UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Factors affecting the utilisation of dietary energy Kese, Adu Gyamfi 1977

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1977_A1 K48.pdf [ 6.6MB ]
Metadata
JSON: 831-1.0094218.json
JSON-LD: 831-1.0094218-ld.json
RDF/XML (Pretty): 831-1.0094218-rdf.xml
RDF/JSON: 831-1.0094218-rdf.json
Turtle: 831-1.0094218-turtle.txt
N-Triples: 831-1.0094218-rdf-ntriples.txt
Original Record: 831-1.0094218-source.json
Full Text
831-1.0094218-fulltext.txt
Citation
831-1.0094218.ris

Full Text

FACTORS AFFECTING THE UTILISATION OF DIETARY ENERGY by ADU GYAMFI KESE D.T.A. , U n i v e r s i t y o f S c i e n c e and T e c h n o l o g y , Kumas i , Ghana, 1961 B . S c , U n i v e r s i t y o f Rhode I s l a n d , K i n g s t o n , R. I . , U .S .A . , 1965 M . S c , U n i v e r s i t y o f Rhode I s l a n d , K i n g s t o n , R . I . , U.S .A. , 1967 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE -REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n THE FACULTY OF GRADUATE STUDIES Depar tment o f P o u l t r y S c i e n c e We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA F e b r u a r y , 1977 0 A d u Gyamfi K e s e , 1977 In presenting th is thesis in pa r t i a l fu l f i lment of the requirements for an advanced degree at the Univers i ty of B r i t i s h Columbia, I agree that the L ibrary shal l make it f ree ly ava i lab le for reference and study. I fur ther agree that permission for extensive copying of this thesis for scho lar ly purposes may be granted by the Head of my Department or by his representat ives. It is understood that copying or pub l i ca t ion of this thesis for f inanc ia l gain shal l not be allowed without my writ ten permission. Depa rtment The Univers i ty of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W.5 Date 4 --4'- 7 7 ABSTRACT Seven d i f f e r e n t but i n t e g r a t e d e x p e r i m e n t s were c o n d u c t e d t o s t u d y t he f a c t o r s a f f e c t i n g t he u t i l i s a t i o n o f d i e t a r y e n e r g y . The f i r s t two e x p e r i m e n t s i n v o l v e d f e e d i n g b r o i l e r c h i c k e n s d i e t s c o n t a i n i n g e i t h e r c o r n o i l o r c o r n s t a r c h as t h e s u p p l e m e n t a r y s o u r c e o f ene rgy a t two p r o t e i n l e v e l s . H e r r i n g meal was used i n a l l d i e t s because o f t h e h i g h b i o l o g i c a l v a l u e o f i t s p r o t e i n . A l l d i e t s were c a l c u l a t e d t o be i s o c a l o r i c and t o c o n t a i n t h e same b a l a n c e o f amino a c i d s ; m i n e r a l s and v i t a m i n s were added t o meet t h e r e q u i r e m e n t s f o r t h e s e n u t r i e n t s . L i v e w e i g h t g a i n and t h e e f f i c i e n c y o f f o o d u t i l i s a t i o n w i t h i n c a l o r i e : p r o t e i n r eg ime were n o t improved when f a t was s u b s t i t u t e d f o r s t a r c h i n i s o c a l o r i c d i e t s . The s u p e r i o r i t y o f t h e l o w - f a t h i g h - p r o t e i n d i e t i n p r o m o t i n g t h e h i g h e s t m e t a b o l i s a b i l i t y o f e n e r g y , q u e s t i o n s t he v a l i d i t y o f t h e c l a i m t h a t added d i e t a r y f a t has an " e x t r a - c a l o r i c " e f f e c t . B i r d s f e d t h e h i g h - f a t l o w - p r o t e i n d i e t w h i c h had a l o w e r c a l o r i e : p r o t e i n r a t i o , d e p o s i t e d more abdomina l a d i p o s e t i s s u e , i n d i -c a t i n g t h a t i n e v a l u a t i n g g rowth p e r f o r m a n c e , t h e b a l a n c e between ene r g y and p r o t e i n i s o f g r e a t e r s i g n i f i c a n c e than t he s o u r c e o f s u p p l e m e n t a r y e n e r g y . F o r m u l a t i o n o f i s o c a l o r i c d i e t s has n e c e s s i t a t e d t he i n c l u s i o n o f t h e s o - c a l l e d n u t r i t i o n a l l y - i n e r t i n g r e d i e n t s such as c e l l u l o s e . S i n c e t he d i e t s used t o t e s t t h e main h y p o t h e s i s o f " e x t r a - c a l o r i c e f f e c t s " a t t r i b u t a b l e t o d i e t a r y f a t i n c o r p o r a t e d c e l l u l o s e , t h e e f f e c t o f t he i i i l a t t e r on the p h y s i o l o g i c a l p a r a m e t e r s unde r s t u d y , was t e s t e d . A t h i g h l e v e l s o f i n c l u s i o n c e l l u l o s e d e p r e s s e d body w e i g h t g a i n . A d v e r s e e f f e c t s o f added d i e t a r y c e l l u l o s e on f o o d c o n v e r s i o n e f f i c i e n c y and ene r gy m e t a b o l i s a b i l i t y were a l s o e v i d e n t . A n o t h e r e f f e c t o f .added d i e t a r y c e l l u l o s e w h i c h i s p a r t i c u l a r l y i n t e r e s t i n g i s t h a t i t d e c r e a s e d abdom ina l a d i p o s e t i s s u e . R e s u l t s o f t h e above s t u d i e s have shown s i g n i f i c a n t d i f f e r e n c e s among the d i f f e r e n t t r e a t m e n t g roups i n body w e i g h t g a i n , e f f i c i e n c y o f f o o d u t i l i s a t i o n and m e t a b o l i s a b i l i t y o f ene r gy w i t h i n t he f i r s t t h r e e weeks p o s t h a t c h i n g . The p o s s i b i l i t y t h a t t h e r e s i d u a l y o l k may i n f l u e n c e t h e m e t a b o l i c p a r a m e t e r s i n q u e s t i o n was c o n s i d e r e d and t e s t e d . Ab sence o f t h e y o l k s a c , e x c i s e d s u r g i c a l l y , d i d n o t i n f l u e n c e t he p e r f o r m a n c e o f b i r d s on t h e b a s i s o f g rowth and ene r gy u t i l i s a t i o n as measured by body w e i g h t g a i n and m e t a b o l i s a b l e e n e r g y v a l u e s , r e s p e c t i v e l y . The r e s i d u a l y o l k d i d n o t i n f l u e n c e f o o d c o n v e r s i o n e f f i c i e n c y i n t he f i r s t and t h i r d weeks o f t h e e x p e r i m e n t a l p e r i o d . However , d e p r e s s i o n o f f o o d c o n v e r s i o n e f f i c i e n c y r e s u l t i n g f r om the remova l o f r e s i d u a l y o l k was f ound t o o c c u r i n t h e s econd week. I t was n o t e d t h a t b i r d s w i t h o u t r e s i d u a l y o l k r e t a i n e d a g r e a t e r amount o f n i t r o g e n compared t o b i r d s w i t h r e s i d u a l y o l k i n t he f i r s t week p o s t h a t c h i n g . The r e s i d u a l y o l k does n o t c o n t r i b u t e s i g n i f i c a n t l y t owa rd s t h e n o u r i s h m e n t o f t h e c h i c k i n t h e f i r s t week p o s t h a t c h i n g as e v i d e n c e d by t h e f a c t t h a t a b s t i n e n c e f r o m f o o d r e s u l t e d i n t h e d e a t h o f bo th t h e g roups r e t a i n i n g y o l k s a c s and t h o s e w i t h o u t y o l k s ac s a t a p p r o x i -m a t e l y t h e same t i m e . The p r e s e n c e o f a l a r g e b a c t e r i a l p o p u l a t i o n i n t h e a v i a n c a e c a 1 V and e x t r a p o l a t i o n o f t h e f e a t u r e s a s s o c i a t e d w i t h b a c t e r i a - h o s t s y m b i o s i s i n r u m i n a n t s and o t h e r a n i m a l s t o the d o m e s t i c c h i c k e n have l e d t o s p e c u l a t i o n t h a t t h e a v i a n c aeca p e r f o r m some c e l l u l o l y t i c and p r o t e o l y t i c f u n c t i o n s . The r e l e v a n c e o f t h e c o n c e p t o f c a e c a - m e d i a t e d n u t r i e n t u t i l i s a t i o n t o t h e t o p i c under s t u d y prompted an e x p e r i m e n t u s i n g i n t a c t and c a e c e c t o m i z e d c h i c k e n s t o i n v e s t i g a t e t h e e f f e c t o f t h e e x c i s i o n o f t h e c a e c a on the u t i l i s a t i o n o f d i e t a r y ene rgy and p r o t e i n . C a e c e c t o m i z e d and i n t a c t c o n t r o l New Hampsh i re c o c k e r e l s were f e d d i e t s used i n the p r e v i o u s s t u d i e s . M e t a b o l i s a b l e energy v a l u e s and u r i c a c i d e x c r e t i o n were used as t h e c r i t e r i a f o r m e a s u r i n g d i e t a r y ene rgy and p r o t e i n u t i l i s a t i o n . Caecectomy d i d no t a f f e c t t he m e t a b o l -i s a b i 1 i t y o f t h e d i e t s . Me tabo l i s a b i l i t y o f t h e d i e t i n c o r p o r a t i n g c o r n s t a r c h was more v a r i a b l e and s l i g h t l y l o w e r w i t h t h e c a e c e c t o m i z e d b i r d s . U r i c a c i d e x c r e t i o n was s i m i l a r f o r t h e c a e c e c t o m i z e d and t h e i n t a c t b i r d s . M a c r o s c o p i c and h i s t o l o g i c a l e x a m i n a t i o n o f s e c t i o n s o f t h e caeca r e v e a l e d t h a t r e g e n e r a t i o n o f t h e c aeca had o c c u r r e d i n f o u r c a e c e c t o m -i z e d b i r d s t h a t s u r v i v e d u n t i l a u t o p s y 85 weeks l a t e r . A l t h o u g h t h e o n s e t o f t h e r e g e n e r a t i o n o f t h e c a e c a was no t o b s e r v e d , i t wou l d appea r t h a t t he deg ree ( o r t h e ab sence ) o f r e g e n e r a t i o n o f t he caeca i n c a e c e c -t o m i z e d b i r d s may be r e s p o n s i b l e f o r t h e d i s c r e p a n c i e s i n t h e f i n d i n g s r e p o r t e d w i t h such b i r d s . V TABLE OF CONTENTS Page ABSTRACT TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES/PLATES ACKNOWLEDGEMENTS Chapter 1 GENERAL INTRODUCTION - 1 2 REVIEW OF LITERATURE 3 2.1 The U t i l i s a t i o n of Energy from Alternate Sources . 3 2.1.1 H i s to r i ca l perspective on energy u t i l i s a t i o n 3 2.1.2 Effect of dietary source of energy on the performance of poultry 3 2.1.2.1 Dietary source of energy 3 2.1.3 Fat as a dietary source of energy 5 2.1.3.1 Fat d i g e s t i b i l i t y and absorbabi l i ty 7 2.1.4 The spec i f i c e f fect of dietary fat on growth rate 8 2.1.5 The importance of nutr ient balance 9 2.1.5.1 Calor ie:prote in ra t i o 9 2.1.5.2 Calorie-nitrogen storage re lat ionship 10 2.1.5.3 Implications of changing nutr ient proportions 10 2.1.5 Protein-carbohydrate interactions 11 2.1.7 Prote in- fat interact ions 12 2.1.8 Fish meal qua l i ty 13 2.1.9 Effects of dietary factors on body composition 14 2.1.10 Effects of ce l lu lo se on metabol i sab i l i ty 15 2.1.11 Species, breed, s t ra in and sex ef fect on energy metabolism 17 2.2 The Avian Caeca and Ef f ic iency of U t i l i s a t i o n of Dietary Protein and Energy 18 2.2.1 Overview 18 2.2.2 Carbohydrate and crude f i b re d i g e s t i b i l i t y 18 2.2.3 Protein d i g e s t i b i l i t y and u t i l i s a t i o n 20 2.2.4 Absorption of nutrients 21 2.2.5 Uric acid production 22 3 PART 1. THE EFFECT OF SUBSTITUTION OF FAT FOR STARCH ON THE PERFORMANCE OF BROILERS 24 i i v vi i i x xi v i Page 3.1 Experiments 1 and 2 24 3.1.1 I n t roduct ion 24 3.1.2 Ma te r i a l s and methods 25 3.1.2.1 Experiment 1 27 3.1.2.2 Experiment 2 27 3.1.3 Experiment 1 - Resu l t s 29 3.1.4 - D i scus s ion 38 3.2.1 Experiment 2 - Resu l t s 42 3.2.2 - D i scus s ion 47 3.3 The E f f e c t of Added C e l l u l o s e on the Performance of B r o i l e r Chicks 51 3.3.1 Experiment 3 - I n t roduc t i on 51 3.3.2 - M a t e r i a l s and methods 52 3.3.3 - Resu l t s 55 3.3.4 - D i scus s ion 67 3.4 The E f f e c t of Residual Yolk on the Performance of Chicks 70 3.4.1 Experiments 4 and 5 70 3.4.1.1 I n t r oduc t i on 70 3.4.2 Experiment 4 - M a t e r i a l s and methods 72 3.4.3 - Resu l t s 75 3.4.4 - D i scus s ion 83 3.5 The E f f e c t of Res idual Yolk on Su rv i va l of Chicks 86 3.5.1 Experiment 5 - I n t roduc t i on 86 3.5.2 - M a t e r i a l s and methods 86 3.5.3 - Resu l t s 86 3.5.4 - D i scus s ion 90 3 PART 2. THE AVIAN CAECA AND EFFICIENCY OF UTILISATION OF DIETARY ENERGY AND PROTEIN 91 3.6 The Role of the Caeca i n Energy and P ro te i n Metabol ism 91 3.6.1 Experiment 6 - I n t roduc t i on 91 3.6.2 - M a t e r i a l s and methods 93 3.6.3 - Resu l t s 98 3.6.4 - D i scus s ion 105 3.7 Regrowth of the Avian Caeca Fo l lowing Caecectomy 108 3.7.1 Experiment 7 - I n t r oduc t i on 108 3.7.2 - M a t e r i a l s and methods 110 3.7.3 - Resu l t s 110 3.7.4 - D i scus s ion 115 v i i Page 4 GENERAL SUMMARY AND CONCLUSIONS 118 5 REFERENCES 125 v i i i L I ST OF TABLES T a b l e Page 1 C o m p o s i t i o n o f e x p e r i m e n t a l d i e t s i n E x p e r i m e n t s 1 and 2 26 2 E f f e c t o f d i e t a r y f a t and p r o t e i n l e v e l s on body w e i g h t g a i n s i n E x p e r i m e n t 1 30 3 E f f e c t o f d i e t a r y f a t and p r o t e i n l e v e l s on w e e k l y body w e i g h t g a i n 32 4 E f f e c t o f d i e t a r y f a t and p r o t e i n l e v e l s on f o o d c o n v e r s i o n e f f i c i e n c y 33 5 P r o t e i n c o n v e r s i o n e f f i c i e n c y 36 6 E f f e c t o f d i e t a r y f a t and p r o t e i n l e v e l s on m e t a b o l i s a b i l i t y o f ene rgy 43 7 E f f e c t o f f a t and p r o t e i n l e v e l s on mean abdomina l a d i p o s e t i s s u e w e i g h t 44 8 M e t a b o l i s a b l e ene r gy i n t a k e p e r gram body w e i g h t g a i n 46 9 C o m p o s i t i o n o f d i e t s f e d i n E x p e r i m e n t s 53 10 E f f e c t o f s o u r c e o f s u p p l e m e n t a r y d i e t a r y ene r gy and c e l l u l o s e on t o t a l body w e i g h t g a i n 56 11 E f f e c t o f s o u r c e o f s u p p l e m e n t a r y d i e t a r y ene r g y and c e l l u l o s e on w e e k l y body w e i g h t g a i n 57 12 E f f e c t o f s o u r c e o f s u p p l e m e n t a r y d i e t a r y ene rgy and c e l l u l o s e on f o o d c o n v e r s i o n e f f i c i e n c y 60 12a E f f e c t o f s o u r c e o f s u p p l e m e n t a r y d i e t a r y ene r gy w i t h o u t c e l l u l o s e component on f o o d c o n v e r s i o n e f f i c i e n c y 61 13 E f f e c t o f s o u r c e o f s u p p l e m e n t a r y d i e t a r y ene r gy and c e l l u l o s e on m e t a b o l i s a b l e ene rgy v a l u e s 63 14 E f f e c t o f s o u r c e o f s u p p l e m e n t a r y d i e t a r y ene r g y and c e l l u l o s e on mean m e t a b o l i s a b l e ene r g y v a l u e s 64 15 E f f e c t o f s o u r c e o f s u p p l e m e n t a r y ene r gy and c e l l u l o s e on f i n a l ( s i x - w e e k ) a d i p o s e t i s s u e w e i g h t s 66 16 C o m p o s i t i o n o f e x p e r i m e n t a l d i e t - E x p e r i m e n t 4 74 i x Tab l e Page 17 E f f e c t o f r e s i d u a l y o l k on w e e k l y body w e i g h t s and t o t a l body w e i g h t g a i n . 