r o n absorption. (6) Lactose Lactose has been reported to promote calcium absorption by many workers (Wasserman et al., 1956; Langemann et al., 1959). Wasserman and Comar (1959) s t a t e d that some other carbohydrates having an a c t i o n s i m i l a r to that of l a c t o s e , stayed f o r some time i n the i n t e s t i n a l lumen ( c e l l o b i o s e , sorbose, r i b o s e and x y l o s e ) , but that carbohydrates that were r a p i d l y absorbed had l i t t l e or no e f f e c t . B i l e 28 acids were reported to increase calcium absorption by improving the s o l u b i l i t y of calcium i n l i p i d s olvents (Webling and Holdsworth, 1966). (7) Vitamins Vitamin D has been reported by a number of i n v e s t i g a t o r s to i n f l u e n c e the absorption of various c a t i o n s . Sobel and Burger (1955) reported that Vitamin D increased the l e v e l s of lead i n blood while Greenberg (1945) showed an increase i n strontium absorption due to v i t a m i n D a d m i n i s t r a t i o n . ; Meintzer and Steenbock (1955) reported that d i e t s low i n v i t a m i n D fed to r a t s depressed magnesium absorption. Workers and Migicovsky (1961a,b) observed that v i t a m i n D increased absorption of calcium, strontium, b e r y l l i u m , magnesium, barium, z i n c and cadmium. Cobalt and cesium were a l s o observed to be i n the l i s t but not sodium, potassium, copper, i r o n and z i n c (Wasserman, 1962). Vitamin D has als o been demonstrated to enhance absorption of i r o n and coba l t (Musahara and Migicovsky, 1963) and z i n c (Kienholz et at., 1964). The r e l a t i o n s h i p between v i t a m i n D and calcium absorption has been studi e d most e x t e n s i v e l y i n the l a s t two decades. Present evidence suggests that i n t e s t i n a l calcium b i n d i n g p r o t e i n (CaBP) i s c o n t r o l l e d by the con c e n t r a t i o n of 1 , 2 5 - d i h y d r o x y c h o l e c a l c i f e r o l (vitamin D d e r i v a t i v e ) i n the c e l l s of t h i s organ ( E d e l s t e i n et at., 1975). The synthesis i s mediated by a s p e c i f i c mRNA r e s u l t i n g from events f o l l o w i n g the binding of 1 , 2 5 - d i h y d r o x y c h o l e c a l c i f e r o l to a chromatin receptor (Emtage et at., 1974). The v i t a m i n D, t h e r e f o r e , enhances the production of CaBP i n the i n t e s t i n e such that the absorption of calcium i s increased. 29 Large amounts of v i t a m i n C ( a s c o r b i c acid) w i l l depress the i n t e s t i n a l absorption of copper apparently by formation o f mercaptides with m e t a l l o t h i o n e i n (Evans et al., 1973"'). High d i e t a r y a s c o r b i c a c i d has been demonstrated i n i n c r e a s i n g the s e v e r i t y of copper d e f i c i e n c y i n chicks ( H i l l and Starcher, 1965) and r a b b i t s (Hunt and C a r l t o n , 1965). (8) A n t i b i o t i c s A n t i b i o t i c s have been reported to improve the mineral a v a i l a b i l i t y i n s w i n e r a t i o n s (Kirchgessner et al., 1961; Kirchgessner, 1965). In balance experiments usi n g pigs and p o u l t r y , the d a i l y r e t e n t i o n of cobal t and z i n c was more than doubled and copper r e t e n t i o n t r i p l e d as the d i e t was supplemented with a n t i b i o t i c s . Increments of manganese and i r o n r e t e n t i o n i n animals r e c e i v i n g a n t i b i o t i c s have a l s o been reported. In a d d i t i o n , Kirchgessner et al. (1961) using balance methods, observed that r e t e n t i o n of phosphorus, magnesium, manganese, copper, i r o n , c o b a l t and s i l i c o n was increased by a n t i o b i o t i c s i n the young but not i n mature p i g s . (9) Species Difference Species d i f f e r e n c e i n the u t i l i z a t i o n of t r a c e minerals were als o recognized. Hay f i b e r i s not a good source of i r o n f o r chick d i e t s even though such hay contains 100 to 200 ppm of i r o n (NRC, 1969). Most of the n u t r i e n t s that are present would not become a v a i l a b l e to non-ruminant animals because they do not d i g e s t such m a t e r i a l s e f f e c t i v e l y . In animal s t u d i e s , l i t t l e d i f f e r e n c e was observed i n the response of chicks and r a t s when as c o r b i c a c i d was added to the t e s t d i e t w i t h 30 known a d d i t i o n of i r o n ( F r i t z et al., 1970; F r i t z and P l a , 1972). However, a s c o r b i c a c i d increases the i r o n absorption i n man ( P l a and F r i t z , 1972). Elwood^ (1965:>^ ^^  f e r r o u s s a l t s were equ'ally'v a v a i l a b l e to the- r a t s but -not "-man". (10) Mineral Interaction E a r l y observations on mineral i n t e r r e l a t i o n s h i p s i n d i c a t e s that low calcium r a t i o n s d i s t u r b phosphorus" balance. "Later i n v e s t i g a t o r s • revealed fundamental interdependencies between calcium and manganese, z i n c and calcium, phosphorus and magnesium, cadmium and z i n c ( H i l l et al., 1963; Forbes, 1963), i r o n and manganese (Thomson,>et al. * 1971). The/influence of a v a i l a b i l i t y of minerals to a considerable degree i s r e l a t e d to competition f o r b i n d i n g s i t e s i n or on mucosal c e l l s and f o r c a r r i e r molecules. High calcium and high i n o r g a n i c phosphorus aggravate.zinc d e f i c i e n c y i n r a t s ( C a b e l l and E a r l e , 1965). Conversely, low calcium intakes can a l l e v i a t e the e f f e c t s o f z i n c d e f i c i e n c y . Less copper was absorbed by mice from a high calcium than from a low calcium d i e t due to an increase i n i n t e s t i n a l pH (Tompsett, 1940) and d i e t s high i n calcium enhance copper t o x i c i t y i n p i g s , persumably due to a lowering of z i n c a v a i l a b i l i t y ( S u t t l e and M i l l s , 1966). Nugara and Edwards (1962) noted that high d i e t a r y phosphorus reduced magnesium r e t e n t i o n at the absorption s i t e i n c h i c k s . I t was a l s o shown by O'Dell et al. (1960) using guinea pigs i n balance s t u d i e s that a high d i e t a r y phosphorus l e v e l decreased 31 magnesium absorption. Forbes (1963) observed that calcium and phosphorus depressed magnesium absorption and high calcium l e v e l s d r a s t i -c a l l y a ffected* phosphorus absorption i r r e s p e c t i v e of magnesium l e v e l s i n the d i e t . The b i o l o g i c a l antagonism between copper and z i n c was demonstrated by Smith and Larson (1946). Van Reen (1953) observed that copner supplementation a l l e v i a t e d the e f f e c t s of z i n c t o x i c i t y w h i l e the reverse r e a c t i o n was reported by R i t c h i e et al. (1963). Van Campen (1969) showed that copper-induced depression i n ^ Z n absorption was mediated at the i n t e s t i n a l l e v e l , p o s s i b l y due to d i r e c t competition between z i n c and copper f o r a common c a r r i e r . Kirchgessner and Grassmann (1969) reported that high l e v e l s of copper s u l f a t e supplementation i n p i g r a t i o n s produced higher r e t e n t i o n of i r o n , z i n c , manganese and c o b a l t . High d i e t a r y l e v e l s of cadmium depress copper uptake and even a r e l a t i v e l y small increase i n cadmium intak e can adversely a f f e c t copper metabolism when copper intakes are marginal (Underwood, 1977). Molybdenum and s u l f a t e can e i t h e r increase or decrease the copper s t a t u s of an animal, depending on t h e i r i n t a k e r e l a t i v e to that of copper (Underwood, 1977). Huisingh et al. (1973) proposed that copper can i n t e r a c t w i t h molybdenum to form a b i o l o g i c a l u n a v a i l a b l e Cu-Mo-complex (cup r i c molybdate). S u t t l e (1975) proposed the three way Cu-Mo-S i n t e r a c t i o n thereby e l i m i n a t i n g the u t i l i z a t i o n of d i e t a r y copper to animal. L a s s i t e r et'al. (1969) reported that increased d i e t a r y calcium enhanced manganese absorption i n r a t s . Conversely, increased manganese 32 i n the d i e t enhanced calcium absorption (Alcock and Maclntyre, 1960). Manganese a v a i l a b i l i t y i s a f f e c t e d by high d i e t a r y l e v e l s of calcium and i s b e l i e v e d to be due to a re d u c t i o n i n s o l u b l e manganese through absorption by s o l i d mineral (Schaible and Bandemer, 1942). Thomason et al. (1971) observed that manganese competes w i t h i r o n and co b a l t f o r common b i n d i n g s i t e s when t r a n s p o r t i n g these minerals from the lumen to mucosal c e l l s then to other p a r t s of the body. This showed that the a d d i t i o n of i r o n c o m p e t i t i v e l y i n h i b i t e d manganese absorption i n i r o n d e f i c i e n t r a t s . Conversely, high manganese intakes reduced i r o n absorption. (11) Feed Prooessing Processing may a f f e c t both the t o t a l q u a n t i t y of the mineral element and i t s b i o - a v a i l a b i l i t y . G rinding i s l i k e l y to make any feed i n g r e d i e n t more d i g e s t i b l e and thereby increase the n u t r i t i o n a l value of e s s e n t i a l n u t r i e n t s . When whole grains are compared with ground g r a i n s , the t o t a l d i g e s t i b l e n u t r i e n t content:".is higher i n the ground m a t e r i a l ( T i t u s and F r i t z , 1971), but the e f f e c t on s p e c i f i c minerals i s not known. Grinding may a l s o add elements to the feed. Ammerman et al. (1970) showed that g r i n d i n g c i t r u s pulp i n a Wiley m i l l s i g n i f i c a n t l y increased the q u a n t i t i e s of i r o n , copper, manganese and sodium. Processing may a f f e c t b i o - a v a i l a b i l i t y as w e l l as the t o t a l q u a n t i t y o f i r o n . Theuer et al. (1971) reported that i r o n added to l i q u i d i n f a n t formulas i n the form of po o r l y u t i l i z e d s a l t s became 33 much more a v a i l a b l e a f t e r r o u t i n e processing. Singsen (1948) demonstrated that a u t o c l a v i n g wheat bran made more of i t s phosphorus a v a i l a b l e to the growing chicken f o r bone development. Marked increase i n the in o r g a n i c phosphorus content by a u t o c l a v i n g was observed with i s o l a t e d soybean meal (O'Dell, 1962), sesame meal (Lease, 1966). Summers et al. (1967) showed that a s i g n i f i c a n t p r o p o r t i o n of the p h y t i n phosphorus of wheat bran can be made a v a i l a b l e to the chick f o r growth by steam p e l l e t i n g . However, p e l l e t i n g and crumbling the p e l l e t s do not a f f e c t the t r a c e minerals c o n t r i b u t i o n of the feed. Crumbled p e l l e t s had about the same mineral content and i r o n b i o -a v a i l a b i l i t y as d i d the mash from which they were made ( F r i t z , 1973). (12) Endocrine Influence Hormones were reported to a f f e c t mineral a v a i l a b i l i t y (Hanna and Maclntyre, 1960). A d m i n i s t r a t i o n of aldosterone to both normal and adrenalectomized r a t s r e s u l t e d i n decreases i n the apparent a v a i l a b i l i t y o f the d i e t a r y magnesium. These r e s u l t s were confirmed by Care and Rose (1963) i n the i n t a c t sheep using deoxy-corticosterone acetate i n s t e a d o f aldosterone. (13) Miscellaneous Factors There are miscellaneous f a c t o r s l i n k e d to mineral a v a i l a b i l i t y . Kienholz (1962) reported a f a c t o r (not phytate) i n peas which i n t e r f e r e d w i t h a v a i l a b i l i t y of z i n c f o r chick growth. Au t o c l a v i n g the peas 34 appeared to improve the s i t u a t i o n . I t was p o s t u l a t e d that .a'-heat • l a b i l e p r o t e i n l i k e l y i n t e r f e r e d w i t h z i n c a v a i l a b i l i t y . I t has al s o been reported by Davis et al. (1962) that a component which x a n bind z i n c , manganese and copper i n i s o l a t e d soybean p r o t e i n causes ch i c k s to develop the r e s p e c t i v e d e f i c i e n c y symptom because o f u n a v a i l a b i l i t y of t h i s m i n e r a l . However, a d d i t i o n of EDTA can improve the s i t u a t i o n , i . e . reduce the requirement of mineral supplementation. 35 MATERIALS AND METHODS Eleven wheat, ten corn and one soybean meal samples were c o l l e c t e d from a l o c a l commercial feed company between January and August, 1977. In a d d i t i o n , three b a r l e y samples were obtained from three d i f f e r e n t sources, a l o c a l feed company, a C h i l l i w a c k producer (B.C.) and Alaska. A t r i t i c a l e sample was obtained from Regina, Saskatcehwan. Wheat, corn and soybean samples were c o l l e c t e d randomly from d i f f e r e n t shipments of grains to the P o u l t r y N u t r i t i o n Unit at the U n i v e r s i t y o f B r i t i s h Columbia. A l l feed grains a r r i v e d i n ground form except the b a r l e y and t r i t i c a l e samples. A l l feed g r a i n s were re-ground with a Wiley M i l l equipped w i t h a one mm screen * i n the P o u l t r y Science Laboratory before being u t i l i z e d i n the experiment. Proximate a n a l y s i s was c a r r i e d out f o r a l l feed samples f o r dry matter, crude p r o t e i n (N x 6.25), ether e x t r a c t and ash content w i t h standardized methods described i n A.O.A.C. (1965). The crude f i b e r ( a c i d detergent f i b e r ) content of the feed i n g r e d i e n t was analysed by the method developed by Waldern (1971). The mineral content of the grains was determined by a dry ashing method followed by atomic absorption procedure (Heckman, 1967) except phosphorus where determinations were by spectro-photometer ( M i n i s t r y of A g r i c u l t u r e , F i s h e r i e s and Food, U.K., 1973). A l l a n a l y t i c a l r e s u l t s were expressed on a dry matter b a s i s . M i n e r a l (calcium, phosphorus, magnesium, manganese, z i n c and copper) 36 a v a i l a b i l i t y s t u d i e s were conducted on i n g r e d i e n t s u s i n g three week o l d growing b r o i l e r c h i c k s . In a d d i t i o n , the a v a i l a b i l i t y of i n o r g a n i c mineral calcium, phosphorus, magnesium, manganesej'zinc and copper, from various sources were stud i e d i n the s e r i e s of experimental t r i a l s . The b r o i l e r c h i c k s u t i l i z e d i n these experimental t r i a l s were purchased at one-day of age from a hatchery i n the.Fraser V a l l e y area of B.C. The chi c k s were r a i s e d i n s t a i n l e s s s t e e l thermostatic c o n t r o l brooder cages to three weeks of age before commencing the experiments. B r o i l e r chicks were fed a 20% crude p r o t e i n commercial s t a r t e d d i e t from day of age to three weeks. Feed and water were su p p l i e d ad libitum. A completely randomized block design"wasemployed.