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Fat utilization by chickens of different genetic backgrounds Katongole, Joseph Bifaki Ddungu 1978

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FAT UTILIZATION BY CHICKENS OF DIFFERENT GENETIC BACKGROUNDS by JOSEPH BJJFAKI DDUNGU KATONGOLE B.Sc, Agric. (Hons.), Maker ere University, Uganda, 1973 M.Sc., Agric. Makerere University, Uganda, 1975 A THESIS SUHOTIED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n THE FACULTY OF GRADUATE STUDIES Department of Poultry Science We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA October, 1978 ©Joseph Bifaki Ddungu Katongole, 1978 In presenting t h i s t h e s i s i n p a r t i a l f u l f i l l m e n t of the r e -quirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree t h a t 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 -able f o r reference and study. I f u r t h e r agree th a t permission f o r extensive copying of 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 granted by the Head of my Department or by h i s repre-s e n t a t i v e s . I t i s understood that copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l gain s h a l l not be allowed without . my w r i t t e n permission. Department of p£?^/ * iZy C^i • The U n i v e r s i t y of B r i t i s h Columbia 20 75 Wesbrook Place Vancouver, Canada V6T 1W5 i i ABSTRACT The objectives of t h i s research were (1) to study the re-l a t i v e a b i l i t y of genetically d i f f e r e n t types of domestic chick-ens to digest and absorb f a t of d i f f e r e n t types, and (2) to re-late f a t absorbability c o e f f i c i e n t s to dietary apparent M. E. values obtained with genetically d i f f e r e n t types of chickens feeding on diets containing the d i f f e r e n t types of f a t , (3) to search for a possible cause of poultry genetic difference i n fat absorbability by examining some of the factors most l i k e l y to influence f a t digestion and absorption i n the genetically d i f f e r e n t types of chickens. Using New Hampshire, White Leghorn and broiler-type birds, i t was found that u n t i l 6 weeks of age the New Hampshires were s i g n i f i c a n t l y (P^0.05) superior to the others i n t h e i r a b i l i t y to u t i l i z e animal tallow. Differences among birds i n the ab-s o r b a b i l i t y of corn o i l were small. Differences i n dietary M. E. estimates were clo s e l y associated with differences i n f a t absorbability values and 2 . . on a 12% tallow diet, the R values computed on a within age between breeds basis, were 0.67, 0.36 and 0.022 at 3, 5, 2 and 9 weeks of age respectively. This general decline i n R values was a r e f l e c t i o n of the narrowing of the range of fat absorbability differences among d i f f e r e n t types of birds as they grew older. The o v e r a l l conclusion based on these r e s u l t s , i s that breed and/or age differences i n M. E. estimates are to a large extent attributable to breed and/or age differences i n the absorbability of dietary l i p i d materials. The search for p o t e n t i a l causes of the observed breed differences 1X1 in fat absorbability was therefore the main theme of the sub-sequent experiments. A study of the feed passage time i n birds of d i f f e r e n t genetic backgrounds f a i l e d to provide any conclusive evidence on whether or not breed differences i n ingesta t r a n s i t time are in measureable terms responsible for f a t absorbability differences. I t was found, however, that with diets contain-ing 12% of animal tallow or corn o i l , feed passage time was s i g n i f i c a n t l y longer regardless of the type of birds. On the basis of the results of an experiment in which in v i t r o pancreatic lipase a c t i v i t y was measured, the New Hampshires ranked f i r s t followed by B r o i l e r s and White Leghorns in that order. However, the magnitude of differences among them was small. Supplementation of the 12% tallow diet with the b i l e s a l t , sodium taurocholate, improved f a t u t i l i z a t i o n s i g n i f i -cantly by the broiler-type and White Leghorn chicks to the ex-tent of 8.6% and 7.2% respectively. The improvement in f a t ab-s o r b a b i l i t y was associated with a s i g n i f i c a n t reduction in the amount of f e c a l soap fa t t y cacids. The e f f e c t of the sodium taurocholate suggested that in the B r o i l e r s and White Leghorn chicks, the supply of b i l e s a l t s was below the c r i t i c a l m i cellar concentration required for e f f i c i e n t tallow f a t absorption. Results from a general study on i n t e s t i n a l f a t t y acid bind-ing protein (FABP) revealed that a f a t t y acid binding protein in the same molecular weight range as that one demonstrated in the rat, e x i s t s in the i n t e s t i n a l mucosa of the adult chickens and in the mesenteric intestine of day-old chicks p r i o r to the ingestion of any feed. i v I t was also observed that under conditions of low dietary f a t intake, there was a proximal-distal FABP concentration gradi-ent which was disturbed by chronic feeding of large amounts of dietary f a t so that a " s p i l l - o v e r " e f f e c t occurred in the lower i n t e s t i n a l segments. The e f f e c t was p a r t i c u l a r l y notable in the case of the broiler-type b i r d s . The e f f e c t of age on the a b i l i t y of the chick to absorb f a t was pa r t l y a r e f l e c t i o n of the i n -crease i n i n t e s t i n a l FABP content with age. It was found that dietary b i l e s a l t affected the synthesis of FABP i n the three i n t e s t i n a l segments of the New Hampshire and broiler-type birds. On the basis of the results of the d i f f e r e n t experiments carr i e d out in course of t h i s study, i t i s concluded that when animal tallow i s fed to chicks at high l e v e l s , e s p e c i a l l y during the early stages of growth, there i s a demonstrable genetic d i f -ference in the e f f i c i e n c y of f a t u t i l i z a t i o n and hence o v e r a l l dietary energy metabolisability. It appears that several factors in concert rather than a single one, are responsible for th i s .• genetic difference in fat u t i l i z a t i o n . TABLE OF CONTENTS ABSTRACT TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES LIST OF APPENDIX TABLES ACKNOWLEDGEMENTS SECTION ONE 1.0 General Introduction 1.1 Objective of the study 1.2 Short note on the experimental birds SECTION TWO 2.0.0 LITERATURE REVIEW 2.1.0 LIPID ABSORPTION 2.1.1 Introduction 2.1.2 Scheme of f a t absorption i n the avian species (chicken) 2.1.3 Concluding note on f a t absorption 2.2.0 Factors Affecting Fat Absorbability 2.2.1 Introduction 2.2 .2,lAnimaiiEactors 2.2.2.1 Species 2.2.2.2 Age of the animal 2.2.2.3 Miscellaneous 2.2.3 L i p i d Characteristics 2.2.3.1 Carbon chain length and degree unsaturation vx Page 2.2.3.2 Position of the fatty acid 20 2.3.0 Effects of Dietary Fat i n Poultry Rations: An Overview 21 SECTION THREE 3.0.0 MATERIALS AND METHODS, RESULTS AND DISCUSSIONS 24 3.1.0 Experiment 1 Fat Absorbability studies and Metabolisable Energy (M.E.) Estimates Using New Hampshires, Broilers and White Leghorn Birds at Different Ages. 24 3.1.1 Objective of the experiment 24 3.1.2 Materials and Methods 24 3.1.2.1 Birds 24 3.1.2.2 Housing 24 3.1.2.3 Experimental treatments 25 3.1.2.4 Laboratory analysis 25 3.1.2.5 Calculations 26 3.1.2.6 S t a t i s t i c a l analysis 27 3.1.3 Results 28 3.1.3.1 Fat absorbability 28 3.1.3.2 Metabolisable energy 31 3.1.4 Discussion 34 3.1.4.1 Fat absorbability 34 3.1.4.2 Performance efficiency indices 37 3.1.4.3 Metabolisable energy 38 3.2.0 Experiment 2 Feed Passage Time i n New Hampshires, Broilers and White Leghorns Feeding on Basal, 12% Tallow and 12% Corn O i l Diets. 3.2.1 Introduction 3.2.2 Experimental procedures 3.2.3 Results 3.2.4 Discussion 3.3.0 Experiment 3 A Comparative Study of the Pancreatic Lipase Activity i n the New Hampshires, Broilers and White Leghorns. 3.3.1 Introduction 3.3.2 Experimental procedures 3.3.3 Results and discussion 3.4.0 Experiment 4 Dietary Bile Salt Supplementation on Tallow Fat Uti l i z a t i o n by the New Hampshires, Broiler and White Leghorn Chicks. 3.4.1 Introduction 3.4.2 Materials and Methods 3.4.2.1 Birds 3.4.2.2 F^cperimental treatments 3.4.2.3 Laboratory analysis 3.4.2.4 St a t i s t i c a l analysis 3.4.3 Results v i i i Page 3.4.4 Discussion 71 3.5.0 A Study on Fatty Acid Binding Protein i n the Chicken Mesenteric Intestine* 80 3.5.1 Objective of the study 80 3.5.2 Experiment 5 Demonstration of Fatty Acid Binding Protein (FABP) i n the Chicken Intestine . 80 3.5.2.1 Introduction 80 3.5.2.2 Materials and Methods 81 3.5.3 Experiment 6 Fatty Acid Binding Protein i n the Intestine of Newly Hatched Chicks. 82 3.5.4 Experiment 7 Relative Amount of FABP i n the Proximal, Middle and Distal Chicken Intestinal Segments. 83 3.5.5 Experiment 8 Relative Amounts of Intestinal FABP i n New Hampshires, Broilers and White Leghorns Fed Basal, 12% Tallow and 12% Corn O i l Diets from Day Old u n t i l 5 Weeks of Age. 83 3.5.5.1 Materials and Methods 84 3.5.6 Experiment 9 Influence of Prolonged Feeding of Tallow and Corn O i l Diets on the Amount of FABP i n the Proximal and Lower Intestinal Segments of the New Hampshire and Broiler-Type Birds. 85 i x Page 3.5.6.1 Intrcxduction 85 3.5.6.2 Materials and Methods 86 3.5.7 Experiment 10 A Study of the Effect of Dietary Bile Salts and Animal Tallow on the Content of FABP (mg/g tissue) of the Proximal, Middle and Distal Intestinal Segments of the 4, 5, and 6 week-old New Hampshire and Broiler-type Chickens i n Relation to Fat Absorbability. 87 3.5.7.1 Introduction' 8 7 3.5.7.2 Materials and Methods 88 3.5.8 Results . 89 3.5.8.1 Experiment 5 89 3.5.8.2 Experiment 6 89 3.5.8.3 Experiment 7 90 3.5.8.4 Experiment 8 90 3.5.8.5 Experiment 9 92 3.5.8.6 Experiment 10 93 3.5.9 Discussion 95 SECTION FOUR 114 SUMMARY AND CONCLUSION 114 REFERENCES 119 APPENDIX TABLES 139 LIST OF TABLES Composition of the diets used i n Experiment 1 Ef f e c t of breed x die t i n t e r a c t i o n on fat ab-so r b a b i l i t y (%) at 3 and 4 weeks of age Eff e c t of breed of birds on fat absorbability (%) at 5 and 6 weeks of age Eff e c t of type of dietary f a t on f a t absorb-a b i l i t y (%) at 5, 6, 7, 9 and 11 weeks of age regardless of breed of b i r d E f f e c t of breed of birds and dietary f a t compos ti o n and apparent metabolishable energy (M. E.) values (cals/g dry feed) at 3, 5 and 9 weeks of age Correlation c o e f f i c i e n t s between f a t absorbabi-lityrand,metabolisable energy values of the two high-fat diets i n New Hampshires, B r o i l e r s and White Leghorns E f f e c t of breed of birds and composition of the die t on performance e f f i c i e n c y indices E f f e c t of breed of birds and composition of the diet on feed e f f i c i e n c y values from 17 days to 6 3 days of age Mean feed passage times (hr:min) i n New Hamp-shires, B r o i l e r s and White Leghorns on basal, 12% tallow and 12% corn o i l diets at 5 weeks of age ( T r i a l one) Mean feed passage times (hrrmin) i n New Hamp-shires, B r o i l e r s and White Leghorns on basal, 12% tallow and 12% corn o i l diets at 7 weeks of age ( T r i a l two) Fresh pancreatic mean weight (g) and lipase a c t i v i t y , mM o l e i c acid/hour/g pancreatic powder i n New Hampshires, B r o i l e r s and White Leghorns Feed composition of the basal d i e t (Diet 1) xi Table Page 13 Composition of experimental diets 75 14 E f f e c t of 12% tallow and dietary b i l e s a l t supplementation on feed e f f i c i e n c y i n New Hampshires, B r o i l e r s and White Leghorns between 3 and 4 weeks of age 76 15 Mean body weight gains (g) of New Hampshires, Br o i l e r s and White Leghorns fed basal and 12% tallow diets with or without sodium taurocholate between 3 and 4 weeks of age 77 16 E f f e c t of dietary supplementation of b i l e s a i t (0.05% sodium taurocholate) on net tallow f a t absorbability by the New Hampshires, B r o i l e r s and White Leghorns 7 8 17 E f f e c t of dietary supplementation with b i l e s a l t (0.05% Na-taurocholate) on f e c a l soap f a t ex-pressed i n milligrams per gram of dry f e c a l weight 79 18 Concentration of FABP i n the small i n t e s t i n e of birds of d i f f e r e n t breeds from hatching to 5 weeks of age 100 19 E f f e c t of dietary f a t content on the concentra-ti o n of FABP (mg/g intestine) regardless of breed of birds from 1 week to 5 weeks of age 101 20 Fat absorbability i n 2 week-old New Hampshire, B r o i l e r and White Leghorn chicks i n Experiment 8 102 21 Individual v a r i a b i l i t y i n weight and FABP con-centration of proximal, and lower intestine of New Hamp-shire and broiler-type birds fed high-fat diets for 10 weeks i n Experiment 9 103 22 E f f e c t of dietary supplementation with 0.05% Nataurocholate on net tallow f a t absorbability by the New Hampshire and Broiler-type chicks i n Experiment 10 104 23 E f f e c t of dietary b i l e s a l t on the amount of fe c a l soap fatty acids (mg/g dry f e c a l weight) excreted by the New Hampshire and Broiler-type chicks i n Experiment 10 105 LIST OF FIGURES' Tallow a b s o r b a b i l i t y % and f e c a l soap f a t (mg/g d i e t ) determined with d i f f e r e n t types of b i r d s at d i f f e r e n t ages i n Experiment 1 Page 50 Corn o i l a b s o r b a b i l i t y and f e c a l soap f a t (mg/g diet) determined wi t h d i f f e r e n t types of b i r d s at d i f f e r e n t ages i n Experiment 1 J-5I Gel f i l t r a t i o n of adult,White Leghorn i n t e s t i n a l mucosa supernate wi t h C - o l e i c a c i d using Sepha-dex G-75 106 Sephadex G-75 g e l f i l t r a t i o n of day-old New Hampshire cljiick mesenteric i n t e s t i n a l super-nate wi t h C - o l e i c a c i d 1 ° 7 Sephadex Gr-75 g e l f i l t r a t i o n of day-old b r o i l e r tyj^e chick mesenteric i n t e s t i n a l supernate wi t h C - o l e i c a c i d Sephadex G-75 g e l f i l t r a t i o n of White Leghorn^ chick mesenteric i n t e s t i n a l supernate wi t h C o l e i c a c i d R e l a t i v e amount of FABP i n the mucosa of the proximal, middle, and d i s t a l i n t e s t i n a l segments of a b r o i l e r - t y p e b i r d fed a d i e t c o n t a i n i n g 3% of f a t f o r 10 weeks 108 109 110 R e l a t i v e amount of FABP i n the mucosa of the proximal, middle, and d i s t a l i n t e s t i n a l segments of a b r o i l e r - t y p e b i r d fed a d i e t c o n t a i n i n g 15% of f a t f o r 10 weeks. I l l Concentration of FABP (mg/bird) i n the mesenteric i n t e s t i n e of New Hampshires, B r o i l e r s and White Leghorns fed d i f f e r e n t d i e t s from day-old to 5 weeks of age 112 Concentration of FABP (mg/g t i s s u e ) i n the p r o x i -mal, middle and d i s t a l i n t e s t i n a l segments of the New Hampshires (A) and B r o i l e r s (B), a f t e r 1, 2, and 3 weeks of feeding on the d i f f e r e n t e x p e r i -mental d i e t s 113 x i i i LIST OF APPENDIX TABLES Table Page 1(A) Experiment 1. S t a t i s t i c a l analysis for com-paring the average f a t absorbability values (on a transformed scale) obtained with New Hampshires, B r o i l e r s and White Leghorns feed-ing on 12% tallow and/or corn o i l at 7 d i f f e r -ent ages. 139 11(A) Experiment 1. S t a t i s t i c a l analysis to test for significance of differences in average feed e f f i c i e n c y values (units feed/unit gain) among treatments 142 III(A) Experiment 1. S t a t i s t i c a l analysis of calculated performance indices for New Hampshires, B r o i l e r s and White Leghorns 143 IV(A) Experiment 1. S t a t i s t i c a l analysis of metaboli-sable energy (M. E.) values determined with New Hampshires, B r o i l e r s and White Leghorns at 3, 5 and 9 weeks of age 14 4 1(B) Experiment 2. S t a t i s t i c a l analysis of feed pas-sage data obtained with birds at 5 weeks of age 11(B) Experiment 2. S t a t i s t i c a l analysis of feed pas-sage time data* obtained with birds at 7 weeks of age 146 147 1(C) Experiment 3. S t a t i s t i c a l analysis to compare pancreas weights and in v i t r o pancreatic lipase a c t i v i t y (mM o l e i c acid/g dry pancreatic powder) between New Hampshires, B r o i l e r s and White Leg-horns 148 1(D) Experiment 4. S t a t i s t i c a l analysis of feed e f f i -ciency data 149 11(D) Experiment 4. S t a t i s t i c a l analysis of body weight gain r e s u l t s 151 III(D) Experiment 4. S t a t i s t i c a l analysis of net f a t absorbability data on a transformed scale 153 IV(D) Experiment 4. S t a t i s t i c a l analysis of amounts of soap fa t t y acids (mg/g dry feces) 155 1(E) S t a t i s t i c a l analysis of results of Experiment 8 157 xiv LIST OF APPENDIX TABLES Table Page 11(E) S t a t i s t i c a l a n a l y s i s f o r comparing the average f a t a b s o r b a b i l i t y values (on a transformed scale) obtained w i t h d i f f e r e n t types of b i r d s i n E x p e r i -ment 8 of the FABP study 160 1(F) S t a t i s t i c a l a n a l y s i s of r e s u l t s of Experiment 9 of the FABP study 161 1(G) Experiment 10. S t a t i s t i c a l a n a l y s i s of f a t ab-s o r b a b i l i t y values (on a transformed scale) ob-t a i n e d with New Hampshires and B r o i l e r s 16 3 XV A C K N O W L E D G E M E N T S I would l i k e t o extend my sincere thanks to my research s u p e r v i s o r , P r o f e s s o r B. E. March, f o r her continuous advice, guidance and c o n s t r u c t i v e c r i t i c i s m s i n the course of t h i s study and i n the prepar a t i o n of the manuscript. My s i n c e r e a p p r e c i a t i o n i s a l s o extended to members of my t h e s i s committee: Drs. D. B. Bragg, R. C. Fitzsimmons, R. G. Peterson and C. W. Roberts, f o r the var i o u s forms of help rendered to me. I wish a l s o to record my p a r t i c u l a r thanks to the Cana-dian I n t e r n a t i o n a l Development Agency f o r awarding me the sc h o l a r s h i p that made t h i s study p o s s i b l e . My thanks a l s o go to the t e c h n i c i a n s i n the p o u l t r y nu-t r i t i o n l a b o r a t o r y and to the p o u l t r y farm workers who i n one way or another, helped me i n the d i f f e r e n t experiments c a r r i e d out i n course of t h i s research. The u n t i r i n g support and encouragement of Pr o f e s s o r J . B i e l y and the f r i e n d l y environment provided by my f e l l o w gradu-ate students i n the Department of P o u l t r y Science, are a l s o acknowledged. F i n a l l y , I would l i k e to dedicate t h i s t h e s i s to the memory of my beloved son Charlse Ssempijja (R. I . P.). J. B. D. Katongole 1 SECTION ONE 1.0 General I n t r o d u c t i o n P r o v i s i o n of adequate and w e l l balanced food to the ever expanding p o p u l a t i o n , e s p e c i a l l y i n developing c o u n t r i e s i s a st r o n g l y f e l t need. I t i s imperative, t h e r e f o r e , t h a t n u t r i -t i o n i s t s and g e n e t i c i s t s i n the l i v e s t o c k i n d u s t r y have to be very co-operative f o r a b e t t e r , e a s i e r and sooner r e a l i s a t i o n of t h a t u l t i m a t e o b j e c t i v e . I t i s obvi o u s l y true t h a t i n l i v e -stock production,'the o b j e c t i v e i s t o u t i l i s e the animal's po-t e n t i a l to convert low q u a l i t y f e e d s t u f f s (forages, farm waste and i n e d i b l e products of food processing) to high q u a l i t y pro-ducts such as meat, m i l k , eggs and wool. The ruminants, de-pending on forages f o r the production of meat and m i l k , compete l e s s w i t h man f o r a v a i l a b l e f e e d s t u f f s , but they, however, s i g -n i f i c a n t l y compete with him f o r a v a i l a b l e space. P r o j e c t e d i n f u t u r e , along w i t h i n c r e a s i n g trends i n world p o p u l a t i o n , the problem of competition f o r space between man and larg e d a i r y and beef animals assumes even great dimensions. Therefore use of s m a l l , fast-growing animals to provide p r o t e i n s of animal o r i g i n w i l l s t i l l continue to be a major p o s s i b l e a l t e r n a t i v e . P o u l t r y i s a p r i o r i t y i n t h i s a l t e r n a t i v e because i n terms of n u t r i t i v e value, the chicken egg i s second to none among the animal p r o t e i n products. The problem i s tha t c h i c k e n s , l i k e other monogastrics, (pigs) d i r e c t l y compete wi t h man f o r g r a i n and other f e e d s t u f f s . I t i s of utmost importance, t h e r e f o r e , to use p o u l t r y s t r a i n s w i t h a c a p a c i t y f o r maximum output (meats and eggs) per u n i t of n u t r i e n t . The reason f o r t h i s i s twofold, one i s the j u s t i f i c a t i o n of continued presence of a p o u l t r y i n -dustry based on r e a r i n g of animals t h a t compete wi t h man f o r a v a i l a b l e feed i n g r e d i e n t s and two i s the w e l l known slogan t h a t i n the economics of animal production the cost of f e e d s t u f f s i s an item of the g r e a t e s t importance, and the keynote to e f f i c i e n c y , i s the proper u t i l i s a t i o n of the n u t r i e n t s they c o n t a i n . B a s i c a l l y , a chicken i s a p o t e n t i a l scavenging animal i f not r e s t r i c t e d . R e s t r i c t i n g chickens i n cages or i n deep l i t t e r houses as i s done under i n t e n s i v e commercial p o u l t r y production systems n e c e s s i t a t e s the p r o v i s i o n of w e l l balanced r a t i o n s to obtain maximum b e n e f i t s . Research has always been d i r e c t e d t o -wards d e f i n i n g what c o n s t i t u t e s a w e l l balanced r a t i o n under various p h y s i o l o g i c a l and developmental s t a t u s of the chicken. I t can h o p e f u l l y be asserted that much has been achieved as f a r as the n u t r i t i o n of the chicken i s concerned. N u t r i t i o n a l d i s -orders have been defined and can be c o r r e c t e d through p r o v i s i o n of the missing n u t r i e n t . More important however, i s the question of response of d i f f e r e n t s t r a i n s of chickens to s p e c i f i c n u t r i e n t s , energy and p r o t e i n sources being the major ones. Evidence t h a t e f f i c i e n c y of feed u t i l i s a t i o n i n chickens i s i n h e r i t e d was r e -ported by Hess (1941) and Macartney and J u l l (19 4 7). There are a l s o l i t e r a t u r e r e p o r t s on genetic d i f f e r e n c e s i n requirements of c e r t a i n n u t r i e n t s which i s p a r t l y a r e f l e c t i o n of genetic d i f f e r e n c e s i n e i t h e r e f f i c i e n c y of u t i l i s a t i o n or r a t e of syn-t h e s i s of the n u t r i e n t s i n question. Genetic d i f f e r e n c e s i n r e -quirements have been demonstrated f o r thiamine, (Thorton e t a l . , 1960); r i b o f l a v i n , (Lamoreux and Hutt, 1948); methionine and c y s t i n e , (MacDonald, 1958; M i l l e r e t a l . , 1960); a r g i n i n e , (Hegsted e t a l . , 1941; Nesheim and Hutt, 1962); and l y s i n e (Griminger and F i s h e r , 1962). The i m p l i c a t i o n of a l l these 3 f i n d i n g s i s that i t i s p o s s i b l e to i d e n t i f y among breeds and/or s t r a i n s of chickens, those t h a t are most e f f i c i e n t i n the u t i l i -s a t i o n of s p e c i f i c n u t r i e n t s . Except f o r the mere suggestion by S i b b a l d et a l . , 1963a, t h a t breed and s t r a i n d i f f e r e n c e s i n n u t r i e n t requirements might be due to a number of f a c t o r s i n -c l u d i n g genetic v a r i a t i o n s i n the a b i l i t y to d i g e s t and/or absorb n u t r i e n t s , research s t u d i e s on genetic d i f f e r e n c e s i n n u t r i e n t (e. g. f a t ) a b s o r b a b i l i t y have not been at l e a s t as numerous as i n other areas of p o u l t r y n u t r i t i o n . However the p o t e n t i a l value of such research s t u d i e s cannot be overemphasized because i n the b r o i l e r i n d u s t r y f o r example, i t has been estimated that j u s t one u n i t change i n feed conversion i n a 4-lb. b i r d i s e q u i v a l e n t to 40 l b s . of feed per 10,000 b i r d s . D i e t a r y energy has o f t e n been r e f e r r e d to as the "pace maker" i n l i v e s t o c k production. Fat compared to other d i e t a r y feed i n g r e d i e n t s has the g r e a t e s t amount of energy per u n i t weight. Therefore the presence of f a t i n p o u l t r y d i e t s ensures th a t the b i r d s can i n g e s t l a r g e q u a n t i t i e s of energy without ove r t a x i n g t h e i r d i g e s t i v e system, and t h i s i s why there i s an ever i n c r e a s i n g i n t e r e s t i n the use of high energy d i e t s f o r b r o i l e r production. DeGroote, (1973) i n d i c a t e d t h a t there was s u f f i c i e n t evidence showing t h a t the n u t r i e n t i n t a k e c a p a c i t y of the b r o i l e r , which increases w i t h higher d i e t a r y energy con-c e n t r a t i o n has a great i n f l u e n c e on the p r o f i t a b i l i t y of b r o i l e r production. The e f f e c t s of adding f a t to p o u l t r y d i e t s have, t h e r e f o r e , f o r a very long time been st u d i e d and w i l l be b r i e f l y reviewed i n the next s e c t i o n . 4 Metabolisable energy (ME) i s now considered to be the most important c r i t e r i o n for expressing c a l o r i f i c value of poultry feedstuffs. I t i s however subject to a l o t of v a r i a b i l i t y due to several factors including species and s t r a i n differences (Slinger, et a l , 1964; Bayley, et a_l. , 1968; Fisher and Shannon, 1973; Forster, 1968; March and Biel y , 1971). The s t r a i n / genetic difference i n ME estimation reported by the various investigators has never been f u l l y i d e n t i f i e d . Since f a t with i t s highest energy content per unit weight contributes s i g n i -f i c a n t l y to the t o t a l ME content of the d i e t , i t would appear that any s l i g h t difference between d i f f e r e n t types of chickens i n the u t i l i s a t i o n of fat would s i g n i f i c a n t l y influence ME estimates to a greater extent than any other dietary ingredients. This study was therefore i n i t i a t e d to test t h i s hypothesis and the s p e c i f i c objectives of the study were as outlined i n the next subsection. 1.1 Objectives of the Study This study was s p e c i f i c a l l y intended to: (a) Establish whether s i g n i f i c a n t s t r a i n differences i n fat absorbability e x i s t among domestic chickens. Cb) Relate f a t absorbability values to ME estimates obtained with d i f f e r e n t types of chickens at d i f f e r e n t ages i n order to f i n d out the extent of v a r i -a b i l i t y i n ME values that i s d i r e c t l y a ttributable to v a r i a t i o n i n f a t d i g e s t i -b i l i t y c o e f f i c i e n t s . (c) Search for a possible cause of poultry-s t r a i n differences in f a t absorbability by examining some of the factors most l i k e l y to influence f a t digestion and absorption in the genetically d i f f e r e n t types of chickens. With regard; to objective (c) experiments were carried out on: (i) feed passage time, ( i i ) lipase a c t i v i t y , ( i i i ) e f f e c t s of dietary supplementation of b i l e s a l t s (Na-taurocholate), (iv) fat t y acid transport protein using three breeds v i z New Hampshire, White Leghorn and a broi l e r - t y p e . 