76 18 E f f e c t o f r e s i d u a l y o l k on f o o d c o n v e r s i o n e f f i c i e n c y 78 19 E f f e c t o f r e s i d u a l y o l k on m e t a b o l i s a b l e ene r gy v a l u e s 80 20 E f f e c t o f y o l k sac on t h e s u r v i v a l o f c h i c k s 87 21 C o m p o s i t i o n o f d i e t s f e d t o i n t a c t and c a e c e c t o m i z e d c h i c k e n s 96 22 M e t a b o T i s a b l e ene rgy v a l u e s o f d i e t s ( c o r r e c t e d f o r n i t r o g e n r e t e n t i o n ) 99 23 U r i c a c i d c o n c e n t r a t i o n i n e x c r e t a 100 24 A p p a r e n t n i t r o g e n a b s o r p t i o n e x p r e s s e d as a p e r c e n t a g e o f n i t r o g e n i n g e s t e d 101 25 Body w e i g h t g a i n s o f i n d i v i d u a l c h i c k e n s 103 26 B a c t e r i a l c o n t e n t o f e x c r e t a o f i n d i v i d u a l c h i c k e n s , p e r c e n t on a d r y m a t t e r b a s i s 104 27 L e n g t h o f i n t a c t and reg rown caeca 113 X LIST OF FIGURES AND PLATES F i g u r e / P l a t e Page 1 E f f e c t o f d i e t a r y f a t and p r o t e i n l e v e l s on body w e i g h t 31 2 E f f e c t o f d i e t a r y f a t and p r o t e i n l e v e l s on f o o d c o n v e r s i o n e f f i c i e n c y ( c u m u l a t i v e ) 35 3 E f f e c t o f s o u r c e o f s u p p l e m e n t a r y d i e t a r y ene r gy and added c e l l u l o s e on body w e i g h t g a i n 58 4 E f f e c t o f s o u r c e o f s u p p l e m e n t a r y d i e t a r y ene rgy and c e l l u l o s e on f o o d c o n v e r s i o n e f f i c i e n c y 62 5 E f f e c t o f s o u r c e o f s u p p l e m e n t a r y d i e t a r y ene r g y and c e l l u l o s e on m e t a b o l i s a b l e ene r g y v a l u e s 65 6 E f f e c t o f r e s i d u a l y o l k sac on t o t a l body w e i g h t 77 7 E f f e c t o f r e s i d u a l y o l k on c u m u l a t i v e f o o d c o n v e r s i o n e f f i c i e n c y 79 8 E f f e c t o f r e s i d u a l y o l k on a p p a r e n t n i t r o g e n r e t e n t i o n 82 9 E f f e c t o f r e s i d u a l y o l k on t he l i v a b i l i t y o f s t a r v e d c h i c k s 89 10 Regrown c a e c a f r o m 85 week o l d c h i c k e n s 111 11 Regrown c a e c a f r om c a e c e c t o m i z e d c h i c k e n and caecum f r om u n o p e r a t e d c h i c k e n 112 12 T r a n s v e r s e s e c t i o n t h r o u g h t h e mid -caecum 114 x i ACKNOWLEDGEMENTS Th roughou t t h e c o u r s e o f t h i s g r a d u a t e programme, I was f o r t u n a t e t o r e c e i v e t h e a d v i c e and encouragement o f many p e o p l e . P r o f e s s o r B.E. M a r c h , my r e s e a r c h s u p e r v i s o r , d e s e r v e s s p e c i a l t hank s f o r t h e g u i d a n c e and s u p p o r t e x t e n d e d t o me d u r i n g t he c o u r s e o f t h i s s t u d y and i n t h e p r e p a r a t i o n o f t h i s m a n u s c r i p t . 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 e x t e n d e d t o members o f my t h e s i s c o m m i t t e e : D r s . D.B. B r a g g , T . L . C o u l t h a r d , W.E. K i t t s and M. T a i t , f o r h e l p g i v e n me i n d i v e r s e f o r m s . The u n f a i l i n g encouragement o f P r o f e s s o r J . B i e l y i s g r a t e f u l l y acknowledged-. G r a t i t u d e i s e x t e n d e d t o t he U n i v e r s i t y o f S c i e n c e and T e c h n o l o g y , Kumas i , Ghana, f o r a generous s t u d y l e a v e and f i n a n c i a l s u p p o r t . The f i n a n c i a l a s s i s t a n c e o f t he Canad i an I n t e r n a t i o n a l Deve lopment Agency i s a l s o g r a t e f u l l y a c k n o w l e d g e d . I w o u l d l i k e t o t hank my w i f e , A f u a N y a r k o , my f a m i l y and o t h e r dependen t s and the e l d e r s and p e o p l e o f A k y e r e n s u a f o r t h e i r a c c e p t a n c e o f h a r d s h i p s and d e p r i v a t i o n s d u r i n g my e x t e n d e d s t a y i n Canada. I t i s my p l e a s u r e t o i n c l u d e a n o t e o f a p p r e c i a t i o n t o Mrs . B a r b a r a T a i t f o r h e r h e l p i n t h e p r e p a r a t i o n o f t h e s e c t i o n s f r o m t h e c a e c a and t h e t e c h n i c a l s t a f f and f a rm o p e r a t o r s f o r s e r v i c e s so o f t e n and c o n g e n i a l l y r e n d e r e d . To a l l t h o s e p e o p l e who h e l p e d me w i t h t h i s p r o j e c t and whose names have been o m i t t e d i n a d v e r t e n t l y o r o t h e r w i s e , I e x t e n d a p p r e c i a t i v e t h a n k s . 1 1. GENERAL INTRODUCTION Energy u t i l i s a t i o n has a c e n t r a l r o l e i n t h e e f f i c i e n c y o f n u t r i e n t m e t a b o l i s m . A c c u m u l a t i n g e v i d e n c e i n d i c a t e s t h a t t h e s o u r c e and l e v e l o f d i e t a r y ene rgy i n f l u e n c e t h e e f f i c i e n c y o f u t i l i s a t i o n o f e n e r g y . C a r b o h y d r a t e s and f a t s a r e t h e p r i n c i p a l and most economic s o u r c e s o f d i e t a r y ene rgy w i t h c a r b o h y d r a t e s b e i n g t h e d i e t a r y ene rgy s o u r c e used more e x t e n s i v e l y . T h i s t r e n d , however , i s c h a n g i n g i n t he l i g h t o f t h e w i d e s p r e a d and c o n s i s t e n t o b s e r v a t i o n t h a t i t i s p o s s i b l e t o o b t a i n e x c e l l e n t p e r f o r m a n c e f r o m c h i c k e n s f e d d i e t s c o n t a i n i n g h i g h f a t l e v e l s . The i n d i c a t i o n s a r e t h a t t he s u b s t i t u t i o n o f f a t f o r g l u c o s e c a l o r i e s p roduces an e n e r g e t i c e f f e c t h i g h e r t han can be a c c o u n t e d f o r by t h e c a l o r i c c o n t e n t o f t h e e n e r g y - y i e l d i n g components o f t h e d i e t . N e a r l y a l l o f t h e s i g n i f i c a n t d a t a a v a i l a b l e on t he " e x t r a - c a l o r i c " e f f e c t a t t r i b u t a b l e t o t he a d j u s t m e n t o f n u t r i e n t r a t i o s by means o f d i e t a r y f a t , have c o n c e r n e d t u r k e y s and c a t e g o r i e s o f c h i c k e n s o t h e r t h a n b r o i l e r s . S i n c e s p e c i e s , b r e e d , s t r a i n and even i n d i v i d u a l d i f f e r e n c e s a r e known to e x e r t s i g n i f i c a n t o r marked d i f f e r e n c e s on v a r i o u s p h y s i o l -o g i c a l phenomena, ou r g e n e r a l u n d e r s t a n d i n g o f t he u t i l i s a t i o n o f ene rgy by p o u l t r y may w e l l be a v e r y r e s t r i c t e d one i n d e e d . The work to be r e p o r t e d h e r e i n was, t h e r e f o r e , c a r r i e d out as a c o n t r i b u t i o n toward s t h e advancement o f t h e s t a t e o f knowledge o f n u t r i t i o n w i t h r e g a r d t o t h e e f f e c t s , o f t h e a d j u s t m e n t o f n u t r i e n t r a t i o s on the. e f f i c i e n t u t i l i s a t i o n o f ene r gy by b r o i l e r c h i c k e n s . The s p e c i f i c o b j e c -t i v e s o f t h e r e s e a r c h we re : To determine the e f f e c t of d i e t a r y f a t on the performance of b r o i l e r ch i ckens , To determine the e f f e c t of added c e l l u l o s e in d i e t s i n co rpo ra t i ng vary ing l e v e l s of d i e t a r y f a t on energy metabol ism, To determine whether the yo l k s a c i n f l uence s energy metabolism i n the e a r l y l i f e of the ch i c ken , and To determine the r o l e of the caeca on energy and p r o t e i n metabol i sm. 3 2. LITERATURE REVIEW 2.1 The U t i l i s a t i o n o f Energy f rom A l t e r n a t e Sou r ce s 2.1.1 H i s t o r i c a l p e r s p e c t i v e on ene r g y u t i l i s a t i o n The c e n t r a l i m p o r t a n c e o f ene rgy m e t a b o l i s m i n t h e economy o f n u t r i -e n t u t i l i s a t i o n has been r e c o g n i z e d f o r a l o n g t i m e , as has been t he i n f l u e n c e o f t h e s o u r c e o f ene r gy on t h e e f f i c i e n c y o f m e t a b o l i s a b l e ene rgy u t i l i s a t i o n . C u r r e n t l y , m e t a b o l i s a b l e ene rgy v a l u e s a r e p o p u l a r among t h e c o n s u l t i n g n u t r i t i o n i s t s ( V o h r a , 1 972 ) , because where use i s made o f compute r f o r m u l a t i o n o f l e a s t c o s t p o u l t r y d i e t s , t h e i n c l u s i o n o r r e j e c t i o n o f a p a r t i c u l a r f e e d i n g s t u f f i s g r e a t l y dependent on t h e metabo l i c a l l y u s e f u l ene rgy v a l u e s (De G r o o t e e_t a]_., 1 971 ) . 2 .1 .2 E f f e c t o f d i e t a r y s o u r c e o f e n e r g y on t he p e r f o r m a n c e o f p o u l t r y 2 .1 .2.1 D i e t a r y s o u r c e o f ene r gy C a r b o h y d r a t e s and f a t s a r e t he p r i m a r y e n e r g y - c o n t a i n i n g m a c r o -n u t r i e n t s used i n p o u l t r y f o r m u l a t i o n s w i t h t he f o r m e r b e i n g t h e d i e t a r y s o u r c e more w i d e l y used f o r t h e pu rpo se o f s u p p l y i n g e n e r g y . I t a p p e a r s , however , t h a t t he body does not r e q u i r e c a r b o h y d r a t e o r f a t per se f o r the s u p p l y o f ene rgy but r a t h e r compounds such as g l y c e r o l and amino a c i d s o r p r e c u r s o r s o f compounds c a p a b l e o f b e i n g o x i d i z e d f o r e n e r g y . When soyabean o i l f a t t y a c i d s were i n c l u d e d i n a c a r b o h y d r a t e -f r e e d i e t f o r c h i c k s , g rowth r a t e and f o o d con sumpt i on were s e v e r e l y d e p r e s s e d d e m o n s t r a t i n g t h a t t h e g l y c e r o l m o i e t y o f t h e f a t i s e s s e n t i a l f o r f a t t y a c i d u p t a k e and u t i l i s a t i o n i n t h e ab sence o f c a r b o h y d r a t e ( H i l l and B r a m b i l l a , 1965; A l l r e d , 1 969 ) . T h i s f i n d i n g forms t h e b a s i s 4 of the wel1-documented fact that the use of either carbohydrate or fa t in the form of t r i g l yce r ides as the exclusive source of non-protein energy does not resu l t in depressed growth or impaired e f f i c iency of . feed u t i l i s a t i o n . Accumulating evidence in the l i t e r a t u r e shows that "carbohydrate-f ree " d iets or diets in which the source of non-protein ca lor ies is pre-dominantly f a t , have produced favourable growth response. Donaldson et a l . (1 957) and Rand et al_. (1958) showed that the chick can use high levels of fa t as a source of energy. The l a t t e r workers reported that the subst i tut ion of f a t ca lor ies for glucose ca lor ies resulted in improved weight gains and greater protein and energy u t i l i s a t i o n . Ev i -dence presented by Begin (1961) indicated that carbohydrate energy can be replaced ca lo r ie for ca lo r ie by f a t . S imilar results were obtained with growing turkeys by Yacowi tz et al_. (1956), Waibel (1958), Touchburn and Naber (1 966), and Jensen et al_. (1970). Forbes et al_. (1946), French et. a_l_. (1948), and Swift and Black (1949) demonstrated s imi lar physiological response in rats . No adverse effects were noted in the growth rate, feed conversion e f f i c iency and nitrogen retention of chicks (Renner and Elcombe, 1964, Renner, 1964) and rats (Dror et al_., 1 973) when fat supplied p r a c t i c a l l y a l l the non-protein ca lo r i e s . Favourable growth response has been shown also in chicks fed diets in which a l l the non-protein ca lor ies were supplied.by glucose (Donaldson, 1964). However, in the work c i ted above, chicks fed " f a t - f r e e " d iets oxidized fa t ty acid maximally at one day of age with the a b i l i t y to oxidize fa t ty acid decl in ing with age. While carbohydrates have been the dominant source of dietary energy and can e f fec t i ve l y replace fats in th i s regard, i t i s evident that under 5 certa in conditions at least , the energy needs can be more e f f i c i e n t l y met by supplying a part of the food energy in the more concentrated form of f a t . The interest being currently shown in the incorporation of fa t into the diets of poultry attests to the v a l i d i t y of the above statement. 2.1.3 Fat as a d ietary source of energy . . The concept on quantitat ive use of fat as dietary source of energy has undergone extensive rev i s ion. Recent advances in nutrient metabolism have changed the view from one suggesting minimal use of dietary fat on account of i t s reported interference in the d igest ion, absorpt ion ' and normal metabolism of other nutrients to that recommending the i n c l u -sion of fa t in the d iet in substantial amounts for improved e f f i c iency of u t i l i s a t i o n of other nutr ients. Vermeersch and Vanschoubroek (1968) carr ied out a comprehensive review on the subject of fat supplementation to poultry diets in an •attempt to establ i sh a quant itat ive e f fect of increasing levels of various fats on the performance of chicks. As a resu l t of a detai led analysis of the data in the l i t e r a t u r e these authors reported that the fats studied: soyabean o i l , soyabean soap-stock, maize o i l , la rd and ta l low, were s imi lar in their effects on food consumption. The food consumption decreases s i gn i f i c an t l y with r i s i ng percentages of dietary fats according to a l inear function. No d i f f e r -ences were noted with regard to kinds of fa t on food consumption. While the incorporation of 2 to 20% of fats in the diets of growing chicks was found to improve body weight gain, there was absence of a re lat ionsh ip 6 between body weight gain and the level of dietary f a t . A cor re lat ion was shown between e f f i c iency of food conversion and the kind and level of f a t : here the improvement is correlated with the level of fa t added - the higher the level of f a t , the better the e f f i c -iency of food conversion. Regarding the kind of f a t , the degree of improvement in the e f f i c iency of food conversion was, in an ascending order: ta l low, l a rd , grease, maize o i l , soyabean soapstock and soyabean o i l . The general conclusion from the review which covered 60 papers spanning the years 1954 to 1966 was that the incorporation of fat in poultry d iets results in a decrease in food consumption and in an improve-ment in the e f f i c iency of food conversion. The review by Herstad (1970) encompassing 15 papers covering fat supplements in b ro i l e r diets confirmed the features established by Vermeersch and Vanschoubroek (1968). The various fats studied increased the rate of gain of b ro i l e r s . The f i r s t 3% of soyabean o i l or grease increased feed consumption; more than 3% fat in the d iet decreased food consumption, although metabolisable energy consumption increased. The increase in consumption of food which incorporated certain fats was attr ibuted to the poor d i g e s t i b i l i t y of the part icu lar fa t s . Vanschoubroek et_ aj_., 1971, reported studies on the comparison of the ef fect of certa in fat on the performance of b ro i le r chicks. Soya-bean o i l included at a level of 4.5% of the d iet improved feed conversion by 4.5% over lard to 4 weeks and by 3.3% to 8 weeks, in agreement with the results previously calculated by Vermeersch and Vanschoubroek (1968) using data from the l i t e r a t u r e . 7 2.1.3.1 Fat d i g e s t i b i l i t y and absorbabi l i ty Poor d i g e s t i b i l i t y and absorbabi l i ty mainly account for the avoid-ance or the inclus ion at a minimal level of fat in poultry diets in the early days. A change or reversal in the att i tude of nu t r i t i on i s t s occurred as a resu l t of remarkable nut r i t iona l advances made in the ensuing years. The metabolisable energy content of a fat is the product of i t s gross energy content and i t s absorbabi l i ty (Whitehead and Fisher, 1975). Several factors are now known to a f fect the d i g e s t i b i l i t y and absorb-a b i l i t y of fa t s . These factors include the type, melting point, f a t t y acid p r o f i l e , and the structure of the t r i g l ycer ides ( i . e . chemical char-a c te r i s t i c s ) of f a t ; the number of fats in the d iet (Young, 1961), the nature of the basal d i e t , the level of contamination of the environment by microorganisms, the level of i n tes t ina l bacteria and the age of the birds. In general, vegetable o i l s with high levels of unsaturated fa t ty acids are more completely digested than animal fa t s . The difference in u t i l i s a t i o n between fats which contain s imi la r levels of fa t ty acids may be attr ibuted to the difference in the d i s t r i bu t i on of fa t ty acids on the t r i g l yce r ide s of the fats concerned (Renner and H i l l , 1960; Mattson, 1967). Young et_ al_. (1963) found that the absorption of lard fa t ty acids was greater when fed in a d iet containing 28 or 30% protein as compared to a 24% protein d ie t . An improvement was observed in the d i g e s t i b i l i t y of fat in four week old chicks fed an t ib i o t i c s (Young et_ aj_., 1963). Supplee (1960) observed a 20% growth response when 13.3% corn o i l was added to the d iet in the presence of 50 mg of oleandomycin phosphate per kg of d i e t , but only a 10% increase in growth in i t s absence. 