^in"-all '• a v a i l a b i l i t y t r i a l s . Chicks were weighed at three weeks of age and d i s t r i b u t e d to s t a i n l e s s s t e e l metabolism cages. The same s t a r t e r d i e t was o f f e r e d during the a c c l i m a t i z a t i o n p e r i o d and water was fed f r e e o f choice. Test d i e t s were o f f e r e d at about 25 days of age. The d e t a i l e d procedure w i l l be discussed l a t e r . Test d i e t consumption was recorded f o r each cage and f e c a l c o l l e c t i o n was c a r r i e d out at the end of each t e s t i n g p e r i o d . Data obtained were subjected to a n a l y s i s of variance (Snedecor, 1956) and a " s t a t i s t i c a l " comparison "of;'mearis was by ;the m u l t i p l e , range t e s t '(Tukey, 1963)': T r i a l 1: Mineral- Availability from-Wheat•iand-,.T-ritioale The t r i a l was conducted to estimate a v a i l a b i l i t y of calcium, phosphorus, magnesium, manganese, z i n c and:.copper from eleven wheat 37 samples and one t r i t i c a l e sample. Two hundred and eighty uniform s i z e three week o l d b i r d s were employed. A l l b i r d s were weighed and t r a n s f e r r e d randomly to the s t a i n l e s s s t e e l metabolism cages with four b i r d s per cage. The t e s t b i r d s remained on s t a r t e r d i e t u n t i l twenty-four days of age t o a c c l i m a t i z e t o the new environment.. •• On the twenty-fourth day, a l l b i r d s were:supplied with a s t a r t e r d i e t c o n t a i n i n g 0.3% f e r r i c oxide marker f o r four hours, then f a s t e d f o r s i x t e e n hours. Following the f a s t p e r i o d b i r d s were fed a s y n t h e t i c d i e t (Table 1) f o r four hours. Bir d s were then f a s t e d f o r another hour before r e t u r n i n g to the marker d i e t . Feces de r i v e d from the s y n t h e t i c d i e t were c o l l e c t e d ( i . e . the feces obtained from the end of f i r s t batch o f marked excreta and the reappearing of the marked e x c r e t a ) . On the t w e n t y - f i f t h day, the same procedure was repeated except the wheat and t r i t i c a l e samples replaced the s y n t h e t i c d i e t . There were four r e p l i c a t e s f o r each test e d i n g r e d i e n t . Feed i n c l u d i n g s y n t h e t i c , t e s t d i e t s and water were o f f e r e d ad t-lbitvm during t e s t i n g p e r i o d . Limited water was given during the s i x t e e n hours f a s t i n g p e r i o d . Feed consumption of both s y n t h e t i c d i e t and t e s t d i e t s were recorded at the end of each p e r i o d . T o t a l marker-f r e e feces were c o l l e c t e d from each i n d i v i d u a l cage. The feces from each cage was oven d r i e d a f t e r c o l l e c t i o n at 85°C f o r 48 hours. The dry feces were weighed and ground i n t o the f i n e powder form with the microgrinder ( K u r z z e r t b e t r i e b ) . and col-lee-tea' f o r ; l a t e r mineral a n a l y s i s . TABLE 1: Composition of S y n t h e t i c Diet used throughout the Experimental T r i a l s Ingredient Percent Starch 40.6 Sucrose 40.6 A l p h a - c e l l u l o s e 13.8 Corn o i l 5.0 100.0 39 The mineral content o f wheat, t r i t i c a l e . s a m p l e s and feces from both s y n t h e t i c and d i e t s were determined by an atomic absorption spectrophotometer f o l l o w i n g a low temperature dry ashing at 450°C i n the muffle furnace f o r 36 hours. The phosphorus as w e l l as other minerals can t h e r e f o r e be determined from the ash sample. The a n a l y t i c a l method was described i n "The A n a l y s i s of A g r i c u l t u r a l M a t e r i a l s " ( M i n i s t r y of A g r i c u l t u r e , F i s h e r i e s and Food, U.K., 1973). Calcium, magnesium, manganese, z i n c and copper were determined by a J a r r e l Ash atomic absorption spectrophotometry. Lathanium oxide (0.5% v/w) was r e q u i r e d i n the t e s t s o l u t i o n to reduce the i n t e r f e r e n c e from phosphorus when calcium and magensium was analyzed. Phosphorus was determined by a Unican SP1800 U l t r a v i o l e t Spectrophotometer f o l l o w i n g c o l o r development with ammonium molybdate. The proximate a n a l y s i s of. wheat and t r i t i c a l e samples i s shown i n Table 2. Content of minerals i n samples determined and expressed on a dry matter b a s i s are shown i n Table 3. The formula used to c a l c u l a t e the percentage a v a i l a b i l i t y of min e r a l s a f t e r a n a l y s i s o f i n g r e d i e n t s and excreta was developed by Nwokolo et al. (1976) as f o l l o w s : Percent mineral a v a i l a b i l i t y = TMI - (TFME - EFME) TMI x 100 where TMI To t a l m i neral i n t a k e from feed i n g r e d i e n t TFME T o t a l f e c a l mineral excreted EFME Endogenous f e c a l mineral excreted TABLE 2: Chemical A n a l y s i s of the Eleven Wheat and One T r i t i c a l e Samples (dry matter ba s i s ) Dry Crude Ether Crude 1 matter p r o t e i n e x t r a c t f i b e r Ash Sample % Wheat #1 87.9 13. 1 2. .1 4. ,2 2. ,1 Wheat #2 92.2 14. 3 2. .4 4. .6 2. .0 Wheat #3 86.4 15. 1 2. .3 4. ,0 . 2. 0 Wheat #4 89.7 15. .6 1. .9 4. .0 1. .9 Wheat #5 90.0 15. 3 2. .1 3. .4 2. .1 Wheat #6 90.0 15. .7 2, .1 2. .3 1. .5 Wheat #7 88.1 14. ,7 2, .1 2. .9 1. .5 Wheat #8 89.7 16. .7 2 .1 2. .8 1. .6 Wheat #9 90.0 16. .2 2. .0 2, .6 1. ,7 Wheat #10 89.6 16. .7 2. .1 2. .7 1, .9 Wheat #11 88.9 17. .7 1 .6 3, .7 1, .6 T r i t i c a l e 92.7 12. .7 1. .6 3, .7 1. .6 Average 89.6 15. .3 2. .0 3 .4 1. .8 A c i d detergent f i b e r 41 TABLE 3: M i n e r a l Content of Eleven Wheat and a T r i t i c a l e Samples (dry matter ba s i s ) Sample Ca P Mg Mn Zn Cu ppm Wheat #1 500 4300 1500 44 38 23 Wheat #2 500 3900 1500 52 40 20 Wheat #3 600 4000 1500 58 52 19 Wheat #4 1000' 4000 1500 29 37 11 Wheat #5 600 3200 1500 48 33 11 Wheat #6 500 3300 1300 41 31 15 Wheat #7 800 3700 1300 29 45 18 Wheat #8 500 4400 1400 44 41 16 Wheat #9 600 4200 1500 45 35 19 Wheat #10 900 4400 1400 46 38 19 Wheat #11 600 4200 1500 39 38 16 T r i t i c a l e 600 3900 1500 43 26 22 Average 64.1+1681 3967+400 1450+80 43±8 38±7 17±:^ Standard d e v i a t i o n o f sample mean 42 The a v a i l a b i l i t y data was subjected to a n a l y s i s of var i a n c e and the s t a t i s t i c a l comparison of mean was the m u l t i p l e range t e s t (Tukey, 1953). Trial 2: 'Mineral Availability from Corn Corn samples were analysed f o r dry matter, crude p r o t e i n , ether e x t r a c t , crude f i b e r and ash as shown i n Table 4. The concentrations of calcium, phosphorus, magnesium, manganese, z i n c and copper i n the samples are shown i n Table 5. The procedure employed was the same as the procedure o u t l i n e d i n T r i a l 1. Trial 3: Mineral Availability from Barley The composition of the b a r l e y i s shown i n Table 6. The~xontent of minerals i s presented i n Table 7. The purpose of the t r i a l was not only to study the calcium, phosphorus, magnesium, manganese, z i n c and copper a v a i l a b i l i t y i n b a r l e y but a l s o the e f f e c t s of l o c a t i o n and source of the g r a i n on mineral a v a i l a b i l i t y . The C h i l l i w a c k and Alaska b a r l e y were obtained i n whole g r a i n form while the b a r l e y samples purchased from a l o c a l feed company was i n ground form. However, a l l b a r l e y samples were ground through a 1-mm siev e by a Wiley m i l l before the experiment. The experimental procedure was the same as o u t l i n e d i n T r i a l 1. TABLE 4: Chemical A n a l y s i s o f the Ten Corn Samples (dry matter b a s i s ) Dry Crude Ether Crude 1 . matter . protein- e x t r a c t f i b e r Ash Sample . . . . . . : : :— %•• — : — — : :  Corn #1 90.2 10. .9 4. .2 4.2 1.9 Corn #2 86.8 10. ,3 4. .2 3.8 1.6 Corn #3 86.8 11. .1 3. .8 4.3 1.9 Corn #4 90.0 10. .9 4. .2 2.9 1.4 Corn #5 90.4 10. .0 4. .2 2.7 1.4 Corn #6 88.1 11. .5 4. .2 2.5 1.3 Corn #7 88.0 11. .5 4. .3 2.4 1.2 Corn #8 89.9 11. ,2 4. .2 4.0 1.6 Corn #9 89.6 10. .3 3. .6 2.0 1.2 Corn #10. 88.1 9. .0 4. .0 • 2.2 1.4 Average 88.8 10. .7 4, .1 3.1 1.5 A c i d detergent f i b e r TABLE 5: Min e r a l Content of Ten Corn Samples (dry matter ba s i s ) Ca P Mg Mn Zn Cu Sample ppm Corn #1 600 3400 1300 35 40 20 Corn #2 500 3000 1100 35 35 21 Corn #3 500 2700 1000 26 23 18 Corn #4 400 3000 1200 13 31 16 Corn #5 700 2900 1300 14 20 16 Corn #6 200 2800 1200 8 29 18 Corn #7 200 2700 1200 9 21 21 Corn #8 500 3100 1200 11 19 16 Corn #9 200 3300 1100 11 22 16 Corn #10 500 3300 1100 11 21 16 Average 430±1>781 3 0-2 0± 25 2 1170+95 17+11 26±'7 18±: Standard d e v i a t i o n o f sample ohean TABLE 6: Chemical A n a l y s i s o f Three Barley Samples from D i f f e r e n t Sources (dry matter b a s i s ) Dry Crude Ether Crude matter p r o t e i n e x t r a c t f i b e r Ash Sample % Barley #1 87.4 12.0 2.2 6.5 3.2 (Commercial) Barley #2 87.0 12.5 2.0 7.6 2.3 ( C h i l l i w a c k ) B a r l e y #3 93.3 15.8 2.4 7.3 1.5 (Alaska) Average 89.2 13.4 2.2 7.1 . 2.2 A c i d detergent f i b e r TABLE 7: The Mi n e r a l Content of Three Barley Samples from D i f f e r e n t Sources (dry matter b a s i s ) Ca P Mg Mn Zn Cu Sample ppm Barley #1 900 4600 : .1500 (Commercial) Barley #2 500 3400 1300 ( C h i l l i w a c k ) Barley #3 700 2800 1400 (Alaska) Average 700±2001 3600±917 14O0±1OO 29±-5 34+6 20+-2 35 26 26 38 27 38 19 19 22 Standard d e v i a t i o n of sample mean 47 Trial 4: Availability 'of 'Mineral in Diet Containing Biffevent Levels  °f Soybean Meal . • The o b j e c t i v e was t o study the e f f e c t on mineral a v a i l a b i l i t y on- the l e v e l s of soybean meal ( i . e . p r o t e i n concentration) i n the feed. Soybean meal was purchased from a l o c a l feed company. The composition of the soybean meal and d i e t a r y treatments were analysed and presented i n Table 8. The mineral content of the soybean meal was shown i n Table 9. The n i t r o g e n and m i n e r a l - f r e e s y n t h e t i c d i e t used i n t h i s t r i a l was the same as was used i n T r i a l 1. Five l e v e l s of soybean were mixed w i t h the appropriate amount of s y n t h e t i c d i e t i n a Hobart mixer (Model D-300). The experimental arrangement was a completely randomized design. There were four r e p l i c a t e s f o r each d i e t a r y treatment, each r e p l i c a t e included four b i r d s (three weeks of age). The procedure was b a s i c a l l y the same as o u t l i n e d i n T r i a l 1. T r i a l 5: Availability of Mineral in Diet Containing Different Levels of Wheat The experimental arrangement was the same as T r i a l 4 except wheat was employed as a t e s t i n g m a t e r i a l . The o b j e c t i v e of the experiment was to study the i n f l u e n c e of mineral a v a i l a b i l i t y of d i f f e r e n t l e v e l s of wheat. The proximate a n a l y s i s of wheat i s shown i n Table 10. The mineral contents of d i e t a r y treatments are shown i n Table 11. Experimental design and procedure were o u t l i n e d i n T r i a l s 1 and 4. TABLE 8: Proximate A n a l y s i s of Diets i n T r i a l --4 (dry matter b a s i s ) -Ether Crudel P r o t e i n e x t r a c t fiber- Ash Treatment % 1. Soybean meal (SBM) 52.0 1. .94 6. ,73 6.27 2. S.D.2 (S.D.) + 75% SBM 39.0 1. .46 5. .05 4.70 3. S.D. + 50% SBM 26.0 0. .97 3, .37 3.14 4. S.D. + 25% SBM 13.0 0, .49 1. .68 1.57 5. S.D. + 12.5% SBM 6.5 0, .24 0, .84 0.78 A c i d detergent f i b e r i. 'Synthetic diet as indicated i n Table 1 TABLE 9: Mi n e r a l Content o f Diets i n T r i a l 4 (dry; matter b a s i s ) ' Treatment Ca P Mg Mn Zn Cu ppm 1. SBM 1(100%) 3280 6500' 3030 41 52 16 2. S.D.2+75% SBM 2460 5000 2270 31 39 12 3. S.D.+50% SBM 1640 3100 1520 21 26 6 4. S.D.+25% SBM 820 1600 760 10 13 3 5. S.D.+12.5 SBM 410 800 380 5 7 2 Soybean meal Sy n t h e t i c d i e t as i n d i c a t e d i n Table 1 TABLE 10: Proximate A n a l y s i s of Diets i n T r i a l . , 5 (dry • matter ba s i s ) . '-. • Ether Crude P r o t e i n e x t r a c t f i b e r Ash Treatment : % 1. Wheat (100%) 17. ,7 1. .60 3. ,70 1. ,60 2. 2" S.D:. . + 75% wheat 13. ,3 1. .20 2. ,78 1. .20 3. S.D. + 50% wheat 8. .9 0. .80 1. ,85 0. .80 4. S.D. + 25% wheat 4. .4 0. .40 0. .93 0. .40 5. S.D. + 12.5% wheat 2. .2 0, .20 0, .46 0. .20 A c i d detergent f i b e r 'Synthetic d i e t as i n d i c a t e d i n Table 1 TABLE 11: Mi n e r a l Content o f Diets" in; T r i a l . 5 r (dry matfer • basi s ) ..."'. . Ca P Mg Mn Zn Cu Treatment ppm :  1. Wheat (100%) 580 3900 1530 39 38 16 •2. S.D.1+75% 435 2925 1148 29 29 12 wheat 3. S.D.+50% 290 1950 765 20 19 6 wheat 4. S.D.+25% 145 975 383 10 10 3 wheat 5. S.D.+12.5% 73 488 192 5 5 2 wheat Synt h e t i c d i e t as i n d i c a t e d i n Table 1 52 Trial 6: Availability of Calcium and Phosphorus from Calcium Phosphate (Dibasic) The calcium and phosphorus i n calcium phosphate has been regarded as h i g h l y a v a i l a b l e to l i v e s t o c k . Calcium and phosphorus content of most common f e e d s t u f f of p l a n t o r i g i n do not adequately support the normal f u n c t i o n s of animals, i n c l u d i n g maintenance, growth and reproduction. Calcium and phosphorus from inorganic sources are u s u a l l y incorporated i n t o predominantly p l a n t type d i e t s to meet the b i o l o g i c a l requirements. The a v a i l a b i l i t y of calcium i n various calcium sources f o r c h i c k s have been reported by many workers (Bethke et al., 1929; Waldroup et al., 1964; Spandrorf and Leong, 1965). The c r i t e r i a used were u s u a l l y growth and t i b i a a s h a n d the most a v a i l a b l e source was used as an index f o r other mineral sources. No t r u e a v a i l a b i l i t y data of calcium phosphate have been reported by using the b i o l o g i c a l assay method developed by Nwokolo et al. (1976) or a s i m i l a r procedure. The o b j e c t i v e of t h i s t r i a l was to study the a v a i l a b i l i t y of calcium phosphate to three-week o l d b r o i l e r c hicks as w e l l as the e f f e c t of l e v e l s of calcium and phosphorus i n the t e s t d i e t on a v a i l a b i l i t y of these minerals to the c h i c k s . Nine l e v e l s o f calcium and phosphorus were s t u d i e d i n t h i s t r i a l . Calcium phosphate was incorporated i n t o the s y n t h e t i c d i e t which was e s s e n t i a l l y m i n e r a l - f r e e . The nine d i e t a r y treatments are shown i n Table 12. The composition of the s y n t h e t i c d i e t was shown i n Table 1 of T r i a l 1. The experimental design and procedure was as o u t l i n e d i n T r i a l 1. Data c o l l e c t e d was subjected to a n a l y s i s o f variance and a s t a t i s t i c a l , comparison of means was by the m u l t i p l e range'test (Tukey, 1953). TABLE 12: O u t l i n e o f D i e t a r y Treatments i n T r i a l 6 Treatment Ca (%)* P (%)* 2 1. S.D. + 0. 0125 + 0. ,0097 2. S.D. + 0. 025 + 0. ,0194 3. S.D. + 0. 050 + 0. ,0388 4. S.D. + 0. 100 + 0. ,0766 5. S.D. + 0. 200 + 0. ,1553 6. S.D. + 0. 400 + 0. .3105 7. S.D. + 0. 800 + 0. .6210 8. S.D. + 1. 200 + 0, .9315 9. S.D. + 1. 