1.2 Short Note on the Experimental Birds In a l l experiments carried out in course of t h i s study, three d i f f e r e n t types of chickens namely New Hampshires, B r o i l e r s and White Leghorns were used. The New Hampshire birds belonged to the UBC inbred l i n e , B r o i l e r s and White Leghorns were Hubbard and Babcock types respectively. In the s t a t i s t i c a l analysis and multiple comparison pro-cedures for comparing treatment means in the Appendix Tables, the New Hampshires, B r o i l e r s and White Leghorns w i l l be designated as types A, B and C respectively. The d i f f e r e n t subscripts on those l e t t e r s w i l l r e f e r to the d i f f e r e n t dietary treatments to which the birds were subjected in the experiment being analysed. 6 SECTION TWO 2.0.0 LITERATURE REVIEW 2.1.0 LIPID ABSORPTION 2.1.1 I n t r o d u c t i o n Studies on l i p i d d i g e s t i o n and absorption i n various species of animals i n c l u d i n g man have been going on f o r q u i t e a long time (over 100 y e a r s ) . This i s because l i p i d s c o n s t i t u t e a very important and heterogenous group of com-pounds wi t h s e v e r a l v i t a l f u n c t i o n s . F i r s t of a l l , f a t by v i r t u e ; of i t s high energy y i e l d per u n i t weight, provides a conveniently p o r t a b l e f u e l . Complex l i p i d s l i k e phospho-l i p i d s are of u n i v e r s a l occurrence i n d i f f e r e n t types of membranesr- t h a t are i n v o l v e d not only i n the s e l e c t i v e p e r m e a b i l i t y of the c e l l but a l s o other d a i l y processes l i k e energy release i n the mitochondria and energy capture i n the c h l o r o p l a s t s . D i e t a r y l i p i d s act as c a r r i e r s of the f a t s o l u b l e vitamins so t h a t i n cases of f a t malabsorption, f a t s o l u b l e v i t a m i n d e f i c i e n c y symptoms may ensue. Further-more, l i p i d s are important egg yolk components making up over 30% of the t o t a l egg yolk weight. I t i s because of these and s e v e r a l other f u n c t i o n s t h a t l i p i d s have c o n s t a n t l y r e c e i v e d research i n t e r e s t by i n d i v i d u a l s i n v a r i o u s d i s c i p l i n e s of study. 2.1.2 Scheme of Fat Absorption i n the Avian Species (chicken) Except f o r some s l i g h t d i f f e r e n c e s i n the mucosal products of absorbed f a t and t h e i r route of t r a n s p o r t , the s t o r y of f a t d i g e s t i o n and absorption i n the avian species i s s i m i l a r to 7 that i n the mammals'. Since the onset of experimental work on f a t d i g e s t i o n and absorption, a number of t h e o r i e s have been advanced. The c l a s s i c a l reviews of Verzar and McDougalil (19 36) and Frazer et, aJL. , (1944) and a h i s t o r i c a l summary by Johnston (196 8) give a good perspective about past t h e o r i e s on f a t d i -g e s t i o n and absorption. The l i p o l y t i c and p a r t i t i o n t h e o r i e s on f a t d i g e s t i o n and absorption have remained the most important ones f o r q u i t e a long time, although none of them e n t i r e l y describes a l l the events o c c u r r i n g during the d i g e s t i o n and absorption of f a t . This i s why there has been a s h i f t of opinion i n favour of the " p a r l i p " theory which i s a merger between the two c l a s s i c t h e o r i e s . A combination of pieces of information from d i f f e r e n t l i t e r a t u r e sources i n d i c a t e s t h a t t r i g l y c e r i d e s consumed as l a r g e f a t globules by the animal^ are digested and absorbed v i a two d i s t i n c t phases namely the luminal and c e l l u l a r phases. The l u m i n a l phase i n v o l v e s the enzymatic h y d r o l y s i s of the t r i g l y c e r i d e and m i c e l i a r s o l u b i l i z a t i o n of the pro-ducts of t h i s r e a c t i o n i n p r e p a r a t i o n f o r uptake by the mucosal c e l l s of the small i n t e s t i n e . During the l u m i n a l phase, the t r i g l y c e r i d e s are s e l e c t i v e l y cleaved by the pan-c r e a t i c l i p a s e which has a marked p o s i t i o n a l s p e c i f i c i t y . The products of the l i p a s e a c t i o n , f r e e f a t t y a c i d s , and 2-monoglycerides form m i c e l l e s w i t h the help of b i l e s a l t s . Formation of m i c e l l e s prevents a r e d u c t i o n i n l i p o l y t i c a c t i -v i t y due to product i n h i b i t i o n phenomenon and at the same time creates c o n d i t i o n s appropriate f o r the uptake of f a t t y 8 acids by the mucosal c e l l s . The c e l l u l a r phase of f a t ab-so r p t i o n i n c l u d e s t r a n s f e r of products of l i p i d d i g e s t i o n from the m i c e l l e s through the membrane of the i n t e s t i n a l mucosal c e l l f o l lowed by a s e r i e s of i n t r a c e l l u l a r enzymatic r e a c t i o n s r e s u l t i n g i n r e e s t e r i f i c a t i o n of these l i p i d s . Some i n t a c t t r i g l y c e r i d e molecules are absorbed by pino-c y t o s i s . Using e l e c t r o n microscope, membrane i n v a g i n a t i o n s have been shown to occur i n the mucosal m i c r o v i l l i during the process of f a t absorption, (Sjostrand, 1963). The short chain f a t t y a c i d s , g l y c e r o l and monoglycerides are e a s i l y taken up by the mucosal c e l l s and are more s o l u b l e i n the ra t h e r aqueous medium of the mucosal c y t o s o l than are the long chain free f a t t y a c i d s . The r e a l problem to the o v e r a l l f a t absorption are therefore the long chain free f a t t y acids f o r two reasons. F i r s t , they get bound to the i n t e s t i n a l m i c r o v i l l i membrane to form a r e l a t i v e l y s t a b l e a s s o c i a t i o n w i t h i t y b e c a u s e recent i n v i t r o experiments have shown tha t when long chain free f a t t y acids get bound to plasma membranes there i s a decrease i n free energy ( S a l l e e , 1975) i . e. the process i s exothermic, meaning th a t the b i n d i n g of long chain f a t t y a c i d s to c e l l membrane i s s u f f i c i e n t l y strong. Secondly, long chain f a t t y acids are q u i t e i n s o l u b l e i n the aqueous medium of the mucosal c y t o s o l . I t was i n view of these observations, s t a b i l i t y of b i n d i n g to c e l l membranes, and i n s o l u b i l i t y i n the c y t o s o l , t h a t the mechanism of how long chain f a t t y acids cross the i n t e s t i n a l mucosal c e l l s to the endoplasmic r e t i c u l u m centres of acyl-CoA l i g a s e , 9 was i n v e s t i g a t e d . F o r t u n a t e l y , Ockner et a l . , (1972) de-monstrated the existence of a s p e c i f i c f a t t y a c i d b i n d i n g p r o t e i n i n the r a t i n t e s t i n a l mucosa. Ockner,et al.,(19 72) f u r t h e r demonstrated t h a t the f a t t y a c i d b i n d i n g p r o t e i n has greater a f f i n i t y f o r the unsaturated f a t t y acids than f o r the saturated ones, an observation that p a r t l y e x p l a i n s the r a p i d rate of t r a n s p o r t of o l e i c or l i n o l e i c a c i d as compared to that of p a l m i t i c or s t e a r i c a c i d . In g e n e r a l , what the f a t t y a c i d b i n d i n g p r o t e i n (FABP) does, i s to f a c i l i t a t e through i t s greater b i n d i n g a f f i n i t y , the udesorption of long chain f a t t y a c i d s from the micro-v i l l i membrane and to t r a n s p o r t them through the c y t o s o l to t h i o - e s t e r i f i c a t i o n c entres, where they are a c t i v a t e d to e s t e r s of coenzyme A (acyl-CoA) which are more r e a c t i v e and s o l u b l e i n the c y t o s o l i c aqueous medium. However, the i n t r i g u i n g question i s , how do the f a t t y acids bound to the FABP get r e l e a s e d . There i s no information i n the l i t e r a t u r e to answer t h i s question. I t i s p o s s i b l e t h a t during the a c t i v a t i o n of f a t t y acids by acyl-CoA l i g a s e , the breakdown of two high energy bonds (ATP—» AMP + 2P^) , provides enough energy to release the f a t t y a c i d s from the FABP. The f i n a l r e a c t i o n s i n the c e l l u l a r phase of f a t ab-s o r p t i o n i n v o l v e r e s y n t h e s i s of t r i g l y c e r i d e s v i a the monoglyceride and/or g l y c e r o l phosphate pathways using a c t i v a t e d f a t t y a c i d s . The r e s y n t h e s i s e d t r i g l y c e r i d e s get a p r o t e i n coating to form chylomicrons i n the mammalian 10 species and very low density li p o p r o t e i n (VLDL) i n the avian species. This difference between the mammalian and avian species, i n mucosal f i n a l products of absorbed f a t i s an important one and explains why i n the mammalian species absorbed l i p i d material has to t r a v e l v i a the lymphatic system before j o i n i n g the blood c i r c u l a t i o n , whereas i n the avian species with a poorly developed lymphatic system absorbed l i p i d s can be transferred from the mucosal c e l l by a process of exocytosis d i r e c t l y into the blood c i r c u l a t i o n (portal vein). The chylomicrons d i f f e r from very low density l i p o -protein (VLDL) i n density, diameter and composition (Oncley, 19 58). The chylomicrons (products of absorbed f a t i n the mammalian species) are quite big p a r t i c l e s with a diameter of 5,000-10,000 8 and high t r i g l y c e r i d e (over 80%) and low protein (about 20%) contents. They, therefore, are not ea s i l y taken up by the blood vessels whose walls contain mucopolysaccharides that appear to i n h i b i t the entry of chylomicrons (Human Physiology Text Book, 1970). The chy-lomicrons are, on the other hand, e a s i l y taken up by the lacte a l s of the lymphatic system. They appear to pass rea d i l y through the i n t e r c e l l u l a r openings of the lymphatic vessels (Senior, 1964). They are transported i n the lymphatic vessels and j o i n the general blood c i r c u l a t o r y system v i a the thoracic duct i n the l e f t subclavian vein. In the avian species (chicken) on the other hand, the mucosal f i n a l products of absorbed fat are very low density lipoproteins which are small i n size with a diameter of 300-700 A*. They can therefore 11 be r e a d i l y taken up by the blood v e s s e l s . A l i p o p r o t e i n l i p a s e i n the w a l l s of the blood c a p i l l a r i e s has been i m p l i c a t e d i n the uptake of l i p o p r o t e i n s , though the mechanism whereby t h i s occurs i s not w e l l understood. Some st u d i e s have i n -d i c a t e d that when very low d e n s i t y l i p o p r o t e i n s are examined by polyacrylamide g e l e l e c t r o p h o r e s i s i n 8M urea, s p e c i f i c peptide patterns are apparent. These peptides, are thought to form an a c t i v e surface f o r the i n t e r a c t i o n between the l i p o p r o t e i n l i p a s e and the very low d e n s i t y l i p o p r o t e i n s (Olivercron. e t a l . , 1976). The ratio:., of c h o l e s t e r o l e s t e r to t r i g l y c e r i d e i n the l i p o p r o t e i n i s an important f a c t o r i n the a c t i v i t y of the l i p o p r o t e i n l i p a s e (Steinberg and Khoo, 19 76). The higher the c h o l e s t e r o l e s t e r - t r i g l y c e r i d e r a t i o , the greater the a c t i v i t y of the enzyme and i m p l i c i t l y the f a s t e r the rate of t r a n s p o r t of l i p o p r o t e i n s i n t o the blood v e s s e l s . The c h o l e s t e r o l e s t e r - t r i g l y c e r i d e r a t i o i n the very low d e n s i t y l i p o p r o t e i n i s four times greater than that i n the chylomicrons (Oncley, 1958). Therefore the l i p o -p r o t e i n l i p a s e i s more a c t i v e on the very low density l i p o -p r o t e i n s than i t i s on the chylomicrons. This p a r t l y e x p l a i n s t h e i r ease of passage through the w a l l s of the i n t e s t i n a l blood v e s s e l s . So i n the avian species (chicken), lack of a w e l l developed lymphatic system does not impair f a t ab-s o r p t i o n because the mucosal products of absorbed f a t (VLDL) can d i r e c t l y pass i n t o the blood stream. 2.1.3 Concluding Note pn Fat Absorption Through use of modern research techniques i n v o l v i n g electronmicroscopy, various chemical and chromatographic 12 techniques, great strides have been made into the understand-ing of the mechanism of i n t e s t i n a l f a t absorption. Demonstra-tion of a f a t t y acid binding protein (FABP) i n the intestine of rats (Ockner et a l . , 1972) and of the chicken (Katongole and March, 19 78) and i t s associated greater binding a f f i n i t y for the unsaturated f a t t y acids compared to the saturated ones, has yet been another landmark in the search for better under-standing of the i n t e s t i n a l f a t absorption process. The faster rate of absorption of unsaturated f a t t y acids frequently observed by various investigators can now be explained on the basis, of: the higher or greater r e l a t i v e binding a f f i n i t y of the FABP for those acids. Since recent developments i n molecular biology have revealed that any rea l genetic difference i s traceable to the production of d i f f e r e n t types of proteins or d i f f e r e n t quantities of the same type of protein, differences in the amount of FABP between or within species can explain genetic differences in f a t absorbability. S i m i l a r l y differences i n absorption rate of free palmitic acid and 2-monopalmitin observed by previous investigators can now be l o g i c a l l y explained. It i s well estab-l i s h e d that in the process of fat digestion, the products are predominantly 2-monoglycerides and free f a t t y acids. The 2-monoglycerides and short chain f a t t y acids are e a s i l y taken up by the i n t e s t i n a l mucosal c e l l s . The obstacle to the o v e r a l l process of fat absorption i s thus the long chain free f a t t y acids because of t h e i r a b i l i t y to adsorb to the v i l l i membrane and th e i r i n s o l u b i l i t y in the mucosal cytosol which i s aqueous i n nature. Therefore, presence of a c y t o s o l i c FABP f a c i l i t a t e s the 13 desorption of long chain f a t t y acids from the v i l l i membrane at a rate dependent on whether they are saturated (slower rate) or unsaturated (faster rate). Free palmitic acid i s therefore poorly absorbed because i t i s saturated and the FABP has lower a f f i n i t y for i t . Last but not l e a s t , explanation for the age dependence for e f f e c t i v e development of the f a t absorptive capacity can possibly be obtained by following changes i n the r e l a t i v e concentration of i n t e s t i n a l FABP associated with growth or age. In the present study, e f f e c t s of dietary f a t , age and s t r a i n of birds on the r e l a t i v e concentration of i n -t e s t i n a l FABP in the chicken were examined. 2.2.0 Factors Affecting Fat Absorbability 2.2.1 Introduction A number of studies have been c a r r i e d out to determine factors which influence f a t absorption in various animal species. The l i t e r a t u r e on t h i s subject i s therefore quite extensive and by no means i s i t possible to cover i n d e t a i l s work done on each one of the factors i n a b r i e f review l i k e t h i s . An attempt w i l l however be made to b r i e f l y mention some of the important factors in l i p i d absorption. A combination of pieces of information from d i f f e r e n t l i t e r a t u r e sources does indicate that i t i s possible to c l a s s i f y a l l the various factors a f f e c t i n g f a t absorbability into two main categories. The f i r s t category includes a l l factors d i r e c t l y associated with the animal consuming the fat, and the second one includes factors pertaining to the type of f a t , the two categories can respectively be referred 14 to as animal f a c t o r s and l i p i d . c h a r a c t e r i s t i c s . 2.2.2 Animal Factors 2.2.2.1 Species* Species d i f f e r e n c e s i n both the o v e r a l l e f f i c i e n c y of u t i l i s a t i o n of d i f f e r e n t f a t s and i n the a b s o r b a b i l i t y of the same f a t have been reported. Robert e t a l . , (1972) obtained e x c e l l e n t growth response by c a t f i s h to t a l l o w and o l i v e o i l , both of which contain high l e v e l s of saturated and monoenoic f a t t y a c i d s . The authors a l s o noted t h a t l i n o l e i c a c i d which i s an e s s e n t i a l f a t t y a c i d f o r mammals and avian s p e c i e s , was poorly u t i l i s e d by c a t f i s h and salmonids. This species d i f -ference i n f a t u t i l i s a t i o n was i n t e r p r e t e d to mean that s a t -urated and monoenoic f a t t y acids are b e t t e r u t i l i s e d by c a t f i s h than by t e r r e s t r i a l species. Species d i f f e r e n c e s i n the a b s o r b a b i l i t y of the same type of f a t were evidenced i n the experiments of Hoagland e t a l . , (1943) and Lloy d and Crampton (1957). Hoagland e t al.,(1943 a,b), i n experiments w i t h r a t s , reported a higher d i g e s t i b i l i t y co-e f f i c i e n t f o r f a t s c o n t a i n i n g long chain (hence high molecular weight, high melting p o i n t f a t ) f a t t y a c i d s . On the other hand, Lloy d e t a l . , (1957) using pigs as t h e i r experimental animals found a s i g n i f i c a n t inverse r e l a t i o n s h i p between apparent f a t d i g e s t i b i l i t y and molecular weight of f a t s and o i l s . Duckworth e t a l . , (1950) found a l s o t h a t chicks digested low melt i n g p o i n t f a t s b e t t e r than they d i d the f a t s with high m e l t i n g p o i n t . Carver et a l . , (1955), Sunde (1956) and March e t a l . , (1957) obtained s i m i l a r r e s u l t s . Species d i f f e r e n c e s i n f a t absorb-15 a b i l i t y might be due to d i f f e r e n c e s i n r e l a t i v e i n g e s t a passage times i n d i f f e r e n t animal species caused by d i f f e r e n c e s i n i n -t e s t i n a l length and GIT hormones i n v o l v e d i n the c o n t r o l of g a s t r i c m o t i l i t y . The d i f f e r e n c e s i n a b s o r b a b i l i t y t h a t might be observed as a r e s u l t of d i f f e r e n c e s i n i n g e s t a passage time can be e x p l a i n e d i n terms of r e l a t i v e time of exposure of the f e e d s t u f f t o the degradative a c t i o n of the d i g e s t i v e enzymes; being short w i t h a high rate of i n g e s t a passage. Summation of s l i g h t species d i f f e r e n c e s i n e i t h e r c a t a l y t i c a c t i v i t y or con-c e n t r a t i o n of l i p o l y t i c enzymes and b i l e s a l t p o o l s i z e might c o n s t i t u t e a s i g n i f i c a n t source of v a r i a t i o n i n f a t absorb-a b i l i t y . Webbling (1965) observed t h a t the r a t ' s b i l e j u i c e contains smaller q u a n t i t i e s of b i l e s a l t s than t h a t of the chicken. There may a l s o be species d i f f e r e n c e s i n the con-c e n t r a t i o n or a f f i n i t y of the f a t t y a c i d t r a n s p o r t p r o t e i n s whose existence was demonstrated i n the r a t (Ockner e t a_l. , 1972) and chicken (Katongole and March, 1978) small i n t e s t i n a l mucosa. 2.2.1.2 Age Of The Animal; The e f f e c t of age of the animal on f a t d i g e s t i b i l i t y has been e x t e n s i v e l y s t u d i e d using d i f f e r e n t animal species. There i s a general agreement among the various l i t e r a t u r e r eports t h a t f a t d i g e s t i b i l i t y c o e f f i c i e n t s obtained w i t h young animals are lower than those determined using a d u l t s . Young c h i c k s , 2 to 3 weeks of age f o r example, absorb f a t s , e s p e c i a l l y the saturated ones, l e s s e f f i c i e n t l y (Duckworth et a l . , 1950 ; Fedde et a l . , 1960 ; Renner and H i l l , 1960) 16 than when they are 4, 7 or 8 weeks of age (Donaldson e t a l . , 1957 ; Whitehead e t a l . , 1975). In p i g s , L l o y d e t al.,(1957) reported t h a t 7-week o l d pigs were more e f f i c i e n t i n d i g e s t i n g f a t than 3—week o l d p i g s . Scherer e t a l . , (1973) a l s o ob-ta i n e d s i g n i f i c a n t l y higher apparent f a t d i g e s t i b i l i t y values w i t h o l d e r pigs (6 and 8 weeks) than w i t h young ones (3 and 4 weeks) when l a r d was fed. S i m i l a r l y , i n humans a l s o , d i g e s t i o n , s o l u b i l i s a t i o n and absorption of d i e t a r y l i p i d , p r o c e e d s i n e f f i -c i e n t l y i n i n f a n t s as compared to adult s (Fomon, 196 7). A number of reasons can t e n t a t i v e l y be advanced to e x p l a i n the i n e f f i -ciency of young animals to absorb d i e t a r y l i p i d s . F i r s t , the enzyme complement i n v o l v e d i n f a t d i g e s t i o n i s l e s s w e l l de-veloped i n young animals. This might not be true f o r pigs be-cause K i t t s e t a l . , (1956) reported that the l i p o l y t i c a c t i v i t y of the d i g e s t i v e system i s r e l a t i v e l y abundant i n the young p i g and remains high w i t h advancing age. Secondly, i n young animals f a t absorptive machinery has not yet matured to the extent com-parable to tha t of the a d u l t . And f i n a l l y , the b i l e s a l t pool s i z e and the rat e of b i l e s a l t synthesis i n young animals as compared to adult s are l i m i t i n g f a c t o r s because the g a l l bladder concentrating f u n c t i o n and the e f f i c a c y of i n t e s t i n a l b i l e s a l t reabsorption i n young animals are not f u l l y developed (Jackson e t a l . , 1971 ; Smallwood e t a l . , 1970 ; 1972). Therefore, i t i s t h i s immature nature of t h e i r f a t absorption mechanism that make young animals l e s s e f f i c i e n t i n the o v e r a l l u t i l i -s a t i o n of d i e t a r y l i p i d s . 1 7 2 . 2 . 2 . 3 M i s c e l l a n e o u s • There are s p e c i e s and i n d i v i d u a l d i f f e r e n c e s i n the micro-f l o r a l environments of the gut., t h a t can i n f l u e n c e f a t absorb-a b i l i t y e i t h e r d i r e c t l y o r i n d i r e c t l y . The type of i n t e s t i n a l m i c r o f l o r a , markedly i n f l u e n c e s the t o t a l f e c a l output i n chickens (Eyssen and DeSomer, 1 9 6 7 ) and Yoshida e t a l . , \ 1 9 6 8 ) found co-e f f i c i e n t s of apparent f a t d i g e s t i b i l i t y t o be s i g n i f i c a n t l y h i g h e r i n germ-free than i n c o n v e n t i o n a l r a b b i t s . Young e t a l . , ( 1 9 6 3 ) had e a r l i e r noted a h i g h l y s i g n i f i c a n t i n c r e a s e i n absorb-a b i l i t y o f l a r d f a t t y a c i d s when the c h i c k s were housed i n a fumi-gated l a b o r a t o r y and/or when a n t i b i o t i c s were i n c l u d e d i n t h e i r d i e t . Some b a c t e r i a l s p e c i e s are known to deconjugate b i l e s a l t s and thus i n d i r e c t l y cause f a t malabsorption (Gustafsson and Norman, 1 9 6 2 ; Booth, 1 9 6 5 ; Rosenberg, 1 9 6 9 ; Shimda, 1 9 6 9 ) be-cause of the reduced f a t s o l u b i l i s i n g and m i c e l l a r forming capa-c i t y . The a b s o r p t i o n of s a t u r a t e d f a t t y a c i d s or f a t s p r e -dominantly c o n s i s t i n g of p a l m i t i c and s t e a r i c a c i d s i s a f f e c t e d mostly by the b a c t e r i a l deconjugation of b i l e s a l t s (Young e t C L L . , 1 9 6 3 ; Evrad e t a l . , 1 9 6 4 ; Boyd e t a l . , 1 9 6 7 ; Cole e t a l . , 1 9 6 7 ) . T h i s i s because s a t u r a t e d f a t r e q u i r e s a r e l a t i v e l y h i g h concentra-t i o n of i n t a c t b i l e s a l t s f o r e m u l s i f i c a t i o n . Furthermore, de-conjugated b i l e a c i d s are p o t e n t i a l l y t o x i c t o the mucosal c e l l s and are not r e a d i l y reabsorbed. The n e t r e s u l t o f deconjugation i s thus a r e d u c t i o n i n the a b s o r p t i v e c a p a c i t y of the i n t e s t i n e , not only f o r l i p i d s but a l s o f o r other d i e t a r y n u t r i e n t s . 18 2.2.3 L i p i d C h a r a c t e r i s t i c s F a t t y a c i d composition of d i e t a r y l i p i d s i s the most im-portant f a c t o r determining t h e i r physio-chemical p r o p e r t i e s which i n turn a f f e c t t h e i r r a t e of absorption by the animal. The e f f e c t of f a t t y a c i d composition on f a t a b s o r b a b i l i t y i s a d i r e c t r e s u l t of 3 main f a t t y a c i d p r o p e r t i e s , namely carbon chain length/molecular weight, degree of unsaturation and p o s i -t i o n of the f a t t y a c i d on the g l y c e r o l moiety of the t r i g l y -c e r i d e molecule. Research s t u d i e s have been c a r r i e d out to f i n d the magnitude of i n f l u e n c e of each one of those 3 prop-e r t i e s on f a t a b s o r b a b i l i t y . 