0 8 Results published by Mattson (1967) of a study on the ef fect of diet on the bacteria found in the in tes t ina l t ract of rats showed that the addition of an t i b i o t i c s reduced caecal coliforms 50 times and to ta l aerobes approximately three times. Cleanliness of chick batteries (Donaldson, 1962) and laboratory (Young et al_., 1963) has been mentioned as a factor a f fect ing the u t i l i s a t i o n of f a t s . These reports suggest that the u t i l i s a t i o n of f a t may be enhanced by cont ro l l ing the level of con-tamination of the environment by microorganisms or the balance of intes -t i na l microf lora. Variations in these factors may account for some of the var iat ion in response to fa t as reported in the l i t e r a t u r e (Salmon, 1972). 2.1.4 The spec i f i c e f fect of dietary fat on growth rate The improvement in growth rate and e f f i c iency of food u t i l i s a t i o n resu l t ing from feeding high levels of f a t to poultry has led to the recognition of f a t as having an " e x t r a - ca l o r i c " ef fect (Touchburn and Naber, 1966; Jensen e_t al_., 1970). Donaldson (1966) explained that i f the tota l energy avai lable for t issue synthesis were s imi lar for chicks fed both f a t and " f a t - f r e e " d i e t s , the fa t - fed chicks would have the advantage of not having to synthesize t issue fa t ty acids and thus might have r e l a t i v e l y more energy ava i lable for t issue protein synthesis. Marion and Edwards (1963) stated a s imi lar hypothesis and referred to the amino-acid-sparing e f fect of dietary f a t . 9 2.1.5 The importance of nutr ient balance The myriad of problems associated with feeding diets containing par t i cu la r nutrients in excess of normal concentrations, could be a t t r i b -uted largely to improper balance resu l t ing from such processes. Studies on the re lat ionsh ip of proportions of dietary nutrients to the overall e f f i c iency of u t i l i s a t i o n of nutrients have made i t increasingly clear that nutr ient metabolism i s affected not only by the composition of indiv idual feedingstuffs but also by the tota l composition of the d i e t . Studies in this area have stressed the importance of balancing nutrients in re lat ion to the energy level and amino acid balance. The work of Biely and March (1954), Munro and Wikramanayake (1954), Thomson and Munro (1955), Munro et al_. (1959), contributed towards the develop-ment of the concepts that interact ion existed between dietary protein, carbohydrate and fat and that dietary carbohydrate "spared" the protein of the d iet by increasing the nitrogen balance of the animal in a pos it ive d i rec t ion . Annison (1971) suggested imbalances in ra t io s between essential amino acids and energy, inadequate consumption of vitamins or trace elements, or' the occurrence of toxic factors in fats as factors respon-s ib le for the poor results experienced by some investigators who fed d ie t s , the energy of which was large ly contributed by fa t to poultry. 2.1.5.1 Calor ie:protein ra t io The cruc ia l role of the ra t i o ex i s t ing between energy and protein in poultry nu t r i t i on was demonstrated by B ie ly and March (1954) who showed that supplementation with fat increased the level of protein 10 necessary for maximum growth of both chicks and poults. This f inding was confirmed by Waibe.l (1958). Donaldson et al_. (1955.) showed.that the r a t i o of energy to protein in the d iet influenced the ca lo r i c intake, feed e f f i c i ency , growth rate and carcass fa t and that further widening of the ca lor ie :prote in ra t i o resulted in impaired growth and increased fat deposition of b ro i l e r chickens. March and Bie ly (1972) showed that the optimum dietary level of e f fect i ve protein is dependent upon the combined energy input from envir-onmental temperature and dietary metabolisable energy and.that increased energy in the form of e ither heat or dietary metabolisable energy is responsible for aggravating the depressing ef fect of dietary amino acid imbalance on feed consumption and growth rate. 2.1.5.2 Calor ie-nitrogen storage re lat ionsh ip Ahrens et al_. (1966) showed that for young rats fed two levels of ca lo r i e intake, there were higher nitrogen gains when rats in the high ca lo r ie group received the nitrogen as casein rather than as a mixture of amino acids simulating casein. This ef fect was not shown in rats of the same age fed diets providing s imi la r nitrogen intakes at a lower ca lo r i e l e v e l , thus indicat ing the dependence of nitrogen storage on ca lo r ie intake rather than the source of nitrogen. 2.1.5.3 Implications of changing nutrient proportions The subst i tut ion of one nutrient for another has i t s metabolic complications. The lack of consistency in the findings reported in the l i t e r a tu re on the ef fect of dietary fa t on body weight gain was soon recognized to be due to r e s t r i c t i o n of nutrient consumption as a resu l t 11 of reduced food intake when diets containing high fat levels were fed. The requirement for methionine (Baldini and Rosenberg, 1955), and lys ine (Schwartz e_t al_., 1958) has been shown to be dependent on the dietary energy l e v e l . Not only protein requirement is affected (Aitken et a l . , T954; Sl inger e_t al_., 1955) but other dietary requirements also were found to increase when fat was added to the d i e t . The requirement for f o l i c acid (March and B ie ly , 1955) and choline (March and B ie ly , 1956) was shown to increase in the presence of a high level of dietary f a t . Other studies have shown that the i soca lo r i c subst i tut ion of f a t for carbohydrate in the d iet of the chick increases i t s requirement for vitamin B]2 (Looi and Renner, 1974a) while i t appears not to a f fect i t s requirement for methionine (Looi and Renner, 1974b). 2.1.6 Protein-carbohydrate interact ions The e f f i c iency of protein u t i l i s a t i o n is large ly influenced by the extent to which the amino acids in the p r o f i l e are avai lable to the animal. Factors that af fect or inter fere with protein d i g e s t i b i l i t y w i l l also a f fect or inter fere with amino acid a v a i l a b i l i t y and ipso  facto, the e f f i c iency of protein u t i l i s a t i o n . Lea and Hannon (1950) studied extensively reactions that occur between proteins and carbohydrates and reported that in the presence of a considerable amount of carbohydrates with reducing sugars, proteins containing amino acids with free amino groups such as lys ine w i l l react to form a protein-carbohydrate complex which may not be u t i l i z a b l e to 12 the an ima l . Nesheim (1965) d i scussed the f a t e of such a compound and suggested two p o s s i b i l i t i e s . The compound could be degraded to y i e l d products of l i t t l e or no n u t r i t i o n a l value to the animal or i t could be complete ly des t royed. Lack of a f r ee amino group (on a p r o t e i n con ta i n i ng an amino a c i d such as l y s i n e ) as a r e s u l t of the l i n kage between i t and the carbo-hydrate would make the p r o t e i n r e s i s t a n t to h yd ro l y s i s by p r o t e o l y t i c enzymes. In such s i t u a t i o n s the p ro te in -ca rbohydra te complex should be expected to appear i n the exc re ta provided i t had not been at tacked by the m i c r o f l o r a o f the lower gut. M i c r o b i a l degradat ion of the p ro te in - ca rbohydra te compound may lead to the product ion and absorpt ion of n i t rogen in a form other than amino a c i d s . Barnes and Kwong (1964) suggested that the n i t rogen may be absorbed in the form of ammonia, a product of b a c t e r i a l fe rmentat ion i n the d i g e s t i v e t r a c t . 2.1.7 P r o t e i n - f a t i n t e r a c t i o n s A v a i l a b l e evidence i n d i c a t e s i n t e r a c t i o n between p ro te i n and f a t s i m i l a r i n nature to that o ccu r r i n g between p ro te in s and carbohydrates. Lea et al_. (1960) reported a drop i n p r o t e i n q u a l i t y as a r e s u l t of the r e a c t i o n between f a t o x i da t i on products and amino a c i d s , p a r t i c u a r l y l y s i n e . There was a f a l l of 8% and 4% r e s p e c t i v e l y i n the a v a i l a b l e l y s i n e of untreated and a n t i o x i d a n t - t r e a t e d he r r i ng meal s tored at 20°C f o r 12 months compared to the a v a i l a b l e l y s i n e content of f r e sh he r r i ng meal. I t i s suggested (Nesheim, 1965) that under storage cond i t i on s which would permit o x i da t i on or au toox ida t i on of f a t , carbonyl products 13 l i b e r a t e d dur ing the o x i d a t i o n of the f a t cou ld r eac t w i th the f r e e amino groups of l y s i n e i n p ro te i n s to produce bonds r e s i s t a n t to the ac t i on s of d i g e s t i v e enzymes or a compound not usefu l as a source of l y s i n e . 2.1.8 F i sh miaal q u a l i t y Herr ing meal i s w ide l y used as a source of high q u a l i t y p r o t e i n . I t conta ins a con s ide rab le quan t i t y of h i gh l y unsaturated f a t t y ac ids and t h i s accounts f o r i t s chemical and n u t r i t i o n a l r e a c t i v i t y . Factors that a f f e c t the n u t r i t i v e value of f i s h meal are we l l documented ( E l -Lakany, 1972). The b i o l o g i c a l va lue of he r r ing meal has been reported to d e c l i n e con s ide rab l y as a r e s u l t of process ing and s torage. During process ing and s to rage, the po ly -unsaturated f a t t y ac ids are subjected to o x i d a t i o n . Depending upon the concent ra t i on of po lyunsaturated f a t t y ac ids and the r a te of o x i d a t i o n , the f i s h meal may undergo spon-taneous heat ing which cou ld r e s u l t i n the d e s t r u c t i o n of amino ac id s (Lakseve la , 1958; Lea e_t a l_ . , 1960), p a r t i c u l a r l y l y s i n e , t r y p s i n , c y s t e i n e and h i s t i d i n e . ( B o g e , 1960). Laksevela (1958) reported tha t the d e t e r i o r a t i o n that r e s u l t e d from spontaneous heat ing was of such magnitude as to cause a se r ious reduct ion i n growth r a te of ch i ckens . There are c o n f l i c t i n g repor t s on the e f f e c t of storage on the n u t r i t i v e q u a l i t y of f i s h meal. B i e l y e_ta]_. (1951) and M i l l e r (1 955) d id not f i n d any adverse e f f e c t on the n u t r i t i v e q u a l i t y of f i s h meal s tored under var ious temperatures f o r per iods of three to twelve months. However, Stansby (1948), A lmqui s t (1956) and Lea et al_. (1958) showed tha t d e t e r i o r a t i o n of the n u t r i t i v e va lue of f i s h meal occurs under 14 var ious storage c o n d i t i o n s . March et al_. (1961) showed that low storage temperature favoured the format ion of p r o t e i n - 1 i p i d complex which leads to a d e c l i n e i n the n u t r i t i v e q u a l i t y of he r r i ng meal. In gene ra l , f i s h meal q u a l i t y v a r i e s w i th the methods o f d r y i n g , process ing and s t o r i n g of the meal. A marked d e c l i n e i n a v a i l a b l e l y s ine occurs i n d i e t s i n which f i s h meal of reduced n u t r i t i v e q u a l i t y i s the on ly source o f p r o t e i n . 2.1.9 E f f e c t s of d i e t a r y f a c t o r s on body compos i t ion The e f f e c t s o f d i e t a r y f a c t o r s on body composit ion of ch ickens were f i r s t descr ibed by Fraps (1943), who was ab le to produce chickens w i th w ide l y va ry ing amounts of body f a t by ad ju s t i n g d i e t a r y components. Subsequently, Donaldson e_t aj_. (1956, 1958), Rand et_ al_. (1957), Spr ing and Wi lk in son (1957), Combs e t al_. (1964), Davidson e t al_. (1964), Summers e_t al_. (1965), Yoshida e t al_. (1966, 1970), Thomas and Combs (1967), Yoshida and Morimoto (1970a, b ) , Thomas and Twinning (1971), and Kubena e t al_. (1972), i n v e s t i g a t e d the s p e c i f i c e f f e c t s of d i e t a r y p r o t e i n , energy and c a l o r i e : p r o t e i n r a t i o on the body compos i t ion of ch i ck s and p o u l t s . Through these s t u d i e s , i t was e s t ab l i s hed that as the d i e t a r y c a l o r i e : p r o t e i n r a t i o widened, energy i n take and carcass f a t depo s i t i on i n c rea sed , wh i l e body water content decreased. Yoshida et a l . (1966, 1970) and Yoshida and Morimoto (1970a, b) have reported that the e f f e c t of d i e t a r y p r o t e i n concen t ra t i on on carcass f a t content i s r ap i d and r e v e r s i b l e . Thomas and Twinning (1971) too , observed con s i de rab le changes i n carcass f a t con tent , as e a r l y as 10 days a f t e r a l t e r a t i o n s 15 were made in protein concentrations. The spec i f i c e f fect of dietary f a t on body composition i s not yet c lear . While most of the reports reviewed above appear to establ ish that increasing the amount of dietary fat increased carcass fat while i t decreased i t s protein content, Edwards and Hart (1971) f a i l ed to observe any change in tota l carcass composition when a l l the non-protein energy was derived from various o i l s . Bartov et_ al_. (1974) reported that dietary o i l supplementation per se did not increase the amount of carcass fat as long as the ca l o r i e : protein ra t i o was kept constant. If there existed any consistent trend at a l l , i t appeared to act in the opposite d i rec t i on : towards a decrease in carcass f a t . 