600 + 1, .2420 ''"Calcium phosphate 2 Syn t h e t i c d i e t as source ( d i b a s i c ) i n d i c a t e d i n Table 1 54 Trial 7: Availability of Magnesium from Magnesium Carbonate Magnesium has been recognized as an important e s s e n t i a l d i e t a r y mineral f o r many years and under a number of feeding s i t u a t i o n s supplemental magnesium i s r e q u i r e d f o r optimum performance. Most work i n magnesium a v a i l a b i l i t y was c a r r i e d out with ruminant animals because of the high incidence of d e f i c i e n c y found i n t h i s species. Data reported i n d i c a t e s the r e l a t i v e a v a i l a b i l i t y r a t h e r than true a v a i l a b i l i t y . Cereal grains are the major feed i n g r e d i e n t s f o r monogastric animals. Cereals g e n e r a l l y supply adequate magnesium to meet monogastric animal needs. Therefore, no inorganic magnesium i s u s u a l l y supplemented to the balanced d i e t . L i t t l e i n f o r m a t i o n on i n o r g a n i c magnesium a v a i l a b i l i t y has been reported i n the l i t e r a t u r e f o r p o u l t r y . The present t r i a l was designed to estimate the tr u e a v a i l a b i l i t y o f magnesium from magnesium carbonate u s i n g growing b r o i l e r c h i c k s . D i e t s .containing s i x " l e y e l s of magnesium were formulated as shown i n Table 13. Levels range from below to an excess of the magnesium requirement according to NRC-- N u t r i e n t Requirements:of.Eoultry (1977). The procedure used f o r the experiment i s the same as o u t l i n e d i n T r i a l 1. Data obtained were subjected to a n a l y s i s of variance and the d i f f e r e n t means were t e s t e d f o r m u l t i p l e range a n a l y s i s (Tukey, 1953). TABLE 13: O u t l i n e of D i e t a r y Treatments i n T r i a l 7 Treatment Mg l e v e l (ppm) 1. S. .D.2 + ; 150 2. S. .D. + 300 3. S. .D. + 450 4. S. ,D. + 600 5. s. ;D. + 750 6. s, .D. + 900 Magnesium carbonate source • 'Synthetic d i e t as i n d i c a t e d i n Table 1 56 Trial 8: Availability of Manganese from Manganese Sulfate Manganese content of the conventional feed i n g r e d i e n t s i s g e n e r a l l y low. Inorganic manganese from various sources i s always included i n the d i e t to prevent manganese d e f i c i e n c y . Very l i m i t e d i n f o r m a t i o n i s a v a i l a b l e concerning the b i o a v a i l a b i l i t y of manganese i n v a r i o u s i n o r g a n i c sources. An e a r l y study by Schaible and Bandemer (1942) reported that manganese i n the forms of oxide, carbonate, s u l f a t e and c h l o r i d e i s e q u a l l y a v a i l a b l e to p o u l t r y . However, l a t e r i n v e s t i g a t i o n i n d i c a t e d that d i f f e r e n c e s e x i s t e d i n manganese a v a i l a b i l i t y from v a r i o u s i n o r g a n i c sources (Henning et al., 1967; Watson et al., 1970; 1971). Most of the work was done q u a l i t a t i v e l y i n s t e a d of q u a n t i t a t i v e l y . Therefore, no tr u e a v a i l a b i l i t y value has been reported f o r b i o l o g i c a l a v a i l a b i l i t y from i n o r g a n i c sources. The present study was designed to evaluate the b i o a v a i l a b i l i t y of manganese i n manganese s u l f a t e as w e l l as the e f f e c t o f d i e t a r y l e v e l s of the manganese supplement on the a v a i l a b i l i t y of manganese f o r growing c h i c k s . The d i e t a r y treatments of t h i s t r i a l are shown i n Table 14. The procedure used f o r the t r i a l was s i m i l a r to that o u t l i n e d i n T r i a l 1. T r i a l 9: Availability of Zinc from Zino Oxide L i t t l e i n f o r m a t i o n i s a v a i l a b l e i n the l i t e r a t u r e regarding the i n o r g a n i c z i n c a v a i l a b i l i t y to animals. Edwards (1959) reported that z i n c i n the form of z i n c s u l f a t e , w i l l e n i t e , z i n c carbonate and zin c oxide (A.R. grade) i s r e l a t i v e l y a v a i l a b l e to the young growing TABLE 14: O u t l i n e of D i e t a r y Treatments i n T r i a l 8 Treatment Mn l e v e l (ppm) 1. S. .D.2 + .'25 2. S. ,D. + 50 3. S. .D. + 75 4. S. .D. + 100 5. S. ,D. + 125 Manganese s u l f a t e source 'Synthetic d i e t as i n d i c a t e d i n Table 1 58 chicks, whereas z i n c i n s p h a l e r i t e (mostly z i n c s u l f i d e ) and i n f r a n k l i n i t e (oxide o f z i n c , i r o n , manganese) i s l a r g e l y u n a v a i l a b l e . There are no tr u e a v a i l a b i l i t y values reported i n the l i t e r a t u r e . The present experiment was conducted tp*-study the a v a i l a b i l i t y of z i n c from z i n c oxide and the i n f l u e n c e o f l e v e l s o f z i n c oxide ' o n " a v a i l a b i : l i t y of Zn to growing c h i c k s . F i v e d i e t a r y treatment l e v e l s were u t i l i z e d as shown i n Table 15. The experimental procedure was the same as o u t l i n e d i n T r i a l 1. Trials' 10 and 11: Availability of Copper from Copper Sulfate S i m i l a r to most other t r a c e m i n e r a l s , the a v a i l a b i l i t y value of copper from v a r i o u s i n o r g a n i c sources i s not a v a i l a b l e . An e a r l y study by Schultze et al. (1936) i n d i c a t e d that copper of copper s u l f i d e or copper prophyrin was not u t i l i z e d by r a t s whereas copper i n oxide, hydroxide and pyrophosphate forms 'twas- r e a d i l y u t i l i z e d . The o b j e c t i v e of the present study was to estimate the a v a i l a b i l i t y of copper i n copper s u l f a t e to the growing b r o i l e r chicks and the i n f l u e n c e of copper l e v e l s i n the d i e t on copper a v a i l a b i l i t y . The d i e t a r y treatments i n T r i a l s 10 and 11 are presented i n Tables 16 and 17. T r i a l 10 was arranged to study the lower l e v e l s of d i e t a r y copper, whereas, T r i a l 11 was c a r r i e d out i n the higher range of d i e t a r y treatments. E i g h t y b i r d s were employed i n these t r i a l s . The experimental procedure was the same as o u t l i n e d i n T r i a l 1. TABLE 15: O u t l i n e of D i e t a r y Treatments i n T r i a l 9 Treatment Zn l e v e l (ppm) 1. S. 2 ,D. + 25 2. S. D. + 50 3. S. ,D. + 75 4. s. ,D. + 100 5. s, .D. + 125 Zinc oxide source 2 S y n t h e t i c d i e t as i n d i c a t e d i n Table 1 TABLE 16: O u t l i n e of D i e t a r y Treatments i n T r i a l 10 Treatment C u ^ l e v e l (ppm) 1. S.D.2 + 2 2. S.D. + 4 3. S.D. + 8 4. S.D. + 16 5. S.D. + 32 Copper s u l f a t e source 'Synthetic d i e t as i n d i c a t e d i n Table 1 TABLE 17: O u t l i n e of D i e t a r y Treatments i n T r i a l 11 1 Treatment Cu l e v e l (ppm) 2 1. S. ,D. + 50 2. S. ;D. + 100 3. S. ,D. + 150 4. S. .D. + 200 5. S. ;D. + 250 Copper s u l f a t e source Sy n t h e t i c d i e t as i n d i c a t e d i n Table 1 62 RESULTS AND DISCUSSION Trial 1 The mineral content of the wheat samples i s shown i n Table 3. Wheat i s high i n phosphorus (average 3,967 ppm) and magnesium (1,4'50 ppm), but low i n calcium (641 ppm), manganese (43 ppm), z i n c (38' ppm) and copper (17 ppm). These were considerable v a r i a t i o n s i n mineral content w i t h i n the samples t e s t e d , e s p e c i a l l y w i t h respect to calcium, manganese, zin c and copper. The v a r i a t i o n s may be due to d i f f e r e n t s o i l type, genetic d i f f e r e n c e of wheat samples and i n f l u e n c e of season and s t a t e of m a t u r i t y (Underwood, 1977). M i n e r a l content i n wheat does not s a t i s f y the minimum n u t r i t i o n a l requirement of l i v e s t o c k . The low mineral content and lack of a v a i l a b i l i t y data c o n t r i b u t e to neglect i n u t i l i z i n g these minerals to advantage i n a f o r m u l a t i o n . The high cost of feed i n g r e d i e n t s , i n c l u d i n g i n o r g a n i c mineral s a l t s , i n the f u t u r e w i l l c e r t a i n l y demonstrate the need to re-evaluate the mineral c o n t r i b u t i o n of wheat and other c e r e a l g r a i n s . The percent a v a i l a b i l i t y of minerals i n wheat samples i s shown i n Table 18. The average r e s u l t s of a l l the minerals t e s t e d i n d i c a t e that copper has the highest a v a i l a b i l i t y (78.6%) i n these g r a i n s . I t was followed by calcium (71%), phosphorus (67.4%), magnesium (53.5%), z i n c (49.6%) and manganese (48.4%). S i g n i f i c a n t v a r i a t i o n was observed among the g r a i n samples t e s t e d i n respect to a l l minerals stud i e d . TABLE 18: Percent A v a i l a b i l i t y of Min e r a l s from-Wheat and T r i t i c a l e Samples A v a i l a b i l i t y (%) Samples Ca P Mg Mn Zn Cu Wheat #1 . 70. ,4 b 69, ,3 C 52, , 3 b c 64, .3 6 50, , 6 d e 92, .9 1 Wheat #2 65. ,4 a 63. , o b c 56. ,3 C 56, . o c d 36. ,6 a 88. , 2 M Wheat #3 65. ,5 a 56. ,3 a 48. , 8 a b 59, . 3 d e 44. , o b 76, , 7 e f Wheat #4 65. ,5 a 62. ,2 b 46. , 6 a b 42, .8 b 44. , 5 b C 66. , 7 b C Wheat #5 82. ,9 d 76. , o d 56. ,1 C 51, .4 C 42. , o b 84. , 5 g h Wheat #6 70. ,5 b • 77. ,8 d 70. ,5 d 52, ,2 C 46. , o b c d 64. , 3 a b Wheat #7 67. ,8 a b 79. , o d 67. ,8 d 41, .4 b 65. , l g 91, .9 1 Wheat #8 64. ,7 a 61. , o a b 44. ,2 a 43. .3 b 48. , 9 C d e 74. , 6 d e Wheat #9 77. 2 C 66. , 2 b c 48. , o a b 41, ,8 b 51. ,7 3 81. , o f g Wheat #10 68. ^ ab 66. , 3 b G 45. ,2 a 39, , o a b 46. : b c d 70. , 8 c d Wheat #11 66. o a b 65. ,4 b 48. 4ab 34. ,9 a 62. ,3 g 60. ,6 a T r i t i c a l e 87. 5 d 66. , 9 b c 58. ,1 C 54. , 2 G d 57. , l f 90. , o h i Average 71:,Q±7.5 67.5±7.0 53.5±8.6 48.4±9-.l 49.6±8\4 78.5±11.3 Means w i t h d i f f e r e n t s u p e r s c r i p t s w i t h i n a column a r e . s i g n i f i c a n t l y d i f f e r e n t (P < 0.05). Standard d e v i a t i o n of sample mean 64 (a) Calcium Results i n d i c a t e a s i g n i f i c a n t / d i f f e r e n c e among samples of wheat and the m u l t i p l e range comparison (Tukey t e s t ) showed no s i g n i f i c a n t d i f f e r e n c e among wheat sample numbers 2, 3, 4, 7, 8, 10 and 11. However, d i f f e r e n c e s were observed when compared to sample, numbers 1, 5, 6, 9 and t r i t i c a l e . Wheat #5 i s s i g n i f i c a n t l y higher than any other wheat sample with the exception that i t d i d not d i f f e r from t r i t i c a l e . In the review o f l i t e r a t u r e , no a v a i l a b i l i t y data f o r minerals i n wheat were reported. This was probably because the low calcium content i n wheat d i d not s t i m u l a t e i n v e s t i g a t i o n , and there was no simple and r a p i d procedure to study the mineral a v a i l a b i l i t y before 1976. The inexpensive calcium source from limestone has al s o discouraged calcium a v a i l a b i l i t y study. However, the r e s u l t s i n t h i s experiment showed that the average calcium a v a i l a b i l i t y of wheat was 71.0%, which was.'.in agreement with d i e t a r y calcium r e t e n t i o n s t u d i e s o f complete d i e t s employing r a d i o a c t i v e isotopes by Driggers and Comar (1949), and more r e c e n t l y by Bragg et al. (1971). These i n v e s t i g a t o r s reported that approximately 70% of the d i e t a r y calcium was r e t a i n e d by l a y i n g hens. Nwokolo et al. (1976), u s i n g three-week o l d b r o i l e r c h i c k s reported s i m i l a r a v a i l a b i l i t y values (72.6%) f o r soybean, rapeseed, cottonseed.., and palm!.kernel meal. Results from t h i s study were a l s o i n agreement w i t h the data published by Armstrong and Thomas (1952), Armstrong 65 et al. (1953), and Armstrong (1957), using various herbs of grassland as w e l l as Devadatta and Appana (1954), i n s t u d i e s o f v a r i o u s vegetables. I t appears that calcium a v a i l a b i l i t y to animals i s s i m i l a r from v a r i o u s p l a n t sources. (b) Phosphorus The phosphorus a v a i l a b i l i t y v a r i e d from sample to sample as shown i n Table 18. The-values ranged from :56.'3 to 79%-for eleven wheat and one t r i t i c a l e samples-. The average phosphorus a v a i l a b i l i t y of eleven samples of wheat and t r i t i c a l e was 67.4%. 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 phosphorus a v a i l a b i l i t y among these g r a i n samples. Phosphorus a v a i l a b i l i t y from wheat sample numbers 5, 6 and 7 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 one another but were s i g n i f i c a n t l y higher than any other sample. Wheat numbers 1, 2, 9 and 10 and t r i t i c a l e - were s i g n i f i c a n t l y higher than wheat number 3. There was no d i f f e r e n c e among wheat numbers 2, 4, 8, 9, 10, 11 and t r i t i c a l e . Wheat number 2 was s i g n i f i c a n t l y higher than wheat number 11. H o s h i i and Hoshida (1978a) reported that v a r i a t i o n e x i s t e d f o r phosphorus a v a i l a b i l i t y i n wheat. They demonstrated a s i g n i f i c a n t d i f f e r e n c e between two s t r a i n s of wheat (Glenlea and P i t i c 62). The wheat samples obtained f o r the present experiment a r r i v e d from the commercial wheat p o o l . Therefore wheat samples may have o r i g i n a t e d at a number of l o c a t i o n s w i t h the d i f f e r e n t date of shipments. V a r i e t y d i f f e r e n c e s are a l s o p o s s i b l e . 66 I t has been g e n e r a l l y considered that phosphorus of p l a n t o r i g i n i s p o o r l y a v a i l a b l e due to the i n f l u e n c e of phytates (Taylor, 1965). However, there i s wide disagreement among.- • i n v e s t i g a t o r s on the a b i l i t y of c h i c k s to u t i l i z e phytate phosphorus. Ashton et al. (1960) observed that four-week o l d c h i c k s r e t a i n e d approximately 20% of phytate phosphorus while six-week o l d c h i c k s r e t a i n e d 36% to 49% of t h i s phosphorus. Nelson et al. (1968) showed th a t phytate phosphorus of commercial soybean meal was completely u n a v a i l a b l e . Temperton and Cassidy (1964) reported that c h i c k s u t i l i z e d approximately 60% of the non-phytate phosphate. Salman and McGinnis (1968) showed that u t i l i z a t i o n of phosphorus from p l a n t o r i g i n i n l a y i n g hens was q u i t e high. Recently, Nwokolo et al. (1976) reported that a v a i l a b i l i t y of phosphorus from p r o t e i n supplements, soybean; rapeseed; c o t t o n s e e d a n d palm ker n e l meal, to four-week o l d b r o i l e r c h i c k s were 89.3, 74.8, 76.9 and 70.8%, r e s p e c t i v e l y . Most r e c e n t l y H o s h i i and Yoshida (1978a)showed that the phosphorus i n wheat and wheat bran were over 60% a v a i l a b l e . However, the n u t r i t i o n a l committee f o r NRC (1969) suggested that the a v a i l a b l e phosphorus from p l a n t o r i g i n was approximately 20-50% f o r c h i c k s or swine. Results i n the t h i s study showed that the a v a i l a b i l i t y of phosphorus i n wheat was 67.4%. This agreed w e l l with the r e s u l t s reported by H o s h i i and Yoshida (1978b),, us i n g toe ash and carcass phosphorus content as c r i t e r i a i n the determination. The e x i s t i n g work i n pigs f o r phosphorus a v a i l a b i l i t y shows/ -rower. •yaiues'''an'most 67 cases fox feed o f p l a n t o r i g i n (Besecker et al., 1967; Bayley and Thomson, 1969; Tonroy et al., 1973). Most of these s t u d i e s u t i l i z e d apparent d i g e s t i b i l i t y as the c r i t e r i o n o f measurement. The apparent a v a i l a b i l i t y values underestimate the true a v a i l a b i l i t y because endogenous phosphorus e x c r e t i o n has not been considered. (a) ' Magnesium S i g n i f i c a n t ' v a r i a t i o n was observed f o r the magnesium a v a i l a b i l i t y i n a l l the wheat samples. Percent a v a i l a b i l i t y ranged from 44.2 to 70.5% and the mean of samples i n c l u d i n g t r i t i c a l e was 53.5%. Wheat numbers 6 and 7 were s i g n i f i c a n t l y higher than any other wheat sample. Wheat numbers 2, 5 andi t r i t i c a l e were s i g n i f i c a n t l y higher than wheat numbers 3, 4, 8, 9, 10 and 11. The former and the l a t e r groups d i d not d i f f e r from each other. The average value i n t h i s study was s l i g h t l y higher than the value (48.1%) reported by Guenter and S e l l (1974), u s i n g intramuscular 28 i n j e c t i o n o f r a d i o a c t i v e Mg. However, most of the values i n wheat ranged between 44.2 to 58.1%. Recently, Nwokolo et al. (1976) reported that the a v a i l a b i l i t y of magnesium i n soybean, rapeseed, cottonseed and palm k e r n e l meals was 77.4, 61.1, 74.6 and 56.4%, r e s p e c t i v e l y . These values were higher than wheat i n the present study. In ruminants, Peer (1972) i n d i c a t e d that magnesium a v a i l a b i l i t y i n forage ranged from 10 to 25% with a mean of approximately 20%. Grains and p r o t e i n concentrates ranged from 30 to 40%. 