2.2.3.1 Carbon Chain Length and Degree of Unsaturation* The carbon chain length of the c o n s t i t u e n t f a t t y a c i d s i n a f a t i s r e s p o n s i b l e f o r the molecular weight and m e l t i n g p o i n t of t h a t f a t . I t i s w e l l known that melting p o i n t of a t r i g l y c e r i d e increases w i t h the carbon chain length but de-creases w i t h the degree of unsaturation of the c o n s t i t u e n t f a t t y a c i d s . Duckworth e t a l . , (1950) found t h a t low m e l t i n g p o i n t f a t s were more d i g e s t i b l e than the high m e l t i n g p o i n t ones when both types of f a t were fed to groups of c h i c k s . March and B i e l y (1957) obtained low d i g e s t i b i l i t y c o e f f i -c i e n t s (50%) of hydrogenated (saturated) f a t when fed to chicks at l e v e l s ranging from 3 to 12 per cent. Poor u t i l i -s a t i o n of high melting p o i n t f a t by the chick was a l s o r e -ported by Carver e t a l . , (1955), who found that hydrogenated t a l l o w and the f a t t y acids of hydrogenated t a l l o w were l e s s 19 w e l l absorbed, while o l e i c a c i d showed high a b s o r b a b i l i t y . Sunde (1956) obtained s i m i l a r r e s u l t s . S t e a r i c a c i d was poorly absorbed i n h i s experiments, while o l e i c , l i n o l e i c and l i n o l e n i c acids with 1, 2 and 3 double bonds respec-t i v e l y were h i g h l y absorbed. March e t a l . , (195 7) showed larg e d i f f e r e n c e s i n apparent a b s o r b a b i l i t y between corn o i l (85-92%), beef t a l l o w (73-75%) and hydrogenated f a t (50%) when fed to growing chickens. Renner and H i l l (1960) reported 70% and 94% d i g e s t i b i l i t y c o e f f i c i e n t s f o r t a l l o w and corn o i l fed to 2 week o l d c h i c k s , the a b s o r b a b i l i t y values increased with age up to 8 weeks wi t h a p e r s i s t e n t d i f f e r e n c e of 13% i n mean a b s o r b a b i l i t y value between corn o i l (95%) and t a l l o w (82%). Carbon chain lengths of the c o n s t i t u e n t f a t t y acids have an e f f e c t on the l i p o l y t i c a c t i v i t y of the p a n c r e a t i c l i p a s e on the t r i g l y c e r i d e molecule. Marked d i f f e r e n c e s i n the rate of h y d r o l y s i s of t r i g l y c e r i d e s by p a n c r e a t i c l i p a s e have always been noted to be a f u n c t i o n of the chain lengths of the e s t e r i f i e d f a t t y acids as reviewed by Desnuelle and Savary (196 3). The sho r t e r chain t r i g l y c e r i d e s are more e a s i l y s p l i t i n the i n t e s t i n a l lumen and the r e s u l t i n g f r e e f a t t y acids are more r e a d i l y transported v i a p o r t a l blood. In any case, the products of p a n c r e a t i c l i p a s e are 2-mono-g l y c e r i d e s which are r e s i s t a n t to f u r t h e r h y d r o l y s i s by the enzyme because of i t s 1, 3 p o s i t i o n a l s p e c i f i c i t y . However, r a p i d h y d r o l y s i s of short chain 2-monoglycerides by the 20 pancreatic lipase sometimes observed,is thought to be due to very fast spontaneous isomerisation to 1 or 3 positions of the glycerol moiety (Entressangles et al.,(1961). 2.2.3.2 Position of the Fatty Acid» Position of a fatty acid within the glyceride molecule may influence the extent to which i t i s absorbed. As a l -ready pointed out i n the previous subsection, the pancreatic lipase s p e c i f i c a l l y cleaves the 1, 3 ester linkages of the t r i g l y c e r i d e molecule, producing as a r e s u l t of i t s action 2-monoglycerides and fat t y acids which together with b i l e s a l t s form micellar solutions necessary for the o v e r a l l fat digestion and absorption process. In the case of palmitic acid, Renner and H i l l (1961) c l e a r l y demonstrated that the chick u t i l i s e s t h i s f a t t y acid to a greater extent, i f i t i s e s t e r i f i e d in the jB-position of the glyceride molecule. The same r e s u l t was obtained for rats (Mattson and Volpenhein, (1962) and Davis and Lewis, (196 8) suggested that this might be true for other species of animals and also for s t e a r i c acid and other long chain saturated f a t t y acids. Mattson and Volpenhein, (1962) also observed, in human infants, greater absorption of palmitic acid from lar d , and associated t h i s r e s u l t with the greater content of 2-monopalmitin and the lower content of free palmitic acid i n the intestine a f t e r hydrolysis of the lar d . Brokerhoff (19 71) showed position of the fat t y acids on the t r i g l y c e r i d e molecule to be unique for d i f f e r e n t fats and o i l s and Mattson and Streck (1974) have recently pointed out that f a t t y acid position e f f e c t may i n -21 fluence the completeness of enzymatic h y d r o l y s i s and the ab-s o r p t i o n from the i n t e s t i n a l t r a c t of the l i p o l y t i c products. 2.3.0 E f f e c t s of Diet a r y Fat i n P o u l t r y Rations: An Overview Research s t u d i e s on the u t i l i s a t i o n of f a t of both p l a n t and animal o r i g i n have r e s u l t e d i n numerous p u b l i c a t i o n s . The e f f e c t s of va r y i n g l e v e l s of d i f f e r e n t types of f a t i n p o u l t r y d i e t s have been e x t e n s i v e l y examined. Some of the repo r t s are, however, c o n t r a d i c t o r y . For b r o i l e r production, i t i s w e l l e s t a b l i s h e d that f a t s , because of t h e i r high energy content, per u n i t mass are ex-tremely u s e f u l d i e t a r y c o n s t i t u e n t s . They are e f f e c t i v e i n promoting growth ra t e (Dam et_ ajL. , 1959 ; Vanschoubroeck, e t a l . , 19 71). The presence of f a t i n the d i e t s has f r e -quently been shown to increase the o v e r a l l e f f i c i e n c y of u t i -l i s a t i o n of d i e t a r y energy, not only by b r o i l e r s but a l s o by l a y i n g hens (Bragg e t a l . , '1972). This e f f e c t , o f t e n c a l l e d the " e x t r a c a l o r i c e f f e c t " of f a t was f i r s t demonstrated f o r growing and mature a l b i n o r a t s by Forbes e t a l . , (19 46); and a s i m i l a r e f f e c t was demonstrated f o r the chickens by Rand e t a_l. , 1958 ; Menge and Denton, 1961 ; and Carew e t a l . , 1964 . Touchburn and Naber (1966) used the term " e x t r a - c a l o r i c b e n e f i t " to describe the improvement i n energy u t i l i s a t i o n or the a s s o c i -a t i v e dynamic e f f e c t upon the a d d i t i o n of f a t to turkey d i e t s . More r e c e n t l y Horani and S e l l , (19 77) used the term " e x t r a metabolic e f f e c t " to describe the change i n r a t i o n M. E. caused by a d d i t i o n of f a t . In an attempt to p a r t i a l l y e x p l a i n t h i s effect.,Leeson and Summers (19 76) put f o r t h an hypothesis which 22 stipulates the existence of an interaction between the fa t t y acids inherent in ration ingredients and the fat t y acids of the added fat which results in changes in the M. E. of the fat and, consequently, of the ration. Several other experiments that have been undertaken with regard to the influence of addition of fat to the diets on per-formance of growing chickens^ have led to the general conclusion that dietary f a t improves feed e f f i c i e n c y ( L i l l i e et a l . , 1952 ; Denton et a l . , 1954 ; Vermeersch and Vanschoubroek, 1968 ; Reid and Weber, 1975 ; S e l l et a l . , 1976 ; Haroni and S e l l , 1977). Vermeersch and Vanschoubroek;: (1968) carried out a comprehensive review of the l i t e r a t u r e on the e f f e c t of adding d i f f e r e n t quantities of d i f f e r e n t types of fat to the diets of the growing chicks. In t h i s review, controversial l i t e r a t u r e reports are quoted. The results of Bie l y and March (1954, 1957) shed some l i g h t on the possible cause of the controversy among l i t e r a t u r e reports on the e f f e c t of supplemental fat on the per-formance of growing chicks. These authors showed that in rations in which the energy content i s raised by addition of fat,the l e v e l of protein which may be u t i l i s e d e f f i c i e n t l y i s higher than in rations of lower energy content. I m p l i c i t l y t h i s finding pin-pointed at the e s s e n t i a l i t y of maintaining a proper c a l o r i e : protein (C:P) r a t i o for the chickens to e f f i c i e n t l y u t i l i s e the high dietary f a t energy for growth. Waibel (195 8) confirmed the proper C:P r a t i o concept when he reported that growth promotion in turkeys due to added fat could only be achieved i f the con-centration of dietary protein was accordingly increased. Bartov 23 et a l . , (1973) re-emphasised the importance of a proper C:P r a t i o , when b r o i l e r d i e t s are supplemented w i t h f a t i n an attempt to increase d i e t a r y c a l o r i f i c d e nsity and at the same time promote e f f i c i e n t growth r a t e . More r e c e n t l y Horani e t a l . , (19 77) have concluded from r e s u l t s of t h e i r experiments, t h a t the grade animal t a l l o w could be b e n e f i c i a l i n l a y i n g hen r a t i o n s when appropriate adjustments i n r a t i o n formulation are made so as to maintain a d e s i r a b l e c a l o r i e : p r o t e i n r a t i o . In c o n c l u s i o n , a c a r e f u l a n a l y s i s of the informat i o n on the subject of supplemental f a t i n chicken d i e t s , prompts one to suggest t h a t d i e t a r y f a t does something e l s e i n the d i e t be-sides c o n t r i b u t i n g i t s i n t r i n s i c energy. The r e a l mechanism of a c t i o n i s a matter of s p e c u l a t i o n at the moment, based on envisaged i n t e r a c t i o n s between f a t t y acids s u p p l i e d by the added f a t and those inherent i n the r a t i o n i n g r e d i e n t s . What-ever the r e a l mechanism may be, on the b a s i s of the " e x t r a -metabolic e f f e c t " concept, i t would appear that supplemental f a t creates an environment w i t h i n the chicken gut that allows f o r increased absorption of some other d i e t a r y components. The question of whether or not d i f f e r e n t types of f a t do t h i s to a s i m i l a r extent opens up research p o s s i b i l i t i e s intended to un-r a v e l the problem of why some f a t s ameliorate the e f f i c i e n c y of food conversion and growth rate more markedly than others even i f a l l other things are h e l d constant. 24 SECTION THREE 3.0.0 MATERIALS AND METHODS, RESULTS AND DISCUSSION 3.1.0 Experiment 1 Fat Absorbability studies and Metabolisable Energy (M. E.) Estimates Using New Hampshires, B r o i l e r s and White Leghorn Birds at Different Ages. 3.1.1 Objective of the Experiment: This experiment was set up f i r s t to study and e s t a b l i s h whether any genetic differences in f a t absorbability existed among the d i f f e r e n t types of chickens; secondly to correlate f a t absorbability values with metabolisable energy estimates obtained with birds of d i f f e r e n t genetic background at d i f -ferent ages i n order to obtain the c o e f f i c i e n t of determina-2 tion (R ) that would indicate the proportion of t o t a l v a r i a -t i o n in M. E. values that i s d i r e c t l y explained by v a r i a t i o n in fat absorbability. 3.1.2 Materials and Methods: 3.1.2.1 Birds: The New Hampshires, B r o i l e r s and White Leghorn type of birds were used in t h i s experiment. The New Hampshire chicks belonged to the U.B.C. inbred l i n e of New Hampshires; the Br o i l e r s and White Leghorns were obtained fromoa commercial hatchery. 3.1.2.2 Housing: A l l day-old chicks were reared in e l e c t r i c a l l y heated thermostatieallycontrolled battery brooders with raised screen f l o o r s . The chicks were fed a basal diet (Diet 1) for two and half weeks afte r which each s t r a i n of birds was randomly d i s t r i b u t e d into six groups of ten birds, each 25 of which was then wingbanded. The d i f f e r e n t groups of b i r d s were randomly assi g n e d to d i f f e r e n t pens i n b a t t e r y cages. 3.1.2.3 Experimental Treatments: The experiment was a 3 x 3 f a c t o r i a l over a completely randomised d e s i g n . There were 3 d i f f e r e n t d i e t s , namely, b a s a l d i e t w i t h 3% f a t content (Diet 1); 12% t a l l o w d i e t (Diet 2) and 12% corn o i l d i e t (Diet 3); fed to d u p l i c a t e groups of ten b i r d s o f each o f the th r e e d i f f e r e n t types o f chi c k e n s , New Hampshires, B r o i l e r s and White Leghorns which are d e s i g n a t e d as type A, B and C r e s p e c t i v e l y i n treatment comparisons i n the Appendix T a b l e s . The composition of the d i e t s i s g i v e n i n Table 1. The b i r d s were s u b j e c t e d to the d i f f e r e n t d i e t a r y treatments, t h r e e days p r i o r t o the f i r s t c o l l e c t i o n o f f e c a l samples. The purpose of t h i s was to a v o i d c o l l e c t i o n o f f e c a l samples other than those a r i s i n g from f e e d i n g the intended experimental d i e t s . F e c a l samples from the d i f f e r e n t treatment s u b c l a s s e s were c o l l e c t e d s t a r t i n g from 3 weeks of age, on a weekly b a s i s up to 7 weeks o f age and then a t 9 and 11 weeks of age. The samples were f r o z e n , l y o p h i l i s e d , ground, and kept f o r l a b o r a t o r y a n a l y s i s f o r dry matter, f a t and n i t r o g e n contents i n order to determine f a t d i g e s t i b i l i t y and m e t a b o l i s a b l e energy (M.E.) v a l u e s . 3.1.2.4 Laboratory A n a l y s i s Feed and f e c a l samples were analysed f o r dry matter con-t e n t by A.O.A.C. (1965) methods. F a t e x t r a c t i o n was done u s i n g the s o x h l e t apparatus. For f e c a l samples, f a t e x t r a c t i o n was carried out in two stages. In the f i r s t stage, approximately 2 grams of fe c a l samples were subjected to ether extraction for 16 hours and amount of extracted f a t was determined. In the second stage, the residue of the f i r s t 16 hours ether ex-tr a c t i o n , in the thimbles were allowed to stand overnight i n a 10% g l a c i a l acetic acid solution in ether to release the free f a t t y acids from f e c a l soaps, which were then extracted with ether the following day. Amounts of f a t from the f i r s t and second ether extraction procedures were added up to give t o t a l f e c a l f a t values which were used in the calculations of fat d i g e s t i b i l i t y (%). Metabolisable energy was determined using f e c a l samples collected at 3, 5 and 9 weeks of age. Feed and f e c a l nitrogen contents at those 3 d i f f e r e n t ages were analysed by the macro-Kjeldhal method. Gross energy of feed and f e c a l samples were determined on a Parr bomb calorimeter. Feed consumption and excreta output were determined by the acid insoluble ash method of Vogtmann et a_l. , (19 75) . 3.1.2.5 Calculations: Fat in the excreta of birds on high f a t diets (Diets 2 and 3) was corrected for fat (metabolic and undigested) excreted by birds fed the basal d i e t (Diet 1), and net f a t d i g e s t i b i l i t i e s (%) were calculated according to the following formula: a i-. 4. r>- -i. i t % F a t in feces % Ash in feed, > , n r. % Fat Dxgestxbility=l-(^—=— z— : 2 — 3 — x „ — 7 - — : ~ ))x 100 3 • 2 % Fat in feed % Ash in feces Feed and f e c a l ash contents were determined by the method of Vogtmann et a l . , (1975). Nitrogen retention at 3,5 and 9 weeks of age was determined and M. E. values were calculated for each 27 treatment subclass w i t h a c o r r e c t i o n of 8.22 Kcal/g n i t r o g e n r e t a i n e d ( H i l l and Anderson, 1958). D i f f e r e n c e s i n t o t a l feed consumption and body weight gains were so l a r g e t h a t i t was considered appropriate to c a l c u l a t e performance e f f i c i e n c y i n d i c e s t h a t would take i n account o v e r a l l body weight gain and feed conversion r a t i o s ( r e c i p r o c a l of feed e f f i c i e n c y ) and at the same time p r o p o r t i o n a t e l y narrow the d i f f e r e n c e s among s t r a i n s . The performance e f f i c i e n c y i n d i c e s were c a l c u l a t e d according to the formula given by C u l l e n e t a l . , (1962). c ~ £ J :. • Weight gain (g)xFeed conversion r a t i o Performance ,Ef f i c i e n c y = 2 - i n n index (PEI) 3.1.2.6. S t a t i s t i c a l A n a l y s i s : Fat a b s o r b a b i l i t y (%). values were subjected to a square root transformation f o r reasons given by S t e e l and Torie (page 157). The f a t a b s o r b a b i l i t y transformed data, meta-b o l i s a b l e energy values , feed e f f i c i e n c y (g feed/g gain) and performance e f f i c i e n c y i n d i c e s were analysed f o r variance using U.B.C. Genelin Computer program to t e s t f o r s i g n i f i c a n c e of d i f f e r e n c e s among the various treatment means. A f i x e d e f f e c t model was assumed i n the a n a l y s i s of variances so t h a t the r e s i d u a l mean square was used c o n s i s t e n t l y to t e s t f o r s i g -n i f i c a n c e due to other sources of v a r i a t i o n . Since experiments s i m i l a r to the one i n the present study are l i k e l y to be c a r r i e d out using d i f f e r e n t types of b i r d s and d i e t s , Tukey's m u l t i p l e comparison t e s t which uses type 1 experiment wise e r r o r r a t e 28 (number of experiments with one or more comparisons i n c o r r e c t l y d e c l a r e d s i g n i f i c a n t d i v i d e d by the t o t a l number o f experiments with a t l e a s t 2 equal means) was thought most a p p r o p r i a t e i n comparing means from treatments w i t h s i g n i f i c a n t F v a l u e s . The s t r i c t n e s s of Tukey t e s t (fewer type 1 e r r o r s are made w i t h i t , Chew, 1977) renders the i n t e r p r e t a t i o n o f data more r e l i a b l e . C o r r e l a t i o n c o e f f i c i e n t s between d i e t a r y M e t a b o l i s a b l e Energy (M.E.) values and f a t a b s o r b a b i l i t y values were computed. Co-2 e f f i c i e n t s of d e t e r m i n a t i o n (R ) were a l s o c a l c u l a t e d to p r o v i d e a measure of v a r i a t i o n i n M.E. v a l u e s d i r e c t l y a t t r i b u t a b l e t o v a r i a t i o n i n f a t a b s o r b a b i l i t y s i n c e t h i s was one of the major o b j e c t i v e s of the experiment. 3.1.3 R e s u l t s 3.1.3.1 Fat A b s o r b a b i l i t y A n a l y s i s of v a r i a n c e o f f a t a b s o r b a b i l i t y transformed data showed t h a t a t d i f f e r e n t ages, f a t a b s o r b a b i l i t y v a l u e s were i n f l u e n c e d by type of b i r d s , type of d i e t a r y f a t and/or the i n t e r a c t i o n between these f a c t o r s . At the ages of 3 and 4 weeks, s i g n i f i c a n t (P-0.05) s t r a i n x d i e t i n t e r a c t i o n e f f e c t s on f a t a b s o r b a b i l i t y were o b t a i n e d . T h i s meant t h a t a t those 2 d i f f e r e n t ages, e f f e c t s of s t r a i n c o u l d not be c o n s i d e r e d independent of the type of d i e t a r y f a t e f f e c t s . T h e r e f o r e , the s t r a i n x d i e t i n t e r a c t i o n means were compared and are presented i n Table 2. T h i s Table c l e a r l y shows t h a t a t 3 weeks of age, s h o r t l y a f t e r the i n t r o d u c t i o n of the t a l l o w and corn o i l d i e t s , the New Hampshires were e q u a l l y 29 e f f i c i e n t in the digestion and absorption of f a t supplied by the two diets. On the other hand, the B r o i l e r s and White Leghorns showed both s i g n i f i c a n t i n t e r - s t r a i n and in t e r - d i e t a r y d i f f e r -ences i n fat absorbability values. Fat supplied by the corn o i l d i e t (Diet 3) was better digested (P^0.05) than that from a 12% tallow diet (Diet 2). It i s further noteworthy that while the White Leghorns on Diet 3 recorded a s i g n i f i c a n t l y lower fat ab-s o r b a b i l i t y value than the B r o i l e r s , the converse was true on a 12% tallow d i e t . However, the New Hampshires on t h i s same die t (12% tallow) had superior (P-0.05) fat absorbability mean value. Week 4 f a t d i g e s t i b i l i t y data show a d i f f e r e n t pattern. At t h i s age, on a 12% corn o i l diet, f a t absorbability values were sim i l a r for a l l strains of birds. However, on a 12% tallow diet, the mean fat absorbability value obtained with the New Hampshires, while comparable to those of the B r o i l e r s and White Leghorns on Diet 3, was s i g n i f i c a n t l y (P^0.05) higher than those of other types of birds (Broilers and White Leghorns) on the same diet. And contrary to what Table 2 figures at the age of 3 weeks show, the 4 week B r o i l e r s compared to the White Leghorns at the same age, had greater (P-0.05) a b i l i t y i n coping up with the 12% tallow d i e t . From 4 weeks of age up to the end of the experimental period, there were no s i g n i f i c a n t s t r a i n x d i e t interaction e f f e c t s . Therefore, s t r a i n and dietary e f f e c t s on f a t absorbability values obtained during t h i s period could be examined independently. Table 3 contains the s t r a i n mean f a t absorbability values 30 at 5 and 6 weeks of age. I t can be seen from Table 3 t h a t r e -gardless of the type of d i e t a r y f a t , the New Hampshires maintained at both ages (as w e l l as the, preceding ones, 3 and 4 weeks) a f a t absorptive c a p a c i t y s i g n i f i c a n t l y (P=0.05) su p e r i o r t o t h a t of White Leghorns and B r o i l e r s between which there were no s i g n i f i -cant d i f f e r e n c e s i n f a t a b s o r b a b i l i t y values at both ages. Table 4 shows the e f f e c t of type of d i e t a r y f a t on f a t d i -g e s t i b i l i t y . The e f f e c t of type of d i e t a r y f a t are examined using f a t a b s o r b a b i l i t y values obtained between 5 and 11 weeks of age when the s t r a i n x d i e t i n t e r a c t i o n e f f e c t s were not s i g n i f i c a n t . Table 4 c l e a r l y shows tha t at 5,6,7,9 and 11 weeks of age, regardless of the breed of b i r d s , f a t s u p p l i e d by the 12% corn o i l d i e t , was much b e t t e r (P-0.05) dige s t e d and absorbed than tha t from the 12% t a l l o w d i e t values. Changes i n f a t absorb-a b i l i t y values with changes i n the age of d i f f e r e n t b i r d s are i l l u s t r a t e d i n Figures 1(a) and 1(b). Each of the f i g u r e s con-t a i n s f a t a b s o r b a b i l i t y graphs (upper part) and graphs showing the amount of f e c a l soap f a t expressed i n m i l l i g r a m s per gram d i e t eaten, t h a t was excreted by each s t r a i n of b i r d s at d i f -f e r e n t ages (lower p a r t ) . The e f f e c t of age on f a t a b s o r b a b i l i t y i s more obvious from Figure 1(a). This f i g u r e shows t h a t between the ages of 3 and 7 weeks, there were n o t i c e a b l e increases i n t a l l o w f a t a b s o r b a b i l i t y e s p e c i a l l y i n the B r o i l e r s and White Leghorns. The d i f f e r e n c e s i n f a t a b s o r b a b i l i t y between those 2 ages (3 and 7 weeks) were of the magnitude of 2 7% and 2 4% f o r the B r o i l e r s and White Leghorns r e s p e c t i v e l y . On the other 31 hand, the capacity of the New Hampshires to digest and absorb tallow f a t was only s l i g h t l y but steadily increased from an average value of 90% at 3 weeks of age to 9 7% at 7 weeks of age (7 percentage units- increase )• Figure 1(a) further shows that i n each of the strains of bi r d s , the average f e c a l soap fat per gram diet shot up to maximum values at 4 weeks of age and declined very rapidly i n e s p e c i a l l y the B r o i l e r s and White Leghorns up to 7 weeks of age. • The 4 to 7 weeks decline i n fe c a l soap f a t excreted by each s t r a i n of birds corresponded to an increase i n fat absorbability figures during that same period. I t appears from the figure that an inverse r e l a t i o n -ship exists between tallow f a t absorbability and fe c a l soap fat excreted. 3.1.3.2 Metabolisable Energy Values: Metabolisable energy (M.E.) values were determined at 3, 5 and 9 weeks of age according to procedures described i n the Material and Methods Subsection. Analysis of variance of M. E. values at each of those ages, showed s i g n i f i c a n t s t r a i n x diet interaction e f f e c t s . Therefore the s t r a i n x di e t i n t e r -action means were compared and are presented in Table 5. A close examination of data i n Table 5 reveals some i n -teresting observations. Predictably, M.E. values of the basal di e t (3% fat) were consistently lower (P-0.05) than those of the diets containing 12% of tallow or corn: o i l . - On a basal di e t at 3 and 5 weeks of age, M.E. values were si m i l a r for a l l the 3 strains of birds . However, at 9 weeks of age, the basal 32 d i e t M.E. value o b t a i n e d with the B r o i l e r s was s i g n i f i c a n t l y lower (P-0.05) compared to the M.E. v a l u e s o b t a i n e d with the New Hampshires and White Leghorns on a s i m i l a r d i e t and age. Secondly, on d i e t 2 (12% t a l l o w ) , a t the age of 3 weeks, M.E. values o b t a i n e d with the New Hampshires and White Leg-horns (3478 and 329 7 c a l s / g d i e t r e s p e c t i v e l y ) were s i m i l a r and comparable to the 12% corn o i l M.E. v a l u e s , but were s i g -n i f i c a n t l y h i g h e r (P=0.05) than the M.E. value o b t a i n e d with B r o i l e r s (3006 c a l s / g d i e t ) . T h i s was the cause of the s i g -n i f i c a n t s t r a i n x d i e t i n t e r a c t i o n e f f e c t s on M.E. v a l u e s determined a t t h i s age. T h i r d l y , the Table shows t h a t c a p a c i t i e s to metabolise energy s u p p l i e d by 12% corn o i l d i e t a t 3 weeks of age and by 12% t a l l o w d i e t a t 5 weeks of age were s i m i l a r f o r a l l the d i f f e r e n t types of b i r d s . At the age of 5 weeks, the 12% corn o i l d i e t M.E. value determined u s i n g White Leghorns, was s i g -n i f i c a n t l y lower (P-0.05) than t h a t o f the 12% corn o i l d i e t o b t ained w i t h the New Hampshires . * Furthermore, i t can be seen from the Table t h a t a t 9 weeks of age, the M.E. v a l u e s of d i e t s 2 and 3 o b t a i n e d with White Leghorns were lower compared to those o b t a i n e d with the B r o i l e r s and New Hampshires on the same d i e t . For the 12% t a l l o w d i e t ( d i e t 2) the s i g n i f i c a n t d i f f e r e n c e i n M.E. values a t the age of 9 weeks was between •the White Leghorns and New Hampshires (3399 vs 3555 c a l s / g diet),whereas f o r the 12% corn o i l d i e t , d i f f e r e n c e s i n M.E. values between White Leghorns and B r o i l e r s (3416 vs 3546) ; 33 White Leghorns and New Hampshires (34IG vs 359 8) were both s i g n i f i c a n t (P^0.05). Lastly, the e f f e c t of age on M.E. values of each of the diets i s not so obvious from the Table because of the d i f f e r e n t s t r a i n x di e t interaction e f f e c t s at the 3 d i f f e r e n t ages. I t can be noted, however, that the 9 weeks M.E. values of a l l diets were higher than those at 3 weeks of age. The c o r r e l a t i o n c o e f f i c i e n t s between fat absorbability and apparent dietary metabolisable energy values of the two high-fat diets obtained for each breed of birds regardless of age, were transformed to a Z d i s t r i b u t i o n and tested for hetero-geneity using the Chi-square method (Steel and Torie, page 189). The Chi-square value (2.27, 2 df) was not s i g n i f i c a n t indicating that the 3 correlation c o e f f i c i e n t s computed for each breed of birds were homogeneous and therefore could be pooled. Co-2 e f f i c i e n t s of determination (R ) were also calculated. The results of the co r r e l a t i o n analyses are summarised in Table 6. The Table shows that the cor r e l a t i o n c o e f f i c i e n t s between f a t absorbability and metabolisable energy (M.E.) values in a l l types of birds were posit i v e and s i g n i f i c a n t (P^0.05). The ov e r a l l correlation c o e f f i c i e n t was 0.87 giving a c o e f f i c i e n t 2 of determination (R ) value of 0.76. This suggests therefore, that v a r i a b i l i t y i n f a t absorbability accounted for 76% of the t o t a l v a r i a b i l i t y in M.E. values obtained with the d i f f e r e n t types of birds feeding on diets containing 112% .of either.'animal tallow or corn o i l . :: .In order to estimate the contribution of breed v a r i a t i o n i n tallow f a t absorbability to the t o t a l v a r i a t i o n i n M.E. values 34 of the 12% tallow diet, values were computed on a within age across breed basis. The results showed that the 3 correlation c o e f f i c i e n t s were s i g n i f i c a n t l y d i f f e r e n t and that, at the age of 3 weeks 6 7% of the t o t a l v a r i a t i o n in M.E. values of the 12% tallow diet was due to breed v a r i a t i o n in tallow fat absorb-a b i l i t y . This contribution was reduced to 36% and 2% at 5 and 9 weeks of age respectively. This dramatic reduction .in R /values was anre: f l e e t ion. of the reduction i n differences between New Hampshires, B r o i l e r s and White Leghorns i n tallow fat absorption e f f i c i e n c y . These results substantiated the hypothesis that poultry breed and/or age differences in dietary M.E. estimates are to a large extent due to breed and/or age differences i n the absorbability of dietary l i p i d components. 