2.1.10 Effect of ce l lu lose on metabo l i sab i l i ty The increased interest in energy nu t r i t i on of the chicken and progressive increase in the level of fat and, consequently, the density of diets used for poultry, has led to the present accepted practice of formulating experimental diets to contain varying levels of f ibrous materials usually in the form of ce l lu lo se . There is c on f l i c t i n g evidence regarding the ef fect of c e l l u -lose on some physiological parameters of the chicken. Reports which indicate that growth and food u t i l i s a t i o n are impaired when diets containing fibrous ingredients are fed to chickens, have been presented by Penquite (1936), Sheehy (1939), Heuser et al_. (1945), Fraps (1946), Carrick and Roberts (1974a, b). Scott et al_. (1947), Robertson et ajL (1943), Panda and Combs (1950), H i l l and Dansky (1954), Peterson et al_. (1954), Mraz e_t al_. (1956), and Richardson et al_. (1956), have explained the 16 d e l e t e r i o u s e f f e c t ( a t t r i b u t a b l e to f i b r e ) on the bas i s of r educ t i on i n energy i n take mediated by the e n e r g y - d i l u t i n g property of f i b r ou s i n g r ed -i e n t s . Hainan (1930), Robertson et al_. (1948), and Wel ls (1963) a t t r i b -uted t h i s e f f e c t to the impos i t i on o f phy s i ca l l i m i t a t i o n on the in take of d i g e s t i b l e n u t r i e n t s . There a r e , however, some repor t s which i n d i c a t e that feed ing moderate amounts of f i b r o u s m a t e r i a l s may inc rease growth and improve the u t i l -i s a t i o n of food above that obta ined on the low f i b r e basal d i e t . Morr i s ejt al_. (1932), Wi lcke and Hammond (1940), Record (1 943), Davis and Br iggs (1947, 1948), Olsson (1948), and Sa i t o e t al_. (1959) are among those who are of the op in ion that f i b r e may be of b e n e f i t i n p ou l t r y d i e t s . S i bba ld and S l i n g e r (1960) fed d i e t s of which c e l l u l o s e formed up to 42% and obta ined data which i n d i c a t e tha t d i l u t i o n of a ch ick s t a r t e r d i e t w i th c e l l u l o s e does not change the metabo l i s ab le energy content . This f i n d i n g was s u b s t a n t i a l l y conf irmed by Po t te r ejt a]_. (1960) who showed that a l p h a - c e l l u l o s e had zero or l e s s .metabol i sable energy va lue . . Begin (1961) us ing i s o c a l o r i c d i e t s and a constant n u t r i e n t balance technique demonstrated that the a d d i t i o n of woodpulp c e l l u l o s e had ne i t he r a growth-depress ing nor a g rowth - s t imu la t i ng e f f e c t when i n c l u -ded i n the d i e t of the c h i c k . He exp la ined tha t the major a t t r i b u t e of c e l l u l o s e when inc luded i n the d i e t wi thout supplementary energy was a depress ion i n growth and feed u t i l i s a t i o n and an o v e r a l l decrease i n the u t i l i s a t i o n of the d i e t as measured by the percentage of the gross energy that was metabo l i sed. Accord ing to Begin (1961), c e l l u l o s e i s i n e r t i n respect of i t s e f f e c t on m e t a b o l i s a b i l i t y or n i t rogen r e t e n t i o n . 17 2.1.11 Spec ie s , breed, s t r a i n and sex e f f e c t on energy metabolism D i f fe rences occur in the response of d i f f e r e n t breeds (Gard iner , 1971) and s t r a i n s of ch ickens to d i e t s w i th the same (Nowland et a l . , 1971) or w i th d i f f e r e n t energy concent rat ions ( F a r r e l l , 1972). Wells (1963) noted d i f f e r e n c e s in energy u t i l i s a t i o n w i th respect to the sex of the b i r d . There i s evidence i n the l i t e r a t u r e which po in t s to species d i f f e r e n c e regard ing metabol i s a b i l i t y o f energy. S l i n g e r ejt al_. (1964) showed tha t ch i ck s metabol i sed more energy from a high-energy d i e t than turkey p o u l t s . Converse ly , pou l t s metabol i sed more energy from Tow-energy d i e t than c h i c k s . A l s o , a s low-growing.breed o f ch ick s metabol i sed more energy from a high-energy d i e t than a fa s t -g rowing breed. Sudgen (1974) noted d i f f e r e n c e s between the bantam ch i c k and the blue-winged t e a l (duck) i n respect of t h e i r a b i l i t y to metabo l i se energy from var ious d i e t a r y sources. SI inger ejt al_. (1964) and Sugden (1974) concluded t ha t metabo l i sab le energy values measured w i t h one k ind of b i r d cannot v a l i d l y be app l i ed to another k i nd . Data presented by Leeson ejt aj_. (1974), do not support the above conc l u s i on . The l a t t e r group of authors found no d i f f e r e n c e between turkeys and chickens i n t h e i r a b i l i t y to metabol i se energy. Values ob-ta ined w i th the turkey f o r more f i b r ou s m a t e r i a l s , however, appeared to be s u b s t a n t i a l l y g reate r than have been found wi th the c h i c k , suggest ing turkeys w i th t h e i r l a r g e r d i g e s t i v e t r a c t s might have a g reate r c apac i t y f o r d i g e s t i n g f i b r ou s foods. 18 2.2 The A v i a n Caeca and E f f i c i e n c y o f U t i l i s a t i o n o f D i e t a r y P r o t e i n  and Energy 2.2.1 O v e r v i e w Ve r y l i t t l e i s known abou t t h e p h y s i o l o g i c a l o r n u t r i t i o n a l r o l e o f t h e a v i a n c a e c a . Fo r many y e a r s t h e r e have been s p e c u l a t i o n s as t o whe the r t h e f u n c t i o n s o f t h e a v i a n c aeca a r e s i m i l a r t o t h o s e o f : o t h e r a n i m a l s , p a r t i c u l a r l y t h e h o r s e . I t has been s u g g e s t e d t h a t t h e caecum may be a s i t e f o r : a ) m i c r o b i a l d i g e s t i o n o f c e l l u l o s e ; b ) d i g e s t i o n o f c a r b o h y d r a t e and p r o t e i n ; c ) m i c r o b i a l s y n t h e s i s and a b s o r p t i o n o f v i t a m i n s ; d ) a b s o r p t i o n o f n o n - p r o t e i n n i t r o g e n e) a b s o r p t i o n o f w a t e r , and/o r f ) b i o s y n t h e s i s o f a n t i g e n s . V a r i o u s , h ypo the se s have been advanced t o s u p p o r t t h e s e s u g g e s t i o n s and o f t h e s e pe rhaps t h e most p o p u l a r has been t he one a t t r i b u t i n g a r u m e n - l i k e f u n c t i o n i n t h e d i g e s t i o n o f c e l l u l o s e and p r o t e i n and t h e b i o s y n t h e s i s and a b s o r p t i o n o f v i t a m i n s . 2 . 2 . 2 C a r b o h y d r a t e and c r u d e f i b r e d i g e s t i b i l i t y Kaupp and I vey (1922) o b t a i n e d c r u d e f i b r e d i g e s t i b i l i t y c o e f f i c i e n t s w i t h p o u l t r y v a r y i n g f r om 2.2 p e r c e n t f o r e x t r a c t e d soybean meal t o 11.7 p e r c e n t f o r o a t s . H u n t e r e t al_. (1930) r e p o r t e d t h a t f i b r e can be d i g e s t e d i n t he a v i a n caecum. Maas (1934) u s i n g f o w l s w i t h a r t i f i c i a l a n u s e s , r e p o r t e d d i g e s t i b i l i t y c o e f f i c i e n t s o f 2.4 p e r c e n t f o r t he c r u d e 19 f i b r e of rye and 3.6 f o r t ha t of wheat. Hainan (1949) presented an e x c e l l e n t review embodying the work of Radeff (1928) and others on crude f i b r e d i g e s t i o n . While the crude f i b r e i n ba r l ey was not d i ge s ted by e i t h e r normal or caecectomized fowls t ha t of wheat was b e t t e r d iges ted by the normal fowl (4.6-5.7 percent) than the caecectomized fowl (1.4 pe r cen t ) . An even more remarkable d i f f e r e n c e was shown w i th the crude f i b r e of maize of which the normal fowl d i ge s ted more (17.1 percent) than the caecectomized fowl which showed zero p e r c e n t . d i g e s t i b i l i t y . The source of f i b r e appears to be of s i g n i f i c a n c e i n r e l a t i o n to i t s degradat ion i n thecaeca. V a r i a t i o n s w i t h i n the same food have been reported by Mangold (1934) who found t h a t the c o e f f i c i e n t s of d i g e s t i b i l i t y of crude f i b r e f o r ba r l ey ranged from 0 to 31.5 wh i l e those of oats ranged from 0 to 6.9 percent . That the av ian caeca possess some c e l l u l o l y t i c f u n c t i o n i s a l s o shown by Dukes (1955) and N i t san and Alumot (1963). Thornburn and W i l l c o x (1965a) s t ud i ed the s i g n i f i c a n c e of the caeca i n the d i g e s t i o n of dry matter , crude f i b r e , c e l l u l o s e , pentosans, and s ta rch by pou l t r y and repor ted a r educ t i on i n the o v e r a l l d i g e s t i b i l i t y of dry matter i n the food a f t e r caecectomy. C e l l u l o s e d i g e s t i b i l i t y was reduced i n i r i d i v -idua l b i r d s a f t e r caecectomy, but when they were compared w i t h i n t a c t b i rd s of i d e n t i c a l age, the reduc t i on i n d i g e s t i b i l i t y was not always ev ident . V a r i a t i o n i n the caeca! f l o r a between b i r d s was used to e xp l a i n the i n con s i s t ency o f r e s u l t s between the i n t a c t and the caecectomized b i r d s (two i n each ca se ) . Not a l l ev idence, however, i s i n accord wi th the above-mentioned f i n d i n g s . The observat ion by Masson (1954) of the presence of potato s t a r ch i n the caeca makes the hypotheses of s t a r ch d i g e s t i o n i n the 20 caeca l e s s acceptab le . Thornburn and W i l l cox (1965b) f a i l e d to produce conc l u s i v e evidence on the d i g e s t i b i l i t y of carbohydrates i n the i n t a c t caecum. Evidence presented by S co t t (1955), Gr iminger (1957), Nelson and No r r i s (1961), McBee (1971), a l s o d i sputes the c l a im of c e l l u l o -l y s i s i n the av ian caeca. The repeated f a i l u r e to f i n d in the domestic b i rd s caeca l b a c t e r i a capable o f hydro l y s ing c e l l u l o s e must have prompted McNab (1973) to express doubt about the caeca as being an organ of s i g n i f i c a n c e in the d i g e s t i o n o f c e l l u l o s e or crude f i b r e . 2.2.3 P r o t e i n d i g e s t i b i l i t y and u t i l i s a t i o n The r o l e played by the av ian caeca i n the u t i l i s a t i o n of p r o t e i n i s equa l l y f a r from c l e a r . Maumus and Launoy (1901) and Maumus (1902) both c i t e d by McNab (1973) s tud ied the a c t i o n of d i f f e r e n t subs t ra tes of caeca l j u i c e from c h i c k s , ducks and geese and reported the presence, i n the caeca, of a p r o t e o l y t i c enzyme s i m i l a r i n a c t i on to t r y p s i n . N i t san and Alumot (1963) examined the caecal contents of ch i ck s which had been fed d i e t s based on raw and heated soyabean meals f o r p ro teo -l y t i c a c t i v i t y and noted high a c t i v i t y on both d i e t s up to four weeks of age. D i f f e rence s were noted i n enzyme a c t i v i t y i n the s i x t h week between b i rd s fed the heated and those fed the raw beans - the former showing a marked decrease and the l a t t e r on ly a s l i g h t decrease in enzyme a c t i v i t y . Increased p r o t e o l y s i s was observed a t e i gh t weeks of age when the ch ickens were t r a n s f e r r e d from a heated to a rawsoyabean based d i e t . F i s he r and Gr iminger (1966) t e s t e d the hypothes is of caecal p ro teo -l y s i s and f a i l e d to accept the suggest ion of N i t san and Alumot (1963) that the observed inc rease i n p r o t e o l y t i c a c t i v i t y in the e i gh t week o ld 21 ch icken was a t t r i b u t a b l e to compensatory p r o t e o l y s i s which occurred to obv ia te i n h i b i t e d p r o t e o l y s i s i n the small i n t e s t i n e . On the bas i s of good growth r a te of the caecectomized ch i ck s i n comparison w i th tha t of unoperated c o n t r o l s . F i s he r and Gr iminger (1966) concluded t ha t caecal d i g e s t i o n of raw soyabean p r o t e i n i s of n e g l i g i b l e consequence i n the growing ch i c ken . Nesheim and Carpenter (1967) fed undamaged and heat-damaged f i s h meal to normal and caecectomized b i rd s and reported t ha t . a s i g n i f i c a n t p ropor t ion of the p r o t e i n and pept ides which escape h yd ro l y s i s and absorp-t i o n i n the small i n t e s t i n e enters the caeca and i s fermented in such a way t h a t the n i t rogen i s l i b e r a t e d as ammonia or some other substance of no n u t r i t i o n a l va lue . Th is view i s strengthened by the work of S a l t e r and Coates (1971) who concluded that m i c r ob i a l a c t i v i t y d id l i t t l e to inc rease the a v a i l a b i l i t y of p r o t e i n to the c h i c k . Payne et al_. (1971) i n v e s t i g a t e d the e f f e c t of caecectomy on appar-ent d i g e s t i b i l i t y of p r o te i n and found t ha t caecectomized b i rd s had a p r o t e i n d i g e s t i b i l i t y c o e f f i c i e n t that was s l i g h t l y (though not s i g n i f i -c a n t l y ) sma l l e r than that of normal i n t a c t b i r d s . Despite the above f i n d i n g s , Payne et al_. (1971) argued that the l a r ge experimental e r r o r coupled w i t h the small number of observat ions per treatment (5 b i r d s ) accounted f o r the lack of s t a t i s t i c a l s i g n i f i c a n c e and concluded that p ro te i n s t ha t are d i ges ted w i t h i n the caecum are absorbed from the caecum and on that bas i s the caeca are i nvo l ved i n p r o te i n d i g e s t i o n . 2.2.4 Absorpt ion of n u t r i e n t s The f a c t t ha t microorganisms i n h a b i t i n g the a l imenta ry t r a c t of 22 ruminants are r e spon s i b l e f o r a c t i v i t i e s o f n u t r i t i o n a l s i g n i f i c a n c e to the host animals has g iven r i s e to cons ide rab le s pecu l a t i on on the involvement of i n t e s t i n a l microorganisms i n the d i g e s t i o n and/or absorp-t i o n of n u t r i e n t s by the domestic f o w l . The presence of a l a r ge popu lat ion of microorganisms i n the a l i -mentary t r a c t , p a r t i c u l a r l y the caeca, has been reported by Shapiro and Sa r le s (1949), Barnes and Shrimpton (1957), and Barnes and Impey (1970). Although the av ian caecum i s one of the areas of g rea te s t m i c ro -b i a l p r o l i f e r a t i o n and a c t i v i t y (Barnes and Impey, 1970), there i s no c l e a r evidence t ha t m i c r ob i a l a c t i v i t y i s b e n e f i c i a l or det r imenta l to the host. One po s s i b l e way i n which the presence of microorganisms can be regarded as b e n e f i c i a l to the domestic fowl i s t ha t carbohydrates or p ro te in s o f d i e t a r y or endogenous o r i g i n that escape d i g e s t i o n i n the upper gut might be c a t a b o l i z e d by m i c r ob i a l a c t i o n i n the lower gut w i th subsequent absorpt ion of the end products such as monosaccharides o r d i s accha r i de s i n the case of carbohydrates , and amino ac id s or amino a c i d degradatory products in the case of p r o t e i n s . This would be i n agreement i n pa r t with the suggest ions of Thornburn and Iii 11 cox (1 965b) and Nesheim and Carpenter (1967). A l t e r n a t i v e l y , they might be of no n u t r i t i o n a l va l ue , i f , f o r the i n s t ance , l a c t i c a c i d is/end product of carbohydrate catabo l i sm and b i o l o g i c a l l y unava i l ab l e pept ides or exces s i ve ammonia are the end pro -ducts of p r o t e i n breakdown. 