68 On the b a s i s of information reported i t appears that a v a i l a b i l i t y of magnesium i s lower i n wheat than was observed i n pl a n t p r o t e i n concentrates. In general, no magnesium supplementation i s r e q u i r e d i n p o u l t r y d i e t s because the feed ingredients, .supply an. adequate amount of a v a i l a b l e magnesium. -(d). Manganese Results i n d i c a t e d that there were s i g n i f i c a n t d i f f e r e n c e s among the wheat and t r i t i c a l e samples t e s t e d . A v a i l a b i l i t y of manganese ranged from 34.9 (wheat 11) to 64.3% (wheat 1) with the mean of 48.4% f o r eleven samples and t r i t i c a l e . Wheat number 1 d i d not d i f f e r from wheat number 3, but was s i g n i f i c a n t l y higher than other wheat samples. Wheat numbers 2, 3 and t r i t i c a l e were s i g n i f i c a n t l y higher than wheat numbers 7, 8, 9, 10 and 11, while wheat numbers 2, 5, 6 and t r i t i c a l e were not s i g n i f i c a n t l y d i f f e r e n t . L i t t l e i n f o r m a t i o n has been reported on manganese a v a i l -a b i l i t y f o r wheat i n the l i t e r a t u r e . The r e l a t i v e l y poor content as w e l l as poor a v a i l a b i l i t y of manganese i n wheat can cause the manganese d e f i c i e n c y problem i n chicks without d i e t a r y manganese supplementation. An i n o r g a n i c manganese s a l t i s u s u a l l y employed as the supplement f o r p o u l t r y d i e t s . Nwokolo (1977) showed that manganese i n palm ke r n e l meal was p o o r l y a v a i l a b l e (45.1%) whereas f a i r l y high a v a i l a b i l i t y was observed i n soybean (76.1%) and cottonseed > (76.3%) and a lower value f o r rapeseed meal (56.7%). 69 (e) Zinc The average z i n c content of wheat samples and t r i t i c a l e was 37 ppm. S l i g h t v a r i a t i o n i n z i n c content was observed except i n wheat number 3 which showed the highest value, 52 ppm. Results (Table 18) showed that z i n c a v a i l a b i l i t y of wheat and t r i t i c a l e ranged from 36.6% (wheat number 3) to 65.1% (wheat number 7) with a mean of 49.6%. Zinc a v a i l a b i l i t y of wheat was higher i n wheat number 7 and 11 and lowest i n wheat number 2. Wheat numbers 3, 4, 5, 6 and 10 were .not s i g n i f i c a n t l y d i f f e r e n t , whereas t r i t i c a l e was higher than any other wheat sample except wheat numbers 7 and 11. The r e s u l t s i n d i c a t e d considerable v a r i a t i o n among the wheat samples. The average value of wheat was lower than soybean meal (66.5%) and rapeseed meal (57.6%) but higher than cottonseed meal (38.0%) and palm ke r n e l meal.(13.9%), reported by Nwokolo et al. (1976). O'Dell et al. (1972) reported that the a v a i l a b i l i t y of z i n c i n sesame meal, soybean meal and f i s h meal were 57.0, 67.0 and 75.0%, r e s p e c t i v e l y f o r c h i c k s . Evans and "Johnson ((1977) a l s o reported that z i n c a v a i l a b i l i t y i n raw corn endosperm was 51.0% f o r r a t s . The zihc-xequiremeht f o r : t h e . growing . b r o i l e r . ; chick i s 40 ppm (NRC, 1977). The low content and low z i n c a v a i l a b i l i t y i n wheat suggests that z i n c supplementation i s needed i f wheat i s used predominantly, as the energy source of the d i e t . if) Copper The r e s u l t s showed that copper i n wheat and t r i t i c a l e samples were h i g h l y a v a i l a b l e . The copper a v a i l a b i l i t y f o r wheat 70 samples ranged from 60.6 (wheat number 11) to 92.6% (wheat number 1) with a mean of 78.5%. This value was higher than that of any other mineral t e s t e d . Wheat numbers 1, 2, 7 and t r i t i c a l e showed the highest a v a i l a b l e copper f o r c h i c k s . These wheat and t r i t i c a l e samples 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 each other, but were s i g n i f i c a n t l y higher than wheat numbers 3, 4, 6, 8, 9, 10 and 11. Wheat number 11 was s i g n i f i c a n t l y lower than oher samples t e s t e d . Nwokolo et al. (1976) reported that the copper a v a i l a b i l i t y values, from' soybean, rapeseed, cottonseed and palm kernel meals were 51, 62.2, 42.3 and 44.7%, r e s p e c t i v e l y . These p r o t e i n supplements had • lower copper a v a i l a b i l i t y ' than wheat i n t h i s , study.. .The d i f f e r e n c e may be due to the higher p r o t e i n content of the p r o t e i n concentrates since copper can form an i n s o l u b l e complex with p r o t e i n and reduce the absorption of copper (Underwood, 1977). Trial 2 The chemical composition of corn samples u t i l i z e d i n t h i s study i s presented i n Table 4. The average crude p r o t e i n , ether e x t r a c t , crude f i b e r and ash were 10.J, .4,1, 3.1 and 1.5% (D.M.), r e s p e c t i v e l y . The mineral content of corn samples was shown i n Table 5. S i m i l a r to wheat, corn was high i n phosphorus (3020 ppm) and magnesium (1170 ppm) but low i n calcium (430 ppm), manganese (17 ppm), z i n c (26 ppm) and copper (18 ppm). A l l values were reported on dry matter b a s i s . The r e s u l t s of mineral (Ca, P, Mg, Mn, Zn and Cu) a v a i l a b i l i t y f o r corn samples to three-week o l d b r o i l e r c h i c k s were shown i n Table 19. TABLE 19: A v a i l a b i l i t y of Minerals from ten Corn.Samples A v a i l a b i l i t y (%) Sample Ca P Mg Mn Zn Cu Corn #1 71. , 7 d e 72. , 2 e 56. , 6 d 70. , 1 6 65. , 5 d 8 6 . 6 b c Corn #2 65. , 2 b 52. 9 a b 55. y C d 77. , 3 f 72. , 5 e 9 2 . 7 e Corn #3 59. , 9 a 49. o a 52. jbcd 63. , l d 46. , 3 b 8 6 . 1 b c Corn #4 70. , 9 c d 65. 9 d 55. yCd 55. , 8 b c 77. . I 6 9 1 . 7 d e Corn #5 75. , 8 f 59. 1 C 51. g b c d 64. ^de 44. 2ab 9 4 . 5 e Corn #6 76. 6 £ 68. 5 d e 50. ^bc 61. ^cd 62, ^ d 8 7 . 7 c d Corn #7 68. 3 b c d 69. Qde 47. 3 a b 56. , 2 b c 41. , 2 a 8 6 . 0 b c Corn #8 68. Q b c d 58. 3 b c 47. ^ab 50. , 4 b 53. ,4 C 8 2 . 9 a b Corn #9 75. 6 e f 59. 3 C 48. 3ab 56. , 3 C 65. , o d 8 1 . 5 a Corn #10 67. 54. 4 b c 44. l a 44. , 6 a 47. , 5 b 8 2 . 5 a b Average 70<0i$:-32 60;'9i7-;7 51::6+4H3 6 0 ^ 9 . 5 57..6+12.7 87v2±4?.5 Means with d i f f e r e n t s u p e r s c r i p t s a&ithin • a'--;"eoljiffii "are' ;sighi'£icantly. different '(.Pfi .0705J Standard d e v i a t i o n of sample mean 72 Corn has been used e x t e n s i v e l y i n p o u l t r y feeding and the mineral a v a i l a b i l i t y data w i l l be v a l u a b l e to formulate l e a s t cost d i e t s . The a v a i l a b i l i t y r e s u l t s showed that s i g n i f i c a n t v a r i a t i o n (B < 0.05) e x i s t e d i n corn samples f o r a l l the minerals .tested. This v a r i a t i o n may be a combination of i n f l u e n c e s such as v a r i e t y , s o i l - t y p e and environmental factors.. Although corn has long been used f o r animal feed, l i t t l e i s known of i t s mineral a v a i l a b i l i t y . The f o l l o w i n g d i s c u s s i o n w i l l deal w i t h the a v a i l a b i l i t y of i n d i v i d u a l minerals to the growing b r o i l e r . (a) Calcium The calcium content of the ten corn samples v a r i e d from 200 to 700 ppm, w i t h an average of 400 ppm-. This was s l i g h t l y higher than values c u r r e n t l y reported (NRC, 1977). The calcium a v a i l a b i l i t y i n ten corn samples ranged from 59.9 to 76.6%" with the mean of 70.0%. V a r i a t i o n s between samples were h i g h l y s i g n i f i c a n t (p < 0.05). Corn numbers 5 and 6 were s i g n i f i c a n t l y higher than other corn samples except corn number 9. Corn number 3 had a" s i g r i i f i c a r i t l y 1 l"ower a v a i l a b i l i t y value than other samples. Corn numbers 2 , 7 , 8 and 10 d i d not d i f f e r s i g n i f i c a n t l y from each other. A s i m i l a r s i t u a t i o n was observed i n corn numbers 1, 4, 7 and 8. The a v a i l a b i l i t y value of calcium i n corn i s moderately high and s i m i l a r to values obtained f o r wheat i n T r i a l 1. Published i n f o r m a t i o n i s l a c k i n g wTth''"'reg.ard-to^calcium a v a i l a b i l i t y i n corn. P h y t i c a c i d has been reported to a f f e c t 73 mineral a v a i l a b i l i t y i n c l u d i n g calcium (Bruce and. Callow, 1934), phosphorus ( G i l l i s et al., 1957; Nelson, 1967), magnesium (Robert and Yudkin, 1961; Lukuski and Forbes, 1956), and z i n c (O'Dell and Salvage, 1960; Ha-vies and N i g h t i n g a l e , 1975), manganese and copper (Daviessand N i g h t i n g a l e , 1975). The p h y t i c content reported f o r corn and wheat was 0.6 and 0.7%, r e s p e c t i v e l y (Nelson et al., 1968). This may e x p l a i n , p a r t l y , the s i m i l a r i t y of calcium a v a i l a b i l i t y f o r these two g r a i n s . (b) Phosphorus Results showed that phosphorus a v a i l a b i l i t y i n corn ranged from 49 to 72.2% w i t h a mean of 60.9%. Corn numbers 1, 6 and 7 were s i g n i f i c a n t l y higher than corn numbers 2, 3, 5, 8, 9 and 10, whereas 5, 8, 9 and 10 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 each other as w e l l as corn number 2, 8, and 10. The N a t i o n a l Research Council (1969) suggested that phosphorus a v a i l a b i l i t y from p l a n t o r i g i n was about 20-50% due to the high phytate content of the g r a i n s ' source. Although the t o t a l phosphate i n corn and wheat i s 66 and 67% of phytate phosphorus, r e s p e c t i v e l y (Nelson et al., 1968), r e s u l t s f o r a v a i l a b l e phosphorus i n corn i s somewhat lower than the value observed f o r wheat i n T r i a l 1. The higher value i n wheat may be explained by the higher phytase a c t i v i t y of wheat (McCance and Widdowson, 1944) which can c a t a l y z e the phytate phosphate d i g e s t i o n i n the gut. There.has always been a controversy regarding the . a v a i l a b i l i t y of phosphate from.ingredients, of p l a n t o r i g i n f o r swine.and p o u l t r y . The 74 low phosphate a v a i l a b i l i t y from p l a n t sources has been reported to be 30-40% i n barley-wheat d i e t s (Woodman and Evans, 1948), 17.7% i n b a r l e y (Besecker et al., 1967), 19% i n corn-soy d i e t s (Bayley and Thomson, 1969), 4.5% i n sorghum (Tonroy, 1973), 16, 51. and 18% i n corn, wheat and soybean meal, r e s p e c t i v e l y . f o r pigs ( M i r a c l e et al., 1977). In most cases, studies were conducted using apparent d i g e s t i b i l i t y as a determination c r i t e r i o n . No endogenous e x c r e t i o n was c o r r e c t e d from the feces. This may e x p l a i n why the value o f a v a i l a b i l i t y was g e n e r a l l y lower. I t i s w e l l known that many other f a c t o r s may a l s o p l a y a r o l e i n rendering the phosphorus a v a i l a b l e i n gra i n s as reported i n the l i t e r a t u r e review. However, i t i s reasonable to b e l i e v e t h a t the phosphorus from p l a n t s i s c u r r e n t l y underestimated. The higher phosphorus a v a i l a b i l i t y from • pl a n t s f o r p o u l t r y -has-been supported by Salman and McGinnis (1968), and Nwokolo et al. (1976). The l a t t e r authors used the endogenous c o r r e c t i o n f o r the phosphorus a v a i l a b l e determination. The r e s u l t of present s t u d i e s a l s o i n d i c a t e d the higher phosphorus a v a i l a b i l i t y from corn f o r the growing b r o i l e r c h i c k s . (c) Magnesium The a v a i l a b i l i t y of magnesium i n corn samples ranged from 44.1 (corn number 10) to 56.6% (corn number 1), w i t h a mean of 51.0%. Magnesium a v a i l a b i l i t y was comparatively lower than the a v a i l a b i l i t y of other minerals " t e s t e d ;on.an, ayerage 'b'as rs'-.' ~ : 'Corn '^numbeF.T Was s ignif i -c a n t l y - h i g h e r than "corn numbers. "6,- 7~- .8, r9'.'and: 10'but" s i m r l a r "to corn 75 numbers 2, 3, 4, and 5. Corn numbers 5, 6, 7, 8 and 9 d i d not d i f f e r s i g n i f i c a n t l y from each other. Corn number 10 was s i g n i f i c a n t l y lower than corn numbers 1, 2, 3, 4, 5 and 6, but not s i g n i f i c a n t l y d i f f e r e n t from corn numbers 7, 8, 9 and 10. This i n d i c a t e s the v a r i a t i o n among samples taken from commercial s u p p l i e s of d i f f e r e n t time p e r i o d s . The average value of magnesium a v a i l a b i l i t y i n t h i s study was s l i g h t l y higher than the value (47.5%) published by Guenter and S e l l (1974), using intramuscular i n j e c t i o n 28 of r a d i o a c t i v e Mg i n r o a s t e r s . A l s o , a s i m i l a r yalue (53.5%) was obtained f o r wheat ( T r i a l 1). However,these values were lower than •that-for. soybean- (77.4.%)., rapeseed ( 6 1 . 1 % ) c o t t o n s e e d (74.6%). 1. and palm kernel"(56,4%) oneals- reported by Nwokolo.-.e'tal. (1976). It",Appears.that, p l a n t p r o t e i n concentrates supply-magnesium i n a more a v a i l a b l e , form.than do the grains (d) Manganese Results showed that the manganese a v a i l a b i l i t y of corn ranged from 44.6% (corn number 10) to 77.3% (corn number 2) with an average of 60% f o r growing b r o i l e r c h i c k s . Corn number 2 was s i g n i f i c a n t l y higher than any other corn samples; conversely, corn number 10 gave the lowest value. Corn numbers 3, 5 and 6 were s i m i l a r but were s i g n i f i c a n t l y higher than corn numbers 8 and 10. Corn numbers 4, 6, 7 and 9 d i d not s i g n i f i c a n t l y d i f f e r from each other. S i m i l a r to other m i n e r a l s , there was a wide v a r i a t i o n among the corn samples regarding manganese a v a i l a b i l i t y . -Since the t r a c e 76 mineral content i n corn was q u i t e low, the v a r i a t i o n may be a t t r i b u t e d to s o i l mineral and f e r t i l i z e r a p p l i c a t i o n on the f i e l d . Although i n o r g a n i c magnanese s a l t s are .currently £sed i n preventing the manganese d e f i c i e n c y , l i t t l e i nformation i s • a v a i l a b l e r e l a t i v e to manganese a v a i l a b i l i t y fxom e i t h e r p l a n t s or i n o r g a n i c s a l t s . The only s t u d i e s on p l a n t s were reported by Nwokolo et al. (1976) on p r o t e i n concentrates. These authors reported that the manganes a v a i l a b i l i t y of soybean, rapeseed, cotton seed and palm kernel meals were 76.1, 56.7, 76.3 and 75.7%, r e s p e c t i v e l y to growing b r o i l e r c h i c k s . Zinc The a v a i l a b i l i t y o f z i n c ranged from.41.2% (corn number 7) to 77.1% (corn number 4 ) , with a mean of 57.5%. Corn numbers 4 and 2 were higher than any other corn samples. Corn numbers 1 and 6 were s i g n i f i c a n t l y higher than corn numbers 3, 5, 7, 8 and 10. Corn number 7 was lowest compared to other corn samples. Corn numbers 3, 5 and 10 were not s i g n i f i c a n t l y d i f f e r e n t to each other. The r e s u l t s a l s o i n d i c a t e the v a r i a b i l i t y o f corn a v a i l a b i l i t y i n d i f f e r e n t samples. Evans and Johnson (1979) showed that z i n c a v a i l a b i l i t y i n raw corn endosperm f l o u r was 51% i n r a t experiments. O'Dell et al. (1972), using growth response of chicks as c r i t e r i a , reported that the a v a i l a b i l i t y of z i n c i n sesame, soybean and f i s h meals were 57, 67 and 75%, r e s p e c t i v e l y . Zinc a v a i l a b i l i t y i n soybean, rapeseed, cottonseed and palm k e r n e l meals was * a l s o reported by Nwokolo et al. (1976). 