3.1.4 Discussion 3.1.4.1 Fat Absorbability: Results of t h i s experiment have demonstrated that the New Hampshire chicks compared to the B r o i l e r and White Leghorn types, are s i g n i f i c a n t l y superior i n digesting and absorbing tallow f a t incorporated in the diet at 12% l e v e l . An average net tallow fat absorbability value of 89.68% obtained with the New Hamp-shire chicks at 3 weeks of age was 24.0 7% and 18.78% higher than the values determined with the B r o i l e r s and White Leghorn chicks respectively. March and B i e l y (1957), using 4 weeks old New Hampshire chicks found the d i g e s t i b i l i t y c o e f f i c i e n t of 12% supplemental tallow fat to be 75.2% when calculated from the t o t a l fatty acid content of the feces. The average net absorb-a b i l i t y values of tallow determined with 3 and 4 weeks old New 35 Hampshire chicks i n this experiment are greater than those reported by March and B i e l y (1957), although i n both cases f e c a l soap fat t y acids and "endogenous" fat (metabolic and undigested die-tary f a t excreted by the chicks fed the basal ration) were taken into account when ca l c u l a t i n g the net absorbability figures. This difference i n results even with somewhat s i m i l a r type of birds (New Hampshires i n both cases) and at the same l e v e l of dietary tallow fat inclusion (12% tallow), i s probably due to differences in the procedures used. The average tallow fat absorbability ob-tained with B r o i l e r s and White Leghorns at 3 weeks of age approxi-mate those obtained by Renner (1960) with 2 weeks old birds and Gomez and Polin (19 76) with B r o i l e r type crossbred chicks at 19 days of age. It was observed that the range of differences i n tallow f a t absorbability between New Hampshires and B r o i l e r s or White Leg-horns were steadily narrowed as the birds grew older u n t i l the age of 7 weeks when a l l of them appeared to have s i m i l a r tallow fat digestive and absorptive capacities. This observed age de-pendence of saturated fat absorptive capacity i s in accord with the previous reports (Duckworth et a l . , 1950 ; Fedde e_t a l . , 1960 ; Renner and H i l l , 1960 ; Scherer et a l . , 1973) and confirms the concept that in young animals digestive and ab-sorptive mechanisms s t i l l require maturation which comes with age, to e f f i c i e n t l y u t i l i s e the saturated types of f a t . However, i t i s noteworthy that the New Hampshires used in t h i s experiment started o f f with a r e l a t i v e l y high fat absorptive capacity and therefore got adapted to a 12% tallow diet sooner than did the 36 B r o i l e r s and White Leghorns. This i s why the age e f f e c t on f a t absorbability was not much pronounced i n the New Hampshires as i t was i n the other two types of birds. Amounts of soap f a t t y acids (mg/g diet) excreted, showed an inverse relationship with d i g e s t i b i l i t y c o e f f i c i e n t s (Figures 1(a) and 1(b). Also in the experiments of Fedde et a_l. , (1960) high apparent f a t absorb-a b i l i t i e s were associated with low amounts of f a t t y acids ex-creted /100 gm feed eaten. In t h i s experiment, the quantity of f e c a l soap f a t t y acids when averaged over the entire experi-mental period was lower in the New Hampshires than in the B r o i l e r s or White Leghorns. On a 12% corn o i l diet, except at 3 weeks of age, there were no s i g n i f i c a n t differences among birds in net f a t absorb-a b i l i t y values. Regardless of the type of birds, corn o i l % absorbability was s i g n i f i c a n t l y greater than tallow f a t % ab-s o r b a b i l i t y throughout the entire period of the experiment. These findings are s i m i l a r to those reported in the l i t e r a t u r e and r e f l e c t the differences i n f a t t y acid composition and degree of unsaturation of corn o i l as compared to tallow. The amount of soap fa t t y acids excreted per gof feed eaten, was greater for the tallow i n contrast to the corn o i l diet . This amount de-creased with age of birds causing an improvement in the f a t d i g e s t i b i l i t y c o e f f i c i e n t s . These two observations taken to-gether appear to suggest that any search to explain differences between diets (tallow vs corn o i l diet) and/or among breeds of birds must not exclude the f a t t y acid absorptive mechanisms, 37 which as the results of t h i s experiment have shown, appear to be less e f f i c i e n t when some birds (Broiler and White Leghorn chicks) are fed a 12% tallow diet but become more e f f i c i e n t with age to cause improved tallow f a t d i g e s t i b i l i t y c o e f f i c i e n t s . 3.1.4.2 Performance E f f i c i e n c y Indices: Data in Table 7 indicate that on a l l the diets, performance e f f i c i e n c y indices were highest for the B r o i l e r s and lowest for the White Leghorns. The New Hampshires were intermediate. The differences among the d i f f e r e n t types of birds were s i g n i f i c a n t (P-0.05). It i s noteworthy from Table 7 that addition of tallow or corn o i l to a basal diet did not s i g n i f i c a n t l y change the per-formance e f f i c i e n c y indices of the New Hampshire and White Leg-horn type of birds as i t did those of the B r o i l e r s . With regard to the B r o i l e r s , the data show that a s i g n i f i c a n t response to the high-fat diets was obtained. The 12% tallow and 12% corn o i l diets caused increments in t h e i r performance e f f i c i e n c y indices of 29% and 37% respectively over and above the 10.85 they re-corded on a basal diet. The results on feed e f f i c i e n c y are summarised in Table 8. It can be seen from t h i s table that, except for the White Leghorns, feed e f f i c i e n c y values were better (P-0.05) when the birds were fed diets 2 (12% tallow) and 3 (12% corn o i l ) . The results i n Table 8 further show that improvement in feed e f f i c i e n c y values obtained with the New Hampshires and B r o i l e r s on diets 2 and 3 as compared to diet l /were not s i g n i f i c a n t l y d i f f e r e n t , but were s i g n i f i c a n t l y better than the feed e f f i c i e n c y values obtained 38 with White Leghorns on sim i l a r d i e t s . The observed improve-ment i n feed e f f i c i e n c y and hence o v e r a l l performance indices of e s p e c i a l l y the B r o i l e r s i s i n accord with the reports of several other workers (Dam et a l . , 1959 ; Carew et al., 1964 ; Vermeersch and Vanschoubroek, 196 8 ; Reid and Weber, 19 75 ; S e l l et a l . , 1976 ; Horani and S e l l , 1977) ind i c a t i n g the b e n e f i c i a l e f f e c t s of fat inc l u s i o n in chicken diets on feed e f f i c i e n c y and growth rate which are a j o i n t product of the improved metabolic e f f i c i e n c y of energy u t i l i s a t i o n due to the added f a t . 3.1.4.3 Metabolisable Energy: Metab o l i s a b i l i t y of dietary energy by the New Hampshire, B r o i l e r and White Leghorn type of birds was determined at 3, 5 and 9 weeks of age. Analysis of variance of the energy meta-b o l i s a b i l i t y data showed consistently s i g n i f i c a n t breed, diet, and breed x diet interaction e f f e c t s . Further examination of the data by way of comparisons revealed that at each of the three d i f f e r e n t ages, the M. E. value of Diet 1 was lower than the M. E. value of ei t h e r Diet 2 or 3. This was as expected due to the presence of r e l a t i v e l y high levels of f a t i n Diet 2 (12% tallow) and 3 (12% corn o i l ) as compared to Diet 1 (3% f a t ) . Sibbald and Slinger (196 3b) noted a l i n e a r increase i n M. E. content of the diet as the l e v e l of dietary f a t was increased. At the age of 3 weeks the metabolisable energy 39 value of the 12% tallow d i e t obtained with the B r o i l e r s was s i g n i f i c a n t l y d i f f e r e n t from the M.E. values determined using the New Hampshires or White Leghorn chicks. This was pa r t l y a r e f l e c t i o n of the differences among the 3 types of birds in th e i r r e l a t i v e a b i l i t i e s to absorb tallow f a t at that age. These findings are contrary to the suggestion by Cullen et a l . , (1962) that rapid growing birds are able to u t i l i s e tallow more e f f i c i e n t l y than the slow growing birds; but they are somewhat in agreement with the results of Slinger et a l . , (1963). These workers found the White Leghorn chicks to be more e f f i c i e n t in metabolising energy from the high energy di e t than the faster growing b r o i l e r chicks. M.E. values for a lower energy di e t were sim i l a r when measured with the two breeds. Sugden (19 74) compared Bantam chickens and Blue-winged Teal on the basis of t h e i r r e l a t i v e a b i l i t y to metabolise energy from six di e t s , f i v e of which contained wild duck foods and found that Bantams meta-bolised s i g n i f i c a n t l y more energy i n four diets; Teal meta-bolised^' s i g n i f i c a n t l y more in only one di e t containing shrimp which i s natural duck food. At 5 weeks of age, f a i l u r e of the White Leghorns to meta-bolis e energy from the 12% corn o i l di e t to the same extent as the New Hampshires (3354 vs 3540) was the cause for the s i g n i -f i c a n t breed x diet interaction e f f e c t s ; while at 9 weeks of age the interaction e f f e c t s were due to the s i g n i f i c a n t l y lower (P-0.05) M.E. values of the diets 1, and* 2 and 3 obtained with the B r o i l e r s (2713) and White Leghorns (3399 and 3416) respec-40 t i v e l y . D e s p i t e . a l l t h e c o m p l i c a t i o n s o f b r e e d x d i e t i n t e r -a c t i o n e f f e c t s on d i e t a r y energy m e t a b o l i s a b i l i t y , t h e New Hamp-s h i r e s compared t o t h e B r o i l e r s o r White Leghorns m a i n t a i n e d on a v e r a g e , a h i g h e r energy m e t a b o l i s i n g c a p a c i t y w h i c h i n essence was a r e f l e c t i o n o f t h e i r r e l a t i v e l y e f f i c i e n t f a t a b s o r p t i v e c a p a c i t y . T h i s o b s e r v a t i o n i s i n a c c o r d w i t h what s e v e r a l o t h e r w o r k ers ( S l i n g e r e t a l . , 1964; March and B i e l y , 1971; March e t a l . , 1974; F a r r e l , 1975; Sugden, 1974; G a r d i n e r , 1971; have r e p o r t e d on t h e e f f e c t o f u s i n g d i f f e r e n t s p e c i e s and/or breeds on M.E. e s t i m a t e s . I t would appear, from th e r e s u l t s o f t h i s e x p eriment t h a t e s t i m a t i n g M.E. o f d i e t s c o n t a i n i n g r e l a t i v e l y h i g h l e v e l s o f e s p e c i a l l y t a l l o w , u s i n g New Hampshires such as t h e ones used i n t h e p r e s e n t s t u d y , may r e s u l t i n an o v e r -e s t i m a t i o n o f t h e energy a c t u a l l y a v a i l a b l e t o B r o i l e r and White Leghorn-type o f b i r d s . The average d i e t a r y M.E. v a l u e s o b t a i n e d w i t h b i r d s a t 5 and 9 weeks o f age, were h i g h e r t h a n t h o s e d e t e r m i n e d a t 3 weeks o f age. I n t h e l i t e r a t u r e , o p i n i o n i s d i v i d e d on t h e e f f e c t o f age on m e t a b o l i s a b l e energy c o n t e n t o f f e e d s t u f f s . S i b b a l d e t a l . , 1960; n o t e d t h a t t h e i n f l u e n c e on t h e M.E. v a l u e o f c o r n was s m a l l and n e g l i g i b l e . B a y l e y e t a_l. , 1974; found no s i g n i f i c a n t d i f f e r e n c e s i n M.E. v a l u e s o f 10 samples o f r a p e s e e d meal d e t e r m i n e d w i t h b o t h c h i c k s and mature r o o s t e r s . On t h e c o n t r a r y , B a l d i n i : 1961; Young 1961; Z e l e n k a 1968; L o d h i e t al.,1969 and March e t al., 1974 p r e s e n t e d d a t a i n d i c a t i n g t h a t t h e M.E. 41 values of some feed i n g r e d i e n t s and d i e t s are h i g h e r f o r mature b i r d s than f o r c h i c k s . I t was p r e v i o u s l y thought t h a t the abun-dant supply of n u t r i e n t s from the r e s i d u a l y o l k sac to the young c h i c k was the cause f o r the low M. E. values o b t a i n e d w i t h c h i c k s ; s i n c e as noted by Zelenka (1968) a b s o r p t i o n o f the r e s i d u a l y o l k sac m a t e r i a l s continues u n t i l about the 14th day i n the l i f e o f the c h i c k . On the o t h e r hand, Katongole (1975, unpublished data) found t h a t a t 4 days of age, the f a t content of the r e s i d u a l y o l k sacs from the s t a r v e d and fed White Leghorn c h i c k s , were s i m i l a r . Kese (19 77) r e p o r t e d t h a t removal at h a t c h i n g of the r e s i d u a l y o l k d i d not have any s i g n i f i c a n t e f f e c t on the chickens a b i l i t y to m etabolise energy. A l l t h i s suggested t h a t n u t r i e n t s s u p p l i e d by the r e s i d u a l y o l k sac do not have a s i g n i f i c a n t d e p r e s s i n g e f f e c t on d i e t a r y M. E. v a l u e s . R e a l i s i n g t h a t i n the p r e s e n t study c o r r e l a t i o n c o - e f f i c i e n t s between M. E. v a l u e s and f a t a b s o r b a b i l i t y computed on a w i t h i n breed b a s i s were p o s i t i v e and s i g n i f i c a n t w i t h an o v e r a l l c o e f f i c i e n t of d e t e r m i n a t i o n of 0.76; and s i n c e r e s u l t s from the p r e s e n t study have demonstrated g e n e t i c e f f e c t s and confirmed age e f f e c t s on a b s o r b a b i l i t y of f a t e s p e c i a l l y the s a t u r a t e d type, the t h e s i s based on data from t h i s study and on the r e s u l t s of other workers, i s t h a t , breed and/or age d i f f e r e n c e s i n d i e t a r y M. E. estimates are to a l a r g e extent a t t r i b u t a b l e t o breed and/or age d i f f e r e n c e s i n the a b s o r b a b i l i t y o f h i g h energy d i e t a r y components ( l i p i d s ) . The cause of t h i s breed and/or age d i f f e r e n c e s was the b a s i s f o r a s e r i e s o f ex-periments whose r e s u l t s are presented and d i s c u s s e d i n the f o l l o w i n g s e c t i o n s . 42 Table 1. Composition of the diets used i n Experiment !• Diet 1 Diet 2 Diet 3 Components B a s a l 1 100 88 88 ingredients 2 Tallow -- 12 Corn o i l — — 12 Fat 3 15 15 ^Basal Ingredients Ground wheat 4 8.0 Soybean meal 30.0 Ground oats 15.0 A l f a l f a 2.0 D i s t i l l e r s * dried solubles 2.0 Calcium phosphate 1.5 Limestone 1.0 Iodized s a l t 0.5 3 Micronutrients + 2Tallow used i n Diet 2 had an average melting point of 36.0°C, and the range was 30°-42° (determined by the c a p i l l a r y method). 3 Micronutrxents supplied per kg of diet; zinc sulphate, 81.3 mg; manganese sulphate, 55.45 mg; DLmethionine, 8.29 gm; Calcium pantothenate, 5 mg; f o l i c acid, 0.25 mg; n i a c i n , 12 mg; r i b o -f l a v i n , 3 mg; Vitamin B^ 2, 0.009 mg; Vitamin A, 1500 I. U.; Vitamin D 3, 400 I C. U.; Vitamin E, 10 mg. 43 Table 2. E f f e c t of breed x d i e t i n t e r a c t i o n on f a t absorb-a b i l i t y (%) a t 3 and 4 weeks of age. Week 3 Week 4 Fat A b s o r b a b i l i t y (%) F a t A b s o r b a b i l i t y (%) Die t 2 D i e t 3 D i e t 2 D i e t 3 ,1 New Hampshires 89.68 92.93 a 91.78 a 95.26 a B r o i l e r s 65.61 s 88.74 b 79.39 b 92.93 a White Leghorns 70.90 d 83.72 C 70.73° 90.44 a Means f o r each age column f o l l o w e d by d i f f e r e n t s u p e r s c r i p t s were found on a transformed s c a l e t o be 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) by Tukey t e s t . Table 3. E f f e c t o f breed o f b i r d s on f a t a b s o r b a b i l i t y (%) at 5 and 6 weeks of age. A G E I N W E E K S Week 5 Week 6 1 New Hampshires 95.84 a + 0.02 97.81 a+ 0.005 Means + S. D. B r o i l e r s 86.49 b+ 0.10 95.26 b+ 0.01 Means + S. D. White Leghorns 87.42 b+ 0.05 96.04 a b+ 0.006 Means + S. D. Means under each age column f o l l o w e d by a d i f f e r e n t s u p e r s c r i p t s were found on a transformed s c a l e t o be 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) by Tukey t e s t . 45 •7 Table 4. E f f e c t of type of d i e t a r y f a t on f a t a b s o r b a b i l i t y (%) a t 5, 6, 7, 9 and 11 weeks of age r e g a r d l e s s o f breed of b i r d . A G E I N W E E K S 5 6 7 9 11 Tallow D i e t , 86.49 b 95.26 b 94.09 b 93.12 b 93.12 b Means + S. D. 0. 11 0.01 0.008 0.02 0.001 Corn O i l D i e t , 93.32 a 97.61 a 97.42 a 97.22 a 96.24 a Means + S. D. 0.03 0.002 0.0001 0.002 • 0.001 Means under each age column 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 (P^0.05) by Tukey t e s t performed on transformed data. Table 5. E f f e c t of breed of b i r d s and d i e t a r y f a t composition " on apparent m e t a b o l i s a b l e energy (M.E.) valu e s ( c a l s / g dry feed) at 3, 5 and 9 weeks of age. A G E I N W E E K S 1 3 5 9 D i e t s D i e t s D i e t s 1 2 3 1 2 3 1 2 3 New Hamp-s h i r e s c l 2606 3478a 3501 a 2522° 3 4 9 3 a b 3540 a 2973° 3555 a 3598 a B r o i l -e r s 2538 C 3006 b 3339 a "2485 C 3 3 5 7 a b 3 4 2 3 a b 2713 d 3518 a b3546 a White Leg-horns 2536° 3297 a 3360 a 2574° 3283 b 3 3 5 4 a b 2889 C 3399 b 3416 b Means under each age column having 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 a t 5% l e v e l of p r o b a b i l i t y by Tukey t e s t . 4 7 Table 6. C o r r e l a t i o n c o e f f i c i e n t s and m e t a b o l i s a b l e energy-d i e t s i n New Hampshires, between f a t a b s o r b a b i l i t y v alues of the two h i g h - f a t B r o i l e r s and White Leghorns. C o r r e l a t i o n c o e f f i c i e n t s (R) C o e f f i c i e n t o f 2 d e t e r m i n a t i o n (R ) P r o b a b i l i t y l e v e l New Hampshires B r o i l e 0.65 0.95 0.42 0.90 =0.05 £0.01 White Leghorns O v e r a l l 0.80 0.87 0.64 0.76 =0.01 =0.01 Table 7. E f f e c t of breed of b i r d s and composition of the d i e t on performance e f f i c i e n c y i n d i c e s . D I E T S D i e t 1 (Basal) D i e t 2 D i e t 3 3% Fat 12% Tallow 12% Corn O i l 1 New Hampshires 5.35 6.55 6.10 B r o i l e r s 10.85 b 14.00 a 14.85 a White Leghorns 3.00 d 2.90 d 3.15 d 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 (P^0.05) by Tukey t e s t . 4y Table 8. E f f e c t of breed of birds and composition of the diet on feed conversion values from 17 days to 6 3 days of age. D I E T S Diet 1 (Basal) Diet 2 Diet 3 3% Fat 12% Tallow 12% Corn Qjl New Hampshires 2 . 1 4 b c l 1.80 a 1.96 a b B r o i l e r s 2 . 2 0 b c d 1.80 a 1.81 a White Leghorns 2.47 d 2.49 d 2 . 4 3 C d Means followed by d i f f e r e n t superscripts 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) by Tukey test. D U eN 100 > 5 o 0) *D C O \ 0> E < u. a < o < o UJ IL 90 C O < ca K 80 O <n a < 70 < 60 20 16 12 A — /A— -a / / ' / / A - y -/ Il \\ // \\ / \ I: A7 " — -0 N E W H A M P S H I R E S A -A B R O I L E R S A " - A W H I T E L E G H O R N S A \ \ \ " \ X 11 Figure 1(a) Tallow absorbability % and fe c a l soap fa t (mg/g diet) determined w i t f r d i f f e r -ent types of birds at d i f f e r e n t ages in Experiment 1. 51 100 90 CQ < CO K O ~ cn .o CQ X < ° - 80 O z tc o o < u . < -o * CO T3 _ l 01 UJ E O -A A a H NEW HAMPSHIRES A A B R O I L E R S A A WHITE L E G H O R N S "<B^-"A- —. A -— a A 5 7 A G E IN W E E K S 11 Figure 1(b). Corn o i l absorbability and f e c a l soap f a t (mg/g diet) determined with d i f f e r e n t types of birds at d i f f e r e n t ages in Experiment 1. 3.2.0 Experiment 2 Feed Passage Time In New Hampshires, B r o i l e r s and White Leghorns Feeding On B a s a l , 12% Tallow and 12% Corn O i l D i e t s . 3.2.1 I n t r o d u c t i o n : The r e s u l t s of the f i r s t experiment which i n d i c a t e d the s i g n i f i c a n t s u p e r i o r i t y of the New Hampshires over the B r o i l e r s and White Leghorns i n d i g e s t i n g and absorbing t a l l o w f a t d u r i n g the f i r s t h a l f p e r i o d of the experiment, s t i m u l a t e d i n t e r e s t i n the search f o r a p o s s i b l e cause. A number of f a c t o r s t h a t i n f l u e n c e f a t a b s o r b a b i l i t y were b r i e f l y reviewed i n S e c t i o n 2. I t was mentioned t h a t d i f f e r e n c e s i n feed passage time c o u l d , i f they o c c u r r e d to a s i g n i f i c a n t e x t e n t , r e s u l t i n d i f f e r e n c e s i n n u t r i e n t a b s o r b a b i l i t y . Rapid r a t e of i n g e s t a passage and consequently s h o r t time of exposure to the degradative a c t i o n of the d i g e s t i v e enzymes leads t o depressed n u t r i e n t d i g e s t i -b i l i t y c o e f f i c i e n t s . T h i s i s e x a c t l y what happens f o r example when the animal's f e e d i n g l e v e l i s g r e a t l y i n c r e a s e d (Reid and Tyre-kl, 1964 ; Parker and Clawson, 1967;'; Shannon, 1971). The r a t e of i n g e s t a passage, i s to a l a r g e e x t e n t i n f l u e n c e d by the r a t e at which the stomach empties due to the p r o p e l l i n g a c t i o n of i t s antrum t h a t i s under the c o n t r o l of neuroendo-c r i n o l o g i c a l mechanisms (Waddle and Wang, 195 3); and the amount of food m a t e r i a l absorbed per u n i t time appears u s u a l l y to be mainly determined by the r a t e a t which i t i s presented to the i n t e s t i n a l mucosa (Hunt, 1959). The e f f e c t s of d i e t a r y l i p i d s on g a s t r i c m o t i l i t y and 53 emptying i n mammals are w e l l known (Card, 1941; Roberts, 1931; Hunt, 1969). The presence of food r i c h i n l i p i d s i n the duodenum, s t i m u l a t e s the s e c r e t i o n of enterogastrone and c h o l e c y s t o k i n i n which i n h i b i t a c i d s e c r e t i o n i n g a s t r i n s t i m u l a t e d stomachs (Ganong, 1973) so t h a t g a s t r i c m o t i l i t y i s reduced, feed t r a n s i t time i n the GIT i s i n c r e a s e d and as a r e s u l t a more e f f e c t i v e l i p o l y s i s takes p l a c e . There are however c o n f l i c t i n g r e p o r t s on the e f f e c t of f a t on i n g e s t a passage time i n the c h i c k e n . Tuckey e t a l . , (1958) r e p o r t e d t h a t up to 12% f a t i n the d i e t of the growing chickens has l i t t l e e f f e c t on the r a t e of food passage or i t s d i g e s t i b i l i t y . Long (1967) observed t h a t i n -f u s i o n of t r i o l e i n i n t o the duodenum of chickens d i d not a f f e c t HCl or p e p s i n s e c r e t i o n and suggested t h a t chickens might not have enterogastrone which i s r e l e a s e d i n mammals when f a t e n t e r s the duodenum and which reduces g a s t r i c s e c r e t i o n , m o t i l i t y and r a t e o f feed passage. However, Lepkovsky e t a l . , (1970) o b t a i n e d experimental evidence t h a t the c h i c k e n has enterogastrone and i m p l i c i t l y , t h e r e f o r e , d i e t a r y f a t must have an e f f e c t on g a s t r i c m o t i l i t y and feed passage time. I t i s not, however, known whether the e f f e c t o f d i e t a r y l i p i d s on feed passage time v i a the e n t e r o -g a s t r o n e / c h o l e c y s t o k i n i n mechanism i s the same i n d i f f e r e n t types of chickens. T h i s experiment was t h e r e f o r e s e t up to f i n d out whether there are any d i f f e r e n c e s i n feed passage times among New Hampshires, B r o i l e r s and White Leghorns f e e d i n g on b a s a l (3% f a t ) , 12% t a l l o w and 12% corn o i l d i e t s , t h a t would p a r t l y account f o r breed d i f f e r e n c e s i n f a t d i g e s t i b i l i t y observed i n Experiment 1. 3 . 2 . 2 Experimental Procedures: The experiment was c a r r i e d out i n two separate but o t h e r -wise i d e n t i c a l t r i a l s . In the f i r s t t r i a l , the b i r d s were 5 weeks o l d and i n the second t r i a l , they were 7 weeks o l d . In each of these t r i a l s , 2 r e p l i c a t e groups of 5 b i r d s from each of the treatment s u b c l a s s e s i n Experiment 1 were randomly a s s i g n e d to cages. The b i r d s were s t a r v e d f o r two hours f o l l o w e d by a f e e d i n g p e r i o d of 2 0 minutes and then given 1 . 0 ml of a 2 0 % sus-pension of f e r r i c oxide s t a b i l i s e d w i t h 0 . 0 5 % methyl c e l l u l o s e (Tuckey e t a_l. , 1 9 5 8 ) as the marker. The times when the marker substance was given and when i t f i r s t appeared i n the feces of each one of the b i r d s were recorded. The d i f f e r e n c e between these two time p e r i o d s was the fe e d passage time i n each treatment s u b c l a s s . 3 . 2 . 3 R e s u l t s : The r e s u l t s on feed passage times i n the f i r s t and second t r i a l s are summarised i n Tables 9 and 1 0 r e s p e c t i v e l y . In both t r i a l s , a n a l y s i s of v a r i a n c e of feed passage times showed h i g h l y s i g n i f i c a n t breed by d i e t i n t e r a c t i o n e f f e c t s . Data i n Table 9 show t h a t a t 5 weeks of age, d i f f e r e n c e s i n feed passage times among New Hampshires, B r o i l e r s and White Leghorns on the same d i e t were not s t a t i s t i c a l l y s i g n i f i c a n t . There were however s i g n i f i -cant d i f f e r e n c e s i n f e e d passage times between d i e t 1 (Basal) and the hi g h f a t d i e t s ( 2 & 3 ) . Feed passage times were on the average s h o r t e r i n b i r d s put on a b a s a l d i e t and l o n g e r i n b i r d s f e e d i n g on the 1 2 % t a l l o w and 1 2 % corn o i l d i e t s . However, i t can be noted from Table 9 that, i n case of New Hampshires, feed 55 passage times of the b a s a l and 12% t a l l o w d i e t s were not s i g n i f i -c a n t l y d i f f e r e n t . On d i e t s 2 (12% tallow) and 3 (12% corn o i l ) feed passage times were on average s i m i l a r . The l o n g e s t (2:44) and s h o r t e s t (1:33) feed passage times (hr:min) recorded a t the age of 5 weeks, were i n the B r o i l e r s f e e d i n g on 12% t a l l o w and b a s a l d i e t s r e s p e c t i v e l y . R e s u l t s o f feed passage times a t the age of 7 weeks are sum-marised i n Table 10. R e s u l t s i n t h i s t a b l e p a r a l l e l those i n Table 9. The s i g n i f i c a n t e f f e c t of hig h d i e t a r y f a t on feed passage time s t i l l p e r s i s t e d . Between d i e t s 2 and 3, s t i l l 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 feed t r a n s i t time. I t can be noted from the t a b l e t h a t a t t h i s age, the New Hampshires on d i e t 1 recorded the lowest feed passage time (1:33) while the B r o i l e r s on d i e t 3 and White Leghorns on d i e t 2 recorded the h i g h e s t and s i m i l a r feed passage time (2:38). 