2.2.5 U r i c a c i d p roduc t i on S ince some p r o t e i n h y d r o l y t i c f u n c t i o n i s suggested f o r the caeca-23 and u r i c a c i d i s t h e main n i t r o g e n o u s e x c r e t o r y s u b s t a n c e i n t he b i r d t he p o s s i b i l i t y e x i s t s t h a t u r i c a c i d c o u l d be i n v o l v e d i n t he m e t a b o l i s m o f t h e c a e c a l m i c r o f l o r a and t h a t t h e m i c r o f l o r a wou l d c o n t a i n a s i g n i -f i c a n t p o p u l a t i o n o f u r i c a c i d - u t i l i z i n g b a c t e r i a . Ba rne s and Impey (1972) f o u n d t h r e e i s o l a t e s o f u s i c a c i d - d e c o m p o s -i n g anae robes and i n s u b s e q u e n t s t u d y ( Ba rne s e t a l _ . , 1972) f ound t h a t t he u r i c a c i d d e g r a d a t o r y o r g a n i s m s were a lway s p r e s e n t a t a m i n i m a l l e v e l o f lC)8-109/g. Mead and Adams (1975) s t u d i e d changes i n t he c a e c a l f l o r a o f c h i c k s aged between a p p r o x i m a t e l y 3 hours and 14 days and r e p o r t e d t h a t d u r i n g t h e 14 -day p e r i o d , a p p r o x i m a t e l y 100 p e r c e n t o f t h e o r gan i sms i s o l a t e d t h r o u g h c o n v e n t i o n a l a n a e r o b i c p l a t i n g method u t i l i z e d u r i c a c i d up t o t h e t h i r d day bu t t h i s a c t i v i t y d e c l i n e d w i t h age t o t he e x t e n t t h a t i n one c a s e i t r e p r e s e n t e d o n l y f o u r p e r c e n t o f t h e t o t a l f l o r a . None o f t h e i s o l a t e s showed an a b s o l u t e r e q u i r e m e n t f o r u r i c a c i d . E x c e p t w i t h a few s t r a i n s t h e r e has been l i t t l e e v i d e n c e f o r t h e u t i l i s a t i o n o f u r i c a c i d as a c a r b o n s o u r c e . However, Ba rnes (1972) f ound t h a t a number o f t h e u r i c a c i d u t i l i s i n g b a c t e r i a u t i l i z e d ammonia as t h e main s o u r c e o f n i t r o g e n . Ba rnes (1972) e x p l a i n s t h a t t h e c o n -t i n u a l p r e s e n c e o f a l a r g e p o p u l a t i o n o f u r i c a c i d r e c y c l i n g b a c t e r i a i n t he a v i a n c a e c a s u g g e s t s t h a t a m a j o r f u n c t i o n o f t he c a e c a c o u l d be t h e m e t a b o l i s m and r e u t i l i s a t i o n o f t h e e x c r e t o r y p r o d u c t s d i v e r t e d i n t o t he c a e c a w i t h the p o s s i b l e r e - a b s o r p t i o n o f w a t e r and any o t h e r o f t h e v i t a m i n s , v o l a t i l e f a t t y a c i d s o r amino a c i d s s y n t h e s i z e d by the m i c r o o r g a n i s m s . A k e s t e r et a l , (1967) have r e p o r t e d t h a t an un -known p h y s i o l o g i c a l mechan i sm, i n d u c e d by t h e a p p r o p r i a t e s t i m u l u s i n i t i a t e c o n t r a c t i o n o f t h e coprodeum w h i c h then r e s u l t s i n t h e r e t r o g r a d e f l o w o f u r i n e and f i n e p a r t i c l e s o f d i g e s t a i n t o t h e c aeca 24 3. PART 1. THE EFFECT OF SUBSTITUTION OF FAT FOR STARCH ON THE PERFORMANCE OF BROILERS 3.1 Experiments 1 and 2 3.1.1 I n t roduc t i on The i n c r ea s i n g wor ld shortage of g ra ins which, h i t h e r t o , have been the predominant d i e t a r y source of energy f o r p o u l t r y , has s t imu -l a t e d i n t e r e s t i n the search f o r a l t e r n a t i v e d i e t a r y source(s ) of energy f o r p o u l t r y . A number of researchers have s tud ied energy u t i l i s a t i o n and have demonstrated the p o t e n t i a l value of f a t not only as an a l t e r n a t i v e , but a l so as an economic source of d i e t a r y energy. The attempts being made are i n the d i r e c t i o n of e s t a b l i s h i n g a d i e t a r y energy concent ra t i on that would promote an e f f i c i e n t u t i l i s a t i o n of n u t r i e n t s , p a r t i c u l a r l y p r o t e i n . Data pub l i shed by Touchburn and Naber (1966) and Jensen et a l . (1970) appear to. e s t a b l i s h a concept that supplemental d i e t a r y f a t has an " e x t r a - c a l o r i c " e f f e c t on the u t i l i s a t i o n of metabo l i s ab le energy by turkey b r o i l e r s . In a s e r i e s of experiments these groups of workers showed that added d i e t a r y f a t improved u t i l i s a t i o n of metabo l i s ab le energy and that "a wider c a l o r i e : p r o t e i n r a t i o could be t o l e r a t e d when f a t was added to the r a t i o n than when no f a t was used" . There i s l i t t l e or no d i r e c t i n fo rmat ion on the b r o i l e r ch icken regard ing the e f f e c t of added d i e t a r y f a t on the u t i l i s a t i o n of metabo l -i s a b l e energy and to l e rance of a wider c a l o r i e r p r o t e i n r a t i o . A study has, t h e r e f o r e , been made of the e f f e c t of p a r t i a l s u b s t i t u t i o n of d i e t a r y f a t f o r g lucose c a l o r i e s on m e t a b o l i s a b i 1 i t y of energy, body weight g a i n , e f f i c i e n c y of food convers ion and carcass f a t content of b r o i l e r ch ickens . 25 3 .1 .2 M a t e r i a l s and Methods T h i s phase o f t h e s t u d y c o m p r i s e d two e x p e r i m e n t s c o n d u c t e d u s i n g b r o i l e r c h i c k s . The same f o r m u l a t i o n o f d i e t s was used i n b o t h e x p e r i -men t s . The c o m p o s i t i o n o f t h e d i e t s i s p r e s e n t e d i n T a b l e 1. The b a s a l d i e t c o n t a i n e d 3% c o r n o i l t o keep down d u s t i n e s s o f t h e mash, and more i m p o r t a n t l y , t o s u p p l y t h e d i e t a r y e s s e n t i a l f a t t y a c i d s , p a r t i c u l a r l y l i n o l e i c a c i d , t h e l a c k o f w h i c h wou ld p r e c i p i t a t e m e t a b o l i c d i s o r d e r s w h i c h , c o n s e q u e n t l y , wou ld a f f e c t t h e e x p r e s s i o n o f t h e p a r a m e t e r s under s t u d y . The re were f o u r d i e t s c o n s i s t i n g o f two l e v e l s o f s u p p l e m e n t a r y f a t , 4% and 8% f e d a t two p r o t e i n l e v e l s 18% and 22%. Fou r hund red .and s i x t e e n c h i c k s were housed i n a 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 e l e c t r i c a l l y - h e a t e d meta l b a t t e r y b r o o d e r s w i t h r a i s e d s c r e e n f l o o r s , and were f e d a h o l d i n g p r a c t i c a l - t y p e b r o i l e r s t a r t i n g d i e t f o r two d a y s . The c h i c k s were then w ing -banded and d i s t r i b u t e d r andomly i n t o two m a j o r l o t s o f s t o c k f o r t h e two e x p e r i m e n t s . The two l o t s o f c h i c k s c o n t i n u e d t o be b rooded i n t h e manner d e s c r i b e d e a r l i e r , f e d t h e same e x p e r i m e n t a l d i e t s , and k e p t i n t he same room e x c e p t where i t i s o t h e r w i s e s p e c i f i e d . Food and w a t e r were p r o v i d e d ad 1 i b i t u m t o a l l t he c h i c k s i n v o l v e d i n the two e x p e r i m e n t s . One l o t o f c h i c k s , c o n s i s t i n g o f one hundred and f i f t y s i x , was r andomly r e d i s t r i b u t e d i n t o f o u r g roups a c c o r d i n g t o t h e number o f d i e t a r y t r e a t m e n t s w i t h t h r e e r e p l i c a t i o n s . The 13 c h i c k s p e r r e p l i c a t e were a s s i g n e d t o one b a t t e r y compar tment . T h i s c o n s t i t u t e d t h e s t o c k f o r t h e f i r s t e x p e r i m e n t . 26 T a b l e 1. C o m p o s i t i o n o f d i e t s used i n e x p e r i m e n t s 1 and 2. Low P r o t e i n H igh P r o t e i n Low F a t H i gh F a t Low Fa t H i gh F a t D i e t Number I n g r e d i e n t , o r c a l c u l a t e d 1 2 3 4 a n a l y s i s P e r c e n t H e r r i n g meal (72%) 13.0 13.0 21 .3 21.3 Wheat ( 12 .45 ) 70 .9 70.9 53.0 53.0 Corn o i l 3.0 7 .0 3.0 11.0 Corn s t a r c h 9.6 - 19.2 -Bone meal 1.5 1.5 1.5 1.5 L i m e s t o n e 1.0 1.0 1.0 1.0 I o d i z e d s a l t 0.5 0.5 0.5 0.5 P remix^ 0.5 0.5 0.5 0.5 C e l l u l o s e 5.6 — 11.2 P r o t e i n 18.19 18.19 21.93 21.93 F a t 5.57 9.57 6.08 14.08 M..E. ( k c a l / k g ) 3345 3347 3382 3385 M i c r o n u t r i e n t s s u p p l i e d pe r kg o f d i e t : manganese s u l p h a t e , 132 mg; r i b o -f l a v i n , 3.12 mg; menad i one , 0.48 mg; c a l c i u m p a n t o t h e n a t e , 9.62 mg; f o l a c i n , 0.55 mg; v i t a m i n B12 , 0.13 meg; p y r i d o x i n e , 2.87 mg; b i o t i n , 0.09 mg; c h o l i n e c h l o r i d e , 1.32 g ; v i t a m i n A , 4400 I .U . , v i t a m i n D3, 440 L C . U . ; v i t a m i n E, 18 I .U . ; z i n c b a c i t r a c i n , 27 mg; c h l o r o t e t r a -c y c l i n e , 124.9 mg; a m p r o l i u m , 11 mg. 27 There was a s l i g h t m o d i f i c a t i o n i n the r e p l i c a t i o n of the d i e t a r y treatment groups of the stock used f o r the metabo l i s ab le energy study. There were f i v e r e p l i c a t e d l o t s of 13 ch i ck s each. This was done i n order to a l l ow each ch i ck the same f l o o r space as i n the f i r s t experiment. With 13 ch i ck s i n each r e p l i c a t e there were 65 ch ick s f o r each of the fou r d i e t a r y treatment groups, making a t o t a l of 260 ch ick s maintained under the same management cond i t i on s as the f i r s t experiment. 3.1.2.1 Experiment 1 This study was. designed to i n v e s t i g a t e the e f f e c t s of d i e t s . v a r y i n g i n f a t and p r o t e i n l e v e l s on the performance of b r o i l e r chickens us ing body weight g a i n , food convers ion e f f i c i e n c y and e f f i c i e n c y of p r o t e i n u t i l i s a t i o n as the c r i t e r i a f o r e va l ua t i n g performance. The ch i ck s were i n d i v i d u a l l y weighed at weekly i n t e r v a l s throughout the exper imental per iod which l a s t ed seven weeks. Food consumption was determined on group bas i s and was done at the time of weighing the c h i c k s . S p i l l e d food was removed from the excreta by screening and added to the remaining feed in the troughs before the feed weigh-back. Data c o l l e c t e d on body weight g a i n , food (convers ion) e f f i c i e n c y and p ro te i n e f f i c i e n c y r a t i o va lues were t r e a t ed by a n a l y s i s o f va r iance (Snedecor, 1956) and s i g n i f i c a n t d i f f e r e n c e s among treatment means were i d e n t i f i e d by Student-Newman-Keuls m u l t i p l e range t e s t . 3.1.2.2 Experiment 2 The second experiment invo lved 240 c h i c k s . At 1, 2, 4 and 7 weeks of age, 60 ch i ck s made up of three ch ick s from each q u i n t u p l i c a t e l o t 28 o f t h e f o u r d i e t a r y t r e a t m e n t groups r e s p e c t i v e l y , were r andomly removed f rom t h e second l o t o f c h i c k s d e s c r i b e d e a r l i e r . The f i f t e e n c h i c k s removed f r om each d i e t a r y t r e a t m e n t g roup a t each s p e c i f i e d p e r i o d were r e d i s t r i b u t e d randomly i n t o t r i p l i c a t e g roups o f f i v e c h i c k s and each group was a s s i g n e d t o an e l e c t r i c a l l y - h e a t e d , 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 a d j u s t a b l e b a t t e r y compartment w i t h r a i s e d w i r e s c r e e n f l o o r s i n a w e l l -v e n t i l a t e d , t e m p e r a t u r e - c o n t r o l l e d c h i c k e n room i n t h e l a b o r a t o r y . The s i z e o f t h e compartments was a d j u s t e d a t each h o u s i n g p e r i o d commensurate w i t h f l o o r space r e q u i r e m e n t . A l l t he c h i c k s were i n d i v i d u a l l y we i ghed a t t h e commencement and t e r m i n a t i o n o f e a c h p e r i o d l a s t i n g one week. Food c o n s u m p t i o n r e c o r d s were kep t f o r each p e r i o d . The c h i c k s were c o n t i n u e d on t he same e x p e r i -menta l d i e t s f o r two and one h a l f d a y s . Food was w i t h d r a w n 18 hour s p r i o r t o t he commencement and t e r m i n a t i o n o f t h e c o l l e c t i o n o f t o t a l e x c r e t a . F e a t h e r s , f o o d and e x t r a n e o u s m a t e r i a l s were c a r e f u l l y p i c k e d f r om the e x c r e t a and t h e t h r e e d a y s ' c o l l e c t i o n s f r om each r e p l i c a t e group were p o o l e d a c c o r d i n g t o t r e a t m e n t and f r o z e n . The f r o z e n e x c r e t a was l y o p h i l i z e d , g round and s t o r e d i n s c r e w - c a p sample j a r s and s t o r e d u n t i l r e q u i r e d f o r a n a l y s i s . M o i s t u r e d e t e r m i n a t i o n was c a r r i e d o u t on a l l samples t o p e r m i t c a l c u l a t i o n s t o be made on d r y w e i g h t b a s i s . A s say f o r e ne r g y c o n t e n t o f bo t h f o o d and e x c r e t a was done u s i n g P a r r Oxygen Bomb P l a i n j a c k e t C a l o r i m e t e r . K j e l d a h l macro -method was f o l l o w e d i n t h e d e t e r m i n a t i o n o f c r u d e p r o t e i n . A t t h e end o f t h e e x p e r i m e n t , a l l t h e c h i c k s were k i l l e d and t h r e e c h i c k s f rom each r e p l i c a t e g roup were s e l e c t e d a t random f o r d e t e r m i n a t i o n o f t h e w e i g h t o f t h e abdomina l a d i p o s e t i s s u e w h i c h i n c l u d e d the abdomina l f a t pad and t h a t a s s o c i a t e d w i t h t he v i s c e r a . 0 29 3 .1 .3 E x p e r i m e n t 1 - R e s u l t s S t a t i s t i c a l a n a l y s i s a p p l i e d t o t he t o t a l body w e i g h t g a i n s (sum-m a r i z e d i n T a b l e 2) shows t h a t t h e c h i c k e n s were a b l e t o a t t a i n p r a c t i c a l l y t he same f i n a l w e i g h t t o a p p r o x i m a t e l y seven weeks o f a ge , r e g a r d l e s s o f the s o u r c e o f d i e t a r y e n e r g y / f a t o r p r o t e i n l e v e l . The a v e r a g e body w e i g h t g a i n s p e r b i r d f e d d i e t s 1 , 2 , 3 and 4 were 1653 , 1665, 1646 and 1704 grams, r e s p e c t i v e l y . F i g . 1 shows t he c l o s e n e s s o f body w e i g h t v a l u e s t h r o u g h o u t t h e e x p e r i m e n t a l p e r i o d . The d a t a ( T a b l e 3) on w e e k l y body w e i g h t g a i n s s u b j e c t e d t o s t a t i s t i c a l a n a l y s i s , r e v e a l e d no s i g n i f i -c a n t d i f f e r e n c e s i n t h i s t r a i t among the d i f f e r e n t d i e t a r y g r o u p s . In t he f i r s t week, s i g n i f i c a n t d i f f e r e n c e s o c c u r r e d among t he d i e t a r y g r o u p s . B i r d s f e d t he l o w - p r o t e i n d i e t i n w h i c h f a t was t he s o u r c e o f s u p p l e -menta r y ene r gy ( d i e t 2) made t he p o o r e s t body w e i g h t g a i n s . W i t h t he e x c e p t i o n o f the f o u r t h week, t h e r e were no s i g n i f i c a n t d i f f e r e n c e s i n w e e k l y body w e i g h t g a i n s among t h e v a r i o u s d i e t a r y g roups f rom the t h i r d week t o t he t e r m i n a t i o n o f t h e e x p e r i m e n t i n t h e s e v e n t h week. The f o o d c o n v e r s i o n e f f i c i e n c y v a l u e s a r e p r e s e n t e d i n T a b l e 4 . W i t h t he e x c e p t i o n o f t h e s econd week i n w h i c h t he f o o d c o n v e r s i o n e f f i c i e n c y was b e s t on t he l o w - f a t h i g h - p r o t e i n d i e t ( d i e t 3 ) , t he b e s t f o o d c o n v e r s i o n e f f i c i e n c y v a l u e s were o b t a i n e d w i t h t he h i g h - f a t h i g h -p r o t e i n d i e t ( d i e t 4 ) . Nex t i n o r d e r o f f o o d c o n v e r s i o n e f f i c i e n c y was t h e l o w - f a t h i g h - p r o t e i n d i e t , i n d i c a t i n g b e t t e r f o o d c o n v e r s i o n e f f i c i e n c y on 30 T a b l e 2 . E f f e c t o f d i e t a r y f a t and p r o t e i n l e v e l s on body w e i q h t g a i n s  i n E x p e r i m e n t 1. D No. I E F a t T P r o t e i n Mean 1 Body We i gh t s i n Grams I n i t i a l 2 F i n a l G a i n 1 Low Low 68 1721 1653a 0 £_ H i gh Low 68 1733 1665a 3 Low H i gh 67 1713 1646a 4 H i g h H i gh 66 1770 1704a Means w i t h i n a co lumn f o l l o w e d by d i f f e r e n t l e t t e r s d i f f e r s i g n i f i c a n t l y (P < 0 . 05 ) B i r d s were 2 days o l d a t i n i t i a t i o n . 31 1500 2 1000 H X CD UJ >-Q O oo < 500 UJ 0 D I • LOW FAT LOW PROTEIN D2 HIGH FAT LOW PROTEIN 0 3 • • LOW FAT HIGH PROTEIN D 4 ^ HIGH FAT HIGH PROTEIN _L 0 1 2 3 4 5 6 AGE (WEEKS) FIG. I: EFFECT OF DIETARY FAT AND PROTEIN LEVELS ON BODY WEIGHT . 