77 (f) Copper Copper a v a i l a b i l i t y was highest among a l l the minerals t e s t e d i n corn. The copper a v a i l a b i l i t y ranged from 81.5% (corn number 9) to 94.5% (corn number 5) with an average of 87.2%. Corn numbers 2, 4 and 5 were s i g n i f i c a n t l y higher than corn numbers 1, 3, 7, 8, 9 and 10 while corn numbers 1, 3, 7, 8 and 10 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 each•other. Corn number'9 (81.5%) had the lowest copper a v a i l a b i l i t y value. The r e s u l t s i n d i c a t e that copper i s h i g h l y a v a i l a b l e i n corn. However, the a v a i l a b i l i t y v a r i e d s i g n i f i c a n t l y among samples. The content of copper i n corn o f the present s t u d i e s was higher than c u r r e n t l y reported (NRC, 1960). The t o t a l amount of copper i n g r a i n i s small and the d i f f e r e n c e of copper content may be- a t t r i b u t e d to v a r i a t i o n , o f s o i l or f e r t i l i z e r a p p l i c a t i o n i n the f i e l d . T r i a l 3 The mineral content of three b a r l e y samples i s shown i n Table 7. The average c o n c e n t r a t i o n o f calcium, phosphorus, magnesium, manganese-, z i n c and copper were 600., 360Q , 1400 , 29, 34 and 20 ppm, r e s p e c t i v e l y . S i m i l a r t o wheat and corn, b a r l e y samples contained a high l e v e l of phosphorus and magnesium but were low i n calcium and tr a c e minerals. The t r a c e mineral content i n b a r l e y samples was higher than expected. The average mineral a v a i l a b i l i t y of commercial b a r l e y (barley number 1), C h i l l i w a c k b a r l e y (barley number 2) and Alaska b a r l e y (barley number 3 ) . f o r calcium, phosphorus, magnesium, z i n c and copper were 68.9, 68.8, 54.9, 54.9, 49.1 and 77.5%, r e s p e c t i v e l y (Table 20). TABLE 20: A v a i l a b i l i t y of Minerals i n Three Barley Samples C o l l e c t e d from D i f f e r e n t Places A v a i l a b i l i t y (%) Samples Ca P Mg r Mn Zn Cu Barley #1 (Commercial) 74.4 b 66.4 a 54. l a 65.8° 39.3 a 73.9 a Barley #2 ( C h i l l i w a c k ) 51.9 a 73. 2 b 53. l a 42.8 a 37.5 a 77.2 a t Barley #3 (Alaska) 80.5° 66. 9 a 57. 5 a 56. 2 b 70.6 b 81.4 b Average 68.9±15.1268 .8+3.8 54. 9±-2 .3 54.9±1T.6 49 .1+18. 6 77.5+3.'8 Means with d i f f e r e n t s u p e r s c r i p t s w i t h i n a column: are s i g n i f i c a n t l y , d i f f e r e n t (P- < 0.05) Standard d e v i a t i o n of sample mean 79 Calcium Results i n d i c a t e d that there were s i g n i f i c a n t v a r i a t i o n s among samples from the'-three d i f f e r e n t sources i n calcium a v a i l a b i l i t y . The calcium a v a i l a b i l i t y was-highest from'Alaska b a r l e y -(80.5%), lower f o r commercial b a r l e y (74.4%) and lowest i n the C h i l l i w a c k b a r l e y (51.9%). The commercial b a r l e y (barley number 1) was a l s o s i g n i f i c a n t l y higher than C h i l l i w a c k b a r l e y (barley number 2). The average calcium a v a i l a b i l i t y f o r b a r l e y (68.9%) was s i m i l a r to wheat (71.0%) and corn (70.0%) i n T r i a l s . 1 and. 2, r e s p e c t i v e l y . The r e s u l t s suggest that the source of grains c o n t r i b u t e s to the v a r i a b i l i t y i n mineral a v a i l a b i l i t y . Phosphorus The r e s u l t s showed that the phosphorus a v a i l a b i l i t y i n b a r l e y was moderately high (68.8%) f o r three-week o l d growing b r o i l e r c h i c k s . B a r l e y number 2 (73.2%) was s i g n i f i c a n t l y higher than b a r l e y number 1 (66.4%) and number 3 (66.9%) whereas there was no s i g n i f i c a n t d i f f e r e n c e between the l a t e r two b a r l e y samples. S i m i l a r phosphorus a v a i l a b i l i t y values were observed i n wheat ( T r i a l 1) and corn ( T r i a l 2). L i t t l e i nformation has been reported f o r phosphorus . ' a v a i l a b i l i t y i n b a r l e y f o r chicks." "Hayes et'al. (1979), u s i n g s u r v i v a l r a t e , growth r a t e , e f f i c i e n c y of feed u t i l i z a t i o n , breaking strength and ash content of the t i b i a as response c r i t e r i a , reported that phosphorus a v a i l a b i l i t y of b a r l e y was 50%. Besecker et al. (1967) reported that the apparent d i g e s t i b i l i t y of phosphorus i n 80 b a r l e y was 17.7% to the growing p i g . The value was r a t h e r low s i n c e endogenous e x c r e t i o n was not taken i n t o account. Therefore phosphorus a v a i l a b i l i t y f o r b a r l e y appears to be underestimated. Co) Magnesium 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 magnesium a v a i l a b i l i t y among the three b a r l e y samples from d i f f e r e n t sources. The a v a i l a b i l i t y o f b a r l e y numbers 1, 2 and 3 were 54.1, 53.1 and 57.5%, r e s p e c t i v e l y . w i t h the mean of 54.9%. This value was i n agreement with the r e s u l t (54.2%) reported by Guenter and S e l l 28 (1974) usi n g muscular i n j e c t i o n of r a d i o i s o t o p e Mg . The magnesium a v a i l a b i l i t y was a l s o s i m i l a r to wheat (53.5%) and corn (51.0%) i n T r i a l s 1 and 2, r e s p e c t i v e l y . (d) Manganese The r e s u l t s showed that there was s i g n i f i c a n t v a r i a t i o n among b a r l e y samples regarding manganese a v a i l a b i l i t y . Barley number 1 gave highest manganese a v a i l a b i l i t y (65.8%), followed by b a r l e y number 3 (56.2%) and b a r l e y number 2 (42.8%). The average manganese a v a i l a b i l i t y f o r three b a r l e y samples was 54.9%. No data i s a v a i l a b l e i n the l i t e r a t u r e concerning manganese a v a i l a b i l i t y i n b a r l e y . The manganese a v a i l a b i l i t y i n b a r l e y was higher than in'wheat (48.8%) and lower than i n corn (60.0%) reported i n T r i a l s 1 and 2, r e s p e c t i v e l y . Nwokolo et al. (1976) reported that the manganese a v a i l a b i l i t i e s i n soybean, rapeseed, cottonseed and palm k e r n e l meals were 76.1, 56.7, 76.3 and 45.7%, r e s p e c t i v e l y f o r growing c h i c k s . 81 (e) Zinc Zinc a v a i l a b i l i t y was s i g n i f i c a n t l y lower i n b a r l e y number 1 (39.3%) and b a r l e y number 2 (37.5%) compared to b a r l e y number 3 (70.6). The zi n c a v a i l a b i l i t y of Alaska ( i . e . b a r l e y number 3) was about two-fold higher than the other two b a r l e y samples from d i f f e r e n t sources. The r e s u l t s i n d i c a t e d that b a r l e y from d i f f e r e n t l o c a t i o n s can be expected to d i f f e r i n zi n c a v a i l a b i l i t y values. However, the average z i n c a v a i l a b i l i t y f o r these three b a r l e y samples was 49.1% which was s i m i l a r to the value of wheat (49.6%) and s l i g h t l y lower than corn (57.5%) reported i n e a r l i e r t r i a l s . (f) Copper The r e s u l t s showed that the a v a i l a b i l i t y of copper was the highest compared to other minerals. The average a v a i l a b i l i t y of these b a r l e y samples was 77.5%. Although the range between the low and high value samples was not great, i t was shown to be s i g n i f i c a n t l y d i f f e r e n t between b a r l e y number 1 (73.9%) and b a r l e y number 3 (81.4%). Barley number 2 (77.2%) d i d not d i f f e r s i g n i f i c a n t l y from other samples. The content of copper appears to be low compared to other minerals t e s t e d . The low requirements,of copper i n p o u l t r y ^explain the lack o f copper.deficiency i n general feeding without i n o r g a n i c copper supplementation. 82 General Discussion of Trials 1, 2 and 3 Wheat, corn and b a r l e y are the most common f e e d s t u f f i n North America and Europe. However, the mineral a v a i l a b i l i t y s t udies f o r these c e r e a l s have been very l i m i t e d . L imited research may be due to the low cost of the i n o r g a n i c minerals on the market and lack of r a p i d techniques to evaluate the t r u e a v a i l a b i l i t y . Most previous work on a v a i l a b i l i t y was concentrated on phosphate or phytate phosphorus because of the high cost of phosphorus. The increased•cost o f a l l feed i n g r e d i e n t s , both at present and i n the foreseeable f u t u r e , may increase i n t e r e s t i n more p r e c i s e knowledge r e l a t e d . t o a v a i l a b i l i t y . o f n u t rients, i n the "feedstuffs.. In g eneral, the minerals (Ca, P, Mg, Mn, Zn and Cu) t e s t e d ranged from moderate t o high i n a v a i l a b i l i t y f o r wheat, corn and b a r l e y i n the growing b r o i l e r c h i c k . Copper appeared to be the most a v a i l a b l e i n these c e r e a l s f o r c h i c k s . The phosphorus a v a i l a b i l i t y i n these c e r e a l s was most i n t e r e s t i n g because higher available-phosphorus was observed than those-reported i n the l i t e r a t u r e . The average r e s u l t s of wheat, corn and b a r l e y mineral a v a i l a b i l i t y are summarized i n Table 21. I t i s apparent that calcium a v a i l a b i l i t y from these c e r e a l s are s i m i l a r . Wheat was the highest (71.0%) followed by corn (70.0%) and b a r l e y (68.9%). The r e s u l t s of these s t u d i e s were i n agreement with d i e t a r y r e t e n t i o n studies using r a d i o a c t i v e isotopes by Drigger and Comar (1949) and Bragg et al. (1971). These i n v e s t i g a t o r s reported that approximately 70% of the d i e t a r y calcium was r e t a i n e d by the l a y i n g b i r d . More r e c e n t l y , Nwokolo et al: 83 TABLE 21: Summary of Min e r a l A v a i l a b i l i t y from Wheat, Corn and Barley A v a i l a b i l i t y (%) Sample Ca P Mg Mn Zn Cu Wheat 71.0 67.4 53.5 48.4 49.6 78.5 Corn 70.0 60.9 51.0 60.0 57.5 87.2 Barley 68.9 68.8 54.9- 54.9 49.1 77.5 84 (1976), using b r o i l e r c h i c k s , showed that the average calcium a v a i l a b i l i t y f o r vegetable p r o t e i n concentrate (soybean, rapeseed, cotton-seed and palm k e r n e l means) was 72.6%. These r e s u l t s are comparable to the r e p o r t s by Armstrong et al. (1953) i n three grasses and Devadatta and Appana (1954) i n v a r i o u s vegetable sources. Phosphorus a v a i l a b i l i t y f o r these c e r e a l s was 65.7% on average. Corn appeared to have lower a v a i l a b i l i t y (60.0%) i n comparison to wheat (67.4%) and b a r l e y (68.8%). I t has long been reported that phosphorus from animal sources i s h i g h l y a v a i l a b l e . G i l l i s et al. (1954) reported that a v a i l a b l e phosphorus f o r bone meal, bone char, bone ash and d i c a l c i u m phosphate was 87, 84, 89 and 100%, r e s p e c t i v e l y . S i m i l a r r e s u l t s were reported by Nelson and Walker (1964) and Dilworth and Day (1964). Conversely, phosphorus of p l a n t o r i g i n i s considered p o o r l y a v a i l a b l e due to the i n f l u e n c e of phytate (Taylor, 1965; Nelson et al., 1968) i n the feed i n g r e d i e n t s . However, c o n f l i c t i n g r e p o r t s e x i s t e d i n t h i s regard. Nelson et al. (1968) reported that phytate phosphorus of commercial soybean meal was completely u n a v a i l a b l e . Ashton et al. (1960) showed that four-week o l d c h i c k s r e t a i n e d approximately 20% of phytate phosphorus while six-week o l d c h i c k s r e t a i n e d 36 to 49% of the phosphorus. Hayes et al. (1979) reported that a v a i l a b i l i t y of phosphorus i n corn, hard wheat, s o f t wheat and b a r l e y was estimated at 12, 43, 58 and 50%, r e s p e c t i v e l y . Temperton and Cassidy (1964) demonstrated that the phosphorus u t i l i z a t i o n was 60% of phytate phosphate. Salmon and McGinnis (1968) a l s o showed a h i g h . " a v a i l a b i l i t y - of phosphorus i n vegetable sources'. Most . 85 r e c e n t l y , Nwokolo et al. (1976) reported that phosphorus a v a i l a b i l i t y from soybean, rapeseed, cotton seed and palm ke r n e l meals was 89.3, 76.9, 74.8 and 70.8%, r e s p e c t i v e l y f o r the growing b r o i l e r c h i c k s . The present r e s u l t s a l s o showed th a t the phosphorus a v a i l a b i l i t y i n c e r e a l s was q u i t e high. Therefore, i t may be concluded that the phosphorus a v a i l a b i l i t y from p l a n t o r i g i n was not as low as p r e v i o u s l y i n d i c a t e d and that phosphorus a v a i l a b i l i t y from p l a n t s has been g r e a t l y underestimated. A v a i l a b i l i t i e s ' - o f magnesium:;in wheat, corn and b a r l e y were 53.5, 51.0 and 54.9%, r e s p e c t i v e l y w i t h the mean of 53.1%. The r e s u l t s of wheat and corn were higher than the values o f 48.1 and 47.5%, r e s p e c t i v e l y reported by Guenter and S e l l (1974). These authors a l s o reported the value f o r b a r l e y (54.9%) s i m i l a r to the present experiment. However, the present r e s u l t s were a l s o lower .than the report by Nwokolo et al. (1976) on the vegetable p r o t e i n source. Although the a v a i l a b i l i t y of magnesium i s only approximately 50%, i t s d e f i c i e n c y i s not a common problem i n p r a c t i c a l d i e t s f o r p o u l t r y . This may be explained by the r e l a t i v e l y high content o f magnesium i n the feed i n g r e d i e n t s f o r p o u l t r y . L i t t l e i s known on the a v a i l a b i l i t y of manganese i n c e r e a l s . The present s t u d i e s showed that manganese a v a i l a b i l i t y was higher i n corn (60.0%) fo l l o w e d by b a r l e y (54.5%) and wheat (48.4%) with the average of 54.5% f o r the c e r e a l s . The content of manganese i n the c e r e a l s was g e n e r a l l y low, t h e r e f o r e manganese d e f i c i e n c y i s a problem i n the conventional d i e t and r e q u i r e s supplementation with i n o r g a n i c manganese. Nwokolo et al. (1976) showed that the a v a i l a b i l i t y of manganese i n the 86 soybean, rapeseed, cottonseed and palm k e r n e l meals were 76.1, 56.7, 76.3 and 45.7%, r e s p e c t i v e l y f o r the growing b r o i l e r c h i c k s . The average z i n c a v a i l a b i l i t y (52.1%) f o r three c e r e a l s was s i m i l a r to magnesium (53.1%) and manganese (54.5%). Zinc i n corn appeared to be more a v a i l a b l e than that of wheat and b a r l e y . Very l i m i t e d a v a i l a b i l i t y data was observed i n the l i t e r a t u r e f o r p l a n t s . - Evan and Johnson (1977) reported t h a t z i n c a v a i l a b i l i t y i