3.2.4 D i s c u s s i o n : R e s u l t s o f t h i s experiment showed t h a t while the e f f e c t o f breed of b i r d s on feed passage time was not c o n s i s t e n t i n both t r i a l s , t h a t o f d i e t a r y f a t was. In the f i r s t t r i a l when the b i r d s were 5 weeks o l d , no s i g n i f i c a n t d i f f e r e n c e s i n feed pas-sage time among New Hampshires, B r o i l e r s and White Leghorns was d e t e c t a b l e . In the second t r i a l however, feed passage time was s i g n i f i c a n t l y delayed i n the B r o i l e r s compared t o the New Hamp-s h i r e s or White Leghorns. When r e s u l t s of t h i s experiment are examined i n r e l a t i o n to those o b t a i n e d i n Experiment 1 i t be-comes d i f f i c u l t to draw any d e c i s i v e c o n c l u s i o n on whether o r not breed d i f f e r e n c e s i n feed passage time genuinely c o n s t i t u t e d 56 an important f a c t o r t h a t i n f l u e n c e d f a t d i g e s t i b i l i t y i n Experiment 1, due to a number of reasons. F i r s t of a l l , there appears to be no r e l a t i o n s h i p between r e s u l t s of t h i s experiment and those of Experiment 1, because s i g n i f i c a n t breed d i f f e r e n c e s i n f a t a b s o r b a b i l i t y d i d not c o i n c i d e w i t h s i g n i f i c a n t breed d i f f e r e n c e s i n feed passage time. This observation, r u l e s out any s p e c u l a t i v e attempt to use feed passage d i f f e r e n c e s to account f o r d i f f e r -ences i n f a t a b s o r b a b i l i t y among b i r d s and/or d i e t s used i n t h i s study. Castle and C a s t l e , (1956) found no s i g n i f i c a n t r e l a t i o n -ship between dry matter d i g e s t i b i l i t y and rate of feed passage i n p i g s . Secondly, Tuckey et a l . , (1958) had evidence showing tha t passage time can be r e a d i l y a l t e r e d i f the b i r d s are e x c i t e d i n the course of the determination, t h e r e f o r e , there i s the p o s s i -b i l i t y t h a t d i f f e r e n c e s between B r o i l e r s and New Hampshires or White Leghorns i n feed passage time were merely due to d i f f e r -ences i n extent of e x c i t i b i l i t y created when the b i r d s were handled and given the marker substance. T h i r d l y , i t i s con-c e i v a b l e that at 7 weeks of age, s i g n i f i c a n t d i f f e r e n c e s between B r o i l e r s and New Hampshires or White Leghorns i n passage time could have been a r e f l e c t i o n of d i f f e r e n c e s i n t h e i r mean body weights at that age. Purdon e t al_. , (1973) reported that g a s t r i c emptying which i s an important f a c t o r i n r a t e of i n g e s t a passage was f a s t e r i n l i g h t e r r a t s than i t was i n the heavier ones. This experiment has however conclusive evidence on the e f f e c t of high d i e t a r y f a t on feed passage time. In both t r i a l s , d i e t 1 (basal) had the s h o r t e s t passage time of any of the d i e t s ; and 57 feed passage time was c o n s i s t e n t l y s i g n i f i c a n t l y longer (P^O.01) wit h the high f a t d i e t s (2 and 3). The f i b r o u s nature and lower energy content and hence high l e v e l of intake by b i r d s feeding on d i e t 1 were probably r e s p o n s i b l e f o r i t s short passage time. Parker and Clawson, (1967) reported a more r a p i d r a t e of passage of the b a r l e y d i e t i n pigs and a s s o c i a t e d i t with the higher d a i l y feed intake and the bulky f i b r o u s nature of the b a r l e y d i e t that made i t more l a x a t i v e . The observation that high d i e t a r y f a t content delayed passage time i n a l l b i r d s i n t h i s experiment i s at variance with the r e s u l t s of Tuckey e t a l . , (1958) but i n accord w i t h the concept t h a t presence of f a t i n the duodenum exerts an i n -h i b i t o r y a c t i o n on g a s t r i c m o t i l i t y and emptying to ensure th a t t r a n s p o r t of l i p i d s through the gut occurs at a rat e s u i t a b l e f o r absorption, (Roberts, 1931 ; Card, 1941 , T i d w e l l e t a l . , 1953 ; Hunt, 1959). Furthermore, i t was observed i n both t r i a l s of t h i s experiment t h a t feed passage times were s i m i l a r f o r the 12% t a l l o w and 12% corn o i l d i e t s , suggesting t h a t i t i s the qu a n t i t y but not the nature of d i e t a r y f a t t h a t i n f l u e n c e s rate of i n g e s t a passage. Sb Table 9. Mean feed passage times (hrrmin) i n New Hampshires, B r o i l e r s and White Leghorns on b a s a l , 12% t a l l o w and 12% corn o i l d i e t s a t 5 weeks of age (T-rial one) . D I E T S 1 2 3 Bas a l 12% Tallow 12% Corn O i l New Hampshires l : 4 4 c d 2:0 7 b c 2:24 a b B r o i l e r s 1:33 d 2:44 a 2:30 a b White Leghorns l : 3 6 d 2:27 a b 2 : 2 9 a b Means f o l l o w e d by 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 P-0.01 by Tukey t e s t . 59 Table 10. Mean feed passage times (hr:min)in New Hampshires, B r o i l e r s and White Leghorns on b a s a l , 12% Tallow and 12% corn o i l d i e t s at 7 weeks of age ( T r i a l two) . D I E T S 1 2 3 Ba s a l 12% Tallow 12% Corn O i l H e „ H a m p s h i r e s LBS*1 2 : 2 2 -B r o i l e r s 2 : 0 6 b c 2:28 a b 2:38 a White Leghorns l : 4 2 c d 2:38 a 2 : 3 2 ^ Means f o l l o w e d by 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 at the 1% l e v e l of p r o b a b i l i t y by Tukey t e s t . bU 3.3.0 Experiment 3 A Comparative Study of the P a n c r e a t i c Lipase A c t i v i t y i n the New Hampshires, B r o i l e r s and White Leghorns. 3.3.1 I n t r o d u c t i o n : Pancreatic l i p a s e i s the sole and most important enzyme i n the d i g e s t i o n of f a t i n the avian and mammalian species. I t i s thus the best ""known and most oft e n i n v e s t i g a t e d of a l l l i p o l y t i c enzymes. Pa n c r e a t i c l i p a s e i s very s p e c i f i c i n i t s mode of a c t i o n , s p l i t t i n g o f f f i r s t f a t t y a c i d s i n the 1 and 3 p o s i t i o n s of the t r i g l y c e r i d e molecule. This p o s i t i o n a l s p e c i f i c i t y described long ago by B a l l s and Matlack (1937), was confirmed by s e v e r a l subsequent i n v e s t i g a t o r s (Schonheyder et a l . , 1954; Borgstrom, 1953; Mattson and Beck, 1955; 1956, Savary and Desnuelle, 1956, Entressangles e t a l . , 1961; Mattson and Volpenhein., 1962) . The l i p o l y t i c a c t i v i t y of the p a n c r e a t i c enzyme i s enhanced by b i l e s a l t s which, through t h e i r l i p i d e m u l s i f i c a t i o n c a p a c i t y , increase the o i l - w a t e r i n t e r f a c i a l area f o r r a p i d enzymatic degradation of the t r i -g l y c e r i d e molecules according to the f o l l o w i n g scheme: T r i g l y c e r i d e s - *1.2-Dialvceride_ 9 2-Monoglyceride 2,3-Diglyceride +Fatty a c i d The t r i p l e combination of free f a t t y a c i d s monoglycerides and b i l e s a l t s form a m i c e l l a r s o l u t i o n which i s very e s s e n t i a l f o r o v e r a l l f a t absorption process. Since r e s u l t s of the previous experiment showed a s i g n i f i c a n t d i f f e r e n c e i n t a l l o w f a t a b s o r b a b i l i t y , between the New Hampshires, B r o i l e r s and White Leghorns, i t was d e s i r e d to know i f t h a t p o u l t r y s t r a i n d i f f e r e n c e i n f a t a b s o r b a b i l i t y could at l e a s t i n p a r t be 61 e x p l a i n e d by d i f f e r e n c e s i n p a n c r e a t i c l i p a s e a c t i v i t y among those d i f f e r e n t types of b i r d s . T h e r e f o r e , an experiment intended to compare the p a n c r e a t i c l i p a s e a c t i v i t y i n the New Hampshires, B r o i l e r s and White Leghorns was s e t up. 3.3.2 Experimental Procedures: B i r d s : New Hampshires, B r o i l e r s and White Leghorns of e i g h t weeks of age were used i n t h i s experiment. Three weeks p r i o r to the s t a r t o f t h i s experiment, the b i r d s were fed a uniform b a s a l d i e t s i m i l a r t o t h a t used i n Experiment 1. P a n c r e a t i c Powder P r e p a r a t i o n : E i g h t b i r d s from each of the 3 s t r a i n s were k i l l e d by neck d i s l o c a t i o n , t h e i r pancreases were q u i c k l y removed, cleaned of any adhering f a t , weighed, put i n i n d i v i d u a l s m a l l beakers con-t a i n i n g c o l d acetone and homogenised t h e r e a f t e r f o r 1 minute. The homogenates were f i l t e r e d to remove the acetone s o l u t i o n . The r e s i d u e was washed wi t h acetone j d i e t h y l - e t h e r s o l u t i o n (1:1), f i l t e r e d , washed again w i t h anhydrous ether and f i n a l l y a i r d r i e d . The dry m a t e r i a l was screened through a 100-mesh screen to separate the f i b e r s from the f i n e p a n c r e a t i c powder which was then kept i n a f r e e z e r f o r l a t e r p a n c r e a t i c l i p a s e a c t i v i t y assay. L i p a s e A c t i v i t y Assay: To 0.5 gm of t r i o l e i n (Substrate) i n a stoppered 125 ml f l a s k , 5 ml ox b i l e ( N u t r i t i o n a l Biochemicals) i n g l y c e r o l 1 were added. G l y c e r o l ox b i l e s o l u t i o n was prepared by adding to the d r i e d b i l e an equal weight of water and h e a t i n g the s o l u t i o n f o r 1 to 2 hours i n the a u t o c l a v e a t 15 pounds p r e s s u r e . 10 cc of g l y c e r o l were then added f o r each gm of d r i e d b i l e and the mix-t u r e was heated on the steam bath u n t i l a c l e a r s o l u t i o n was ob t a i n e d . ( B a l l s , e t a l . , 1937.) 62 This mixture was shaken for sometime to allow complete emul-s i f i c a t i o n of the f a t . Then 10 ml of 0.05 M NH4C1 (pH, 6.5), 2+ and 10 ml of CaC^ solution (equivalent to 100 mg Ca ) were added. The crude lipase extract was obtained from 0.05 gm of each of the fine pancreatic powders according to the method described by B a l l s , et a l . , (1937). This enzyme extract was added l a s t to the mixture, which was then incubated under constant shaking at 4 3°C for 1 hour. At the end of 1 hour period, a 5 cc sample from each of the incubation mixtures was pipetted into 75 cc of a mixture of 9 volumes of alcohol and 1 volume of ether and t i t r a t e d , with 0.01 N a l c o h o l i c KOH, with phenolphthalein as an indicator. Lipase a c t i v i t y was expressed as millimoles of o l e i c acid l iberated per hour per gram of pancreatic powder. 3.3.3 Results and Discussion: Fresh mean weights (g) of pancreases from the New Hampshires, B r o i l e r s and White Leghorns, and values of lipase a c t i v i t y (mM o l e i c acid released/hour/g defatted pancreatic powder) are pre-sented i n Table 11. Results i n Table 11 show that pancreatic weights of B r o i l e r s were on the average heavier (P^0.05) and more variable than those of the New Hampshires and White Leghorns. Differences i n lipase a c t i v i t y among strains of birds were not s i g n i f i c a n t . It i s noteworthy however, that the New Hampshires ranked f i r s t i n pancreatic lipase a c t i v i t y followed by B r o i l e r s and White Leghorns i n that order. These differences i n pancreatic a c t i v i t y regard-less of t h e i r l e v e l of s t a t i s t i c a l s i g n i f i c a n c e , could i n a b i o l o -63 g i c a l sense, be a f a c t o r p a r t l y c o n t r i b u t i n g to the s t r a i n d i f f e r e n c e i n f a t a b s o r b a b i l i t y observed i n the f i r s t experiment. T h i s i s because p a n c r e a t i c l i p a s e i n presence of conjugated b i l e s a l t s has the most potent h y d r o l y t i c a c t i o n upon i n g e s t e d f a t . T h e r e f o r e , any s l i g h t d i f f e r e n c e s i n p a n c r e a t i c l i p a s e a c t i v i t y e i t h e r due to d i f f e r e n c e s i n the r e l a t i v e c o n c e n t r a t i o n s or c a t a l y t i c e f f i c i e n c y of the enzyme might cause 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 s i n f a t d i g e s t i b i l i t y . P a n c r e a t i c l i p a s e has f r e q u e n t l y been r e p o r t e d to be an i n d u c i b l e enzyme; the i n d u c t i o n i s dependent on l e v e l o f d i e t a r y f a t (Bucko and Kopec, 1968; Snook, 1971; Gidez, 1973) . T h e r e f o r e a p o s s i b i l i t y of s t r a i n d i f f e r e n c e s i n r a t e of p a n c r e a t i c i n d u c t i o n cannot be r u l e d out. Although t h i s p o s s i b i l i t y c o u l d p a r t l y e x p l a i n ease of a d a p t a b i l i t y to a t a l l o w f a t d i e t demonstrated by the New Hampshires i n the f i r s t experiment, t h e r e i s no experimental evidence to support the h y p o t h e s i s . 6 4 Table I I . F r e s h p a n c r e a t i c mean weight (g) and l i p a s e a c t i v i t y , mM o l e i c a c i d / h o u r / g p a n c r e a t i c powder i n New Hamp-s h i r e s , B r o i l e r s and White Leghorns. Number o f b i r d s used Mean Pancreas New Hampshires B r o i l e r s White Leghorns w e i g h t (g) , b + S. D . 2 . 9 8 + 0 . 5 1 5 x 4 . 9 1 + 1 . 3 4 1 3 . 2 4 + 0 . 4 0 3 Mean L i p a s e a c t i v i t y a a + S. D . 0 . 3 2 1 + 0 . 0 7 8 0 . 2 8 5 + 0 . 0 6 0 4 0 . 2 3 7 + 0 . 0 4 8 1Means i n a row w i t h t h e same s u p e r s c r i p t s are n o t s i g n i f i c a n t l y d i f f e r e n t a t t h e 5 % l e v e l o f p r o b a b i l i t y by Tukey t e s t . 65 3.4.0 Experiment 4 D i e t a r y B i l e S a l t Supplementation on Tallow F a t U t i l i s a -t i o n by the New Hampshire, B r o i l e r and White Leghorn Chicks. 3.4.1 I n t r o d u c t i o n ; I n e f f i c i e n c y o f a b s o r p t i o n of s a t u r a t e d f a t by c h i c k s has been r e p o r t e d by v a r i o u s i n v e s t i g a t o r s (Duckworth, e t a l . , 1950 ; Fedde e t a l . , 1960 ; Donaldson, e t a l . , 1957 ; Renner and H i l l , 1960 ; Gomez and P o l i n , 19 76). T h i s i n e f f i c i e n c y has a l s o been demonstrated i n h e a l t h y , normal newborn human i n f a n t s (Watkins,et a l , 19 73). Low b i l e s a l t p ool and r a t e o f b i l e s a l t s y n t h e s i s i n young animals as compared to a d u l t s have been suggested as l i m i t -i n g f a c t o r s s i n c e the g a l l b l a d d e r c o n c e n t r a t i n g f u n c t i o n and the e f f i c a c y of i n t e s t i n a l b i l e s a l t r e a b s o r p t i o n i n young animals are not f u l l y developed (Jackson, et. a l . , 1971 ; Smallwood, e t a l . , 1970 ; 1972). S e r a f i n and Nesheim (1967, 1970) found t h a t c h i c k s are unable t o r e p l e n i s h b i l e s a l t s l o s t by e x c r e t i o n as r e a d i l y as o l d e r b i r d s . B e n e f i c i a l e f f e c t s of b i l e s a l t supple-mentation i n chic k d i e t s have been demonstrated (Edwards, 1962 ; Gomez and P o l i n , 1974; 1976). Since r e s u l t s of the p r e v i o u s ex-periments showed t h a t the New Hampshire b i r d s were more e f f i c i e n t (P=0.01) i n d i g e s t i n g and absorbing f a t s u p p l i e d by the 12% t a l l o w d i e t than e i t h e r the B r o i l e r s or White Leghorns, an hy p o t h e s i s t h a t b i l e s a l t i n s u f f i c i e n c y i n these two types of b i r d s ( B r o i l e r s and White Leghorns) might be an important f a c t o r l i m i t i n g t h e i r maximum t a l l o w f a t d i g e s t i o n and a b s o r p t i o n c a p a c i t y was advanced. T h i s experiment was t h e r e f o r e s e t up to t e s t t h a t h y p o t h e s i s . A 66 more p r e c i s e and accurate method of examining breed d i f f e r e n c e i n adequacy of the b i l e s a l t p ool would have been to measure h e p a t i c b i l e s y n t h e s i s and s e c r e t i n g c a p a c i t y of each of the three d i f f e r e n t types of b i r d s u s i n g duct c a n n u l a t i o n technique. However, due t o the minute c a l i b r e of the b i l e ducts i n a young c h i c k , t h i s was not p o s s i b l e . T h e r e f o r e , an i n d i r e c t method based on measurement of d i f f e r e n c e s i n response ( l i v e weight g a i n , feed e f f i c i e n c y and f a t a b s o r b a b i l i t y ) was adopted i n t h i s experiment. 3.4.2 M a t e r i a l s and Methods 3.4.2.1 B i r d s : Day-old New Hampshire c h i c k s were obtained from the U.B.C. p o u l t r y farm. The B r o i l e r and White Leghorn c h i c k s were ob-t a i n e d from B. C. Western Commercial hatchery. The c h i c k s were re a r e d i n t h e r m o s t a t i c a l l y - c o n t r o l l e d and e l e c t r i c a l l y -heated b a t t e r y cages f o r 3 weeks du r i n g which time they were f e d ad l i b i t u m a b a s a l d i e t . The composition of t h i s d i e t i s given i n Table 12. 3.4.2.2 Experimental Treatments: Two days p r i o r to 3 weeks of age, the c h i c k s were wing-banded and randomly d i s t r i b u t e d i n groups of 10 b i r d s of each breed to 2 4 compartments of the b a t t e r y cages ( i . e. there were 8 compartments f o r each b r e e d ) . The f o l l o w i n g day they were s t a r v e d f o r 24 hours, weighed t h e r e a f t e r and subsequently sub-j e c t e d to f o u r d i e t a r y treatments. The experimental d i e t s (Table 13) i n c l u d e d a b a s a l d i e t (Diet 1) with a composition shown i n Table 12 and a 12% t a l l o w d i e t (Diet 3). D i e t s 2 and 4 were formulated by adding b i l e s a l t (sodium t a u r o c h o l a t e ) t o D i e t s 1 67 and 3 a t l e v e l of 0.05% of the d i e t . Each d i e t was fed ad l i b i t u m to two r e p l i c a t e groups of 10 b i r d s of each breed. Therefore, the experiment assumed a 4 x 3 f a c t o r i a l over a completely-ran-domized design, with 2 r e p l i c a t e s of 10 b i r d s per treatment. The experiment was c a r r i e d out i n two phases. In the f i r s t phase (3 -3h weeks of age) the b i r d s were fed f o r 3 days and starved f o r 24 hours before the onset of the second phase. T o t a l e x c r e t a pro-duced over t h i s p e r i o d was c o l l e c t e d , f r o z e n , l y o p h i l i z e d , then weighed and ground and kept f o r a n a l y s i s to determine f a t d i g e s t i -b i l i t y . Records were a l s o taken on t o t a l feed i n t a k e . In the second phase of the experiment (3% - 4 weeks of age), the same pro-cedure was repeated. The experiment was terminated at 4 weeks of age when a l l the b i r d s were weighed i n order to c a l c u l a t e body weight gain and feed e f f i c i e n c y of each type of b i r d s on each of the 4 d i e t s . 3.4.2.3 Laboratory A n a l y s i s : Feed and f e c a l samples were analyzed f o r dry matter by A.O.A.C. (1965) methods. F e c a l e t h e r - e x t r a c t a b l e f a t and soap f a t t y acids were e x t r a c t e d and determined separately using a soxhlet apparatus according t o a procedure described i n Experiment 1. The values of % f a t i n the ex c r e t a of b i r d s fed Diets 1 and 2 were used to c o r r e c t f o r endogenous f a t and f a t c o n t r i b u t e d by the constant d i e t i n g r e d i e n t s i n Diet s 3 and 4; then the net f a t a b s o r b a b i l i t y of these 2 d i e t s were c a l c u l a t e d using the adjusted % e x c r e t a f a t as f o l l o w s : OTVT J . J= J. i ~ w i • -i • • F e c a l output (g)x% Fat In f e c e s v . , n U %Net f a t a b s o r b a b 1 l 1 t y = ( l - F e e d ± n t a k e ( * ) x % F a t - n f e e d )xlOO b« 3.4.2.4 S t a t i s t i c a l A n a l y s i s : Data on feed e f f i c i e n c y , weight g a i n s , and f a t absorb-a b i l i t y were s u b j e c t e d to an a n a l y s i s of v a r i a n c e to t e s t f o r s i g n i f i c a n c e of d i f f e r e n c e s among the d i f f e r e n t treatment sub-c l a s s e s . F at d i g e s t i b i l i t y (%) values were s u b j e c t e d to a square r o o t t r a n s f o r m a t i o n and a n a l y s i s of v a r i a n c e was c a r r i e d out using the transformed data. 3.4.3 R e s u l t s In t h i s experiment records were taken on mean body weight gains and feed e f f i c i e n c y v a l u e s were c a l c u l a t e d to determine the e f f e c t o f supplementing d i e t s with b i l e s a l t on growth and feed u t i l i z a t i o n by the three types o f b i r d s . The r e s u l t s on these two parameters are summarized i n Tables 14 and 15. Res u l t s i n Table 14 c l e a r l y demonstrate t h a t i n a l l b i r d s , feed e f f i c i e n c y values were s i g n i f i c a n t l y (P-0.05) b e t t e r when 12% t a l l o w was i n c l u d e d i n the d i e t (Diets 3 and 4 vs 1 and 2). Regardless o f d i e t s , feed e f f i c i e n c y values were b e t t e r (P-0.05) f o r the B r o i l e r s than f o r the White Leghorns or New Hampshires. A b e n e f i c i a l e f f e c t , though not s t a t i s t i c a l l y s i g n i f i c a n t , on feed e f f i c i e n c y was o b t a i n e d by adding 0.05% sodium t a u r o c h o l a t e t o B r o i l e r and White Leghorn d i e t s ( D i e t s 2 and 4). The New Hampshire on the c o n t r a r y , d i d not show any n o t i c e a b l e improve-ment i n feed e f f i c i e n c y due to d i e t a r y supplementation o f sodium t a u r o c h o l a t e . On a 12% t a l l o w d i e t , the presence of 0.05% Na-ta u r o c h o l a t e s l i g h t l y depressed feed u t i l i z a t i o n e f f i c i e n c y i n New Hampshires i n c o n t r a s t to B r o i l e r s or White Leghorns. The 69 f i g u r e s i n Table 15 show t h a t mean body weight gains i n the New Hampshires and White Leghorns were not 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) on a l l the d i e t s . These r e s u l t s r e v e a l t h a t over t h i s experimental p e r i o d of one week the New Hampshire and White Leg-horn type of b i r d s showed a n o n s i g n i f i c a n t weight gain response t o e i t h e r d i e t a r y f a t or b i l e s a l t supplementation. I t i s noteworthy t h a t on D i e t 4, while the White Leghorns recorded an average body weight gain of 50.9, the New Hampshires recorded 42.3 which was 3.1 gm lower than what they recorded on D i e t 3. Mean body weight gains i n B r o i l e r s on the other hand, had a completely d i f f e r e n t p a t t e r n . F i r s t of a l l , as might be expected, the B r o i l e r s con-s i s t e n t l y had s i g n i f i c a n t l y (P-0.01) h i g h e r mean body weight gains than e i t h e r the White Leghorns or the New Hampshires on a l l the d i e t s . Secondly, 12% t a l l o w d i e t s s i g n i f i c a n t l y improved t h e i r mean body weight g a i n s . I t i s a l s o i n t e r e s t i n g t o note t h a t , i n the B r o i l e r s , there was a d i f f e r e n c e i n mean body weight gain of 10.2 gm and 10.7 gm between D i e t s 2 and 1 and 4 and 3 r e -s p e c t i v e l y . For the White Leghorns, d i f f e r e n c e s between those d i e t s were 5.9 gm and 6.9 gm; and f o r the New Hampshires the d i f f e r e n c e s were -0.5 gm and -3.1 gm r e s p e c t i v e l y . The e f f e c t of d i e t a r y supplementation of b i l e s a l t (0.05% Na-taur o c h o l a t e ) on f a t d i g e s t i o n and a b s o r p t i v e c a p a c i t y of New Hampshire^ B r o i l e r s and White Leghorns was examined i n two separate, otherwise i d e n t i c a l t r i a l s ; s i n c e t h i s was the major o b j e c t i v e of the whole experiment. Net f a t a b s o r b a b i l i t y values of D i e t s 3 and 4 (12% t a l l o w d i e t s ) were c a l c u l a t e d as d e s c r i b e d i n the 70 experimental procedures. The r e s u l t s are summarised i n Table 16. These data c l e a r l y show t h a t a d d i t i o n of sodium t a u r o c h o l a t e d i d not s i g n i f i c a n t l y i n f l u e n c e net f a t a b s o r b a b i l i t y values ob-t a i n e d with the New Hampshires. On the c o n t r a r y , the B r o i l e r s and White Leghorns s i g n i f i c a n t l y responded to d i e t a r y supplemen-t a t i o n of b i l e s a l t . As can be observed from the t a b l e , i n both t r i a l s the B r o i l e r s and White Leghorns, when f e d a 12% t a l l o w d i e t supplemented with 0.05% sodium t a u r o c h o l a t e , showed an i n c r e a s e d c a p a c i t y to u t i l i z e d i e t a r y f a t . To get an i d e a of the mode of a c t i o n of d i e t a r y sodium t a u r o c h o l a t e supplementation i n improving f a t a b s o r b a b i l i t y i n B r o i l e r s and White Leghorns and not i n the New Hampshires, data on e x t r a c t e d f e c a l f a t were reexamined. T o t a l % f e c a l f a t e x t r a c t e d was then p a r t i t i o n e d i n t o two components; e t h e r - e x t r a c t a b l e f a t and soap f a t t y a c i d s . R e s u l t s i n Table 17 show t h a t there was no s i g n i f i c a n t d i f -ference between D i e t s 3 and 4 i n the amount of f e c a l soap f a t t y a c i d e x c r e t e d by the New Hampshires i n e i t h e r t r i a l . S i m i l a r l y , the amounts of soap f a t t y a c i d s e x c r e t e d by New Hampshires and B r o i l e r s on D i e t 3 i n the f i r s t t r i a l d i d not d i f f e r s i g n i f i c a n t l y but were s i g n i f i c a n t l y lower than the soap f a t t y a c i d s value ob-t a i n e d w i t h the White Leghorns. Conversely, on the same d i e t (3), i n the second t r i a l , a l l b i r d s d i f f e r e d s i g n i f i c a n t l y i n the amounts of f e c a l soap f a t e x c r e t e d . A very n o t i c e a b l e f e a t u r e of the f i g u r e s i n Table 17 i s the tremendous r e d u c t i o n i n the f e c a l soap f a t values o b t a i n e d with B r o i l e r s and White Leghorns t h a t were f e d D i e t 4 compared with D i e t 3 i n both t r i a l s . '.z 71 T h i s r e d u c t i o n i n amount of soap f a t t y a c i d s i s most l i k e l y a t t r i -b u t a b l e to presence of 0.05% sodium t a u r o c h o l a t e i n D i e t 4. 