32 T a b l e 3. E f f e c t o f d i e t a r y f a t and p r o t e i n l e v e l s on week ly body  w e i g h t g a i n . D I E T Mean 1 Body We igh t Ga i n s i n Grams No. Fat- P r o t e i n 1 2 3 Weeks 4 5 6 7 1 Low Low 93bc 162b 214a 225b 277a 344a 338a 2 H igh Low 89c 167b 218a 224b 266a 360a 341a 3 Low H igh 99b 169b 209a 222b 269a 344a 334a .4 High H i gh 107a 178a 221a 253a 272a. 338a 334a Means w i t h i n a co lumn f o l l o w e d by d i f f e r e n t l e t t e r s d i f f e r s i g n i f i c a n t l y (P < 0 . 0 5 ) . 33 Table 4. E f f e c t o f d i e t a r y f a t and p r o t e i n l e v e l s on food conversion  e f f i c i e n c y ^ , 2 . D I E T Weeks No. Fat P r o t e i n 1 2 3 4 5 6 7 O v e r a l l 1 Low Low 1.51 1 .48 1.71 1.75 2.15 2.21 2.42a 1.89a 2 High Low 1.53 1 .46 1.73 1.74 2.16 2.16 2.45a 1.89a 3 Low High 1.34 1 .32 1.74 1,58 2.02 2.14 2.25a 1.77b 4 High High 1.24 1 .33 1.62 1.44 2.00 2.04 2.30a 1.71b ^Units o f food consumed per u n i t o f body weight g a i n . 7 Values w i t h i n a column followed by the same l e t t e r s are 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). 34 t h e h i g h - p r o t e i n d i e t s . The re was no d i f f e r e n c e i n t h e o v e r a l l f o o d c o n v e r s i o n e f f i c i e n c y between t h e b i r d s f e d t h e two l o w - p r o t e i n d i e t s . These b i r d s gave c o n s i s t e n t l y l o w e r f o o d c o n v e r s i o n v a l u e s d u r i n g a l l w e e k l y p e r i o d s o f t h e e x p e r i m e n t . T h e r e was a c o n s i s t e n t d e c l i n e w i t h age i n t h e e f f i c i e n c y o f f o o d c o n v e r s i o n o f b i r d s f e d d i e t 4 e x c e p t d u r i n g t h e f o u r t h week when t h e r e was an improvement i n t h i s c r i t e r i o n . T h i s t r e n d was a l s o shown by b i r d s f e d t h e o t h e r h i g h - p r o t e i n d i e t ( d i e t 3) w h i c h had e x h i b i t e d a s i m i l a r t e n d e n c y i n t h e second e x p e r i m e n t a l week. B i r d s f e d t h e l o w - p r o t e i n d i e t s showed improvement i n t h e second week a f t e r w h i c h t h e y showed a c o n s i s -t e n t d e c l i n e i n e f f i c i e n c y o f f o o d c o n v e r s i o n . The l e v e l o f d i e t a r y f a t i n l o w - p r o t e i n d i e t s does n o t a p p e a r t o i n f l u e n c e t h e e f f i c i e n c y o f f o o d c o n v e r s i o n as e v i d e n c e d by t h e f a c t t h a t b i r d s f e d t h e b a s a l d i e t a r y f a t ( d i e t 1) c o n v e r t e d f o o d w i t h e q u a l e f f i c -i e n c y as t h o s e f e d t h e a d d i t i o n a l f a t ( d i e t 2) i n t h e l o w - p r o t e i n c a t e g o r y . B i r d s f e d t h e b a s a l f a t , h i g h - p r o t e i n d i e t ( d i e t 3) gave p r a c t i c a l l y t h e same f o o d c o n v e r s i o n e f f i c i e n c y v a l u e as t h o s e f e d t h e h i g h - f a t h i g h -p r o t e i n d i e t ( d i e t 4 ) . The t r e n d f o r t h e c u m u l a t i v e f o o d c o n v e r s i o n e f f i c i e n c y v a l u e s f o r t h e v a r i o u s d i e t a r y g roup s i s shown i n F i g . 2 . • T a b l e 5 shows t h a t t h e p r o t e i n c o n v e r s i o n e f f i c i e n c y (body w e i g h t g a i n / p r o t e i n consumed) by t h e b i r d s f e d t h e two l o w - p r o t e i n d i e t s , was s i g n i f i c a n t l y b e t t e r t h a n t h a t o b t a i n e d by b i r d s f e d t h e two h i g h - p r o t e i n d i e t s . B i r d s f e d d i e t s c o n t a i n i n g t h e b a s a l f a t l e v e l s ( d i e t s 1 and 3) gave t h e g r e a t e s t p r o t e i n c o n v e r s i o n e f f i c i e n c y v a l u e s . As no t ed i n t h e c a s e o f f o o d c o n v e r s i o n e f f i c i e n c y , t h e s o u r c e o f d i e t a r y ene r g y o r t h e l e v e l o f d i e t a r y f a t i n t h e l o w - p r o t e i n d i e t s d i d no t i n f l u e n c e t h e 35 FIG. 2: EFFECT OF DIETARY FAT AND PROTEIN LEVELS ON FOOD CONVERSION EFFICIENCY (CUMULATIVE). T a b l e 5. P r o t e i n c o n v e r s i o n e f f i c i e n c y D i E • j Body We ight G a i n s / P r o t e i n Consumed (g g~^) .  Weeks No. F a t P r o t e i n 1 2 3 4 5 6 7 0 -7 1 Low Low 3, .63 3.72 3.22 3.15 2.56 2 .49 2 .27 3.01 2 H i g h Low 3. .59 3.77 3.18 3.15 2.55 2.54 2.24 3.00 3 Low H i gh 3. .41 3.45 2.61 2.89 2 .26 2 .13 2 .03 2 .68 4 H i gh H igh 3. .69 3.44 2.81 3.16 2 .28 2.24 1.98 2 .80 CO CTl 37 u t i l i s a t i o n o f d i e t a r y p r o t e i n as r e f l e c t e d i n t h e l a c k o f d i f f e r e n c e between t h e two l o w - p r o t e i n d i e t s w h i c h d i f f e r e d o n l y i n t h e s o u r c e o f s u p p l e m e n t a r y ene r gy and f a t l e v e l . . I t i s i n t e r e s t i n g t o n o t e t h a t a s i m i l a r r e l a t i o n s h i p e x i s t e d between b i r d s f e d t h e two h i g h - p r o t e i n d i e t s w h i c h d i f f e r e d a l s o i n the s o u r c e o f s u p p l e m e n t a r y ene rgy and d i e t a r y f a t l e v e l . 38 •3.1.4 Experiment 1 - Discussion Although chickens fed the high-fat high-protein d iet grew s i g n i f i -cantly heavier in the f i r s t , second and fourth weeks than those fed the other experimental d ie t s , the f i na l body weight gain data (Table 2), the weekly body weight gain data (Table 3), and the closeness of data on overal l growth rate (Fig. 1) do not demonstrate the concept that has been established for turkeys that supplementary fat promotes superior growth. The absence of a s i gn i f i cant difference in l a te r weeks in the f i n a l body weights between chickens fed either fat-based or carbohydrate-based diets indicates that the influence of dietary fat on growth rate would be exhibited in early rather than late in the l i f e of the b i rd . This obser-vation is in close agreement with the f inding of Touchburn and Naber (1966) who reported that the benef ic ia l e f fect of supplementary fat on the performance of turkeys became less apparent in the f i n a l i n t e r v a l , 12 to 14.5 weeks of age and that of Salmon (1972) who did not obtain a s i gn i f i can t difference in the f i n a l weights between turkeys fed a high-fat d iet for the ent i re 24 week experimental period compared with others fed a high-fat d iet from 16 to 24 weeks. The observation that no s i gn i f i cant differences existed in the f i n a l body weights and the overal l body weight gains among the d i f fe rent d i e t -ary groups could be reconciled with two wel l -establ ished concepts. It has been documented that as dietary fat increases, lipogenesis assumes r e l a t i v e l y less importance (Donaldson, 1966) and that dietary fat has a sparing ef fect on amino acid conversion to fa t ty acids. As Donaldson (1966) explains, " i f the tota l energy avai lable for t issue synthesis were 39 s i m i l a r f o r c h i c k s f e d bo th f a t and ' f a t - f r e e ' d i e t s , t he f a t - f e d c h i c k s wou ld have t h e advan tage o f no t h a v i n g t o s y n t h e s i z e t i s s u e f a t t y a c i d s and t hu s m i g h t have r e l a t i v e l y more ene rgy a v a i l a b l e f o r t i s s u e p r o t e i n s y n t h e s i s " . The l e v e l o f d i e t a r y f a t o f s i x p e r c e n t and t e n p e r c e n t i n t h e l o w - p r o t e i n d i e t s may have been h i g h enough t o d e p r e s s l i p o g e n e s i s and i n d u c e t i s s u e p r o t e i n s y n t h e s i s . In t h e o t h e r s e r i e s , t h e d i e t a r y f a t l e v e l o f s i x p e r c e n t may have s i m i l a r l y d e p r e s s e d l i p o -g e n e s i s w h i l e t h e p r o t e i n l e v e l s may have been a d e q u a t e . The p r o t e i n e f f i c i e n c y r a t i o d a t a ( T a b l e 5) p r o v i d e e v i d e n c e wh i ch s u p p o r t s t h i s v i e w . R a t i o s o f u n i t s o f body w e i g h t g a i n pe r u n i t o f p r o t e i n - i n g e s t e d were h i g h e r f o r t h e l o w - p r o t e i n d i e t s t h a n t h e h i g h -p r o t e i n d i e t s . These r e s u l t s a r e i n agreement w i t h t h o s e o f B i e l y and March (1954) and Wa ibe l (1958) who f ound t h a t g rowth p r o m o t i o n i s a c h i e v e d o n l y i f t he c o n c e n t r a t i o n o f d i e t a r y p r o t e i n i s i n c r e a s e d i n a c c o r d a n c e w i t h t h e d i e t a r y ene r gy c o n c e n t r a t i o n . S i n c e t h e d i e t a r y ene rgy c o n c e n -t r a t i o n w i t h i n t h e p r o t e i n s e r i e s was t h e same and s i n c e t h e r e 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 g rowth between t h e d i e t a r y g roups w i t h i n t h e p r o t e i n s e r i e s , i t appea r s ene r g y t o p r o t e i n r a t i o i s a f a c t o r o f g r e a t e r s i g n i f i c a n c e i n t h e p r o m o t i o n o f g r owth t h a n t h e s o u r c e o f d i e t a r y e n e r g y . T h i s o b s e r v a t i o n s u p p o r t s t h e s t a t e m e n t o f S c o t t e t al_. (1969) t h a t , " D i e t s c o n t a i n i n g as much as 35 t o 40 p e r c e n t f a t and 45 t o 50 p e r c e n t p r o t e i n ^ w i t h l i t t l e o r no c a r b o h y d r a t e , and w i t h ene rgy v a l u e s as h i g h as 5000 k c a l ME/kg, w i l l s u p p o r t e x c e l l e n t g rowth i n young c h i c k s , . a s l o n g a s , t h e p r o t e i n and amino a c i d l e v e l s a r e m a i n t a i n e d a t t he optimum r a t i o s t o t he e n e r g y " . The l a c k o f s i g n i f i c a n t d i f f e r e n c e s i n o v e r a l l body w e i g h t g a i n 40 among t he d i f f e r e n t d i e t a r y g roups seems t o s u g ge s t a l s o t h a t t h e r e was a s u p e r f l u o u s s u p p l y o f p r o t e i n and amino a c i d s i n t he h i g h - p r o t e i n d i e t s . The w i d e r r a t i o ( K c a l : p e r c e n t p r o t e i n ) , 186:1 h a v i n g p r oduced the same g rowth r e spon se as t h e n a r r o w e r r a t i o , 1 5 4 : 1 , c o u l d be c o n s i d e r e d • as b e i n g more e f f i c i e n t as f a r as p r o t e i n l e v e l i s c o n c e r n e d . P o u l t s g i v e n a l ow l e v e l o f added d i e t a r y f a t r e q u i r e d a n a r r o w e r e n e r g y : p r o t e i n r a t i o t o f o u r weeks o f age and were more s e n s i t i v e t o e n e r g y . p r o t e i n i m b a l a n c e than t h o s e g i v e n h i g h e r l e v e l s o f added d i e t a r y f a t ( S a lmon , 1974 ) . C h i c k e n s i n v o l v e d i n t h i s s t u d y may have r e a c t e d i n a s i m i l a r manner t o t h e d i f f e r e n t d i e t a r y e n e r g y : p r o t e i n r a t i o s , p a r -t i c u l a r l y the w i d e r r a t i o i n t he f i r s t f o u r weeks and t h i s c o u l d a c c o u n t f o r t h e v a r i a t i o n i n g rowth i n t he p e r i o d unde r r e f e r e n c e . The d a t a on body w e i g h t s o f b i r d s s t u d i e d i n t h i s e x p e r i m e n t c o n f i r m t h e f i n d i n g o f Ve rmee r s ch and Van schoub roek (1968) t h a t , w h i l e d i e t a r y f a t i n c o r p o r a t e d a t l e v e l s r a n g i n g f r om 2 t o 20 p e r c e n t imp rove s body w e i g h t g a i n , t h e r e i s no r e l a t i o n s h i p between body w e i g h t and l e v e l o f d i e t a r y f a t . The o v e r a l l r e s u l t s r e l a t i n g t o e f f i c i e n c y o f f o o d u t i l i s a t i o n ( T a b l e 4) show t h a t c o r n o i l s u b s t i t u t e d i s o c a l o r i c a l l y f o r c o r n s t a r c h does n o t improve t h e e f f i c i e n c y o f f o o d u t i l i s a t i o n . The r e s u l t s r a t h e r show t h a t p r o t e i n l e v e l a f f e c t s t h i s t r a i t . In i n t e r p r e t i n g t h e s e r e s u l t s w h i c h appea r t o c o n t r a d i c t t h e f i n d i n g s o f Touchburn and Nabe r , 1966; Ve rmeer sch and Van s choub roek , 1968; H e r s t a d , 1970; J e n s e n e t , 1970 and Vanschoubroek e t a l _ . , 1971 , s i g h t s h o u l d n o t be l o s t o f t he f a c t t h a t when f a t r e p l a c e s s t a r c h g r a v i m e t r i c a l l y r a t h e r t han i s o c a l o r i c a l l y t h e r e i s a change n o t o n l y i n c a l o r i e d e n s i t y bu t a l s o i n t he r a t i o b e -tween ene r g y and o t h e r n u t r i e n t s . 41 The l a c k o f s i g n i f i c a n t d i f f e r e n c e s i n t he e f f i c i e n c y o f f o o d c o n v e r s i o n between t h e c h i c k e n s f e d on t he l o w - f a t l o w - p r o t e i n d i e t (1) and t h o s e f e d on t he h i g h - f a t l o w - p r o t e i n d i e t (2 ) t h r o u g h o u t t h e d u r a t i o n o f t he e x p e r i m e n t and t h e s u p e r i o r i t y o f t h e group f e d on the d i e t i n c o r -p o r a t i n g h i g h - f a t h i g h - p r o t e i n (4) o v e r t h e group f e d on the d i e t c o n t a i n -i n g l o w - f a t h i g h - p r o t e i n (3 ) i n t h e o v e r a l l s t a t i s t i c a l a n a l y s i s demon-s t r a t e a g a i n t he v a l i d i t y o f t h e s u g g e s t i o n t h a t d i e t s i n c o r p o r a t i n g f a t s s h o u l d c o n t a i n a c o n c o m i t a n t l e v e l o f p r o t e i n i n o r d e r t o a c h i e v e a s a t i s f a c t o r y f o o d c o n v e r s i o n e f f i c i e n c y v a l u e . A p o s s i b l e e x p l a n a t i o n f o r t he b e t t e r f o o d c o n v e r s i o n v a l u e s o b t a i n e d w i t h c h i c k e n s f e d the h i g h - f a t h i g h - p r o t e i n d i e t i s t h a t t h i s d i e t c o n t a i n e d a more s a t i s f a c t o r y m e t a b o l i s a b l e ene r g y c o n c e n t r a t i o n a s s o c i a t e d w i t h a f a v o u r a b l e c a l o r i e : p r o t e i n r a t i o . T h i s i s c o n s i s t e n t w i t h t h e r e p o r t e d low ene rgy c o s t o f f a t h y d r o l y s i s i n and t h e a b s o r p t i o n o f f a t f r om the i n t e s t i n e , o f t r i g l y c e r i d e r e s y n t h e s i s i n t he e p i t h e l i u m and o f t r a n s p o r t and d e p o s i t i o n r e l a t i v e t o t he e f f i c i e n c y w i t h w h i c h f a t t y a c i d s and c a r b o h y d r a t e s s u p p l y a c e t y l CoA f o r ene r gy r e q u i r e m e n t o r f a t s y n t h e s i s ( A n n i s o n , 1 971 ) . 42 3.2.1 Experiment 2 - Resu l t s The metabo l i s ab le energy values (ME) f o r the fou r exper imental d i e t s are presented i n Table 6. In the f i r s t week, b i r d s which were fed the l ow - f a t h i g h - p r o t e i n d i e t ( d i e t 3) metabol i sed energy s i g n i f i c a n t l y b e t t e r than b i rd s fed a l l other exper imental d i e t s . The d i f f e r e n c e s between a l l other d i e t a r y treatments dur ing the r e s t of the exper imental per iods 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 . However, there was a s i g -n i f i c a n t d i f f e r e n c e i n the combined values f o r the e n t i r e exper imental pe r i od . The t rend observed i n the f i r s t week was repeated in the o v e r a l l m e t a b o l i s a b i 1 i t y of the d i e t s w i th the value f o r the b a s a l - f a t h i gh -p r o t e i n d i e t s being s i g n i f i c a n t l y h igher than the two l ow-p ro te i n d i e t s . The added f a t appeared to i n f l uence m e t a b o l i s a b i 1 i t y of the d i e t s i n c o r -pora t ing the low p r o t e i n l e v e l s as evidenced by the s i g n i f i c a n t l y h igher ME values f o r the l ow-p ro te i n d i e t ( d i e t 2) which conta ined four percent more f a t than the o the r . As shown in Table 7, no s i g n i f i c a n t d i f f e r e n c e s were observed i n adipose t i s sue , among the four d i e t a r y groups. B i rds fed the l ow-p ro te i n d i e t i n which f a t rep laced s t a r ch ( d i e t 2) gave the h ighest adipose t i s s u e weights each week throughout the whole exper imental pe r i od . B i rds fed the h i g h - p r o t e i n d i e t in which f a t rep laced s ta r ch ( d i e t 4) gave the second h ighest adipose t i s s u e weights . The lowest adipose t i s s u e weights were obta ined i n b i r d s fed the d i e t i n c o r p o r a t i n g the basal l e v e l of d i e t a r y f a t and high l e v e l of p r o t e i n ( d i e t 3 ) . There were observable v a r i a t i o n s w i t h i n the d i e t a r y groups dur ing each week. 43 Table 6. E f f e c t of d i e t a r y f a t and p ro te i n l e v e l s on m e t a b o l i s a b i l i t y  of energy. D I E T C a l o r i e s 1 per gran i o f food Weeks No. Fat P r o t e i n 1 2 4 7 Overal1 1 Low Low 3343a 3460a 3568a 3560a 3483a 2 High Low 3270a 3482a 3530a 3516a 3450a 3 Low High 3429b 3532a 3604a 3533a 3525b 4 High High 3280a 3469a 3618a 3560a 3482a Means w i t h i n a column fo l lowed by d i f f e r e n t l e t t e r 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). 