n raw corn endosperm f l o u r was 51%. O'Dell et at, (1972) observed that z i n c a v a i l a b i l i t y i n sesame, soybean and f i s h meal was 57, 67 and 75%, r e s p e c t i v e l y . Nwokolo et al. (1976) showed that soybean, rapeseed, cottonseed and palm k e r n e l meals had a z i n c a v a i l a b i l i t y o"f 66.5, 44.0, 38.0 and 13.9%, r e s p e c t i v e l y . The high crude f i b r e and phytate content i n cottonseed and palm kernel meals was suggested to be the f a c t o r rendering the low a v a i l a b i l i t y of z i n c i n these meals (Nwokolo and Bragg, 1977). O'Dell and Savage (1960) i n d i c a t e d that monogastric animals r e q u i r e d higher l e v e l s of d i e t a r y z i n c on d i e t s c o n t a i n i n g p l a n t p r o t e i n s than on d i e t s c o n t a i n i n g animal p r o t e i n because of the phytate content i n p l a n t p r o t e i n s . Phytate has been known to bind the z i n c i n a complex form which i s not r e a d i l y r e l e a s e d f o r absorption i n animals. The copper a v a i l a b i l i t y appeared to be the highest i n c e r e a l grains compared to other minerals t e s t e d w i t h an average of 81.0%. L i t t l e i s known about the chemical form i n which copper e x i s t s i n food. Copper absorption and u t i l i z a t i o n may be markedly a f f e c t e d by s e v e r a l other mineral elements and d i e t a r y components (Underwood, 1977). Phytate appeared to reduce absorption and r e t e n t i o n of copper (Davis 87 etal., 1962; Da^/iies and N i g h t i n g a l e , 1975). Nwokolo et al. (1976) reported t h a t the copper a v a i l a b i l i t y . o f p l a n t p r o t e i n supplements, soybean, rapeseed, cotton seed and palm ke r n e l meals was - f a i r l y low. Cereals contained l i t t l e phytate compared to p l a n t p r o t e i n supplements. The f i b r e content of the p l a n t p r o t e i n source reported by Nwokolo and Bragg (1977) was higher than the c e r e a l s t e s t e d i n these s t u d i e s . The high f i b r e content i s a l s o known to s i g n i f i c a n t l y decrease the copper a v a i l a b i l i t y . ( N w o k o l o and Bragg, 1977). This may e x p l a i n why the ce r e a l s w i t h lower phytate and crude f i b r e content r e s u l t e d i n higher copper a v a i l a b i l i t y . Other d i e t a r y f a c t o r s a s s o c i a t e d with p r o t e i n s and ce r e a l s may a l s o i n f l u e n c e the d i f f e r e n c e i n absorption and u t i l i z a t i o n of copper. Trial 4 The o v e r a l l mineral a v a i l a b i l i t y : : . i n d i f f e r e n t l e v e l s of soybean i n the d i e t i s shown i n Table 22. The r e s u l t s showed that the value:of mineral a v a i l a b i l i t y improved as the soybean l e v e l decreased. I t was apparent that a d i l u t i o n e f f e c t was i n f l u e n c i n g the a v a i l a b i l i t y . The increased r e t e n t i o n w i t h decreasing soybean, meal conc e n t r a t i o n " . may be explained by the improvement of d i g e s t i b i l i t y and l e s s competition f o r the bi n d i n g s i t e s f o r mineral t r a n s p o r t . .. TABLE 22:• A v a i l a b i l i t y of M i n e r a l s i n D i e t s - C o n t a i n i n g D i f f e r e n t - Levels of'Soybean Meal A v a i l a b i l i t y (%)' Treatment Ca P Mg Mn Zn Cu 1. Soybean meal (SBM) 54. , 2 a 73. , 8 a 47. , 9 a b 43. , l a 57. , 3 a 47. , 5 a 2. S.D.2 + '75% SBM 57. , 7 a 75. , 9 a 46. , 8 a 44. , 2 a 60. , 8 a 57. , 7 b 3. S.D. + 50% SBM 67. , 5 b 83. , 9 b 50. , o a b 55. , 6 b "66. , 8 b 63. , 6 C 4. S.D. + 25.0% SBM 76. , 1 C 85. , 8 b 52, , 2 b c 56. , o b 73. . 4 ° 65. , 3 C 5. S.D. + 12.5% SBM 77. , 8 C 88. , 4 b 56. .0° 55. , 4 b 81, , o d 67. , 8 C Means w i t h d i f f e r e n t s u p e r s c r i p t s w i t h i n a column a r e . s i g n i f i c a n t l y d i f f e r e n t (P < Jp .05) . S y n t h e t i c d i e t as i n d i c a t e d i n Table 1. 89 (a) Calcium The calcium a v a i l a b i l i t y of treatment 1, 2, 3,4, and'5, ( T l , T2, T3, T4, and T5) was 54.2, 57.7, 65.5, 7611 and 77.8%, r e s p e c t i v e l y . T l and T2 d i d "hot. d i f f e r s i g n i f i c a n t l y from each-other and n e i t h e r d i d T4 and T5. T3, however, was s i g n i f i c a n t l y higher than T l and T2 but lower than T4 and T5. The cause of improvement i n calcium a v a i l a b i l i t y may be due e i t h e r to the decrease i n mineral concentration of the mixture or the p r o t e i n concentration of the d i e t . (b) Phosphorus The phosphorus a v a i l a b i l i t y f o r T l , T2, T3, T4 and T5 was"- 73.8, 75.0, 83.9, 85.8 and 88.0%, r e s p e c t i v e l y . T l and T2 d i d not d i f f e r s i g n i f i c a n t l y from each other but were s i g n i f i c a n t l y lower than T3, T4 and T5. The l a t t e r three treatments d i d not s i g n i f i c a n t l y d i f f e r from each other but a v a i l a b i l i t y order was T5 > T4 > T3. The r e s u l t s showed that phosphorus i n soybean meal was h i g h l y a v a i l a b l e to growing c h i c k s . Although phosphate of p l a n t o r i g i n i s considered p o o r l y a v a i l a b l e due to the i n f l u e n c e of phytate (Taylor, 1965), c o n f l i c t i n g r e p o r ts have appeared i n the l i t e r a t u r e as discussed e a r l i e r . Phosphorus a v a i l a b i l i t y a l s o increased with the decrease of phosphorus c o n c e n t r a t i o n i n the treatment. The whole soybean meal ( T i J d i e t showed 73.8% a v a i l a b l e phosphorus whereas the low soybean concentration diet(T5) had 88.4% a v a i l a b l e phosphorus. 90 (a) Magnesium Although magnesium (Mg) a v a i l a b i l i t y ; impxpyed"with decreasing Mg concentration of the d i e t , t h e r e was no s i g n i f i c a n t improvement u n t i l the l e v e l o f soybean meal dropped to 12.5% o f the mixture. The Mg a v a i l a b i l i t y w i t h 12.5% soybean meal d i e t . T5 (56.0%), was s i g n i f i c a n t l y higher than the T l (47.9%), T2 (46.8%) and T3 (50.0%). No s i g n i f i c a n t d i f f e r e n c e was observed between T4 (52.2%) and T5 (56.0%). The present study a l s o showed that the a v a i l a b i l i t y o f Mg appeared to be low i n soybean meal. The improvement of Mg a v a i l a b i l i t y d i d not increase d r a s t i c a l l y even though the Mg concentration was reduced q u i t e s i g n i f i c a n t l y from T l to T5. The r e s u l t s obtained was lower than that reported by Nwokolo et al. (1976) and Guenter and S e l l (1974), t o be 77.4 and 60.4%, r e s p e c t i v e l y . (d) Manganese Results i n d i c a t e d that the manganese (Mn) a v a i l a b i l i t y f o r T l , T2, T3, T4 and T5 were 43.1, 44.2, 55.6, 56 and 55.4%, r e s p e c t i v e l y . Mn a v a i l a b i l i t y i n T l and T2 was s i g n i f i c a n t l y lower than T3, T4 and T5, while there was no s i g n i f i c a n t d i f f e r e n c e w i t h i n the former ..-pT.'---the l a t t e r treatment groups. No f u r t h e r improvement of Mn a v a i l a b i l i t y lower than the 50% soybean treatment was observed. I t appeared that manganese i n soybean meal was q u i t e p o o r l y u t i l i z e d . Gallup and N o r r i s (1935a,b) and Wilgus and Patton (1939) 91 a l s o noted the poor u t i l i z a t i o n of mineral d i e t s . Inorganic Mn i s u s u a l l y supplemented i n conventional d i e t s f o r p o u l t r y to prevent Mn d e f i c i e n c y . •, I t can be understood with the low content and poor a v a i l a b i l i t y of Mn from p l a n t s . Zinc The a v a i l a b i l i t y of z i n c (Zn) i n treatment 1 (Tl) was 57.3%. The a v a i l a b l e value increased with the decrease of z i n c concentration i n these d i e t s . Zn a v a i l a b i l i t y of T2, T3, T4 and T5 were 60.8, 66.8, 73.4 and 81%, r e s p e c t i v e l y . T l d i d not d i f f e r s i g n i f i c a n t l y from T2. T3 was s i g n i f i c a n t l y higher than T l and T2 but s i g n i f i c a n t l y lower than T4 and T5. T5 was a l s o s i g n i f i c a n t l y higher than T4. Nwokolo et al. (1976) reported that Zn a v a i l a b i l i t y of soybean was 66.5% which i s s i m i l a r to T3. Homeostasis' of body Zn regulates the degree of Zn absorption and endogenous e x c r e t i o n (Underwood, 1977). The low Zn c o n c e n t r a t i o n i n the d i e t seemed to enhance the Zn absorption, thus i n c r e a s i n g a v a i l a b i l i t y . Copper The r e s u l t s showed that copper (Cu) a v a i l a b i l i t y improved with decreasing Cu c o n c e n t r a t i o n - i n the diet" from, -soybean^ _The .100% soybean meal d i e t (Tl) gave 47.5% a v a i l a b l e Cu to the growing ch i c k s whereas 12.5% soybean meal d i e t (T5) o f f e r e d 67.8% a v a i l a b l e Cu. T2 (57.7%) was s i g n i f i c a n t l y higher than T l (47.5%) but s i g n i f i c a n t l y 92 lower than T3 (63.6%), T4 (65.3%) and T5 (67.8%). The l a t t e r treatment groups were not d i f f e r e n t s t a t i s t i c a l l y from one another. Nwokolo et al. (1976) reported a s i m i l a r Cu a v a i l a b i l i t y value (51%) of soybean meal f o r the growing c h i c k s . Trial 5 The r e s u l t s of the mineral a v a i l a b i l i t y are presented i n Table 23. There i s a gradual increase i n mineral a v a i l a b i l i t y as the concentration of wheat decreased. I t appeared that there was a . d i l u t i o n e f f e c t i n f l u e n c i n g the a v a i l a b i l i t y . The increased:Z l ' . .* r e t e n t i o n w i t h decreasing of g r a i n concentration ( i . e . mineral concentration) may be explained by the improvement of d i g e s t i b i l i t y and l e s s competition f o r the b i n d i n g s i t e s of the p r o t e i n ligands f o r mineral transport:r> (.a) Calcium Calcium a v a i l a b i l i t y of T5 (90%) and T l (66%) were the highest and lowest, r e s p e c t i v e l y to a l l the d i e t a r y treatments. T3 (75.4%) was s i g n i f i c a n t l y higher than T l and T2 (70.1%) but s i g n i f i c a n t l y lower than T4 (85.9%) and T5. There was no s i g n i f i c a n t d i f f e r e n c e between Tl.and T2 or between T4 arid T-5.. Many f a c t o r s have been recognized to a f f e c t the i n t e s t i n a l absorption of calcium such as v i t a m i n D, calcium and phosphorus 93 r a t i o . I t i s reasonable to b e l i e v e that at lower calcium concen-t r a t i o n s i n the d i e t there i s improved e f f i c i e n c y of calcium absorption and r e t e n t i o n as i n d i c a t e d by Bragg et at. (1971). I t has been shown that calcium absorption r e l i e s on the v i t a m i n D dependent calcium b i n d i n g p r o t e i n (CaBP) i n the i n t e s t i n a l mucosa of c h i c k s (Wasserman and T a y l o r , 1968). This p r o t e i n was i n t i m a t e l y i n v o l v e d i n the t r a n s l o c a t i o n of calcium across the i n t e s t i n a l e p i t h e l i u m . Hurwitz and Bar (1969) have shown that i n l a y i n g fowls, the CaBP i s independent of the l e v e l of calcium fed, but i n c h i c k s d i e t a r y l e v e l s below 0.7% increased CaBP. Walling and Rothman (1970) a l s o reported that d i e t a r y calcium r e s t r i c t i o n caused increased a f f i n i t y f o r calcium i n the c a r r i e r . In the present.studies the calcium l e v e l s f o r a l l the d i e t a r y treatments were w e l l below the requirement level'..: This may suggest that CaBP. i s - a c t i v e l y "inyolyed i n the absorption process. The higher calcium a v a i l a b i l i t y f o r the lower calcium c o n c e n t r a t i o n d i e t may be due to higher CaBP production to enhance the calcium absorption. Phosphorus The phosphorus a v a i l a b i l i t y (Table 23) i n T l was 65.4% whereas T5 was 92.5%. S i g n i f i c a n t d i f f e r e n c e s were observed among T l (65.4%), T2 (75.9%), T3 (81.3%), T4 (91.4%) and T5 (92.5%) with the exception of T4 and T5 which d i d not d i f f e r from each other. I t i s apparent that phosphorus a v a i l a b i l i t y could be very high at low phosphorus con c e n t r a t i o n i n the d i e t s . TABLE 23: A v a i l a b i l i t y o f M i n e r a l s i n . D i e t s Containing D i f f e r e n t - L e v e l s of Wheat A v a i l a b i l i t y (%) Treatment Ca P Mg Mn Zn Cu 1. Whole wheat 66. 0 a 65. 4 a 48.4 a 34.9 a 62. 3 a 60.6 a 2. S.D.2 + 75% wheat 7 0 . l a 75. 9 b 52.2 a 38.6 a 6 6 . 7 a b 63.5 a 3. S.D. + 50% wheat 75.4 b 81. 3 C 65.6 b 51.6 b 7 2 . 6 b c 75. 2 b 4. S.D. + 25% wheat 85. 9 C 91. 4 d 71.4 b 5 7 . 0 b C 75.7° 78.0 b 5. S.D. + 12.5% wheat 90.1° 92. 5 d 88.5° 60. 2 C 77.7 C 90.6 C Means w i t h d i f f e r e n t s u p e r s c r i p t s w i t h i n a column are s i g n i f i c a n t l y d i f f e r e n t (Tukey t e s t P < 0.05). S y n t h e t i c d i e t as i n d i c a t e d i n Table 1. 95 Magnesium The r e s u l t s i n d i c a t e d that the a v a i l a b l e magnesium i n the d i e t s increased w i t h the decrease of d i e t a r y magnesium conce n t r a t i o n . The magnesium a v a i l a b i l i t y of T l , T2, T3, T4 and T5 (Table 23) were 48.4, 52.2, 65.6, 71.4 and 88.5%, r e s p e c t i v e l y . There was no s i g n i f i c a n t d i f f e r e n c e between T l and T2 and between T3 and T4. However, t h e l l a t t e r two treatments were s i g n i f i c a n t l y higher than the former two. T5 was s i g n i f i c a n t l y higher than a l l other treatments. Although a number of f a c t o r s have.been known to a f f e c t the magnesium absorption, no s i n g l e f a c t o r appears to p l a y a dominant 28 r o l e i n the magnesium abso r p t i o n . Several s t u d i e s u s i n g Mg suggest that absorption of magnesium i s i n f l u e n c e d by the load presented to the i n t e s t i n a l mucosa (Aikawa, 1959; Graham et at., 1960). Graham et:al. (1960) demonstrated that on an ord i n a r y d i e t c o n t a i n i n g 20 m Eq of magnesium, 44% of the ingested r a d i o a c t i v i t y was absorbed per day; on low magnesium d i e t s (47 m Eq per day), absorption was decreased to 24%. This seems to agree with the present study, i . e . the absorption increases w i t h the decrease of d i e t a r y concen-t r a t i o n of magnesium i n wheat. Manganese Results showed that there was. s i g n i f i c a n t l y i d i f f e r e n t manganese a v a i l a b i l i t y among treatments (Table 23). T3 (51.6%) was s i g n i f i c a n t l y higher than T l (34.9%) and T2 (38.6%) but 96 s i g n i f i c a n t l y lower than T5 (60.2%). T4 (57.0%) and T5 d i d not d i f f e r from each other but were s i g n i f i c a n t l y higher than T l and T2. The p r e c i s e g a s t r o i n t e s t i n a l l o c i which are concerned with the absorption of manganese-are s t i l l unknown. The evidence i n d i c a t e s that the amount of element absorbed i s ^ p r o p o r t i o n a l to that presented f o r absorption (Underwood, 1977). The present r e s u l t s i n d i c a t e that low manganese concentration i n the d i e t produced the higher e f f i c i e n c y of absorption, although the highest a v a i l a b i l i t y i s low compared with other minerals t e s t e d . Zinc S i m i l a r to other m i n e r a l s , the a v a i l a b i l i t y of z i n c i n the d i e t i s i n v e r s e l y r e l a t e d to the z i n c c oncentration i n the d i e t (Table 23). Results of the present study i n d i c a t e