3.4.4 D i s c u s s i o n B i l e s a l t s have long been known to be important i n the hy-d r o l y s i s and a b s o r p t i o n of l i p i d s . The predominantly s a t u r a t e d nature of t a l l o w f a t makes i t much more d i f f i c u l t to e m u l s i f y and thus r e q u i r e s a h i g h e r c o n c e n t r a t i o n of b i l e s a l t s to b r i n g i t i n a m i c e l l a r form s u i t a b l e f o r i t s d i g e s t i o n and a b s o r p t i o n . The i n a b i l i t y o f young animals to e f f e c t i v e l y d i g e s t and absorb s a t u r a t e d f a t has t h e r e f o r e been a t t r i b u t e d to t h e i r low b i l e -s a l t p o o l and r a t e of b i l e s a l t s y n t h e s i s (Jackson, e t a l . , 1970 ; Smallwood, e t a l . , 1970 ; 1972). R e s u l t s obtained i n t h i s study are i n t e r e s t i n g i n t h a t , i t has been p o s s i b l e to show t h a t the b e n e f i c i a l e f f e c t of adding b i l e s a l t s p r e v i o u s l y i m p l i e d by Edwards, (1962) and by Gomez and P o l i n , (1974, 1976) depends not only on the age of the b i r d s but a l s o on the type of b i r d s one i s u s i n g . For i n s t a n c e , i n t h i s experiment, mean body weight gains (Table 15) i n B r o i l e r s and White Leghorns were improved (though not to a s i g n i f i c a n t e x t e n t ) , when b i l e s a l t (sodium t a u r o c h o l a t e ) was added to the d i e t s . The New Hampshires, however, recorded lower mean body weight g a i n s , when f e d d i e t s c o n t a i n i n g 0.05% Na-taurocholate compared t o the unsupplemented d i e t s (1 and 3). Furthermore, feed e f f i c i e n c y v a l u e s were s l i g h t l y lower - i . e. showed an improvement, when the B r o i l e r s and White Leghorns were fed d i e t s c o n t a i n i n g 0.05% N a - t a u r o c h o l a t e . The New Hampshires, once more f a i l e d to show any noteworthy p o s i t i v e response. S i g -72 n i f i c a n t improvements i n feed e f f i c i e n c y were, however, ob-served i n a l l breeds of b i r d s on 12% t a l l o w d i e t s . T h i s ob-s e r v a t i o n i s i n agreement w i t h t h a t o f L i l l e , e t a l . , 1952 ; Denton, e t a l . , 1954 ; and Hochreich, e t a l . , 1958 ; and Horani and S e l l , (19 77) who found t h a t the e f f i c i e n c y o f food u t i l i z a t i o n was improved when f a t was i n c l u d e d i n the d i e t . I t i s noteworthy t h a t r e s u l t s on net t a l l o w f a t absorb-a b i l i t y showed a t r e n d p a r a l l e l t o those on mean body weight gains and feed e f f i c i e n c y v a l u e s o b t a i n e d w i t h B r o i l e r s and White Leghorns on 12% t a l l o w d i e t s w i t h o r without 0.05% Na-t a u r o c h o l a t e . A d d i t i o n o f sodium t a u r o c h o l a t e t o the 12% t a l l o w d i e t r e s u l t e d i n hi g h e r (P=0.01) f a t a b s o r b a b i l i t y v a l u e s o b t a i n e d i n both t r i a l s w i t h the B r o i l e r s and White Leghorns. The New Hampshires, on the other hand, d i d not s i g n i f i c a n t l y respond to d i e t a r y supplementation of b i l e s a l t , although they c o n s i s t e n t l y maintained t h e i r s u p e r i o r i t y over the B r o i l e r and White Leghorn c h i c k s i n t a l l o w f a t d i g e s t i o n and a b s o r p t i o n c a p a c i t y . T h i s r e s u l t p r o v i d e d an important c l u e t o a t l e a s t one of the l i k e l y causes of the c o n s i s t e n t breed d i f f e r e n c e i n f a t a b s o r b a b i l i t y . I t appears from the r e s u l t s o f t h i s experiment t h a t B r o i l e r and White Leghorn c h i c k s compared t o New Hampshires have a sub-optimal supply o f b i l e s a l t s f o r maximum t a l l o w f a t d i g e s t i o n and a b s o r p t i o n , and t h e r e f o r e w i l l respond t o d i e t a r y b i l e s a l t supplementation. Mechanism o f a c t i o n o f exogenous b i l e s a l t (sodium t a u r o c h o l a t e ) i n improving o v e r a l l f a t a b s o r b a b i l i t y values i n B r o i l e r s and White Leghorns was examined by par-t i t i o n i n g t o t a l f e c a l f a t ex c r e t e d i n t o e i t h e r e x t r a c t a b l e f a t and f e c a l soap f a t t y a c i d s . 73 There was a s i g n i f i c a n t r e d u c t i o n i n f e c a l soap f a t t y a c i d s ex-c r e t e d by B r o i l e r and White Leghorn c h i c k s f e d the 12% t a l l o w d i e t supplemented with b i l e s a l t (sodium t a u r o c h o l a t e ) . Con-comitant to t h i s r e d u c t i o n i n f e c a l soap f a t t y a c i d s was a s i g -n i f i c a n t i n c r e a s e i n t a l l o w f a t a b s o r b a b i l i t y v a l u e s . There-f o r e , the a c t i o n o f exogenous b i l e s a l t was mainly a t the s i t e o f f a t a b s o r p t i o n causing improved f r e e f a t t y a c i d a b s o r p t i o n and hence l e s s formation of c a l c i u m s a l t of f a t t y a c i d s i n the Broilerr.; and White Leghorn c h i c k s . Watkins, e t a l . , (1973), suggested t h a t f o r optimal l i p i d a b s o r p t i o n , b i l e s a l t s must be a v a i l a b l e a t the s i t e s of i n t e s t i n a l l i p o l y s i s and a b s o r p t i o n i n c o n c e n t r a t i o n s i n excess of the minimum necessary f o r m i c e l l e formation - i . e., the c r i t i c a l m i c e l l a r c o n c e n t r a t i o n . The o v e r a l l i n t e r p r e t a t i v e i n f e r e n c e from the r e s u l t s of t h i s ex-periment i s t h a t , while b i l e s a l t , c o n c e n t r a t i o n i n the s m a l l i n t e s t i n e of the New Hampshire c h i c k s was probably equal or g r e a t e r than the c r i t i c a l m i c e l l a r c o n c e n t r a t i o n , t h a t of the B r o i l e r s and White Leghorns was below t h i s c o n c e n t r a t i o n . Therefore, inadequate b i l e s a l t supply d u r i n g the process of f a t d i g e s t i o n and a b s o r p t i o n i n the s m a l l i n t e s t i n e of the B r o i l e r and White Leghorn c h i c k s , i s very l i k e l y t o be a t l e a s t one of the f a c t o r s l i m i t i n g maximum f a t a b s o r p t i o n i n these two types of b i r d s compared to the New Hampshires. However, whether the inadequate b i l e s a l t supply i s due to h e p a t i c b i l e a c i d s y n t h e s i s or s e c r e t i o n r a t e , cannot be deduced from r e s u l t s of t h i s experiment. /4 Table 12. Feed composition of the b a s a l d i e t (Diet 1) Ingredients Ground wheat 4 8 Soybean meal 32 Ground oats 15 Dehydrated a l f a l f a 2 Calcium phosphate 1.5 Limestone 1.0 Iodized s a l t 0.5 M i c r o n u t r i e n t s 1 + % P r o t e i n 22.8 % Fat 3.0 M i c r o n u t r i e n t s s u p p l i e d per kg. of d i e t : z i n c sulphate, 8 1 . 3 mg; manganese sulphate, 55.45 mg; DLmethionine, 8.29 gm; calcium panthothenate, 5 mg; f o l i c a c i d , 0.25 mg; n i a c i n , 12 mg; r i b o f l a v i n , 3 mg; vitamin A 1500 IU; vi t a m i n D^ , 400 ICU; vitamin E, 10 mg; vitamin B,„, 0.009 mg; .. : Table 13. Composition of experimental d i e t s D I E T S I n g r e d i e n t s % % % % Bas a l d i e t 100 99.05 88 87.05 Tallow 0 0 12 12 Sodium t a u r o c h o l a t e 0 0.05 0 0.05 T o t a l % f a t 3.0 3.0 15.0 15.0 76 Table 14. E f f e c t of 12% tallow and dietary b i l e s a l t supple-mentation on feed e f f i c i e n c y i n New Hampshires, Br o i l e r s and White Leghorns between 3 and 4 weeks of age. D I E T S Sodium taurocholate - + - + Tallow - - + + Overall means for breeds b New Hampshires 2.93 2.89 2.45 2.58 2.71 Br o i l e r s 2.40 2.23 2.01 1.94 2.15a White Leghorns 3.41 3.02 2.69 2.49 2.90b Overall means for diets 2.91c 2.71C :2.38d 2.34d 1 Overall tneans with d i f f e r e n t superscripts 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). 7 7 Table 1 5 . Mean body weight gains (g) of New Hampshires, B r o i l e r s and White Leghorns fed b a s a l and 1 2 % t a l l o w d i e t s w i t h or without sodium t a u r o c h o l a t e between 3 and 4 weeks of age. D I E T S Sodium Taurocholate Tallow New Hampshires B r o i l e r s + + + 3 7 . 8 3 7 . 3 4 5 . 4 4 2 . 3 O v e r a l l Means f o r breeds 4 0 . 7 a 9 7 . 0 1 0 7 . 2 1 2 2 . 3 1 3 3 . 0 1 1 4 . 9 ; White Leghorns 3 6 . 9 4 2 . 8 4 4 . 0 5 0 . 9 4 3 . T O v e r a l l means f o r d i e t s 5 7 . 2 C 6 2 . 4 ° 7 0 . 6 d 7 5 . 4 d . O v e r a l l 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 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 . 0 1 ) . Table 16. E f f e c t o f d i e t a r y supplementation of b i l e s a l t (0.05% sodium t a u r o c h o l a t e ) on net t a l l o w f a t a b s o r b a b i l i t y by the New Hampshires, B r o i l e r s and White Leghorns. F i r s t T r i a l Second T r i a l D i e t s Tallow + + + + Sodium t a u r o c h o l a t e - + - + New Hampshires 90.46 a 95.06 a 92.16 a 95.97 a B r o i l e r s 77.18 C 84.82 b 80.78 b 90.29 a White Leghorns 74.48 c 81.72 b 76.00 b 83.20 b For each t r i a l , means with different superscripts were found to be significantly different (P=0.01) on a transformed scale. 79 Table 17. E f f e c t of d i e t a r y supplementation w i t h b i l e s a l t (0.05% Na-taurocholate) on f e c a l soap f a t ex-pressed i n m i l l i g r a m per gram of dry f e c a l weight. F i r s t T r i a l Second T r i a l D i e t s 3 4 3 4 Tallow + + + + Sodium t a u r o c h o l a t e - + - + 1 New Hampshires 20.6 a 17.90 a 9.85 a 10.40 a B r o i l e r s 20.7 a 2.60° 39.00 b 4.80 d White Leghorns 26.8 b 6.10° 18.45° 2.10 d For each t r i a l , means f o l l o w e d by 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 (P-0.05). su 3.5.0 A Study on F a t t y A c i d Binding P r o t e i n i n The Chicken  Mesenteric I n t e s t i n e 3.5.1 Objective of The Study This study was a c o n t i n u a t i o n of the research e f f o r t s i n -tended to e x p l a i n the breed d i f f e r e n c e i n t a l l o w f a t absorb-a b i l i t y observed i n the e a r l y stages of experiment.. 1. The study was s t i m u l a t e d by the demonstration of the e x i s t -ence of a s p e c i f i c f a t t y a c i d b i n d i n g p r o t e i n i n the r a t i n t e s -t i n e (Ockner, e t al., 1972); which i s i n v o l v e d i n the t r a n s p o r t of long chain f a t t y acids i n the r a t i n t e s t i n a l mucosa (Ockner, 19 74). S i x d i f f e r e n t experiments were conducted i n course of t h i s study. 3.5.2 Experiment 5 Demonstration of F a t t y A c i d B i n d i n g P r o t e i n (FABP) i n the Chicken I n t e s t i n e . 3.5.2.1 I n t r o d u c t i o n : I t i s only r e c e n t l y that mechanisms underlying i n t e s t i n a l f a t absorption have, to a c e r t a i n extent, been e l u c i d a t e d (Hofmann, et a l . , '1962, ; Senior, 1964). There i s now evidence to ..indicate that the i n t e s t i n a l uptake of l i p i d m a t e r i a l s i s a dynamic b i -d i r e c t i o n a l process not e n t i r e l y e xplained by passive d i f f u s i o n ( D a n n i e H i , 1963 ; Wright, 1971 ; a n d M i s h k i n , e t a l . , 1973). Two p r o t e i n s , normally r e f e r r e d to as Y and Z were shown to be important i n the t r a n s f e r of organic ions from plasma i n t o the l i v e r (Reyes,et a l . , 1970) and to have an a f f i n i t y f o r f a t t y acids ( L e v i , e t a l . , 1969 ; Levine,et a l . , 1971 ; Mishkin, e t 81 a l . , 1972'; 1974). Ockner, e t a l . , (1972) demonstrated the existence of a s p e c i f i c f a t t y a c i d b i n d i n g p r o t e i n (FABP) i n the r a t small i n t e s t i n e . There i s no i n f o r m a t i o n i n the l i t e r -ature regarding the existence of f a t t y a c i d b i n d i n g p r o t e i n i n the i n t e s t i n e of the domestic chicken i n s p i t e of i t s being a very u s e f u l experimental animal i n a l o t of f a t u t i l i s a t i o n s t u d i e s that have been c a r r i e d out i n the past three decades. This experiment was t h e r e f o r e c a r r i e d out using e s s e n t i a l l y the same procedures as those of Ockner, e t a l . , (1972) to f i n d out whether any f a t t y a c i d b i n d i n g p r o t e i n e x i s t e d i n the chicken i n t e s t i n e . 3.5.2.2 M a t e r i a l s and Methods: An'adult White Leghorn cock e r e l that had been on a uniform d i e t (3% fat) f o r a t l e a s t 8 weeks was used. The b i r d was k i l l e d by neck d i s l o c a t i o n and p a r t of i t s small i n t e s t i n e ex-tending from the p a n c r e a t i c ducts p o s i t i o n on the d i s t a l end of the duodenal loop down to the i l e o - c e c a l - c o l i c j u n c t i o n was removed. I t was immediately cleaned by washing i t w i t h c o l d 0.01M phosphate b u f f e r i n 0.154M KCl (pH, 7.4). The clean seg-ment was cut open to expose the mucosal l i n i n g which was care-f u l l y extruded and homogenised i n 15 ml; of b u f f e r . The homo-genate was immediately subjected t o p r e p a r a t i v e u l t r a c e n t r i f u -g ation at 100,000xg f o r 2 hours. The supernatant was kept f o r column chromatography. Chromatography: Two ml of the 100,000xg supernatant were chromatographed 82 on Sephadex G-75 (Pharmacia Fine Chemicals Co.) g e l column 2.6 x 37 cm. E l u t i o n was performed w i t h 0.01M phosphate i n 0.154M KC l , pH 7.4, using downward g r a v i t y flow. S i x ml f r a c t i o n s of e f f l u e n t were c o l l e c t e d and p r o t e i n concentration i n each was estimated from UV absorbance at 2 80nm. Cytochrome C, molecular weight 12,400, was used as molecular weight marker and was e l u t e d w i t h a volume of 160 ml ,' from the column. In assaying f o r the f a t t y a c i d b i n d i n g a f f i n i t y of the mucosal c y t o s o l p r o t e i n s , 2 ml a l i q u o t s of the 100,000 x g super-nates were incubated with 1 /\Ci of o l e i c a c i d at room tem-perature f o r 5 minutes. The incubation mixture was then chromato-graphed as before. R a d i o a c t i v i t y i n each of the 6 ml f r a c t i o n s was measured on 1 ml a l i q u o t s added to 12 ml of Bray's s o l u t i o n (Bray, 1960) i n s c i n t i l l a t i o n v i a l s using a Nuclear Chicago Mark 1 l i q u i d s c i n t i l l a t i o n counter. C o r r e c t i o n f o r quenching was made by the channel r a t i o method ( B a i l i e , 19 60). 3.5.3 Experiment 6 F a t t y A c i d Binding P r o t e i n i n The I n t e s t i n e of Newly Hatched Chicks. In t h i s experiment the presence, of the f a t t y a c i d b i n d i n g p r o t e i n i n the mesenteric i n t e s t i n e was i n v e s t i g a t e d i n newly hatched chicks before feeding. Tissues from a New Hampshire, a B r o i l e r and a White Leghorn c h i c k , were examined. The e n t i r e mesenteric i n t e s t i n e was e x c i s e d from each c h i c k , homogenised as described f o r Experiment 5, and the supernate a f t e r c e n t r i -f u g a t i o n was subjected to g e l f i l t r a t i o n on Sephadex G-75 column. 83 P r o t e i n concentrations i n successive 6 ml., f r a c t i o n s of the e l u a t e were estimated from UV absorbance at 2 80 nm. F a t t y a c i d b i n d i n g capacity of the p r o t e i n s was assayed w i t h -^C o l e i c a c i d i n the same way as i n Experiment 5. 3.5.4 Experiment 7 R e l a t i v e Amount of FABP i n the Proximal, Middle and D i s t a l Chicken I n t e s t i n a l Segments. Results of the f i r s t two experiments of t h i s study demon-s t r a t e d the presence of f a t t y a c i d b i n d i n g p r o t e i n (FABP) i n the i n t e s t i n e of a d u l t b i r d s and newly hatched chicks p r i o r to feed-i n g . This experiment was set up to i n v e s t i g a t e the d i s t r i b u t i o n and r e l a t i v e amounts of FABP i n the proximal, middle and d i s t a l segments of a d u l t B r o i l e r fed a b a s a l d i e t (3% fat) and of a male b r o i l e r fed a h i g h - f a t d i e t (15% fat) f o r 8 weeks. Mesenteric i n t e s t i n e was e x c i s e d from each one of the b i r d s and cut i n t o 3 equal pieces representing the proximal, middle and d i s t a l segments. The segments were cleaned and supernates prepared and chromatographed as already described. 3.5.5 Experiment 8 R e l a t i v e Amounts of I n t e s t i n a l FABP i n New Hampshires, B r o i l e r s and White Leghorns Fed B a s a l , 12% Tallow and 12% Corn O i l Diets from Day Old u n t i l 5 Weeks of Age. This experiment was set up to determine the v a r i a b i l i t y i n the amounts of the FABP i n the i n t e s t i n e of b i r d s of d i f f e r e n t genetic background fed d i e t s c o n t a i n i n g widely divergent types of f a t (corn o i l vs animal t a l l o w ) . 84 3.5.5.1 M a t e r i a l s and Methods: Day o l d New Hampshire, B r o i l e r and White Leghorn c h i c k s were randomly d i s t r i b u t e d i n b a t t e r y brooders i n r e p l i c a t e groups of 6 c h i c k s . Each r e p l i c a t e group was f e d one of the 3 d i e t s , namely b a s a l , 12% t a l l o w and 12% corn o i l d i e t s . These d i e t s were s i m i l a r i n composition to the ones used i n Experiment 1. At day o l d p r i o r to f e e d i n g , 2 New Hampshire, B r o i l e r and White Leghorn c h i c k s were k i l l e d by neck d i s l o c a t i o n . Mesenteric i n t e s t i n e was removed from each ch i c k and washed with phosphate b u f f e r ; b l o t t e d and weighed. The i n t e s t i n e was then cut i n t o small p i e c e s , homogenised and volume of each homogenate measured. The homogenates were s u b j e c t e d to p r e p a r a t i v e u l t r a - c e n t r i f u g a t i o n a t 100,000x g f o r 2 hours. Volume of the supernates was recorded and p r o t e i n s i n 2 ml?: of i t were f r a c t i o n a t e d on Sephadex G-75 column. P r o t e i n c o n c e n t r a t i o n was e s t imated from UV absorbance at 2 80nm, i n column e f f l u e n t s s t a r t i n g o n l y with those t h a t c o r -responded to 120 ml; e l u t i o n volume up to when no more p r o t e i n was coming out of the column. S i m i l a r procedures were repeated f o r determinations c a r r i e d out at 1, 3, 4 and 5 weeks of age, ex-cept t h a t due to the c o n s i d e r a b l e l e n g t h of time i n v o l v e d i n c a r r y i n g out the d e t e r m i n a t i ons, o n l y a s i n g l e b i r d of each breed on a b a s a l d i e t was used f o r the f i r s t , t h i r d and f o u r t h week deter m i n a t i o n s ; two b i r d s were however, used from the o t h e r d i e t a r y treatments. FABP (mg/g i n t e s t i n e ) was c a l c u l a t e d as f o l l o w s : FABP (mg/g i n t e s t i n e ) P r o t e i n cone. i n column V o l . i n V o l . of V o l . of f r a c t i o n s f r a c t i o n s homogenate supernate V o l . ( 2 ml,) V o l . (10 ml.) ' Weight of a p p l i e d to x u l t r a c e n t r i f u g e d x i n t e s t i n e the column (g) 85 Fat a b s o r b a b i l i t y t r i a l was c a r r i e d out when the b i r d s were 2 weeks o l d using the t o t a l f e c a l c o l l e c t i o n procedure. In t h i s t r i a l , b i r d s were s t a r v e d f o r 2 4 hours before and a f t e r the two days' f e e d i n g p e r i o d . T o t a l e x c r e t a produced over t h i s p e r i o d was collected,, l y o p h i l i z e d , then weighed and ground and kept f o r a n a l y s i s t o determine f a t a b s o r b a b i l i t y u s i n g procedures a l r e a d y d e s c r i b e d i n Experiments 1 and 4. Records were a l s o taken on t o t a l feed i n t a k e . 3.5.6 Experiment 9 I n f l u e n c e of Prolonged Feeding of Tallow and Corn O i l D i e t s on the Amount of FABP i n the Proximal and Lower I n t e s t i n a l Segments of the New Hampshire and B r o i l e r - T y p e B i r d s . 3.5.6.1 I n t r o d u c t i o n : Fat a b s o r p t i o n was shown to take p l a c e i n the f i r s t p a r t of the proximal i n t e s t i n a l segment a f t e r the p a n c r e a t i c and b i l e ducts e n t r y p o i n t at the d i s t a l end of the duodenum'of the c h i c k (Renner, 1965) and l a y i n g fowl (Hurwitz, e t al_. , 1973). T h i s cannot be taken to mean t h a t o t h e r p a r t s of the s m a l l i n t e s t i n e cannot p a r t i c i p a t e i n f a t a b s o r p t i o n , because there i s i n c r e a s i n g evidence t h a t the lower s e c t i o n of the animal gut i s capable of undergoing adaptive changes i n an attempt to i n c r e a s e ab-s o r p t i v e c a p a c i t y i f circumstances warrant t h i s . The r a t ' s s m a l l i n t e s t i n e , f o r example, has been shown t o undergo f u n c t i o n a l com-pensatory hypertrophy a f t e r r e s e c t i o n i n order to i n c r e a s e the a b s o r p t i v e s u r f a c e per u n i t length of the remaining s e c t i o n . I l e a l a d a p t a t i o n v i a the compensatory h y p e r p l a s i a mechanism was 8 6 also shown for substances absorbed d i f f u s e l y through the small i n t e s t i n e of the rat (Dowling, et a l . , 1 9 7 3 ) . No information i s available now on whether a si m i l a r s i t u a t i o n exists i n the chicken. This experiment was therefore conducted for two main reasons. The f i r s t one was to confirm results of Experiment 7 i n which a noticeable increase i n r e l a t i v e amounts of FABP occurred i n the lower sections (middle and d i s t a l ) of the male b r o i l e r - b i r d that had been fed a high tallow f a t d i e t for eight weeks. The second reason was to t e s t the hypothesis that i l e a l adaptive changes leading to increased fat absorptive capacity observed by other investigators (Hoving, et a l . , 1 9 6 9 ; Singh, et a l . , 1 9 7 1 ) when they fed high fat diets are due to an increase i n the FABP content of the lower section of the small i n t e s t i n e . 3 . 5 . 6 . 2 Materials and Methods: Five week-old New Hampshire and broiler-type birds that had been fed either 1 2 % tallow or 1 2 % corn o i l d i e t i n Experiment 8 were continued on the same diets for another 5 weeks. At 1 0 weeks of age, two birds of each type from each of the two high-fat diets were k i l l e d and t h e i r mesenteric i n t e s t i n e removed and divided into two parts representing the proximal and lower segments which were 1 / 3 and 2 / 3 of the entire mesenteric i n t e s t i n a l length re-spectively. Supernates were prepared from these segments and subjected to Sephadex G - 7 5 gel chromatography as already described for other experiments. The FABP concentrations i n both segments were estimated according to procedures si m i l a r to those of Experiment 8 . 87 3.5.7 Experiment 10 A Study of the E f f e c t of D i e t a r y B i l e S a l t s and Animal Tallow on the Content of FABP (mg/g t i s s u e ) of the P r o x i -mal, Middle and D i s t a l I n t e s t i n a l Segments of the 4, 5, and 6 week-old New Hampshire and B r o i l e r - t y p e Chickens i n R e l a t i o n to Fat A b s o r b a b i l i t y . 3.5.7.1 I n t r o d u c t i o n : The s e t t i n g up of t h i s experiment was s t i m u l a t e d by the r e s u l t s of two p r e v i o u s experiments: one on the e f f e c t of d i e t a r y b i l e s a l t supplementation on t a l l o w f a t a b s o r b a b i l i t y i n New Hampshire, B r o i l e r and White Leghorn c h i c k s ; and the other on the e f f e c t o f prolonged f a t f e e d i n g on the content of FABP of the proximal and lower gut of the New Hampshire and b r o i l e r - t y p e b i r d s . A b e n e f i c i a l e f f e c t of d i e t a r y supple-mentation o f b i l e s a l t s on t a l l o w f a t a b s o r b a b i l i t y i n the B r o i l e r s and White Leghorns; and a s i g n i f i c a n t l y lower and h i g h e r FABP content of the proximal and d i s t a l segments r e -s p e c t i v e l y of the B r o i l e r s i n c o n t r a s t to the New Hampshires, were evidenced i n those two experiments. The b i l e s a l t s , i n a d d i t i o n to t h e i r m i c e l l a r s o l u b i l i -s a t i o n of l i p i d s , a f f e c t i n t r a c e l l u l a r processes i n v o l v i n g the a c t i v i t i e s of l i p i d r e e s t e r i f y i n g enzymes (Tandon, e t a l . , 1972 ; Mansbach, 1975). The p o s s i b l e mechanism of a c t i o n of b i l e s a l t s i n s t i m u l a t i n g mucosal enzymes i s not y e t c l e a r , though i t has been p o s t u l a t e d t h a t i t may be due t o i n t r a -c e l l u l a r l e v e l s of f r e e f a t t y acids.. Base:d .on- t h i s concept, the e f f e c t of b i l e s a l t s on FABP which predominantly p a r t i c i p a t e s i n the t r a n s f e r of f r e e f a t t y a c i d s i n t o the aqueous c y t o s o l , 88 r e q u i r e d i n v e s t i g a t i o n . T h i s experiment was t h e r e f o r e s e t up to t e s t the h y p o t h e s i s t h a t a d d i t i o n of b i l e s a l t t o d i e t s f e d to the b r o i l e r - t y p e b i r d s , improves f a t d i g e s t i b i l i t y c o e f f i -c i e n t s v i a a d i r e c t and/or an i n d i r e c t e f f e c t on the s y n t h e s i s of the f a t t y a c i d b i n d i n g p r o t e i n . 3.5.7.2 M a t e r i a l s and Methods: The experimental treatments and procedures used i n c a r r y i n g out t h i s experiment were s i m i l a r t o those used i n Experiment 4 t h a t examined the i n f l u e n c e of d i e t a r y b i l e s a l t on t a l l o w f a t a b s o r b a b i l i t y with the e x c e p t i o n t h a t , o n l y two breeds of chickens (New Hampshires and B r o i l e r s ) were used. T h i s e x p e r i -ment s t a r t e d when the b i r d s were 3 weeks of age and i n a d d i t i o n to the f a t d i g e s t i b i l i t y t r i a l s , the FABP content of the p r o x i -mal, middle and d i s t a l i n t e s t i n a l segments of those 2 breeds of chickens was determined a f t e r 1, 2 and 3 weeks o f f e e d i n g the experimental d i e t s . The d i e t s used i n t h i s experiment were s i m i l a r i n composition to those used i n Experiment 4. The pro-cedures used i n p r e p a r i n g the i n t e s t i n a l segment supernatants were s i m i l a r t o those a l r e a d y d e s c r i b e d i n other experiments of the FABP study. A one ml. sample of each of the i n t e s t i n a l segment supernates was chromatographed on Sephadex G-75 column and p r o t e i n i n the column e f f l u e n t s was c o n t i n u o u s l y and auto-m a t i c a l l y monitored by absorbance a t 2 80 nm u s i n g a« Unicam SP 1800 u l t r a v i o l e t spectrophotometer equipped with a flow-through c e l l and an automatic r e c o r d i n g device t o p l o t absorbance curves. 89 The p r o t e i n c o n c e n t r a t i o n of the FABP absorbance peaks was estimated. 3.5.8 R e s u l t s 3.5.8.1 Experiment 5: R e s u l t s o f g e l f i l t r a t i o n of mucosal c y t o s o l p r o t e i n s of the a d u l t c o c k e r e l are shown i n F i g u r e 2. In t h i s f i g u r e , the b i n d i n g of l a b e l l e d o l e i c a c i d t o the d i f f e r e n t peaks of the c y t o s o l p r o t e i n s i s a l s o i n d i c a t e d . The p r o t e i n absorbance curve (280 nm) shows t h a t most of the p r o t e i n was a s s o c i a t e d w i t h 2 p r o t e i n peaks. One peak oc c u r r e d a t an e l u t i o n volume of 165 mlo Cytochrome C was e l u t e d from the column w i t h a volume of 160 ml, i n d i c a t i n g t h a t the second peak of mucosal p r o t e i n had a molecular weight s l i g h t l y below 12,400. The r a t i n t e s -t i n a l FABP r e p o r t e d by Ockner, e t a l . , (1972) was l i k e w i s e 14 s i m i l a r to Cytochrome C i n m olecular weight. The C r a d i o -a c t i v i t y curve superimposed on the p r o t e i n absorbance curve c l e a r l y shows t h a t the g r e a t e s t amount of l a b e l l e d o l e i c a c i d was a s s o c i a t e d with the low m olecular weight p r o t e i n peak. T h i s was evidence t h a t the i n t e s t i n a l mucosa of the c h i c k e n c o n t a i n s a f a t t y a c i d b i n d i n g p r o t e i n i n the same molecular weight range as the FABP demonstrated by Ockner and a s s o c i a t e s i n the r a t mucosa (1972) . 