44 T a b l e 7. E f f e c t o f f a t and p r o t e i n l e v e l s on -mean abdominal a d i p o s e  t i s s u e w e i g h t . Grams D I E T Weeks No. F a t P r o t e i n 1 2 4 7 1 Low Low 1 . 5 7 ± 0 ? 0 7 4.87+0.84 15.30+0.72 22.76+4.84 2 H i gh Low 2.10+0.21 6 .20 ±o . 03 17.67+1.23 32.67^-2.70 3 Low H igh 1 .60 *0 ,06 4.80+TJ.33 13.07+1,39 19.03+1.36 4 H igh H i gh 1.60+0.17 6.17+0.50 13.07+0.83 27.00+1.31 S t a n d a r d e r r o r o f means. 45 The u t i l i s a t i o n o f m e t a b o l i s a b l e ene r gy f o r body w e i g h t g a i n was e s s e n t i a l l y t h e same f o r c h i c k e n s f e d t h e l o w - p r o t e i n d i e t s ( T a b l e 8 ) . A s i m i l a r r e l a t i o n s h i p was shown by c h i c k e n s f e d t h e h i g h e r p r o t e i n d i e t s f o r t h e second and t h e s e v e n t h weeks o f t h e e x p e r i m e n t . However, i n t he f i r s t week t h e r e was a d i f f e r e n c e between t h e two g roups f e d d i e t s c o n -t a i n i n g h i g h l e v e l s o f p r o t e i n . B i r d s f e d t h e l o w - f a t h i g h - p r o t e i n d i e t u t i l i s e d l e s s m e t a b o l i s a b l e ene rgy f o r a u n i t g a i n i n body w e i g h t . Com-p a r i s o n o f t h e m e t a b o l i s a b l e ene r gy i n t a k e pe r gram o f body w e i g h t g a i n r e v e a l e d l e s s i n t a k e f o r c h i c k e n s f e d t h e d i e t s w i t h h i g h - p r o t e i n l e v e l s up t o t he f o u r t h week. T h i s d i f f e r e n c e between t he two p r o t e i n - l e v e l g roups d i d no t e x i s t i n t h e s e v e n t h week. A l l g roups o f b i r d s u t i l i s e d m e t a b o l i s a b l e ene r gy w i t h t h e same e f f i c i e n c y i n t he f i r s t two weeks e x c e p t t h e g roup t h a t was f e d t h e h i g h - f a t h i g h - p r o t e i n d i e t wh i ch u t i l i s e d l e s s m e t a b o l i s a b l e ene r gy i n t h e f i r s t week. An i n c r e a s e i n m e t a b o l i s a b l e ene r gy i n t a k e pe r gram o f body w e i g h t g a i n was shown by a l l d i e t a r y g roups i n t h e f o u r t h and s ub sequen t weeks . M o r t a l i t y among t h e d i e t a r y g roups was s l i g h t and v a r i a b l e . The r e s p e c t i v e d e a t h s were 4 , 2 , 1 and 3 f o r d i e t a r y g roups 1, 2 , 3 and 4. A l l t h e l o s s e s o c c u r r e d between t he f o u r t h and s i x t h weeks and were a t t r i b u t a b l e t o p e r o s i s . 46 Metabolisable energy intake per bird per gram body  weight gain D I . • E T WEEKS1 No. Fat Protein Factor 1 2 4 7 1 Low Low ME (kcal/kg d iet) 3343 • 3460 3568 3560 Food intake (g)^ 20.1 34.2 54.2 117.0 ME intake (kcal) . 67.3 118.5 193.5 416.4 Weight gain (g) 13.3 23.2 31.1 48.3 ME/Weight gain 5.1 5.1 6.2 8.6 2 High Low ME (kcal/kg d iet ) 3270 3482 3530 3516 Food intake (g) 19.5 34.8 55.2 114.9 ME intake (kcal) 63.6 121.1 194.8 404.0 Weight gain (g) 12.7 23.9 31.6 46.8 ME/Weight gain 5.0 5.1 6.2 8.6 3 Low High ME (kcal/kg diet) 3429 3532 3604 3533 Food intake (g) 19.0 31.9 49.8 107.3 ME intake (kcal) 65.0 112.7 176.6 379.0 Weight gain (g) 14.2 24.1 31.5 47.7 ME/Weight gain 4.6 4.7 5.7 7.9 4 High High ME (kcal/kg d iet) 3280 3469 3618 3560 Food intake (g) 19.4 32.6 50.6 110.3 ME intake (kcal) 63.5 113.1 182.9 392.6 Weight gain (g) 15.6 24.6 35.0 47.9 ME/Weight gain 4.1 4.6 5.2 8.2 The birds were 2 days old at the commencement of feeding experimental d ie t s . Food intake per b i rd . 47 3.2.2 Experiment 2 - D i scuss ion The r e s u l t s of the metabo l i s ab le energy determinat ions (Table 6) suggest the need f o r d i e t a r y carbohydrate c a l o r i e s e a r l y in the l i f e of the b r o i l e r ch i cken . The f a c t that the d i e t s i n co rpo r a t i n g h igher f a t l e v e l s were more poor l y metabol i sed makes i t reasonable to assume tha t high d i e t a r y f a t l e v e l depresses m e t a b o l i s a b i l i t y of d i e t s i n young ch i ck s to one week of age. I t i s known that f a t s and o i l s have normal ly a very high a v a i l a b i l i t y of metabo l i s ab le energy (Tasaki and S aku ra i , 1969). However, the metabo l i s ab le energy content of a f a t i s the product of i t s gross energy content and i t s a b s o r b a b i l i t y (Whitehead and F i s h e r , 1975). I t has been e s t a b l i s h e d that corn o i l i s r e a d i l y absorbed by ch ick s (Renner and H i l l , 1960) and tha t the l e v e l of a b s o r b a b i l i t y remains the same up to 8 weeks of age. More recent determinat ions by Carew e_t a l . (1972) of a b s o r b a b i l i t i e s of corn o i l by ch i ck s i n d i c a t e tha t the newly hatched ch i ck to 7 days of age does not have f u l l p h y s i o l o g i c a l c apac i t y f o r f a t ab so rp t i on . I t i s suspected that the ch i ck s invo lved i n t h i s study must have absorbed f a t at a sub-optimal e f f i c i e n c y and t h i s cou ld have r e s u l t ed i n a lowered metabo l i s ab le energy i n take i n the f i r s t week. I t i s d i f f i c u l t to e x p l a i n the d i screpancy between the observed h igher body weight gains on the h i g h - f a t d i e t s in the f i r s t week (Table 3) and the lower metabo l i s ab le energy values on the same d i e t s i n the same pe r i od . The higher adipose t i s s u e content of the high f a t d i e t s may have con t r i bu ted to the h igher body weights . There i s evidence that 10 to 15 percent more energy was depos i ted i n the carcass of ch ickens 48 r e c e i v i n g d i e t s con ta i n i ng 5 to 10 percent f a t compared w i th s i m i l a r d i e t s low i n f a t and that t h i s phenomenon occurred even when metabo l i s -ab le energy i n take from the two d i e t s was the same (Carew et a l _ . , 1964). Forbes and Sw i f t (1944) observed t h i s phenomenon in r a t s and termed i t the a s s o c i a t i v e dynamic a c t i on of f a t s . The improvement i n ene rge t i c e f f i c i e n c y can be a t t r i b u t e d to a lower metabo l i c cost of u t i l i s i n g f a t s i n comparison to the other major source of d i e t a r y energy - carbohydrate. The suggest ion that poor a b s o r b a b i l i t y may have con t r i bu ted to the observed depress ion i n metabo l i s ab le energy values of the h i g h - f a t d i e t s seems v a l i d i n the l i g h t of the observed improvement in the metabo l i s a -b i l i t y of d i e t s i n co rpo r a t i n g high d i e t a r y f a t i n subsequent weeks when they had developed t h e i r p h y s i o l o g i c a l c apac i t y f o r f a t ab so rp t i on . The lack of s i g n i f i c a n t d i f f e r e n c e s i n the metabo l i sab le energy values of the d i e t s from two through seven weeks i s i n t e r e s t i n g from the po int of view of i t s economic i m p l i c a t i o n s . In terms of metabo l ic i m p l i c a t i o n , i t has been reported that p r o t e i n i s not the on ly d i e t a r y f a c t o r that must be adjusted commensurate w i th d i e t a r y f a t l e v e l (A i tken et_ a l_ . , 1954; S l i n g e r et_ a]_. , 1955). The l e v e l s of other n u t r i e n t s , notably some v i t a m i n s , r equ i r e adjustment (March and B i e l y , 1955, 1956; Looi and Renner, 1974a). I t f o l l o w s tha t the s u b s t i t u t i o n of f a t c a l o r i e s f o r s ta rch c a l o r i e s w i thout changing the propor t ions of other d i e t a r y f a c t o r s , p a r t i c u l a r l y the m i c r o n u t r i e n t s , c reates an imbalance among n u t r i e n t s . The inc idence on the h i g h - f a t d i e t s of p e r o s i s , a c ond i t i o n a t t r i b u t a b l e to a d e f i c i e n c y of manganese could have been p r e c i p i t a t e d by n u t r i e n t imbalance. F a r r e l l et al_. (1973) observed small d i f f e r e n c e s i n metabol i s a b l e energy values comparable to those being reported i n t h i s study and exp la ined the poor 49 growth r a te of b r o i l e r s fed d i e t s of va ry ing energy concent ra t ions on the bas i s of n u t r i e n t imbalance or d e f i c i e n c y . Wide v a r i a b i l i t y occurred w i t h i n the d i e t a r y groups and t h i s could have con t r i bu ted to the lack of s i g n i f i c a n t d i f f e r e n c e s i n adipose t i s s u e accumulat ion among the d i f f e r e n t treatment groups i n the f i r s t two weeks of the exper imental pe r i od . Chickens fed the h i g h - f a t l ow-p ro te i n d i e t (2) showed a s i g n i f i c a n t l y heav ier adipose t i s s u e weight i n the f ou r t h and seventh weeks (Table 7 ) . I t i s i n t e r e s t i n g to note that the per iods i n which the b i r d s fed the h i g h - f a t l ow-p ro te i n d i e t s depos i ted s i g n i f i -c a n t l y more adipose t i s s u e co i nc i ded w i th the per iods i n which the group i n quest ion gave the lowest metabo l i s ab le energy va lues . S ince the d i f -ferences i n the l a t t e r response c r i t e r i o n d id not reach s t a t i s t i c a l s i g -n i f i c a n c e (P < 0.05) there was l i t t l e or no bas i s to exp lore the p o s s i b i l i t y of a s t a t i s t i c a l r e l a t i o n s h i p . The reasons f o r the d i f f e r e n c e s i n f a t depo s i t i on among the treatment groups are not immediately obvious. S ince the h ighest depo s i t i on of f a t occurred i n b i rd s fed the h i g h - f a t low-p r o t e i n d i e t , the p o s s i b i l i t y e x i s t s t ha t the 18 percent p r o t e i n l e v e l was adequate i n terms of amino a c i d l e v e l s and ba lance. With an adequate supply of amino ac ids and preformed f a t t y a c i d s , the magnitude of n u t r i e n t i n te r conve r s i on s would be comparat ive ly l e s s and t h i s would r e s u l t in a sav ing i n energy which would have been expended on b i o s yn the s i s of n u t r i e n t s t ha t might be r e q u i r e d . The " s u r p l u s " energy could have been converted i n t o f a t . I t i s noteworthy that f a t depo s i t i on i n b i r d s fed the h i g h - f a t h i g h - p r o t e i n d i e t was l e s s than tha t i n b i r d s fed the h i g h - f a t l ow-p ro te i n d i e t . The p o s s i b i l i t y e x i s t s that the energy saved as a r e s u l t of the s p e c i f i c dynamic e f f e c t of f a t was d i r e c t e d towards u t i l i s i n g more p ro te i n f o r muscle t i s s u e s . Th is view becomes more a t t r a c t i v e when. i t i s cons idered 50 that b i r d s fed the l ow - f a t h i g h - p r o t e i n d i e t , which was i s o c a l o r i c w i th the other d i e t s , depos i ted the l e a s t amount of adipose t i s s u e . The r e s u l t s r e l a t i n g to the e f f i c i e n c y of metabo l i s ab le energy u t i l i s a t i o n us ing the number of c a l o r i e s of metabo l i sab le energy per a gram of body weight gain as a response c r i t e r i o n (Table 8) were the same f o r the d i e t s con ta i n i ng the low p r o t e i n l e v e l . A . s i m i l a r e f f e c t was shown between the h i g h - p r o t e i n d i e t s . The lower r a t i o s obta ined on the d i e t s i n co rpo r a t i n g h igher p r o t e i n l e v e l s and which contained a narrower c a l o r i e r p r o t e i n r a t i o , again emphasize the importance of t h i s p r i n c i p l e w i th regard to the e f f i c i e n t metabolism of d i e t a r y energy and n u t r i e n t s . The conc lus ions to be drawn on the r e s u l t s of t h i s study agree e s s e n t i a l l y w i th those reported by Payne and Lewis (1964), F a r r e l l ejt al_. (1973), and F a r r e l l (1974), i n that there appears to be an optimum energy concent ra t i on in the d i e t beyond which performance of b i rd s does not appear to improve and i n some cases a c t u a l l y d e t e r i o r a t e s . Payne and Lewis (1964)- found tha t growth ra te of b r o i l e r chickens d id not increase at energy l e v e l s above 3.1 Meal ME/kg and c a l o r i e s consumed per gram of gain were the same f o r d i e t s above 3.2 Meal ME/kg. 51 3.3 The E f f e c t o f Added C e l l u l o s e on t h e Pe r f o rmance o f B r o i l e r C h i c k s 3.3.1 E x p e r i m e n t 3 - I n t r o d u c t i o n The d o m e s t i c c h i c k e n has l i m i t e d d i g e s t i v e c a p a c i t y f o r f i b r o u s f o o d s . C e l l u l o s e has been used f r e q u e n t l y as an i n e r t f i l l e r i n many p o u l t r y e x p e r i m e n -t a l d i e t s . In a d d i t i o n t o i n c r e a s i n g t h e b u l k o f f o o d , c e l l u l o s e i s known t o a c c e l e r a t e t he r a t e o f pa s sage w h i c h means a s h o r t e n e d t i m e f o r s u b -s t r a t e - e n z y m e c o n t a c t and a c o n s e q u e n t r e d u c t i o n i n d i g e s t i o n o f f o o d and a b s o r p t i o n o f n u t r i e n t s . The p r e s e n c e and l e v e l o f . a d d e d c e l l u l o s e i n p o u l t r y d i e t s , t h e r e f o r e , imposes a v e r y i m p o r t a n t p r ob l em t h a t has n o t been i n v e s t i g a t e d s u f f i c i e n t l y . The r e s u l t s o f E x p e r i m e n t 2 j u s t i f y an a s s u m p t i o n t h a t t h e p r e s e n c e o f c e l l u l o s e must have c o n t r i b u t e d t o t h e p o o r e r m e t a b o l i s a b i l i t y o f t h e d i e t s w h i c h i n c l u d e d t h a t i n g r e d i e n t as compared w i t h t h o s e d e v o i d o f added c e l l u l o s e i n t h e e a r l y l i f e o f t h e c h i c k e n . U n f o r t u n a t e l y , most o f t h e . p a p e r s p u b l i s h e d on m e t a b o l i s a b i 1 i t y o f d i e t s i n c o r p o r a t i n g added c e l l u l o s e have i n v o l v e d c h i c k s w h i c h were o l d e r t h a n one week. The p a u c i t y o f i n f o r m a t i o n as i n d i c a t e d above prompted t h e f o l l o w i n g e x p e r i m e n t t o be c o n d u c t e d w i t h t h e o b j e c t i v e o f e v a l u a t i n g t h e e f f e c t o f added c e l l u l o s e on g rowth r a t e , f o o d c o n v e r s i o n e f f i c i e n c y , m e t a b o l -i s a b i l i t y o f ene r gy and f a t d e p o s i t i o n . 