d that 62.3% of z i n c i n the a l l wheat (Tl) was a v a i l a b l e f o r r e t e n t i o n while 77.7% z i n c was a v a i l a b l e c i h the 12.5% a l l wheat d i e t . No s i g n i f i c a n t d i f f e r e n c e was observed between T l (62.3%) and T2 (66.7%), T2 and T3 (72.6%) or T4 (75.0%) and T5 (77.7%). However, z i n c a v a i l a b i l i t y i n T3 was s i g n i f i c a n t l y lower than T4 and T5 which were a l s o s i g n i f i c a n t l y higher than T l and T2. I t has been recognized that homeostatic c o n t r o l of body zin c i n accordance with needs i s achieved through r e g u l a t i o n of z i n c absorption ( M i l l e r , 1969; W i l k i n et- al., 1972) as w e l l as endogenous e x c r e t i o n by the way of feces. Less z i n c w i l l be absorbed i n t o the of animals fed an adequate d i e t a r y l e v e l o f z i n c ( M i l l e r et al., 97 1966). The homeostatic c o n t r o l of z i n c absorption and e x c r e t i o n may e x p l a i n the increase o f z i n c a v a i l a b i l i t y i n the decreasing amount of z i n c concentration i n the d i e t s . (f) Copper The copper content of the wheat t e s t e d was 16 ppm. The copper a v a i l a b i l i t y of whole wheat was 60.6%. Copper a v a i l a b i l i t y increased as the amount of copper i n the d i e t s decreased (Table 23). T l (60.6%) and T2 (63.5%) d i d not d i f f e r s i g n i f i c a n t l y from each other; neither-,.did T.3.. (75.2%) and T4 "(78V0%) . The l a t t e r was, however, s i g n i f i c a n t l y higher than .the former group. T5 (90.6%) was s i g n i f i c a n t l y higher than any other treatments. The r e s u l t s suggest that chicks seem to be able to absorb according to the copper concentration of the d i e t s . Although l i t t l e i n f o r m a t i o n i s present i n the l i t e r a t u r e on t h i s type of study, there i s evidence t h a t copper absorption from the i n t e s t i n e i s r e g u l a t e d i n accordance with b o d i l y n e e d a t l e a s t at the low d i e t a r y copper l e v e l s . Schwartz and Kirchgessner (1974) demonstrated that both copper uptake by the i n t e s t i n a l w a l l and i t s t r a n s f e r to the s e r o s a l s o l u t i o n were elevated i n copper d e f i c i e n c y . Under the c o n d i t i o n of decreasing copper concentration i n the d i e t , s i m i l a r mechanism may a l s o occur to improve the absorption and t r a n s f e r r i n g of copper. Consequently, the a v a i l a b i l i t y of the d i l u t e d copper d i e t s have improved markedly. 98 Trial 6 The r e s u l t s of calcium (Ca) and phosphorus (P) a v a i l a b i l i t y from v a r y i n g concentrations o f calcium phosphate ( d i b a s i c ) are shown i n Table 24. Results i n d i c a t e that the d i e t a r y l e v e l of calcium and phosphorus can s i g n i f i c a n t l y a f f e c t the b i o a v a i l a b i l i t y of these m i n e r a l s . (a) Calcium Calcium i s h i g h l y a v a i l a b l e at a low l e v e l of Ca supple-mentation as shown i n treatments 1, 2, 3, 4, 5 and 6 when the Ca was supplemented up to 0.4% of the d i e t . I t s a v a i l a b i l i t y reduced s i g n i f i c a n t l y to 63.5% at 0.8% of the d i e t . A f u r t h e r decrease of Ca a v a i l a b i l i t y was observed i n treatment 8 (51.2%) and 9 (35.2%). There were s i g n i f i c a n t d i f f e r e n c e s among a l l l e v e l s of Ca supplementation except T l and T2 and T2 and T4. Treatments 8 and 9 contained 1.2% and 1.6% Ca, r e s p e c t i v e l y and had the lowest a y a i l a b l e v a l u s . The r e d u c t i o n of a v a i l a b i l i t y at the higher l e v e l s of supplementation was due to the excess. Studies i n r a t s a l s o showed a very high Ca absorption when animals were on a low Ca i n t a k e l e y e l and the absorption r a t e dropped as the intake of calcium increased (Hansard et al., 1954). These r e s u l t s , are i n agreement w i t h the present experiment. Although considerable amounts of research have been done onthe b i o a v a i l a b i l i t y o f v a r i o u s calcium inorganic • sources, i n v e s t i g a t i o n s o f s e v e r s l researchers f a i l e d to r e v e a l any d i f f e r e n c e i n b i o l o g i c a l a v a i l a b i l i t y between d i f f e r e n t calcium TABLE 24: A v a i l a b i l i t y o f Calcium and Phosphorus from Calcium Phosphate in' the Growing Chicks Treatment Ca % p A v a i l a b i l i t y Ca (%)* P 1. S.D. + 0. .0125 + 0. .0097 9 9 . l a 99. 0 a 2. S.D. + 0. .025 + 0. .0194 98.9 a 98. 5 a 3. S.D. + 0. .050 + 0, .0388 95. l b 98.3 a 4. S.D. + 0, .100 + 0. .0776 94.3 b 97.9 a 5. S.D.. + 0. .200 + 0, .1553 86.1° 91.0 b 6. S.D. + 0. ,400 + 0. .3105 82.5 d 83.4° 7. S.D. + 0. .800 + 0. .6210 63.8 e 70.0 d 8. S.D. + 1. ,200 + 0. .9315 51.2 f 60.0 e 9. S.D. + 1. .600 + 1. .2420 35. 2 g 47.1 £ Means with d i f f e r e n t s u p e r s c r i p t s w i t h i n a column are s i g n i f i c a n t l y d i f f e r e n t , (Tukey •test P '< 0.05.), 1 'Synthetic d i e t as i n d i c a t e d i n Table 1. 100 sources u s i n g bone ash and weight gain as a c r i t e r i a of response i n c h i c k s . The sources studied i n these various comparisons, included calcium carbonate, calcium s u l f a t e , oyster s h e l l , limestone, various calcium phosphate, gypsum, calcium gluconate and f i s h meal (Bethke et al., 1929; Waldroup et al., 1964; Sandrof and M u l l a , 1965; Spandorf and Leong, 1965). In c o n t r a s t to these r e p o r t s , however, a number of researchers have reported d i f f e r e n c e s i n b i o l o g i c a l a v a i l a b i l i t y between various calcium c a r r i e r s f o r young c h i c k s . Motzok et al. (1965), observed that the calcium i n s o f t phosphate was 70% as a v a i l a b l e as that i n calcium carbonate assuming that calcium carbonate was 100% a v a i l a b l e . Hurwitz- and Rand (1965) reported that the calcium i n gypsum was 90%, as a v a i l a b l e as limestone when feed i n t a k e was equal. D i l w o r t h et al. (1964), showed th a t the r e l a t i v e calcium a v a i l a b i l i t y i n v a rious feed grade calcium phosphate ranged from 68 to 95% as compared to calcium carbonate. Reid and Weber (1976) observed the percent calcium a v a i l a b i l i t y of ground limestone samples v a r i e d from 73.3 to 109.4% i n comparison with calcium carbonate. Most of these s t u d i e s were based on body weight and bone ash content and calcium carbonate was assumed to be 100% a v a i l a b l e . Therefore, the r e s u l t obtained was the r e l a t i v e a v a i l a b i l i t y r a t h e r than " t r u e " a v a i l a b i l i t y . The current s t u d i e s demonstrated the true a v a i l a b i l i t y o f calcium f r o n calcium phosphate at v a r i o u s l e v e l s when calcium phosphate was the s o l e source of Ca i n the d i e t . 101 (b) Phosphorus A s i m i l a r p a t t e r n of a v a i l a b i l i t y was obtained f o r phosphorus compared to calcium a v a i l a b i l i t y as shown i n Table 24. Phosphorus i n d i c a l c i u m phosphate was h i g h l y a v a i l a b l e to the growing b r o i l e r chicks when the supply was not i n excess. There was a d r a s t i c drop of phosphorus a v a i l a b i l i t y values when the d i e t a r y c oncentration of phosphorus was i n excess of 0.3%. Very high a v a i l a b l e phosphorus was observed i n treatment (Tl) 99%, T2 (98.5%), T3 (98.3%) and T4 (97.9%). No s t a t i s t i c a l d i f f e r e n c e was found among these low phosphorus d i e t a r y treatments. In the d i e t c o n t a i n i n g 0.155% (T5) and 0.32%'(T6) phosphorus, the phosphorus a v a i l a b i l i t y decreased t o 91.0% and 83.4%, r e s p e c t i v e l y . These values were s i g n i f i c a n t l y lower than the low phosphorus d i e t s ( T l , T2, T3 and T4) and s i g n i f i c a n t l y higher than T4 (70.0%), T8 (60.0% and T9 (47.1%). T5 was a l s o s i g n i f i c a n t l y higher than t h a t . o f T6. A l a r g e number of s t u d i e s have been conducted to determine the r e l a t i v e b i o l o g i c a l value o f the various i n o r g a n i c phosphate sources f o r c h i c k s . Assuming b e t a - t r i c a l c i u m phosphate to be 100% a v a i l a b l e , G i l l i s and a s s o c i a t e s (1954) reported that the r e l a t i v e value f o r monocalcium phosphate, d i c a l c i u m phosphate, def l u o r i n a t e d phosphate were 113, 98, 98, and 87%, r e s p e c t i v e l y . S i m i l a r r e s u l t s were obtained by Nelson and Walker (1964) and D i l w o r t h and Day (1964), however, l i t t l e i n f o r m a t i o n was reported 102 concerning the r e l a t i o n s h i p between the l e v e l s of phosphorus regarding b i o a v a i l a b i l i t y . The present t r i a l i n d i c a t e s that the phosphorus from calcium phosphate was h i g h l y . a v a i l a b l e to the growing b r o i l e r c h i c k s . The excess phosphorus o f f e r e d i n the d i e t i s excreted i n the feces of the b i r d s . Trial 7 The r e s u l t s of magnesium (Mg) a v a i l a b i l i t y from magnesium carbonate (4MgC03-Mg(0H)3-5H.2C) to the growing c h i c k s are shown i n Table 25. Results i n d i c a t e d that s i g n i f i c a n t l y d i f f e r e n t a v a i l a b i l i t y values were observed at va r i o u s d i e t a r y l e v e l s . The Mg requirement recommended by NRC (1*977) i s 500 ppm. High Mg a v a i l a b i l i t y was observed i n treatments 1 ( T l ) , 2 (T2) and 3;(T3). The degree o f a v a i l a b i l i t y decreased g r a d u a l l y w i t h higher Mg concentration. There was no s i g n i f i c a n t d i f f e r e n c e between T l (82.3%) and T2 (81.4%).. at 150 ppm and 300 ppm Mg d i e t , r e s p e c t i v e l y . However, Mg a v a i l a b i l i t y of T3 (79.4%) was s i g n i f i c a n t l y lower than T l and T4 (73.4%) was s i g n i f i c a n t l y higher than T5 (67.1%) and T6 (61.9%). The high l e v e l Mg d i e t , i . e . T5 (750 ppm) and T6 (900 ppm) was s i g n i f i c a n t l y lower than other treatments, although Cook (1973) reported that magnesium carbonate was the most a v a i l a b l e form among magnesium s a l t s . The present experiment i n d i c a t e d that only 82.4% of Mg was a v a i l a b l e from magnesium carbonate o f f e r e d at the lowest l e v e l (150 ppm). This was determined under the c o n d i t i o n of maximum absorption, i . e . no i n t e r f e r e n c e from other d i e t a r y minerals i n the i n t e s t i n e . TABLE 25: A v a i l a b i l i t y of Magnesium from Magnesium Carbonate i n the Crowrng-'Chicks Treatment Mg l e v e l (Ppm) A v a i l a b i l i t y (%) 1 Mg 1. S.D.2 + 150 82. ,3 e 2. S.D. + 300 81. ,4 6 3. S.D. + 450 79. ,4 d 4. S.D. + 600 73. ,6 C 5. S.D. + 750 67. , l b 6. S.D. + 900 61, ,9 a Means with d i f f e r e n t s u p e r s c r i p t s are s i g n i f i c a n t l y d i f f e r e n t between treatments (P < 0.05). Syn t h e t i c d i e t as i n d i c a t e d i n Table 1. 104 Lim i t e d i n f o r m a t i o n has- been ^ reported, concerning i n o r g a n i c magnesium s a l t : u t i i r z a t i p n by p o u l t r y , " Guenter and S e l l . .(1974), using a r a d i o i s o t o p technique, showed that the a v a i l a b i l i t y of Mg from MgSO^•7H2O was 57.4%. No s i g n i f i c a n t d i f f e r e n c e was observed between two l e v e l s o f Mg ( i . e . 200 ppm and 400 ppm) supplementation i n the d i e t . The present study was conducted on the n i t r o g e n and m i n e r a l - f r e e b a s i s . The high l e v e l s o f d i e t a r y Mg caused a s i g n i f i c a n t decrease i n a v a i l a b i l i t y . This may be explained by the excess d i e t a r y Mg which cannot be absorbed e f f i c i e n t l y i n the gut or by. d i e t a r y l e v e l s higher than re q u i r e d f o r metabolism and t h e r e f o r e being -excreted Tn "th'e^feces. 28 Several s t u d i e s u s i n g Mg suggest t h a t the absorption of magnesium i s i n f l u e n c e d by the load presented to:the i n t e s t i n a l mucosa (Aikawa, 1959; Graham et al., 1960). Graham et al. (1960) demonstrated that a d i e t c o n t a i n i n g 20 m Eq of Mg absorbed 44% of the ingested r a d i o a c t i v i t y per day. On a low magnesium d i e t (1.9m Eq/day) 76% was absorbed. On a higher magnesium d i e t (47 m Eq/day) absorption was decreased to 24%. The trend o f Mg absorption w i t h q u a n t i t y i s i n agreement w i t h the present s t u d i e s where excess amounts of Mg were su p p l i e d . T r i a l 8 Limited i n f o r m a t i o n i s a v a i l a b l e i n the l i t e r a t u r e regarding the manganese a v a i l a b i l i t y from i n o r g a n i c sources. Most of the data published concerning i n o r g a n i c Mn were q u a l i t a t i v e r a t h e r than q u a n t i t a t i v e . The present study provides i n f o r m a t i o n on Mn a v a i l a b i l i t y 105 of manganese s u l f a t e (MnSO^'H^O) f o r the growing b r o i l e r c h i c k s . Results (Table 26) i n d i c a t e d that Mn as manganese s u l f a t e was p o o r l y a v a i l a b l e to the growing b r o i l e r . The l e v e l s of treatment v a r i e d from 25 ppm to 125 ppm which in c l u d e s l e v e l s above and below the NRC (1977) Mn requirement f o r growing b r o i l e r s (75 ppm). The values f o r a v a i l a b i l i t y o f Mn from manganese s u l f a t e i n treatment 1 to treatment 5 ranged from 44.5 to 47.3%. There was no s i g n i f i c a n t : d i f f e r e n c e .among a l l the treatments. Results suggest that Mn from manganese s u l f a t e i s poorl y a v a i l a b l e f o r growing c h i c k s . Therefore, l a r g e r q u a n t i t i e s of manganese s u l f a t e are'needed to meet the d i e t a r y requirement. Schaible and Bandemer (1942) reported that manganese oxide, manganese carbonate, manganese s u l f a t e , manganese c h l o r i d e were e q u a l l y v a l u a b l e as sources of Mn i n p o u l t r y , however, d i f f e r e n c e s do e x i s t . Watson.et al. (1970) and Henning et al. (1967), using r a d i o a c t i v e "^Mn demonstrated that ^^MnCl^ was incorporated i n t o the body of chic k s 54 54 to a grea t e r extent than that s u p p l i e d as MnSO^ or MnO. Watson et al. (1971), u s i n g b i o l o g i c a l assay a l s o showed that the a v a i l a b i l i t y of Mn was d i f f e r e n t between carbonate and the oxide form. Since Mn i s an important t r a c e mineral i n b r o i l e r feed, the poor a v a i l a b i l i t y and content of Mn i n p l a n t sources does not meet the requirements of chickens f o r maintaining optimum growth and preventing d e f i c i e n c i e s . Inorganic supplement i s re q u i r e d to meet these needs. The poor a v a i l a b i l i t y from manganese s u l f a t e i n t h i s t r i a l i n d i c a t e s that l a r g e r q u a n t i t i e s of manganese s u l f a t e are needed.for optimum requirement. TABLE 26: A v a i l a b i l i t y o f Manganese from.Manganese S u l f a t e in.:'th>e;Growi%iCSieks" . Treatment Mn l e v e l (ppm) A v a i l a b i l i t y {%) Mn 2 1. S.D. + 25 44.6a 2. S.D. + 50 44.5 a 3. S.D. + 75 47.3 a 4. S.D. + 100 46.4 a 5. S.D. + 125 4 6 . I a Means with d i f f e r e n t s u p e r s c r i p t s are s i g n i f i c a n t l y d i f f e r e n t between treatments (P < 0.05). Syn t h e t i c d i e t as i n d i c a t e d i n Table 1. 