3.5.8.2 Experiment 6 The r e s u l t s of t h i s experiment are summarized i n F i g u r e 3. The f i g u r e shows p r o t e i n peaks r e s o l v e d by Sephadex G-75 column 90 chromatography of the i n t e s t i n a l supernates from the da y - o l d New Hampshire, B r o i l e r and White Leghorn c h i c k s . The graphs i n F i g u r e 3 show the d i f f e r e n c e s among the New Hampshire, B r o i l e r and White Leghorn-type c h i c k s i n the amount of l a b e l l e d o l e i c a c i d b i n d i n g t o the low mo l e c u l a r weight FABP as w e l l as i n the r e l a t i v e amount of the FABP prese n t i n the i n t e s t i n e . R e s u l t s o f t h i s experiment have e s t a b l i s h e d the presence of FABP i n the i n t e s t i n e of the c h i c k s a t the time of h a t c h i n g and before any feed i s i n g e s t e d . 3.5.8.3 Experiment 7: The r e s u l t s o f t h i s experiment are summarised i n F i g u r e s 4A and 4B. F i g u r e 4A shows the column chromatographic p a t t e r n s of the mucosal c y t o s o l p r o t e i n s from 3 d i f f e r e n t i n t e s t i n a l seg-ments of a 12-week-old b r o i l e r - t y p e b i r d f e d a low f a t d i e t . I t can be seen from the f i g u r e t h a t the FABP f r a c t i o n d e c l i n e d pos-t e r i o r l y and so d i d the albumin f r a c t i o n of the a d u l t White Leg-horn f e d a low f a t d i e t . When a d i e t c o n t a i n i n g 15% of f a t was fed f o r 8 weeks p r i o r to the de t e r m i n a t i o n s , the r e l a t i v e amounts of FABP i n a l l the 3 d i f f e r e n t s e c t i o n s were s i m i l a r (Figure 4B). This was an i n d i c a t i o n t h a t h i g h d i e t a r y f a t p r o v i d e d the s t i -mulus f o r the i n c r e a s e i n FABP content of the lower s e c t i o n s of the b r o i l e r gut. 3.5.8.4 .Experiment 8: Re s u l t s of FABP determinations at d i f f e r e n t ages are sum-marised i n Tables 18 and 19. At day o l d and one week of age, 91 the B r o i l e r s had a s i g n i f i c a n t l y lower (P-0.05) FABP content than the New Hampshires or White Leghorns; the d i f f e r e n c e s be-tween the l a t t e r were s l i g h t and i n s i g n i f i c a n t a t those 2 ages. The i n t e s t i n a l FABP contents of the B r o i l e r s and White Leghorns were s i m i l a r at 3 weeks of age, t h a t of the New Hampshires was s t i l l s i g n i f i c a n t l y h i g h e r u n t i l 4 weeks of age when a l l types of b i r d s appeared t o have s i m i l a r FABP contents. At 5 weeks of age FABP content was h i g h e r once again i n the New Hampshires than i n the B r o i l e r or White Leghorns. Data i n Table 19 i n d i c a t e t h a t d i f f e r e n c e s between d i e t s i n the amount of FABP i n the b i r d s were s i g n i f i c a n t o n l y a t 3 weeks of age. At t h i s age, i t appears from the r e s u l t s , t h a t both q u a n t i t y and nature of d i e t a r y f a t had some i n f l u e n c e on i n t e s t i n a l FABP content. A g e n e r a l i n t e r e s t i n g p a t t e r n r e -v e a l e d by data i n Tables 18 and 19 i s t h a t , r e g a r d l e s s of the composition of d i e t or type of b i r d s , there was a g e n e r a l i n -crease i n i n t e s t i n a l FABP contents as the b i r d s grew. This r e s u l t , when viewed i n r e l a t i o n t o the commonly observed age dependence on f a t a b s o r p t i v e c a p a c i t y of young b i r d s , p o s s i b l y e x p l a i n s the i n c r e a s e d a b i l i t y of b i r d s to absorb d i e t a r y f a t as they grow up. In order to examine t h i s age dependence of FABP content of the i n t e s t i n e s of b i r d s f e d d i f f e r e n t d i e t s , the absolute amounts of i n t e s t i n a l FABP (mg/bird) were p l o t t e d a g a i n s t age of b i r d s on the a b s c i s s a (Figure 5). The f i g u r e shows t h a t i n a l l types of b i r d s on a l l d i e t s the t o t a l amount 92 of FABP (mg/bird) i n c r e a s e d with age. I t can be seen from F i g u r e 5 that i n absolute terms the B r o i l e r s had the g r e a t e s t i n c r e a s e i n t o t a l FABP because t h e i r i n t e s t i n a l weights were l a r g e r than those of the New Hampshires or White Leghorns a t any one age. However on a per u n i t weight b a s i s the s i t u a t i o n i s d i f f e r e n t as data i n Table 18 showed. I t i s noteworthy t h a t a t day-old (0 week) and one week of age, the t o t a l amount of FABP was g r e a t e r i n the New Hampshires i n s p i t e o f t h e i r r e l a t i v e l y small i n t e s -t i n a l weights when compared t o those of the B r o i l e r s . In order to r e l a t e FABP data o b t a i n e d with d a y - o l d and one week o l d c h i c k s t o f a t a b s o r p t i v e c a p a c i t y , a f a t a b s o r b a b i l i t y t r i a l was conducted d u r i n g the second week of t h i s experiment. The r e s u l t s of t h i s t r i a l are summarised; i n Table 20. Table 20 shows t h a t the B r o i l e r s were l e s s e f f i c i e n t (P^0.05) i n t a l l o w a b s o r p t i o n than the New Hampshires or White Leghorns. Other d i f f e r e n c e s between d i e t s and/or breeds were not s i g n i f i -cant. On the b a s i s of t h e i r FABP content (mg/g i n t e s t i n e ) de-termined a t day-old and one week of age, the b i r d s were ranked: New Hampshires f i r s t f o l l o w e d by White Leghorns and then B r o i l e r s i n t h a t order (Table 18). This r a n k i n g i s a l s o r e f l e c t e d i n the f a t a b s o r b a b i l i t y c o e f f i c i e n t s o b tained with 2-week-old b i r d s (Table 20). Therefore the r e l a t i v e l y poor t a l l o w f a t absorp-t i v e c a p a c i t y of the B r o i l e r s a t 2 weeks of age was p a r t l y due to a lower i n t e s t i n a l FABP content a t an e a r l y age. 3.5.8.5 Experiment 9: This experiment examined the v a r i a b i l i t y i n proximal and 93 lower gut FABP content i n the-New Hampshire and B r o i l e r type b i r d s f e d a 12% t a l l o w or 12% corn o i l d i e t f o r 10 weeks. The r e s u l t s o f t h i s experiment are presented i n Table 21. D i e t a r y d i f f e r e n c e s i n the amount o f FABP e i t h e r i n the proximal o r i n the lower gut were not s i g n i f i c a n t , however d i f f e r e n c e s among b i r d - t y p e s were s i g n i f i c a n t . I t can be observed from Table 21 t h a t the proximal i n t e s t i n a l FABP content of New Hampshires was g r e a t e r than t h a t of the B r o i l e r s . The r e v e r s e was however t r u e f o r the lower gut FABP content. The B r o i l e r s had n e a r l y 1^ 5 times the content of FABP i n the lower gut of the New Hamp-s h i r e s . With regard to the i n t e s t i n a l segment weights, there were no d i e t a r y or breed e f f e c t s on the proximal segment, although the lower segment was h e a v i e r (P=0.05) i n the B r o i l e r s than i n the New Hampshires. 3.5.8.6 Experiment 10: The r e l a t i v e amounts o f FABP (mg/g t i s s u e ) determined at 4, 5 and 6 weeks of age or 1, 2 and 3 weeks a f t e r i n t r o d u c t i o n o f the experimental d i e t s , are summarised i n F i g u r e 6. A number o f o b s e r v a t i o n s can be made from r e s u l t s i n t h i s f i g u r e . F i r s t , i t i s noteworthy from the f i g u r e t h a t a t 4 and 5 weeks o f age (1 and 2 weeks a f t e r f e e d i n g the experimental d i e t s ) the New Hampshire proximal i n t e s t i n a l segment FABP content v a l u e s remained constant on a l l the d i e t s and were s l i g h t l y h i g h e r than the FABP values determined on the b r o i l e r proximal segments. Secondly, i t can be observed t h a t f o r the 94 b r o i l e r - t y p e b i r d s , d i e t a r y supplementation w i t h sodium taurocho-l a t e r e s u l t e d i n i n c r e a s e d l e v e l s o f FABP i n a l l the segments. The f i g u r e f u r t h e r shows t h a t the r e l a t i v e amounts of FABP were s i m i l a r i n a l l segments when the b r o i l e r - t y p e b i r d s were f e d D i e t 4 (12% t a l l o w + sodium t a u r o c h o l a t e ) f o r the f i r s t two weeks of the experiment. On D i e t 3 (12% t a l l o w d i e t ) d u r i n g the same p e r i o d , the amount of FABP was h i g h e r i n the d i s t a l gut s e c t i o n compared to the middle and proximal segments of the b r o i l e r s . T h e r e f o r e , s i m i l a r to r e s u l t s of Experiment 7, the p r o x i m a l - d i s t a l FABP c o n c e n t r a t i o n g r a d i e n t i n t h i s experiment was p e r s i s t e n t o n l y i n b i r d s which were fed a b a s a l d i e t w i t h a low f a t content. T h i r d l y , the f i g u r e r e v e a l s t h a t the FABP content of a l l segments determined d u r i n g the second and t h i r d week of the experiment was h i g h e r than t h a t of the f i r s t week de t e r m i n a t i o n s . However, a t the end of the experiment, the lower s e c t i o n s of the New Hampshire gut had a r a t h e r s m a l l i n c r e a s e i n FABP content when compared to t h a t of t h e i r c o u n t e r p a r t s i n the B r o i l e r s . R e s u l t s i n Tables 22 and 23 are s i m i l a r i n t r e n d to those of an e a r l i e r s i m i l a r experiment. The b r o i l e r - t y p e b i r d s once more respond p o s i t i v e l y to the d i e t a r y supplementation w i t h sodium t a u r o c h o l a t e . In both t r i a l s , a d d i t i o n o f the b i l e s a l t to the d i e t caused a s i g n i f i c a n t improvement i n the a b s o r p t i o n o f t a l l o w f a t . T h i s improvement was a s s o c i a t e d w i t h a s i g n i f i c a n t r e d u c t i o n i n the amount of f e c a l f a t t y a c i d s . 9 5 3 . 5 . 9 Discussion Results of th i s study have conclusively demonstrated the existence of a fat t y acid binding protein (FABP) i n the i n -testines of adult birds and day-old chicks. Assessment of the segmental d i s t r i b u t i o n of FABP revealed that under conditions of low dietary f a t intake, the amount of FABP decreased p o s t e r i o r l y when measured i n the i n t e s t i n a l regions extending from the pancreatic ducts entry point on the d i s t a l end of the duodenum to the i l e a l - c a e c o - c o l i c junction. This r e s u l t agrees with what i s known about the s i t e of fat absorption i n the chick (Renner, 1 9 6 5 ) and the laying fowl (Hurwitz, et a l . , 1 9 7 3 ) . The observed greater amount of FABP (mg/g intestine) i n the New Hampshires at an early age explains t h e i r more e f f i c i e n t f a t absorptive capacity compared to that of the B r o i l e r and the White Leghorn chicks. This r e s u l t established, at least i n part, the genetic basis of the differences i n fat absorbability among New Hampshire, B r o i l e r and White Leghorn chicks, since i t i s known from molecular biology concepts that any r e a l genetic d i f f e r -ence i s traceable i n the f i n a l analysis, to the production of d i f f e r e n t types of protein and/or d i f f e r e n t quantities of the same type of protein. It i s further known, according to the one gene-one polypeptide theory, that the amino acid sequence of a polypeptide chain (and hence what that polypeptide does i n b i o l o g i c a l system) i s dictated by the sequence of nucleotides i n the corresponding gene. The i n t e s t i n a l FABP content of a l l 96 birds increased with age. This observed increase in FABP content due to age of b i r d s , can be correlated with the age dependence of fat absorptive capacity of young birds. There-fore, i t appears that maturation of the f a t absorption machinery in b i r d s , involves the production of greater amounts of f a t t y acid transport protein as the birds grow. Results summarised in Figure 5 indicated that the rate of FABP production was 2 times faster i n the B r o i l e r s than in the New Hampshires or White Leghorns. This i s possibly what enabled the B r o i l e r s to become as e f f i c i e n t as the New Hampshires in fat absorption. A general increase in FABP content of the lower gut sections (middle and d i s t a l ) due to prolonged fat feeding, indicated by the results of Experiment 7 (Figure 4B) and confirmed by the results obtained with the B r o i l e r s in Experiment 9, leads to the conclusion that the chicken lower gut FABP content i s subject to inductive mechanisms which are stimulated by the amount of fat in the ingesta reaching the lower i n t e s t i n a l parts. Ockner,et a l . , (1974) reported that feeding rats a high f a t d i e t caused a s i g n i f i c a n t increase i n the amounts of FABP in the middle and d i s t a l i n t e s t i n a l segments due to what may be termed a " s p i l l over e f f e c t " that causes the lower portions of the in t e s t i n e to become involved in the f a t absorptive process. The results of Experiment 9 showed greater and lesser (P^0.05) amounts of FABP in the proximal and lower gut sections respectively of the New Hampshires compared with the B r o i l e r s . 9 7 T h i s complete r e v e r s a l of events i n the d i f f e r e n t i n t e s t i n a l segments of the d i f f e r e n t types of b i r d s c o u l d , on a t h e o r e t i c a l b a s i s , be i n t e r p r e t e d i n terms of the d i f f e r e n c e i n the f a t con-t e n t o f the i n g e s t a r e a c h i n g the lower gut s e c t i o n s . The hig h FABP content o f the proximal i n t e s t i n e of the New Hampshire b i r d s p o s s i b l y i n c r e a s e d the e f f e c t i v e n e s s of f a t a b s o r p t i o n i n the proximal r e g i o n o f the s m a l l i n t e s t i n e . As a r e s u l t , t h e i n g e s t a r e a c h i n g the d i s t a l r e g i o n of the i n t e s t i n e was low i n f a t con-t e n t . On the c o n t r a r y , however, due t o the l i m i t e d amounts of FABP i n the proximal i n t e s t i n e of the B r o i l e r s , the i n g e s t a r e a c h i n g the lower gut s e c t i o n s was r i c h i n f a t content and thus caused a more pronounced " s p i l l over e f f e c t " t h a t s t i m u l a t e d the p r o d u c t i o n o f l a r g e q u a n t i t i e s o f FABP i n these s e c t i o n s . On the b a s i s o f t h i s l i n e of reasoning, i t may be hy p o t h e s i s e d t h a t i l e a l a d a p t a t i o n to a h i g h d i e t a r y f a t in t a k e observed by other i n v e s t i -g ators (Hoving, e t al_. , 1969 ; Singh, e t al_. , 1971) i s not due to amounts of f a t i n g e s t e d per se but i t i s probably due to the f a t content of the i n g e s t a r e a c h i n g the lower p o r t i o n s of the i n -t e s t i n e . The r e s u l t s of Experiment 10 confirmed t h a t supplement-in g d i e t s c o n t a i n i n g l a r g e q u a n t i t i e s of t a l l o w with sodium t a u r o -c h o l a t e , improves the f a t a b s o r b a b i l i t y c o e f f i c i e n t s o b t a i n e d with the B r o i l e r s . I t was a l s o observed i n t h i s experiment t h a t the lower s e c t i o n s of the b r o i l e r gut have the c a p a c i t y to undergo adaptive changes t o i n c r e a s e the b i r d s ' e f f i c i e n c y f o r a b s o r p t i o n of d i f f u s e l y absorbable type of l i p i d m a t e r i a l . The age e f f e c t 98 on the FABP content of the d i f f e r e n t i n t e s t i n a l segments of the New Hampshire arid b r o i l e r - t y p e b i r d s was a l s o apparent. I t i s i n t e r e s t i n g t o note t h a t the FABP content of the lower gut sec-t i o n s of the B r o i l e r s f e d a h i g h t a l l o w f a t d i e t was g r e a t e r than t h a t of the New Hampshires and t h a t a d d i t i o n of sodium t a u r o c h o l a t e to a t a l l o w d i e t caused a s l i g h t r e d u c t i o n i n the output of t h i s p r o t e i n i n the same s e c t i o n s . These two obser-v a t i o n s j o i n t l y c o n s i d e r e d suggest t h a t i t i s the f a t content of the i n g e s t a with which the lower gut s e c t i o n i s i n c o n t a c t , t h a t p o s s i b l y s t i m u l a t e s i l e a l v i l l u s growth and i n c r e a s e d s y n t h e s i s of the FABP v i a i n d u c t i v e mechanisms. V i l l u s growth i n the lower gut s e c t i o n s of the r a t due to i n c r e a s e d l u m i n a l n u t r i t i o n r e s u l t i n g from a r i c h e r n u t r i t i o n a l l o a d r e a c h i n g the lower gut was r e p o r t e d by Dowling, (1973). I t has been suggested t h a t an i n c r e a s e i n p a n c r e a t i c s e c r e t i o n s , b i l e s a l t s and changes i n b l o o d flow due to h i g h d i e t a r y f a t i n t a k e may a l l c o n t r i b u t e to the adaptive changes of the ileum (Altman, 19 71). R e s u l t s of the f a t d i g e s t i b i l i t y t r i a l s confirmed those of the Experiment 4. In t h i s experiment as b e f o r e , the improvement i n f a t d i g e s t i b i l i t y c o e f f i c i e n t s when B r o i l e r s were f e d the 12% t a l l o w d i e t supplemented wi t h sodium t a u r o c h o l a t e , was due to a s i g n i f i c a n t r e d u c t i o n i n the amounts of f e c a l soap f a t t y a c i d s . In t h i s experiment, the c h a i n of events l e a d i n g to im-proved f a t a b s o r b a b i l i t y may be deemed to have f o l l o w e d t h i s t r e n d i n the B r o i l e r s : Presence o f exogenous b i l e s a l t i n the 99 t a l l o w d i e t ensured e f f e c t i v e l i p o l y s i s and m i c e l l a r s o l u b i l i -s a t i o n of the products ( f r e e f a t t y a c i d s , mono-glycerides and g l y c e r o l ) ; then, the i n c r e a s e d l u m i n a l c o n c e n t r a t i o n of f r e e f a t t y a c i d s induced the s y n t h e s i s of more FABP t o r a p i d l y t r a n s p o r t these f a t t y a c i d s i n the mucosal c y t o s o l t o undergo the r e - e s t e r i f i c a t i o n p r o c e s s . The New Hampshire b i r d s i n t h i s experiment, as i n the pre -v i o u s ones, were more e f f i c i e n t i n absorbing t a l l o w f a t than the B r o i l e r s . When r e s u l t s o f the f a t d i g e s t i b i l i t y t r i a l s are exa-mined i n r e l a t i o n to those of the i n t e s t i n a l segment FABP d e t e r -minations, i t can be concluded t h a t i t i s the h i g h e r proximal i n t e s t i n a l FABP content t h a t c o n s i s t e n t l y made the New Hampshires exceed the B r o i l e r s i n t a l l o w f a t a b s o r p t i v e c a p a c i t y . I t i s how-ever noteworthy t h a t with time, continued exposure o f the lower b r o i l e r gut to the i n g e s t a r i c h i n f a t t h a t had bypassed the p r o x i -mal i n t e s t i n a l f a t a b s o r p t i v e s u r f a c e , evoked an adaptive r e -sponse i n an e f f o r t t o i n c r e a s e the B r o i l e r s ' l i p i d a b s o r p t i v e c a p a c i t y t o a l e v e l comparable t o t h a t o f the New Hampshires. F i n a l l y , presence of a high and low proximal FABP contents i n the New Hampshires and B r o i l e r s r e s p e c t i v e l y , and the observa-t i o n t h at i n the B r o i l e r s , the lower gut showed a marked response to a high d i e t a r y f a t exposure, do e x p l a i n : 1) the e a r l y d i f -ference i n f a t a b s o r b a b i l i t y , among b i r d s b e f o r e the ad a p t a t i o n of t h e i r small i n t e s t i n e s to high d i e t a r y f a t i n t a k e s and 2) why the B r o i l e r s f o r example catch up i n time with the New Hampshires i n f a t a b s o r p t i v e c a p a c i t y . 100 Table 18. Con c e n t r a t i o n of FABP i n the small i n t e s t i n e of b i r d s of d i f f e r e n t breeds from h a t c h i n g t o 5 weeks of age. Conc e n t r a t i o n of FABP (mg/g i n t e s t i n e )  New Hampshire B r o i l e r White Leghorn Day-old 35.87 a ( 2 ) 2 18.82 b(2) 32.02 a(2) Week 1 28.26 a(5) 16.22 b(5) 25.33 a(5) Week 3 23.99 a(5) 20.22 b(5) 20.13 b(5) Week 4 27.35 a(5) 30.44 a(5) 29.10 a(5) Week 5 36.13 a(6) 31.59 b(6) 30.21 b(6) O v e r a l l Mean 30.32 2 3.46 2 7.36 "*"Means i n a row f o l l o w e d by a d i f f e r e n t s u p e r s c r i p t are s i g n i -f i c a n t l y d i f f e r e n t a t the 5% p r o b a b i l i t y l e v e l . 2 F i g u r e s i n p a r e n t h e s i s r e f e r to number of b i r d s used i n the dete r m i n a t i o n s . 1 0 1 Table 19. E f f e c t of d i e t a r y f a t content on the c o n c e n t r a t i o n o f FABP (mg/g i n t e s t i n e ) r e g a r d l e s s of breed of b i r d s from 1 week t o 5 weeks of age. Con c e n t r a t i o n of FABP (mg/g i n t e s t i n e )  B a s a l D i e t Tallow D i e t Corn O i l D i e t F a t content 3% 15% 15% 1 „ Week 1 19.28 a (3) 24.02 a(b) 24.61 a(6) Week 3 18.25 C(3) 21.15 b(6) 23.35 a(6) Week 4 26.10 a(3) 29.14 a(6) 30.23 a(6) Week 5 3 0 . 2 9 a ( 6 ) 3 3 . 2 8 a ( 6 ) 3 4 . 3 5 a ( 6 ) Over a l l , mean 23.48 26.90 a 28.14 a "'"Means i n a row f o l l o w e d by the same s u p e r s c r i p t are not s i g n i -f i c a n t l y d i f f e r e n t at the 5% l e v e l of p r o b a b i l i t y . 2 F i g u r e s i n p a r e n t h e s i s r e f e r t o number of b i r d s used i n the dete r m i n a t i o n s . 102 Table 20. Fat a b s o r b a b i l i t y i n 2 week-old New Hampshire, B r o i l e r and White Leghorn c h i c k s i n Experiment 8. % Fat A b s o r b a b i l i t y Tallow Corn O i l a 1 a New Hampshires 90.06 91.01 B r o i l e r s 71.74 b 89.30 a White Leghorns 85.00 91.01 Means f o l l o w e d by the same s u p e r s c r i p t were found on a t r a n s -formed s c a l e to be not s i g n i f i c a n t l y d i f f e r e n t a t the 5% l e v e l o f p r o b a b i l i t y by Tukey t e s t . 103 Table 21. I n d i v i d u a l v a r i a b i l i t y i n weight and FABP c o n c e n t r a t i o n of proximal and lower i n t e s t i n e of New Hampshire and b r o i l e r - t y p e b i r d s f e d h i g h - f a t d i e t s f o r 10 weeks i n Experiment 9. Proximal i n t e s t i n e Lower i n t e s t i n e FABP i n FABP i n Weight mg/g t i s s u e Weight mg/g i n t e s t i n e Number of b i r d s * 8 8 • 8 8 1 16.00 22.50 20.80 10.56 2 14.00 19.90 19.70 9.63 New Hampshires: 3 11.00 21.64 17.50 7. 71 4 16 . 50 26.47 24. 80 7.96 Mean 14 . 37 22.63 20.70 8.96 1 29.00 10.70 40.50 19 . 88 B r o i l e r s : 2 16.70 10.27 31. 80 12. 84 3 20.50 14.5 7 33.70 12 .03 4 24.00 16. 89 26.30 12.66 Mean 22 .55 13.11 33.08 14.35 F-Test P>0.0 5 P^O.005 P^0.05 P^ O.O *The f i r s t two b i r d s of each breed were f e d 12% of t a l l o w i n the d i e t , while the l a s t two were f e d 12% of corn o i l i n the d i e t . 104 Table 22. E f f e c t of dietary supplementation with 0.05% Na-taurocholate on net tallow f a t absorbability by the New Hampshire and Broiler-type chicks in Ex-periment 10. F i r s t T r i a l Second T r i a l 3 4 Diets 3 4 Tallow + + + + Na-taurocholate + - + 1 New Hampshires 84.64a 87.70a 87.24a 86.03 a B r o i l e r s 72.16b 89.49 a 83.17b 86.86 a For each t r i a l , means followed by the d i f f e r e n t superscripts were found to be 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) on a trans-formed scale. 105 Table 23. E f f e c t of d i e t a r y b i l e s a l t on the amount of f e c a l soap f a t t y a c i d s (mg/g dry f e c a l weight) e x c r e t e d by the New Hampshire and B r o i l e r - t y p e c h i c k s i n Experiment 10. F i r s t T r i a l Second T r i a l D i e t s 3 4 3 4 Tallow + + + + Na-taurocholate - + - + 1 h h New Hampshires 39.10° 34.05° 18.80 14.70 B r o i l e r s 88.88 a 57.42 b 49.90 a 26.85 b For each t r i a l , means f o l l o w e d by 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 (P=0.05). 106 3 2 0 0 / I I \ I \ I \ \ \ w 80 100 '20 ]40 , 6 0 ELUTfOSV V O L U M E (ml) \ \ \ 180 2 0 0 2 8 0 0 •? 2400 2 0 0 0 " o ** IS 3 o 1600 _ S \ E a 1200 T w >• r-8 0 0 4 00 r-o < o 5 Gel f i l t r a t i o n of a d u l t White Leghorn i n t e s t i n a l 14 mucosa supernate with C - o l e i c a c i d u s i n g Sephadex G - 7 5 . 107 A 1 .0 0.8 < E c o 0.6 CO CM h-< UI 0.4 O z < CQ 0.2 o to a < 0 40 N e w H a m p s h i r e A, / V / / \ \ A / / 1* — A l , ' - l r - | - . . l 1800 1600 <J 1400 1200 1000 ~ t> re • 3 800 0 600 E a. 4 0 0 -200 O < O Q < a. 60 80 100 120 140 160 E L U T I O N V O L U M E C ml ) 180 200 F i g u r e 3 ( a ) . Sephadex G-75 g e l f i l t r a t i o n o f day-old New Hampshire chick mesenteric i n t e s t i n a l 14 supernate with C - o l e i c a c i d . 108 | 0.6 o 03 N ^ 0.4 UJ O z < m 02 o </) co < 0 40 / \ / \ I A, b r o i l e r - t y p e 1400 I 1200 1000 ~ re 3 O 800 600 a >-r-400 -> 60 80 200 U a < 1 0 0 , 2° '40 160 180 200 E L U T I O N V O L U M E C ml ) Figure 3(b). Sephadex G-75 gel f i l t r a t i o n of day-old b r o i l e r type chick mesenteric i n t e s t i n a l 14 supernate with C - o l e i c acid. 1 U J •4 | 0.6 O CO I-< 0.4 Lit o 2 < CO 0.2 O CQ < n 40 I -a White Leghorn • A \ I lj\ \ I U l - A - X \ 1 / V / / \ 60 80 1 0 0 120 140 160 ELUTIOPJ VOLUME (ml) 180 1000 800 600 E a T 3 400 . > p 200 O o a < 0 K 200 Figure 3(c). Sephadex G-75 gel f i l t r a t i o n of White Leghorn chick mesenteric i n t e s t i n a l 14 supernate with C - o l e i c acid. 11U 2.0 1.6 E c o CO CM I -< LU U z < m K o w < 1.2 0.8 OA I \ \ T O \ _,o-o. o P \ 1 P / Q - - B - a \ 1 0 " o PROXIMAL SEGMENT o o MIDDLE • a DiSTAL A " f e d 3 % f a t 30 50 7 0 9 0 " 110 ~ ~ i ^ 0 ~ " 1 5 0 ~ ~ E L U T I O N V O L U M E (ml) ; P - « - a  aS%~ 170 190 Figure 4A. Relative amount of FABP in the mucosa of the proximal, middle, and d i s t a l i n t e s t i n a l seg-ments of a broiler-type b i r d fed a diet con-taining 3% of f a t for 10 weeks. XX X 3.2 2.8 2.4 nm 2.0 O CO CM 1 . 6 < UJ O 2 1 . 2 < CO a: O CO 0.8 ca < 0.4 30 / I / I o o I / A W • / / \ \ \ ° / - •'• \ / d / \\\ V , ° \\\ V 50 70 90 110 • : ° PROXIMAL SEGMENT O— O MIDDLE B a DISTAL B - f e d 1 5 % f a t /if \, / 130 150 170 E L U T I O N VOLUME C ml ) 1 _ 190 F i g u r e 4B. R e l a t i v e amount of FABP i n the mucosa of the proximal, middle, and d i s t a l i n t e s t i n a l segments of a b r o i l e r - t y p e b i r d f e d a d i e t c o n t a i n i n g 15% of f a t f o r 10 weeks. 112 o «°° K 0. o Z 500 Q . Z IT •7 / 7 7 Y AC-O B A S A L D I E T 1 2 % T A L L O W D I E T • 1 2 % , . C O R N O I L D I E T Z / 8 / / 4 / 'a i 2 3 4 N E W H A M P S H I R E S 0 I 2 B R O I L E R S 3 4 5 W H I T E L E G H O R N S A C E I N W E E K S F i g u r e 5, C o n c e n t r a t i o n of FABP (mg/bird) i n the mesenteric i n t e s t i n e of New Hampshires, B r o i l e r s and White Leghorns f e d d i f f e r e n t d i e t s from day-old to 5 weeks of age. 1 1 3 80 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 BASAL DIET B A S A L DIET 1296 T A L L O W 12Q6 T A L L O W & BILE SALT & BILE S A L T F i g u r e 6. C o n c e n t r a t i o n of FABP (mg/g t i s s u e ) i n the p r o x i m a l , middle and d i s t a l i n t e s t i n a l segments of the New Hampshires (A) and B r o i l e r s (B), a f t e r 1 , 2 , and 3 ^weeks of f e e d i n g on the d i f f e r e n t experimental d i e t s . 114 SECTION FOUR  SUMMARY AND CONCLUSIONS This t h e s i s study was o r i e n t e d towards the exist e n c e of s i g n i f i c a n t breed d i f f e r e n c e s i n f a t a b s o r b a b i l i t y among domestic chickens and to f i n d out the extent to which these f a t absorb-a b i l i t y d i f f e r e n c e s accounted f o r v a r i a t i o n i n M. E. estimates. The underlying o b j e c t i v e of the study was th e r e f o r e to i d e n t i f y the major cause of the f r e q u e n t l y observed v a r i a b i l i t y i n M. E. estimates due t o age or breeds of b i r d s . In p u r s u i t of t h i s ob-j e c t i v e , b i r d s of d i f f e r e n t genetic background, namely New Hamp-s h i r e s , B r o i l e r s and White Leghorns were compared i n the f i r s t experiment, on the b a s i s of t h e i r r e l a t i v e a b i l i t i e s to absorb two types of f a t w i t h widely divergent p r o p e r t i e s (corn o i l vs animal t a l l o w ) . Dietary energy m e t a b o l i s a b i l i t y by the 3 d i f -f e r e n t types of b i r d s at 3, 5, and 9 weeks of age was estimated and compared with f a t a b s o r b a b i l i t y data. Results of t h i s experiment revealed t h a t i n the e a r l y stages of growth ( 3 - 6 weeks of age) the New Hampshires were s i g n i f i -c a n t l y s u p e r i o r to the B r o i l e r s and White Leghorns i n t a l l o w f a t absorption e f f i c i e n c y . Corn o i l was w e l l absorbed by a l l types of b i r d s . D i f f e r e n c e s i n d i e t a r y M. E. estimates were c l o s e l y a s s o c i a t e d w i t h d i f f e r e n c e s i n f a t a b s o r b a b i l i t y values and on 2 a 12% t a l l o w diet;, the R values computed on a w i t h i n age between breeds b a s i s were 0.67, 0.36 and 0.022 at 3, 5, and 9 weeks of 2 age r e s p e c t i v e l y . This general d e c l i n e i n R values was a r e -115 f l e c t i o n of the narrowing of the range of f a t a b s o r b a b i l i t y d i f -f e rences among the d i f f e r e n t types of b i r d s as they grew o l d e r . The o v e r a l l c o n c l u s i o n based on the r e s u l t s of t h i s experiment which demonstrated breed e f f e c t s and confirmed age e f f e c t s on a b s o r b a b i l i t y of f a t e s p e c i a l l y the s a t u r a t e d type, i s t h a t , breed and/or age d i f f e r e n c e s i n M. E. esti m a t e s are to a l a r g e e xtent a t t r i b u t a b l e t o breed and/or age d i f f e r e n c e s i n the ab-s o r b a b i l i t y of hig h energy d i e t a r y components ( L i p i d s ) . There-f o r e the subsequent experiments were devoted t o the search f o r an e x p l a n a t i o n f o r the breed d i f f e r e n c e s i n f a t a b s o r b a b i l i t y . R e s u l t s of the feed passage time experiment showed t h a t w h i le the e f f e c t of breed of b i r d s was not c o n s i s t e n t i n both t r i a l s , t h a t of d i e t a r y f a t was. In both t r i a l s , D i e t 1 (3% f a t ) , because of i t s f i b r o u s nature, had the s h o r t e s t passage time of any of the d i e t s ; and feed passage was c o n s i s t e n t l y s i g n i f i c a n t l y l o n g e r with the high f a t d i e t s (2 and 3). The o b s e r v a t i o n t h a t corn o i l and t a l l o w f a t had s i m i l a r e f f e c t s on f e e d passage time l e d to the c o n c l u s i o n t h a t i t i s the quan-t i t y and not the nature of d i e t a r y f a t t h a t i n f l u e n c e s r a t e of i n g e s t a passage. Lack of c o n s i s t e n t breed e f f e c t on fe e d pas-sage time coupled with the o b s e r v a t i o n t h a t s i g n i f i c a n t breed d i f f e r e n c e s i n f a t a b s o r b a b i l i t y d i d not c o i n c i d e with s i g n i f i -cant breed d i f f e r e n c e s i n feed passage time, r u l e d out any spec-u l a t i v e attempt t o use feed passage time d i f f e r e n c e s t o account f o r d i f f e r e n c e s i n f a t a b s o r b a b i l i t y among b i r d s used i n t h i s study. 116 On the b a s i s of t h e i r p a n c r e a t i c l i p a s e a c t i v i t y d e t e r -mined i n Experiment 3, the New Hampshires ranked f i r s t f o l l o w e d by B r o i l e r s and White Leghorns i n t h a t o r d e r . The d i f f e r e n c e s among them were however s t a t i s t i c a l l y not s i g n i f i c a n t . In Experiment 4, the response ( f a t a b s o r b a b i l i t y and feed e f f i c i e n c y ) to d i e t a r y supplementation of b i l e s a l t s by the New Hampshire, B r o i l e r and White Leghorn c h i c k s , was s t u d i e d i n order t o f i n d out whether or not the lower t a l l o w f a t a b s o r b a b i l i t y v a l u e s obtained with B r o i l e r and White Leghorn c h i c k s compared to the New Hampshires, might have been p a r t l y due t o the b i l e s a l t i n s u f f i c i e n c y i n the former type of c h i c k s . The r e s u l t s of t h i s experiment showed t h a t a d d i t i o n of sodium t a u r o c h o l a t e to a 12% t a l l o w d i e t improved the f a t a b s o r b a b i l i t y c o e f f i c i e n t s obtained with the B r o i l e r and the White Leghorn c h i c k s . The i n -crease i n net' f a t a b s o r b a b i l i t y v a l u e s when exogenous b i l e s a l t s were prese n t i n a 12% t a l l o w d i e t , was due t o a tremendous r e -d u c t i o n i n the amount of f e c a l soap f a t t y a c i d s . These r e s u l t s were rep e a t a b l e i n a separate but i d e n t i c a l experiment u s i n g t h i s time New Hampshire and B r o i l e r c h i c k s only. T h i s p r o v i d e d an i n -d i r e c t evidence t h a t i n the B r o i l e r and White Leghorn c h i c k s the supply of b i l e s a l t s was below the c r i t i c a l m i c e l l a r c o n c e n t r a t i o n r e q u i r e d f o r optimal t a l l o w f a t a b s o r p t i o n . Hofman (19 61) i n d i -c a t e d t h a t under normal i n t e s t i n a l c o n d i t i o n s , o r d i n a r y carboxy-l a t e soaps are not s u f f i c i e n t l y s o l u b l e t o form m i c e l l a r s o l u t i o n s and t h a t s o l u b i l i s a t i o n of soaps of s a t u r a t e d f a t t y a c i d s such as p a l m i t a t e begins a t a m i c e l l a r c o n c e n t r a t i o n much h i g h e r than t h a t 117 of the unsaturated f a t t y a c i d soaps. The o v e r a l l i n t e r p r e t a -t i v e i n f e r e n c e based on the r e s u l t s of t h i s experiment, i s t h a t , a d d i t i o n of b i l e s a l t s t o h i g h t a l l o w f a t d i e t s would be o f s i g n i -f i c a n t advantage to the B r o i l e r and White Leghorn c h i c k s f e e d i n g on such d i e t s . The search f o r an e x p l a n a t i o n of breed d i f f e r e n c e s i n t a l l o w f a t a b s o r b a b i l i t y among chickens was extended to a g e n e r a l study on f a t t y a c i d t r a n s p o r t p r o t e i n i n the i n t e s t i n e of the domestic chicken. T h i s study was s t i m u l a t e d by experimental r e s u l t s of Ockner and a s s o c i a t e s (19 72) which demonstrated the e x i s t e n c e of a s p e c i f i c f a t t y a c i d b i n d i n g p r o t e i n (FABP) and i t s i n v o l v e -ment i n the t r a n s p o r t of long chain f a t t y a c i d s i n the small i n -t e s t i n e o f the r a t . Using experimental procedures s i m i l a r to those o u t l i n e d by Ockner, ejt a l . , (1972), the e x i s t e n c e of a f a t t y a c i d b i n d i n g p r o t e i n (FABP) peak i n the mesenteric i n t e s t i n e of the a d u l t chickens and day o l d c h i c k s p r i o r to the i n g e s t i o n of any feed, was e s t a b l i s h e d i n the f i r s t s e r i e s of experiments of t h i s study. An assessment of the segmental d i s t r i b u t i o n of FABP, r e v e a l e d t h a t under c o n d i t i o n s of low d i e t a r y f a t i n t a k e , the r e -l a t i v e amount of t h i s p r o t e i n decreases p o s t e r i o r l y , which .is a r e f l e c t i o n o f the r o l e p l a y e d by the upper i n t e s t i n a l segments as compared t o the lower ones i n f a t a b s o r p t i o n p r o c e s s . However, ch r o n i c f e e d i n g of h i g h d i e t a r y f a t d i s t u r b e d t h i s p r o x i m a l - d i s t a l FABP c o n c e n t r a t i o n g r a d i e n t e s p e c i a l l y i n the b r o i l e r - t y p e chickens with r a t h e r low proximal i n t e s t i n a l FABP content compared to t h a t of the New Hampshires. T h e r e f o r e , the n o t i c e a b l e i n c r e a s e i n 118 FABP content of the lower s e c t i o n of the B r o i l e r gut was probably one of the major causes of the improvement i n f a t a b s o r b a b i l i t y v a l u e s . The observed i n c r e a s e i n i n t e s t i n a l FABP content with age e x p l a i n s a t l e a s t i n p a r t the age dependence of c h i c k s ' f a t absorp-t i v e c a p a c i t y . I t can t h e r e f o r e be concluded t h a t maturation o f the f a t a b s o r p t i v e machinery i n young b i r d s , i n v o l v e s , among other f a c t o r s the p r o d u c t i o n of g r e a t e r amounts of FABP, and t h a t exogenous b i l e s a l t s probably have both d i r e c t and i n d i r e c t e f f e c t s on the synthe-s i s o f FABP. F i n a l l y , c o - o r d i n a t i o n of the r e s u l t s of the d i f f e r e n t e x p e r i -ments c a r r i e d out i n course of t h i s r e s e a r c h , u s i n g the New Hamp-s h i r e , B r o i l e r and White Leghorn type of chickens, l e a d s to the con-c l u s i o n t h a t when c e r t a i n type o f f a t i s f e d a t hig h l e v e l s e s p e c i -a l l y d u r i n g the e a r l y preadaptive stages of growth, there i s a con-s i s t e n t l y demonstrable breed d i f f e r e n c e i n f a t a b s o r b a b i l i t y . I t appears t h a t s e v e r a l f a c t o r s i n c o n c e r t r a t h e r than a s i n g l e one, may be r e s p o n s i b l e f o r t h i s breed d i f f e r e n c e . In t h i s p r e s e n t study f o r example, the New Hampshires were s u p e r i o r t o B r o i l e r and/or White Leghorns i n f a t a b s o r b a b i l i t y and hence i n the o v e r a l l d i e t a r y energy m e t a b o l i s a b i l i t y because of t h e i r s l i g h t l y h i g h e r p a n c r e a t i c a c t i v i t y ; a p p a r e n t l y adequate b i l e s a l t supply (based on i n d i r e c t evidence) and an e a r l y comparatively h i g h i n t e s t i n a l content of the FABP t h a t p l a y s an important r o l e d u r i n g the f a t a b s o r p t i o n p r o c e s s . 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Wostmann. 196 8. E f f i c i e n c y of d i g e s t i o n i n germ-free and c o n v e n t i o n a l r a b b i t s . Br. J . Nutr., 22:723-737. Young, R. J . 1961. The energy value of f a t s and f a t t y a c i d s f o r c h i c k s . P o u l t r y S c i . , 40: 1225-1233. Young, R. J . , R. L. Ga r r e t and M. G r i f f i t h . 1963. F a c t o r s a f f e c t i n g the a b s o r b a b i l i t y o f f a t t y a c i d mixtures h i g h i n s a t u r a t e d f a t t y a c i d s . P o u l t r y S c i . , 42: 1146-1154. Zelenka, J . 196 8. I n f l u e n c e of the age of chi c k e n on the m e t a b o l i s a b l e energy val u e s of p o u l t r y d i e t s . B r i t . P o u l t . S c i . , 9: 135-142. A P P E N D I X T A B L E S A - G Table 1(A). Experiment 1. S t a t i s t i c a l analysis for comparing the average fat absorbability values (on a transformed scale) obtained with New Hampshires, B r o i l e r s and White Leghorns feeding on 12% tallow and/or corn o i l at 7 d i f f e r e n t ages. i) Analysis of Variance: Table of Mean Squares. A G E I N W E E K S 3 4 5 6 7 9 11 M E A N S Q U A R E S Source df Breed 2 0. * * * 82203 0 * * * . 50623 0 *** .29080 0 .01778* 0 NS .008175 0 .0181N S 0 .00116 N S Diet 1 1. * * * 6428 1 *** . 3400 0 * * * .40333 0 .04201* 0 *** .08333 0 ** .12813 0 ** * .078408 Breed x Diet 2 0. *** 3307 0 * * * .21863 0 .03463 N S 0 .00341 N S 0 .00 811 N S 0 NS .02123 0 NS .002558 Residual 6 0. 00282 0 .002479 0 .007133 0 .003075 0 .0020667 0 .00665 0 .0009083 *** Signigicant P=0.001 ** 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 NS Not s i g n i f i c a n t Table 1(A) cont. i i . Mean comparisons by Tukey t e s t at 5% p r o b a b i l i t y l e v e l . Ranked Means: 5, 6, 7, 9 and 11 weeks means f o r the d i e t s . W E E K S 5 6 7 9 11 12% 15% 12% 12% 12% 12% 12% 12% 12% 12% Tallow Corn o i l Tallow Corn o i l Tallow Corn o i l Tallow Corn o i l Tallow Corn o i l d i e t d i e t d i e t d i e t d i e t d i e t d i e t d i e t d i e t d i e t 9.30+ 9.66+ 9.76+ 9.88+ 9.70+ 9.87+ 9.65+ 9.86+ 9.65+ 9.81+ 0.33 0.17 0.102 0.042 0.09 0.014 0.144 0.054 0.036 0.036 b a b a b a b a b a Means + S. D. Conclusion (P=0.05) : Ranked Means: 5 and 6 weeks means f o r the breeds. W E E K S 5 New White New White Hampshires B r o i l e r s Leghorns Hampshires B r o i l e r s Leghorns Means + 9.79+.13 9.30+.32 9.35+.23 9.89+.068 9.76+.104 9.80+082 Conclusion i - 1 (P=0.05) : a b b a b ab o 141 Table 1(A) cont. i i ) Mean comparisons by Tukey t e s t at 5% p r o b a b i l i t y l e v e l . Ranked Means: 3 Weeks Breed x D i e t Mean Fat D i g e s t i b i l i t y V a l u e s 1 . B2 C2 C3 B3 A2 A3 8.10 8.42 9.15 9.42 9 .47 9.64 e d c b ab a Conclusion (P^0.05): Ranked Means: 4 Weeks Breed x D i e t Mean F a t D i g e s t i b i l i t y V alues. C o n c l u s i o n (P^0.05): C2 B2 C3 A2 B3 A3 8. 41 8.91 9.51 9.58 9.64 9 .76 c b a a a a Values are on a transformed s c a l e . A, B, C repr e s e n t New Hampshires, B r o i l e r s and White Leghorns r e s p e c t i v e l y and the accompanying number 2, 3 stand f o r d i e t s 2 (12% tallow) and 3 (12% corn o i l ) r e s p e c t i v e l y . 142 Table 11(A). Experiment 1. S t a t i s t i c a l a n a l y s i s t o t e s t f o r s i g n i f i c a n c e of d i f f e r e n c e s i n average feed e f f i c i e n c y v a l u e s ( u n i t s f e e d / u n i t gain) among treatments. i . A n a l y s i s of v a r i a n c e : Source of v a r i a t i o n df MS Breed D i e t Breed x D i e t R e s i d u a l 0.52527 89.281 =0.0005 0.10271 17.547 ^=0.001 4 0.031431 5. 343 ==0.01 0.0058833 i i . Mean comparison by Tukey t e s t a t 5% p r o b a b i l i t y l e v e l . Ranked Means: Breed x D i e t mean feed e f f i c i e n c y v a l u e s . Treatment combinations: A2 Means: C o n c l u s i o n : (P=0.05) B2 B3 A3 A l B l C3 C l C2 1.80 1.80 1.81 1.96 2.14 2.20 2.43 2.47 2.49 a a a ab be bed cd d d *A, B, C r e p r e s e n t New Hampshires, B r o i l e r s and White Leghorns r e s p e c t i v e l y and the f i g u r e s 1, 2 or 3 accompanying each l e t t e r stand f o r D i e t s 1 ( B a s a l ) , 2 (12% Tallow) and 3 (12% Corn o i l re spe c t i v e l y . 14 3 Table I I I (A). Experiment J:, S t a t i s t i c a l a n a l y s i s of c a l c u l a t e d performance i n d i c e s f o r New Hampshires, B r o i l e r s and White Leghorns. i . A n a l y s i s of va r i a n c e : Source of v a r i a t i o n df MS F P Breed 2 1.6560 884.50 ^0.0005 Diet 2 0.047217 25.219 ^0.0005 Breed x Diet 4 0.024633 13.157 ^0.001 Residual 9 0.0018723 i i ) Mean comparison by Tukey t e s t at 5% p r o b a b i l i t y l e v e l . Ranked Means: Breed x Diet mean performance i n d i c e s . Treatment combination: C2 C l C3 A l A3 A2 B l B2 B3 Means: 2.90 3.00 3.15 5.35 6.10 6.55 10.85 14.00 14.85 Conclusion: (P^0.05) d d d c c c b a a 144 Table IV (A). Experiment 1. S t a t i s t i c a l a n a l y s i s of metaboli-sable energy (M.E.) v a l u e s determined with New Hampshires, B r o i l e r s and White Leghorns a t 3, 5 and 9 weeks of age. i) A n a l y s i s of v a r i a n c e : Table of mean squares. A G E I N W E E K S 3 5 Source of v a r i a t i o n df M E A N S Q U A R E S *** ** *** B r e e d 2 82448.00 22746.00 40251.00 * * * * **** ***: D i e t 2 1215457.69 1554414.57 816297.27 Breed x D i e t 4 29927.00 13424.00 18776.00 Re s i d u a l 9 4446.20 3451.80 1439.50 * ** ^ ^  ^  ^  S i g n i f i c a n t P^0.0005 ic ~k ic S i g n i f i c a n t P^O.001 * * S i g n i f i c a n t P^O.01 * S i g n i f i c a n t P=^0.05 Table IV(A) cont. i i ) Mean comparison by Tukey Test a t 5% l e v e l of p r o b a b i l i t y . Ranked Means: 3 weeks Breed x D i e t subclass mean M. E. values ( c a l s / g dry feed) Treatment Combinations Means: C o n c l u s i o n : (P&0.05) C l B l A l B2 B3 C3 C2 A2 A3 2536 2538 2606 3006 3339 3360 3297 3478 3501 Ranked Means: 5 weeks Breed x D i e t s u b c l a s s mean M. E. values ( c a l s / g dry feed) Treatment Combinations: B l A l C l C2 C3 B2 B3 A2 A3 Means 2485 2522 2574 328.3 3354 3357 3423 3493 3540 C o n c l u s i o n : (P=0.05) c c c b ab ab ab ab a Ranked Means: 9 weeks Breed x D i e t s u b c l a s s mean M. E. values ( c a l s / g dry feed) Treatment Combinations: B l C l A l C2 C3 B2 B3 A2 A3 Means: 2713 2889 2973 3399 3416 3518 3546 3555 3598 C o n c l u s i o n : (P=0.05) d c c b b ab 146 Table 1(B). Experiment 2. S t a t i s t i c a l a n a l y s i s of feed passage data obtained with b i r d s at 5 weeks of age. i ) A n a l y s i s of variance of 5 weeks feed .passage time P =0.05 =0.0005 =0.001 Residual 81 0.0 89222 i i ) Mean comparison by Tukey t e s t at 1% l e v e l of p r o b a b i l i t y . Ranked Means: Breed x Diet mean feed passage time (hours). Treatment B l C l A l A2 A3 C2 C3 B3 B2 combination: Means 1:33 1:36 1:44 2:07 2:24 2:27 2:29 2:30 2:44 (hrs:mins.): Conclusion: d d cd be ab ab ab ab ab (P=0.01) Source of v a r i a t i o n df MS F Breed 2 0.23075 2.5863 Diet 2 6.7598 75.764 Breed x Diet 4 0.42596 4.7742 147 Table 11(B). Experiment 2. S t a t i s t i c a l a n a l y s i s of feed passage time data obtained w i t h b i r d s at 7 weeks of age. i ) A n a l y s i s of variance of 7 weeks feed passage time data. Source of v a r i a t i o n df MS F P Breed 2 0.84492 8.8305 ^0.001 Diet . 2 4.9562 51. 798 =^0.0005 Breed x Di e t 4 0.2378 2.4853 ^0.05 Residual 81 0.095682 i i ) Mean comparison by Tukey t e s t at 1% l e v e l of p r o b a b i l i t y . Ranked Means: Breed x Diet mean feed passage time (hours). Treatment A l C l B l A3 A2 B2 C3 C2 B3 combinations: Means: (hrs: mins.): 1:33 1:42 2:06 2:19 2:22 2:28 2:32 2:38 2:38 Conclusion: d cd be ab ab ab ab a a (P^O.01) 148 Table 1(C). Experiment 3. S t a t i s t i c a l analysis to compare pancreas weights and in v i t r o pancreatic lipase a c t i v i t y (mM o l e i c acid/g dry pancreatic powder) between New Hampshires, B r o i l e r s and White Leghorns. i) Analysis of variance: Table of mean squares Source of v a r i a t i o n df Pancreas Weight Lipase A c t i v i t y Breed Residual *** „^„NS 1.092 3.3258 21 0.0689 2.8486 ie ie ie S i g n i f i c a n t P^O.005 NS Not s i g n i f i c a n t i i ) Between breeds comparison by Tukey te s t at 5% l e v e l of p r o b a b i l i t y (pancreas weights) B r o i l e r s White Leghorns New Hampshires Means Conclusion (P^0.05): 4.91 3.24 2.98 149 Table I (D). Experiment 4. S t a t i s t i c a l a n a l y s i s o f feed e f f i c i e n c y d a ta. i ) A n a l y s i s o f v a r i a n c e Source of v a r i a t i o n df - MS Breed 1.2578 29.87 =0.0005 D i e t Breed x D i e t 3 6 0.5736 0.034617 13.62 0.822 =0.001 >0.5 R e s i d u a l 12 0.0421 i i ) Mean comparison by Tukey t e s t a t 5% l e v e l o f p r o b a b i l i t y . a) Between d i e t s comparions D i e t 1 D i e t 2 D i e t 3 D i e t 4 Means: 2.91 2.71 2.38 2.34 Concl u s i o n : (P<0.05) b) Between breeds comparisons New White Hampshires B r o i l e r s Leghorn Means: 2.71 2.15 2.90 C o n c l u s i o n : b a b (P<0.05) 1 5 1 Table I I (D). Experiment 4 . S t a t i s t i c a l a n a l y s i s o f body weight g a i n r e s u l t s . i ) A n a l y s i s o f v a r i a n c e Source of v a r i a t i o n df MS Breed 905.657 13.20 ^0.005 D i e t 2 7 9 3 . 6 7 4 0 . 7 3 ^ 0 . 0 0 5 Breed x D i e t 104.433 1.52 ^ 0 . 1 R e s i d u a l 12 58.598 i i ) Mean comparison by Tukey t e s t a t 5 % l e v e l o f p r o b a b i l i t y , a) Between d i e t s comparisons D i e t 1 D i e t 2 D i e t 3 D i e t 4 Means: 57.2 62.4 70.6 75.4 C o n c l u s i o n : c c d d (P<0.05) Table I I (D) cont. b) Between breeds comparisons New White Hampshires B r o i l e r s Leghorns Means: 40.7 C o n c l u s i o n : a (P<0.05) 114.9 b 43. / 1 5 3 Table I I I (D). Experiment 4 . S t a t i s t i c a l a n a l y s i s o f net f a t a b s o r b a b i l i t y data on a transformed s c a l e . i ) A n a l y s i s of v a r i a n c e : Table of mean squares Source o f v a r i a t i o n Breed D i e t Breed x D i e t R e s i d u a l df T r i a l One *** 0 . 8 2 3 8 0 . 3 6 9 7 0 . 0 2 4 8 NS 0 . 0 0 7 7 5 T r i a l Two 0 . 4 4 8 9 * * 0 . 4 2 0 3 0 . 0 1 5 1 NS 0 . 0 1 0 6 1 i i ) Mean comparison by Tukey t e s t a t 1% p r o b a b i l i t y l e v e l . a) Between d i e t s comparisons T r i a l One T r i a l Two D i e t 3 D i e t 4 D i e t 3 D i e t 4 Means: 8 . 9 8 9 . 3 4 9 . 1 1 9 . 4 8 C o n c l u s i o n : ( P < 0 . 0 1 ) Table I I I (D) cont. b) Between breeds comparisons T r i a l One  New Hampshires B r o i l e r s means: 9 . 6 3 9 . 0 0 C o n c l u s i o n : a b ( P < 0 . 0 1 ) T r i a l Two White New White Leghorns Hampshires B r o i l e r s Leghorns 8 . 8 3 9 . 7 0 9 . 2 5 8 . 9 2 155 Table IV (D). Experiment 4. S t a t i s t i c a l a n a l y s i s o f amounts of soap f a t t y a c i d s (mg/g dry feces) i ) A n a l y s i s of v a r i a n c e : Table of mean squares Source of v a r i a t i o n Breed D i e t Breed x D i e t df T r i a l One 150.684 155.993 * * * T r i a l Two 796.081 * * **** *** 574.083 833.333 173.6647 *** R e s i d u a l 7.151 6.952 i i ) Mean comparison by Tukey t e s t a t 5% p r o b a b i l i t y l e v e l Ranked means: Breed x D i e t s u b c l a s s means f o r T r i a l One Treatment Combinations Means: B 4 C4 A4 A3 B3 C3 2.60 6.10 17.90 20.60 20.70 26.80 C o n c l u s i o n : (P<0.05) 156 Table IV (D) cont. Ranked means: Breed x D i e t s u b c l a s s means f o r T r i a l Two. Treatment c 4 B 4 A 3 A 4 c 3 B 3 Combinations: Means: 2.10 4.80 9.85 10.40 18.45 39.00 C o n c l u s i o n : d d a a c b (P<0.05) Table I (E). S t a t i s t i c a l analysis of results of Experiment 8. i) Analysis of variance of FABP (mg/g intestine) at one week of age. Source df SS MS F P Breed 2 394.955 197.298 21.64 =0.005 Diet 2 60.560 30.560 3.35 =0.1 Breed x Diet 4 189.754 47.438 5.20 =0.05 Residual 6 64.709 9.118 i i ) Mean comparison by Tukey test at 5% level of probability a) Between breeds comparisons New Hampshires Broilers 'White Leghorns Means: 28.26 16.22 25.33 Conclusion: a b a (P40.05) 158 Table I (E) cont. i ) A n a l y s i s o f v a r i a n c e of FABP (mg/g i n t e s t i n e ) a t three weeks o f age. Source df SS MS F P Breed 2 48.483 24.242 14.72 ^0.005 D i e t 2 52.836 26.418 16.04 ^0.005 Breed x D i e t 4 15.123 3.781 2.29 ^0.5 R e s i d u a l 6 9.882 1.647 i i ) Mean comparison by Tukey t e s t a t 5% l e v e l o f p r o b a b i l i t y a) Between breeds comparisons New Hampshires B r o i l e r s White Leghorns Means: 23.99 20.22 20.13 Co n c l u s i o n : a b b (P<0.05) b) Between d i e t s comparisons B a s a l D i e t Tallow D i e t Corn O i l D i e t Means: 18.25 21.15 23.35 C o n c l u s i o n : c b a (P<0.05) 159 Table 1 (E) cont. i ) A n a l y s i s of v a r i a n c e of FABP (mg/g i n t e s t i n e ) a t 4 weeks c age. Source df SS MS F P Breed 2 23.951 11.976 1.55 >0.1 D i e t 2 34.317 17.158 2.22 >0.1 Breed x D i e t 4 2.192 0.548 0.071 >.0.25 Re s i d u a l 6 46 .394 '7.7 32 i ) A n a l y s i s of v a r i a n c e of FABP (mg/g i n t e s t i n e ) a t 5 weeks c age. Source df SS MS F P Breed 2 115.201 57.6005 5.285 4.0.05 D i e t 2 53.282 26.641 2.44 ;>0.1 Breed x D i e t 4 24 .145 6 .036 0.554 >0 .25 R e s i d u a l 7 76.276 10.897 i i ) Mean comparison by Tukey t e s t a t 5% l e v e l of p r o b a b i l i t y a) Between breeds comparisons New Hampshires B r o i l e r s White Leghorns Means: 36. 13 31.59 30.21 C o n c l u s i o n : a b b (P<0 .05) 1 6 0 Table I I (E) S t a t i s t i c a l a n a l y s i s f o r comparing the average f a t a b s o r b a b i l i t y values (on a transformed s e a l obtained w i t h d i f f e r e n t types of b i r d s i n E x p e r i ment 8 o f the FABP study. i ) A n a l y s i s of variance Source df MS F P Breed 2 0.26481 16.551 =0.005 Diet 1 0.61201 38.251 =0.001 Breed x Diet 2 0.29951 18.719 =0.005 Residual 11 0.016 i i ) Mean comparison by Tukey t e s t at 5% p r o b a b i l i t y l e v e l Ranked Means: Breed x Diet f a t a b s o r b a b i l i t y mean values Treatment Combinations: Means: Conclusion (P=0.05): B2 C2 B3 A2 C3 A3 8.47 9.22 9.45 9.49 9.54 9.54 b a a a a a 161 Table 1 (F) S t a t i s t i c a l a n a l y s i s of r e s u l t s of Experiment 9 of the FABP study. i) A n a l y s i s of v a r i a n c e : Table of mean squares. M E A N S Q U A R E S Proximal gut Lower gut Source df Weight: FABP content Weight FABP content Breed 1 132.031NS 181.261*** 306.281* 58.05* D i e t 1 1.531NS 32.808NS 13.781NS 19.69NS Breed x D i e t 1 0.152NS 19.69NS 24.852NS 1.54NS Re s i d u a l 4 24.454 4.457 23.119 6.36 * 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^0.005) NS Not S i g i f i c a n t 1 6 2 Table I (F) cont. i i ) Mean comparisons by " t " - t e s t at 5% l e v e l of p r o b a b i l i t y Proximal gut FABP content (mg/g tissue) New Hampshires B r o i l e r s Means: 22.63 13.11 Conclusion: a b (P=0.05) Lower gut weight (g) New Hampshires B r o i l e r s Means: 20.70 33.08 Conclusion: b a (P=0.05) Lower gut FABP content (mg/g t i s s u e ) New Hampshires B r o i l e r s 8 . 9 6 1 4 . 2 0 Means Conclusion: b a (P=0.05) 16 3 Table 1(G). Experiment 10. S t a t i s t i c a l a n a l y s i s of f a t ab-s o r b a b i l i t y values (on a transformed scale) ob-t a i n e d with New Hampshires and B r o i l e r s . i ) A n a l y s i s of v a r i a n c e : Table of mean squares Source of v a r i a t i o n df T r i a l One T r i a l Two Breed 1 0.18605* 0.06478* k k k ftf C Diet 1 0.63845 0.01531 k k k k Breed x d i e t 1 0.320 0.00911 Residual 4 0.0144 0.0013 * * * S i g n i f i c a n t P^O.005 k k S i g n i f i c a n t P^O.01 * S i g n i f i c a n t P^0.05 NS Not s i g n i f i c a n t 1 6 4 Table 1 (G) cont. i i ) Mean comparisons by Tukey te s t at 5 % p r o b a b i l i t y l e v e l . Ranked Means: Breed x Diet Mean Fat D i g e s t i b i l i t y Values T r i a l O n e T r i a l T w o Treatment B4 A4 A3 B3 Combina- 9 . 4 6 9 . 3 6 9 . 2 0 8 . 5 0 tion Conclusion: a (P=0.05) a a b a a a b 

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