107 Trial 9 The values f o r z i n c (Zn) a v a i l a b i l i t y are shown i n Table 27. Results i n d i c a t e d that z i n c from z i n c oxide was w e l l u t i l i z e d by growing b r o i l e r c h i c k s . The a v a i l a b i l i t y of Zn ranged from 84.4 to 93% f o r a l l the treatments c o n t a i n i n g 25 ppm to 125 ppm of z i n c . Zn a v a i l a b i l i t y was not s i g n i f i c a n t l y d i f f e r e n t among T2 (90.6%), T3 (85.7%), T4 (84.4%) and T5 (84.9%). However, T l (93%) which contained the lowest Zn concentration (25 ppm) was s i g n i f i c a n t l y higher than T4 and T5 which had the higher Zn con c e n t r a t i o n (100 ppm and 125 ppm, r e s p e c t i v e l y ) . I t appears that the a v a i l a b i l i t y o f Zn from z i n c oxide seems to l e v e l o f f at 100 t o 125 ppm. Evans et al. (1979), us i n g r a d i o a c t i v e d i l u t i o n techniques w i t h r a t s showed that the percentage of Zn absorption decreased wit h the d a i l y . Z n obtained. This seems to be i n agreement with the present study. A c o n t r o v e r s i a l o pinion has been expressed on the mechanism of body Zn homeostasis. Several i n v e s t i g a t o r s suggested that Zn homeostasis was re g u l a t e d at the s i t e of Zn absorption (Schwarz and Kirchaessner, 1974; W i l k i n et al., 1972). However, work by other i n v e s t i g a t o r s (Evans et al., 1979"; M i l l e r et al., 1966) demonstrated that homeostasis i n r a t s i s maintained by z i n c s e c r e t i o n from the i n t e s t i n e r a t h e r than by r e g u l a t i o n of Zn absorption. Trials 10 and 11 The a v a i l a b i l i t y o f copper (Cu) from copper s u l f a t e i s presented i n Table 28. These r e s u l t s i n d i c a t e that Cu i n copper s u l f a t e at l e v e l s of 2 to 30 ppm was- w e l l absorbed by growing b r o i l e r c h i c k s . I t appeared TABLE 27: A v a i l a b i l i t y of Zinc from Z i n c O x i d e .in the -.Growing- Chi cks Zn l e v e l A v a i l a b i l i t y .(%) Treatment (ppm) Zn 1. s . .D.2 + 25 93 . , o b 2. S. ,D. + 50 90. ,ab , 6 3. S. ,D. + 75 85. ^ab 4 . S. .D. + 100 84. , 4 a 5. S, .D. + 125 84, . 9 a Means with d i f f e r e n t s u p e r s c r i p t s are s i g n i f i c a n t l y d i f f e r e n t between treatments (P < 0.05). S y n t h e t i c d i e t as i n d i c a t e d i n Table 1. 109 that Cu was more a v a i l a b l e at the lowest l e v e l (2 ppm) than at the higher l e v e l . T l (80.2%) was s i g n i f i c a n t l y higher than T4 (72.2%) and T5 (72.1%). No s i g n i f i c a n t d i f f e r e n c e was observed among T2, T3, T4 and T5 as w e l l as between T l , T2 (74,8%) and T3. D e f i n i t i v e data on the minimum Cu requirement of chicks f o r growth and egg production have not been e s t a b l i s h e d . Diets c o n t a i n i n g 4-5 ppm Cu can be considered adequate so long as these d i e t s do not contain excessive amounts of elements that are antagonists of Cu such as i r o n , z i n c , cadmium and molybdenum (Underwood, 1977). Cu i s absorbed from the stomach and a l l p o r t i o n s of the small i n t e s t i n e , p a r t i c u l a r l y the upper small i n t e s t i n e (Owen, 1964 1964; Van Camper and M i t c h e l l , 1965). In most species, d i e t a r y copper i s p o o r l y absorbed (Comar, 1950). The extent o f absorption i s i n f l u e n c e d by the amounts and chemical form of the Cu ingested, by the d i e t a r y l e v e l of s e v e r a l other metal ions and organic substances and by the age of the animal (Underwood, 1977). The present study showed that a v a i l a b l e Cu from copper s u l f a t e was about 72 to 75% when l e v e l s of Cu fed were from 4-32 ppm. As p r e v i o u s l y mentioned, Cu a v a i l a b i l i t y i s a f f e c t e d by many f a c t o r s . The i n f l u e n c i n g f a c t o r , however, d i d not e x i s t i n t h i s p a r t i c u l a r study i n which a copper p u r i f i e d • d i e t was employed. The G u - a v a i l a b i l i t y from Cu s u l f a t e remained q u i t e s i m i l a r although the absolute q u a n t i t y of absorption f o r t h i s i o n increased. Results o f higher d i e t a r y copper l e v e l s were t e s t e d i n T r i a l 11. Results of t h i s t r i a l (Table 29) i n d i c a t e d that there was no TABLE 28: A v a i l a b i l i t y of Copper from Low-Dietary.Levels of Copp Sulfate"- in" ..th'eT-,Grlp,wi-ng:""Ghicks Cu l e v e l A v a i l a b i l i t y (%) Treatment (pp m) Cu 1. S. .D.2 + 2 80. ,2 b 2. S. ,D. + 4 74. , 9 a b 3. S. ,D. + 8 74. 4ab 4. S. .D. + 16 72. ,2 a 5. S. ,D. + 32 72. , l a "Means with d i f f e r e n t s u p e r s c r i p t s are s i g n i f i c a n t l y d i f f e r e n t between treatments (P < 0.05). Syn t h e t i c d i e t as i n d i c a t e d i n Table 1. TABLE 29: A v a i l a b i l i t y of Copper from High D i e t a r y Level's of Copp S u l f a t e -in. the'Growing Chicks" Treatment Cu l e v e l (ppm) A v a i l a b i l i t y (%)* Cu 2 1. S.D. 50 62.6a 2. S.D. 100 62.6 a 3. S.D. 150 63.6 a 4. S.D. 200 62.7 a 5. S.D. 250 61.8 a '''Means with d i f f e r e n t s u p e r s c r i p t s are between treatments (P < 0.05). s i g n i f i c a n t l y d i f f e r e n t 2 Syn t h e t i c d i e t as i n d i c a t e d i n Table 1. s i g n i f i c a n t d i f f e r e n c e i n a v a i l a b i l i t y of Cu when the d i e t a r y l e v e l increased from 50-250 ppm. The a v a i l a b i l i t y values ranged from 61.8-63.6%. 113 SUMMARY AND CONCLUSIONS The a v a i l a b i l i t y of s i x minerals (Ca, P, Mg, Mn, Zn, and Cu) i n commercial wheat, t r i t i c a l e , corn and b a r l e y samples was determined wit h three-week o l d growing b r o i l e r c h i c k s . E f f e c t s o f the l e v e l of d i e t a r y soybean and of d i e t a r y wheat on mineral a v a i l a b i l i t y from these two f e e d s t u f f s was a l s o evaluated. Furthermore, a v a i l a b i l i t y of these minerals from v a r i o u s i n o r g a n i c s a l t s s s u c h as calcium phosphorus ( d i a b a s i c ) , magnesium carbonate, manganese s u l f a t e , z i n c oxide and copper s u l f a t e was a l s o determined. The c e r e a l s under t e s t i n c l u d e d eleven samples of wheat, one sample of t r i t i c a l e , ten samples o f corn and three samples of b a r l e y from v a r i o u s sources. The i n o r g a n i c minerals were purchased from l o c a l chemical s u p p l i e r s . The concentration o f phosphorus and magnesium f r o n a l l the c e r e a l g r a i n s was high whereas the concentration of calcium, manganese, z i n c and copper was g e n e r a l l y low. Results i n d i c a t e that the a v a i l a b i l i t y of copper (78.5%), calcium (71.0%), and phosphorus (67.4%) from wheat and t r i t i c a l e samples ranged from moderate to high f o r the b r o i l e r c h i c k s . However, magnesium (53.5%), z i n c (49.6%) and manganese (48.4%) were low i n a v a i l a b i l i t y . S i g n i f i c a n t v a r i a t i o n (P < 0.01) was observed among the , samples t e s t e d . Corn samples showed the highest a v a i l a b i l i t y f o r copper (87.2%), followed by calcium (70.0%), phosphorus(60.9%), manganese (60.0%), z i n c (57.5%) and magnesium (51.0%). S i m i l a r t o the wheat samples, there was s i g n i f i c a n t v a r i a t i o n among the corn samples f o r a l l the minerals t e s t e d . The a v a i l a b i l i t y of calcium, phosphorus, 114 magnesium, manganese, z i n c and copper i n b a r l e y was 68.9, 68.8, 54.9, 54.9, 49.1 and 77.5%, r e s p e c t i v e l y . Copper appeared to be the most a v a i l a b l e ^ f o r c h i c k s whereas the z i n c was the l e a s t a v a i l a b l e . The study of b a r l e y a l s o i n d i c a t e s that mineral a v a i l a b i l i t y i s i n f l u e n c e d by the o r i g i n of the samples. Growing b r o i l e r chicks appear to have d i f f e r e n t c a p a c i t i e s to dig e s t and absorb n u t r i e n t s . A v a i l a b i l i t y values of minerals were s i g n i f i c a n t l y d i f f e r e n t when v a r i o u s l e v e l s of the feed i n g r e d i e n t were te s t e d . F i v e l e v e l s (100, 75, 50, 25, and 12.5%) of soybean meal and wheat were t e s t e d i n separate mixtures. The r e s u l t s show that a v a i l a b i l i t y of minerals increases w i t h lower l e v e l s of :the feed i n g r e d i e n t although the r e l a t i o n s h i p s between mineral a v a i l a b i l i t y and f e e d - s t u f f l e v e l s i s not l i n e a r . I t i s apparent that chicks have greater a b i l i t y to d i g e s t and absorb minerals from the lower feed s t u f f l e v e l s . The increase i n r e t e n t i o n with a decrease of soybean or wheat conc e n t r a t i o n ( i . e . mineral concentration) may be due to the improvement of d i g e s t i b i l i t y and l e s s competition f o r the binding s i t e s of p r o t e i n ligands f o r mineral t r a n s p o r t s i n the gut. A v a i l a b i l i t y o f calcium and phosphorus from calcium phosphate i n d i c a t e d that each element was h i g h l y a v a i l a b l e to growing c h i c k s . Values of a v a i l a b i l i t y decrease with i n c r e a s i n g calcium and phosphorus concentration. The a v a i l a b i l i t y of calcium ranged from 99.1% to 35.2%, r e s p e c t i v e l y f o r 0.0125% and 1.6% calcium i n the d i e t . The phosphorus a v a i l a b i l i t y ranged from 99.0 to 47.1% f o r 0.009% and 1.242% phosphorus, r e s p e c t i v e l y . The r e d u c t i o n i n a v a i l a b i l i t y value with 115 the increase o f calcium and phosphorus i n the d i e t was due, i n p a r t , to the excess mineral i n t a k e r a t h e r than t o ^ d i g e s t i b i l i t y and r e t e n t i o n per se. A v a i l a b i l i t y of magnesium from magnesium carbonate i n d i c a t e d t h a t magnesium was h i g h l y a v a i l a b l e to growing b r o i l e r s . The a v a i l a b i l i t y of magnesium ranged from 82.3 to 61.9% f o r 150 to 900 ppm d i e t a r y magnesium, r e s p e c t i v e l y . The magnesium absorption was b e t t e r with low co n c e n t r a t i o n than with excess magnesium i n the d i e t s . Manganese from manganese s u l f a t e was p o o r l y a v a i l a b l e f o r growing c h i c k s . The a v a i l a b i l i t y of manganese ranged from 44.5 to 47.3%. Various l e v e l s o f manganese s u l f a t e d i d not i n f l u e n c e the a v a i l a b i l i t y value. Therefore, a l a r g e r q u a n t i t y of manganese s u l f a t e i s needed as a supplement to meet the n u t r i e n t requirements. Zinc a v a i l a b i l i t y from z i n c oxide was h i g h l y a v a i l a b l e f o r growing b o i l e r c h i c k s . The a v a i l a b i l i t y o f z i n c ranged from 84.4 to 93% f o r a l l the d i e t s c o n t a i n i n g 25 to 125 ppm of z i n c . Copper from copper s u l f a t e was moderately a v a i l a b l e to growing b r o i l e r c h i c k s . The a v a i l a b i l i t y values ranged from 80.2 to 72.1% f o r the supplementation of 2 ppm to 32 ppm of copper, r e s p e c t i v e l y . The higher l e v e l of copper supplemen-t a t i o n ( i . e . 50 to 250 ppm) r e s u l t e d i n copper a v a i l a b i l i t y values ranging from 61.8 to 63.6%. The a v a i l a b i l i t y of copper tended to~decrease at higher d i e t a r y l e v e l s . 116 REFERENCES 28 Aikawa, J . K. 1959. 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The minimum l e v e l of p r o t e i n i n t a k e c o n s i s t e n t w i t h the maximum r a t e o f growth. J . Agr. S c i . 38: 354-365. Worker, N. A. and B.;B. Migicovsky. 1961a. E f f e c t of v i t a m i n D on the u t i l i z a t i o n of b e r y l l i u m , magnesium, calcium, strontium and barium i n the c h i c k . J . Nutr. 74: 490-494. Worker, N. A. and B. B. Higicovsky. 1961b. E f f e c t of v i t a m i n D on the u t i l i z a t i o n of z i n c , cadmium and mercury i n the c h i c k . J . Nutr. 75: 222-224, Yoshida, M. and H. H o s h i i . 1977. Improvement o f b i o l o g i c a l assay to determine a v a i l a b l e phosphate. Japan P o u l t r y S c i . 14: 33-43. APPENDIX-1: A n a l y s i s . o f Variance "for Mineral A v a i l a b i l i t y from Wheat and T r i t i c a l e 0 ^ Mean Square Source o f 2 : v a r i a n c e d.f. Ca P Mg Mn Zn Cu Treatment 11 0.7594** 0.7161** 1.3077** 1.6990** 1.3865** 1.6416** Re p l i c a t e s 3 0.0152 0.0242 0.0186 0.0063 0.0397 0.0061 E r r o r 33 0.0131 0.0242 0.0296 0.0326 0.0181 0.0148 * * S i g n i f i c a n t (P < 0.01) APPENDIX 2: A n a l y s i s of Variance f o r Mineral A v a i l a b i l i t y from Corn Source of variance d.f. Ca Mean Square Mg Mn Zn Cu Treatment 0.4055** 0.9894** 0.3572** 1.4896** 2.8001** 0.2288* R e p l i c a t e s 0.0435 0.0086 0.0878 0.0212 0.0209 0.0293 E r r o r 27 0.0090 0.0237 0.0273 0.0266 0.0177 0.0102 * * S i g n i f i c a n t (P < 0.01) APPENDIX 3: A n a l y s i s o f Variance f o r Mineral A v a i l a b i l i t y from Barley Source of variance d.f. Mean Square Ca Mg Mn Zn Cu Treatment 3.5267** 0.2031** 0.0949 NS 2.5077** 6.5378** 0.1978* R e p l i c a t e s 0.0208 0.0213 0.0194 0.0888* 0.0050 0.0176 E r r o r 0.0077 0.0163 0.0406 0.0183 0.0228 0.0172 ^ N o t S i g n i f i c a n t * S i g n i f i c a n t (P < 0.05) * * S i g n i f i c a n t (P < 0.01) APPENDIX 4: . Analysis.- .of. Variance -for. .Mineral"' A v a i l a b i l i t y 'in- -Diets.. Containing .Different' Levels of Soybean Meal Source o f variance d.f. Ca Mean Square Mg Mn Zn Cu Treatment 1.7008** 0.5037** 0.2644** 0.8861** 1.3312** 1.1582** R e p l i c a t e s 0.0052 0.0168 0.0292 0.0161 0.0142 0.0084 E r r o r 12 0.0230 0.0231 0.0242 0.0455 0.0115 0.0274 * * S i g n i f i c a n t (P < 0.01) APPENDIX 5: A n a l y s i s of Variance f o r M i n e r a l ' A v a i l a b i l i t y i n - D i e t s Containing D i f f e r e n t Levels of Wheat _ Mean Square Sourve of 2 variance d.f. Ca P Mg Mn Zn Cu Treatment 4 1.3538** 1.6117** 3.8814** 2.7110** 0.5872** 1.9568* Re p l i c a t e s 3 0.0206 0.0159 0.0120 0.0328 0.0095 0.0068 E r r o r 12 0.0122 0.0161 0.0298 0.0401 0.0257 0.0296 * * S i g n i f i c a n t (P < 0.01) APPENDIX 6:. A n a l y s i s of Variance f o r t h e - A v a i l a b i l i t y of Calcium and Phosphorus from Calcium Phosphate (Dibasic) r Mean Square Source of _ variance d.f. Ca Treatment 8 8.1496** 5.1131** Re p l i c a t e s 3 0.0036 0.0072 E r r o r 24 0.0055 0.0029 * * S i g n i f i c a n t (P < 0.01) APPENDIX 7: Ana-lysis.-of Variance f o r the A v a i l a b i l i t y Magnesium from Magnesium Carbonate Source o f Mean Square variance d.f. Mg Treatment 5 0.9629** Re p l i c a t e s 3 0.0077 E r r o r 15 0.0090 * * S i g n i f i c a n t (P < 0.01) APPENDIX 8: A v a i l a b i l i t y of A n a l y s i s of Variance f o r the Manganese S u l f a t e , Zinc Oxide and Copper S u l f a t e Source of variance Treatment R e p l i c a t e s E r r o r d.f. 12 Mn from manganese s u l f a t e ( T r i a l 8) 0.0327 0.0103 0.0369 NS Mean Square Zn from zinc oxide ( T r i a l 9 ) 0.1654^ 0.0170 0.0297 Cu from copper s u l f a t e ( T r i a l 10) 0.1436* 0.0164 0.0290 Cu from copper s u l f a t e ( T r i a l 11) 0.0066 0.0054 0.0203 NS N S N o t s i g n i f i c a n t * S i g n i f i c a n t (P < 0.01) * * S i g n i f i c a n t (P < 0.05) 4^  

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