52 3 .3 .2 E x p e r i m e n t 3 - M a t e r i a l s and Methods D a y - o l d b r o i l e r c h i c k s were r andomly d i s t r i b u t e d i n t o 12 g roups o f s i x c h i c k s e a c h . A l l g roups were p l a c e d i n a s i x - t i e r b a t t e r y b r o o d e r e q u i p p e d w i t h w i r e f l o o r s and 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 h e a t i n g u n i t s . The g roups were a s s i g n e d a t random t o f o u r e x p e r i m e n t a l t r e a t m e n t s , t h r e e g roups pe r t r e a t m e n t . The t r e a t m e n t s were f o u r d i e t s d e s i g n a t e d , r e s p e c -t i v e l y , as d i e t s 1, 2 , 3 and 4 . The c o m p o s i t i o n o f t h e d i e t s a r e shown i n T a b l e 9. D i e t s 1 and 3 were d e v o i d o f added c e l l u l o s e w h i l e 2 and 4 each c o n t a i n e d 11.2 p a r t s added c e l l u l o s e D i e t s 1 and 2 d i f f e r e d f rom d i e t s 3 and 4 i n c o n t a i n i n g c o r n s t a r c h as t h e s o u r c e o f s u p p l e m e n t a r y e n e r g y . The l a t t e r c o n t a i n e d c o r n o i l as t h e s o u r c e o f s u p p l e m e n t a r y e n e r g y . Each g roup o f c h i c k e n s was f e d i t s e x p e r i m e n t a l d i e t and w a t e r ad  1 i b i t u r n f o r s i x weeks . Reco rd s were kep t o f w e e k l y f o o d con sumpt i on and i n d i v i d u a l body w e i g h t s . Food c o n v e r s i o n e f f i c i e n c y v a l u e s were computed f r om t h e w e e k l y f o o d c o n s u m p t i o n and body w e i g h t g a i n d a t a . Samples o f e x c r e t a were c o l l e c t e d a t 2 4 - hou r i n t e r v a l s on t h e l a s t t h r e e days o f each e x p e r i m e n t a l week. The d a i l y c o l l e c t i o n s were i m m e d i a t e l y f r o z e n and t h e t h r e e - d a y c o l l e c t i o n s f o r each g roup were p o o l e d t o g e t h e r , l y o p h i -l i z e d , f i n e l y g round and kep t i n s c r e w - c a p p e d g l a s s j a r s f o r v a r i o u s a n a l y s e s . M o i s t u r e was d e t e r m i n e d a c c o r d i n g t o A .O .A .C . method. D e t e r m i n a t i o n o f n i t r o g e n c o n t e n t o f t h e d i e t and f a e c a l samples was c o n d u c t e d by t h e Kj e l d a h l method and g r o s s ene rgy by bomb c a l o r i m e t r y u s i n g P a r r p l a i n j a c k e t oxygen bomb c a l o r i m e t e r . The s u b s t a n c e used as an i n d e x f o r 53 T a b l e 9. . C o m p o s i t i o n o f d i e t s f e d i n E x p e r i m e n t 3. D I E T I n g r e d i e n t 1 2 3 4 w e i g h t H e r r i n g meal 21 .3 2 1 . 3 21 .3 2 1 . 3 Ground wheat 53 .0 53 .0 53 .0 53 .0 Corn s t a r c h 19.2 19.2 - -Corn o i l 3 .0 3.0 11.0 11 .0 C a l c i u m pho spha te 1.5 1.5 1.5 1.5 L i m e s t o n e 1.0 1.0 1.0 1.0 S a l t 0.5 0.5 0.5 0.5 P r e m i x 1 0.5 0 .5 0.5 0.5 C e l 1 u l o s e • - 11.2 - 11.2 T o t a l w e i g h t 100.0 111.2 88 .8 100.0 C a l c u l a t e d c h e m i c a l a n a l y s i s % P r o t e i n 21 .9 19 .8 24 .7 21 .9 ME ( k c a l / k g ) 3382 3046 3814 3385 ME: CP 154 154 154 154 M i c r o n u t r i e n t s as i n T a b l e 1. 54 d i g e s t i b i l i t y c o e f f i c i e n t was 4N HC1 i n s o l u b l e a s h . The method used i s e s s e n t i a l l y t h e one d e s c r i b e d by Vogtmann e_t al_. ( 1 975 ) . Fo r f o o d and e x c r e t a , a p p r o x i m a t e l y 10 and 5 grams r e s p e c t i v e l y o f d r y samp le s were u s e d . The samples were h y d r o l y s e d by means o f b o i l i n g i n 100 ml o f 4N HC1 f o r 30 m i n u t e s . The h y d r o l y s a t e s were f i l t e r e d t h r o u g h a s h l e s s f i l t e r p a p e r , and washed w i t h d i s t i l l e d w a t e r u n t i l f r e e o f a c i d ' ( f i n a l d rops o f f i l t r a t e t e s t e d w i t h l i t m u s p a p e r ) . The f i l t e r pape r s w i t h t h e h y d r o l y s a t e s were a shed a t 600°C f o r a minimum o f s i x h o u r s . The m e t a b o l i s a b l e ene r g y v a l u e s c o r r e c t e d t o n i t r o g e n e q u i l i b r i u m were d e t e r m i n e d u s i n g t h e f o l l o w i n g e q u a t i o n : MEd = CEd - CEe X-.-j^j- - 8 .22 (Nd - Ne X ^ ) w h e r e , MEd = M e t a b o l i s a b l e ene r g y i n k i l o - c a l o r i e s p e r gram o f d i e t CEd = C o m b u s t i b l e ene r gy pe r gram o f d i e t CEe = C o m b u s t i b l e ene r gy p e r gram o f e x c r e t a Ad = Ash p e r gram o f d i e t Ae = Ash p e r gram o f e x c r e t a Nd = N i t r o g e n p e r gram o f e x c r e t a 8.22 = C o m b u s t i b l e ene r gy o f u r i c a c i d ( k c a l / g o f N) The d a t a were a n a l y s e d s t a t i s t i c a l l y u s i n g t h e a n a l y s i s o f v a r i a n c e and t h e S tuden t -Newman -Keu l s m u l t i p l e r ange t e s t s were used t o t e s t means w h i c h a r e s i g n i f i c a n t l y d i f f e r e n t . T h i s e x p e r i m e n t was o r i g i n a l l y d e s i g n e d t o l a s t t h r e e weeks but i t was c o n t i n u e d t o s i x weeks b e f o r e i t was t e r m i n a t e d . T h i s n e c e s s i t a t e d t h e m i x i n g o f a s econd b a t c h o f d i e t s a t f o u r weeks f o r t h e e x t e n d e d p e r i o d o f t i m e . 55 3.3.3 Experiment 3 - Resu l t s A summary of the e f f e c t of the d i e t a r y treatments on t o t a l body weight gain i s presented i n Table 10. Average body weight gain obta ined w i t h the l ow - f a t c e l l u l o s e - added d i e t was s i g n i f i c a n t l y lower than that obta ined w i th the h i g h - f a t c e l l u l o s e - e x c l u d e d d i e t . On the bas i s of source o f d i e t a r y energy, h igher t o t a l body weight gains were obta ined w i t h the fa t -based than w i th the s tarch-based d i e t s . With in the set r e l a t i n g to energy source, h igher body weight gains were obta ined w i th the d i e t s which d i d not i nco rpo ra te c e l l u l o s e . When the data on body weight gain were analysed on weekly bas i s (Table 11), i t was shown that the b i rd s fed the d i e t s wi thout added c e l l u l o s e were gene ra l l y s l i g h t l y heav ier than those fed the d i e t s i n co rpo r a t i n g added c e l l u l o s e . The p rog res s i ve increases i n body weight gain on the " c e l l u l o s e - f r e e " d i e t s were r e f l e c t e d in s i g n i f i c a n t d i f f e r e n c e s i n mean weekly body weight gains among the d i e t a r y groups i n the t h i r d and s i x t h weeks of the exper imental pe r i od . F i g . 3 shows the trend of growth, among the d i f f e r e n t d i e t a r y groups. The a d d i t i o n of f a t r e s u l t e d i n improved e f f i c i e n c y of food convers ion in the f i r s t three weeks. B i rds fed the d i e t s i n co rpo r a t i n g added c e l -l u l o s e made poorer convers ion of food. The poorest food convers ion e f f i c i e n c y values were obta ined c o n s i s t e n t l y w i th the b i rd s fed the low-f a t c e l l u l o s e - i n c l u d e d d i e t (Table 12). The r e l a t i o n s h i p e x i s t i n g among the determined food convers ion e f f i c i e n c y values as p l o t t e d aga in s t each weekly per iod of time i s markedly a l t e r e d when the adjusted food conver-s ion e f f i c i e n c y values are s i m i l a r l y p l o t t e d . As shown in F i g . 4, the 56 T a b 1 e 1 0 - E f f e c t o f s o u r c e o f s u p p l e m e n t a r y d i e t a r y energy and  c e l l u l o s e on t o t a l body w e i g h t g a i n . D I E T Mean body we i gh t ^ i n grams No. S t a r c h F a t C e l 1 u l o s e I n i t i a l F i n a l G a i n 1 +2 Basa l 1 33 1227 1194ab 2 + Basa l + 33 1170 1137b 3 - + - 32 1327 1295a 4 - + + 32 1286 1254ab Means w i t h i n a column f o l l o w e d by d i f f e r e n t l e t t e r s a r e s i g n i f i c a n t l y d i f f e r e n t (P < 0 . 0 5 ) . (+)> (-)> s i g n i f i e s p r e s e n t , a b s e n t , r e s p e c t i v e l y . 57 T a b 1 e 1 T ' E f f e c t o f s o u r c e o f s u p p l e m e n t a r y d i e t a r y ene rgy and  c e l l u l o s e on w e e k l y body w e i g h t g a i n s . D I E T Mean body w e i g h t p a i n s i n grams Weeks No. S t a r c h F a t C e l l u l o s e I n i t i a l 1 2 3 4 5 6 1 Basa l _2 (33) 55a 138a 203ab 233a 261a 306ab 2 + Basa l + (33) 55a 127a .188b 229a 272a 267b .3 - + - (32) 61a 135a 221a 252a 295a 331a 4 - + + (32) 64a 139a 221a 240a 292a 297ab Means i n a column f o l l o w e d by d i f f e r e n t l e t t e r s a r e s i g n i f i c a n t l y d i f f e r e n t (P < 0 . 0 5 ) . (+)•> ( - ) , s i g n i f i e s , p r e s e n t , a b s e n t , r e s p e c t i v e l y . 58 1500 r -X CD UJ >-o o GO < Ul 2 1000 500 -* 3% OIL, NO ADDED CELLULOSE DI D2 D3 D4 ^ ||%0IL,II.2% ADDED CELLULOSE// 3% OIL, 11.2% ADDED CELLULOSE - • 1I%0IL, NO ADDED CELLULOSE 0 2 3 4 AGE (WEEKS) FIG.3 EFFECT OF SOURCE OF SUPPLEMENTARY DIETARY ENERGY AND CELLULOSE ON FOOD CONVERSION EFFICIECY. 59 d i f f e r e n c e s among t h e t r e a t m e n t g roups a r e v i r t u a l l y e l i m i n a t e d o r n o n - e x i s t e n t i n t h e a d j u s t e d v a l u e s as compared t o t he d e t e r m i n e d f o o d c o n v e r s i o n e f f i c i e n c y v a l u e s ( T a b l e 1 2 a ) . The r e s u l t s o f t h e d e t e r m i n a t i o n s o f m e t a b o l i s a b l e ene r gy v a l u e s a r e p r e s e n t e d i n T a b l e 13. S e ve r e d e p r e s s i o n o f m e t a b o l i s a b i 1 i t y o f ene r gy was o b s e r v e d w i t h t h e d i e t s i n c o r p o r a t i n g c e l l u l o s e . The g r e a t e s t d e p r e s s i o n o c c u r r e d i n t h e f i r s t week. F o r t h e f i r s t t h r e e weeks t he m e t a b o l i s a b l e ene rgy v a l u e s were p r o g r e s s i v e l y h i g h e r f o r a l l d i e t s . The i n t r o d u c t i o n o f a s econd mix o f d i e t was a t t e n d e d w i t h a d e c r e a s e i n m e t a b o l i s a b l e ene r gy v a l u e s i n t h e f o u r t h week. There was a r i s e i n m e t a b o l i s a b i 1 i t y o f ene rgy i n t h e s ub sequen t weeks . A c o m p a r i s o n between t h e d e t e r m i n e d m e t a b o l i s a b l e ene rgy v a l u e s ( T a b l e 13) and t h e c o r r e s p o n d i n g a d j u s t e d m e t a b o l i s a b l e ene rgy v a l u e s ( T a b l e 1 4 ) , shows c l e a r l y t h e e f f e c t o f t h e added c e l l u l o s e on t h e e f f i c -i e n c y o f ene r gy m e t a b o l i s m . The r e l a t i o n s h i p e x i s t i n g among t h e d e t e r -mined v a l u e s i s compared t o t h a t e x i s t i n g among t h e a d j u s t e d v a l u e s ( F i g . 5 ) . The mean a d i p o s e t i s s u e w e i g h t s a r e p r e s e n t e d i n T a b l e 15. The d i e t a r y s o u r c e o f ene r gy appea red t o have no i n f l u e n c e on f a t d e p o s i t i o n i n t h i s e x p e r i m e n t . A l t h o u g h t h e b i r d s f e d d i e t s w i t h f a t as t he ma jo r s o u r c e o f ene rgy l a i d down more f a t t han t h o s e f e d d i e t s w i t h c a r b o h y d r a t e as t he m a j o r s o u r c e o f e n e r g y , t h i s d i f f e r e n c e becomes n e g l i g i b l e when t h e v a l u e s a r e compared on t h e b a s i s o f c e l l u l o s e l e v e l . The b i r d s w h i c h were f e d d i e t s w h i c h d i d no t c o n t a i n added c e l l u l o s e had t he h e a v i e r a d i p o s e t i s s u e t h a n t h o s e f e d d i e t s c o n t a i n i n g added c e l l u l o s e . 60 Tab l e 12. E f f e c t o f s o u r c e o f s u p p l e m e n t a r y ene rgy and c e l l u l o s e  on f o o d c o n v e r s i o n e f f i c i e n c y . U n i t s o f f ood per u n i t o f g a i n D I E T Weeks No. S t a r c h F a t Ce l 1 u l o s e 0-1 0 -2 0-3 0 -4 0-5 0-6 O v e r a l T 1 + Basa l 1.24 1.28 1.47 1.52 1.67 1.81 1.50 a 2 + Ba sa l +2 1.50 1.55 1.61 1.74 1.90 2.01 1.72 c 3 - + - 1.18 1.23 1.24 1.36 1.50 1.58 1.35 b 4 - + +2 1.21 1.37 1.38 1.53 1.73 1.91 1.52 a V a l u e s w i t h i n a co lumn f o l l o w e d by t h e same l e t t e r do no t d i f f e r s i g n i f i c a n t l y (P < 0 . 0 5 ) . 61 e 1 2 ( a ) . E f f e c t o f s o u r c e o f s u p p l e m e n t a r y d i e t a r y ene rgy component on f o o d c o n v e r s i o n e f f i c i e n c y c a l c u l a t e d on t h e b a s i s o f i n g r e d i e n t s o t h e r than added c e l l u l o s e . D I E T A d j u s t e d u n i t s " 1 o f f ood pe r u n i t o f g a i n Weeks No.. S t a r c h F a t C e l l u l o s e 0.1 0.2 0.3 0.4 0.5 0.6 Ove r a l 1 1 + Basa l - 1.24 1.28 1.47 1.52 1.67 1.81 1.50 a 2 + Basa l + 2 1.35 1.39 1.45 1.56 1.71 1.81 1.55 a 3 - + 1.18 1.23 . 1.24 1.36 1.50 1.58 1.35 b 4 + + 2 1.07 1.22 1.23 . 1 . 3 7 1.54 . 1.71 1.36 b V a l u e s w i t h i n a co lumn f o l l o w e d by t h e same l e t t e r do no t d i f f e r s i g -n i f i c a n t l y (P < 0 . 0 5 ) . The added c e l l u l o s e was no t used i n c a l c u l a t i o n . 62 i cn < CD X (D LU >~ Q O CD Lu O LU Q_ Q LU LU CO r-1.8 1.6 h 1.4 1.2 1.0 DATA ADJUSTED FOR CELLULOSE DI — D 2« D3 • D4 - 3 % OIL, NO ADDED CELLULOSE •- 3 % OIL , 11.2 % ADDED CELLULOSE - 1.1% OIL, NO ADDED CELLULOSE 2.0 r 11% OIL, 11.2% ADDED CELLULOSE 1 2 3 4 5 6 AGE (WEEKS) FIG. 4 : EFFECT OF SOURCE OF SUPPLEMENTARY DIETARY ENERGY AND CELLULOSE ON FOOD CONVERSION EFFICIENCY. 63 E f f e c t o f s o u r c e o f s u p p l e m e n t a r y d i e t a r y ene r gy and  c e l l u l o s e on m e t a b o l i s a b l e ene rgy v a l u e s . C a l o r i e s per gram o f d i e t D No. I S t a r c h E T Fa t C e l l u l o s e 1 2 Weeks 3 4 6 1 +2 B a s a l 2 3349 3652 3777 3608 3608 c 2 Ba sa l + 2966 3148 3444 3177 3264 a 3 - + 3252 3867 3933 3651 3863 d 4 + + 2591 3268 3556 2972 3349 a Means i n a co lumn f o l l o w e d by d i f f e r e n t l e t t e r s a r e s i g n i f i c a n t l y d i f f e r e n t (P < 0 . 0 5 ) . ( + ) » ( - )» s i g n i f i e s p r e s e n t , a b s e n t , r e s p e c t i v e l y . T a b l e 14. E f f e c t o f d i e t a r y s o u r c e o f s u p p l e m e n t a r y d i e t a r y ene r gy on m e t a b o l i s a b l e  energy v a l u e s c a l c u l a t e d on t h e b a s i s o f i n g r e d i e n t s o t h e r t h a n added  c e l l u l o s e . A d j u s t e d ene r g y v a l u e s 1 i n • n T r T c a l o r i e s / g o f d i e t u 1 L 1 Weeks No. S t a r c h F a t C e l l u l o s e 1 2 3 4 6 o v e r a l 1 1 + 2 B a s a l _2 3349 3652 3777 3608 3608 3596a 2 + B a s a l + 3298 3500 3830 3532 3630 3558a 3 + - 3252 3867 3933 3651 3863 3713b 4 + + 2917 3680 4004 3346 3771 3544a ^Means i n a column f o l l o w e d by d i f f e r e n t l e t t e r s a r e s i g n i f i c a n t l y d i f f e r e n t (P<. 0 . 0 5 ) . ( + ) , ( - ) , s i g n i f i e s p r e s e n t , a b s e n t , r e s p e c t i v e l y . 65 UJ Q < ce o cc ui CL CO UJ DC O -J < o 4000 3500 3000 DATA ADJUSTED FOR ADDED CELLULOSE *-..\ D 3% OIL, NO ADDED CELLULOSE 4000 r-3500 3000 2500 D 2 - - 3% OIL, 11.2% ADDED CELLULOSE D3 • • 11% OIL, NO ADDED CELLULOSE D 4 » . _ ||% OIL, 11.2% ADDED CELLULOSE ORIGINAL DATA. _ i _ 2 3 4 AGE (WEEKS) FIG. 5: EFFECT OF SOURCE OF SUPPLEMENTARY DIETARY ENERGY AND CELLULOSE ON FOOD CONVERSION EFFICIENCY. 66 T a b l e 15. E f f e c t o f s o u r c e o f s u p p l e m e n t a r y d i e t a r y ene r gy and  c e l l u l o s e on f i n a l ( s i x - w e e k ) a d i p o s e t i s s u e w e i g h t s . Q j £ j Grams o f mean abdomina l f a t No. S t a r c h F a t C e l l u l o s e ( s i x - w e e k ) 1 + 2 B a s a l - 2 25.72 ± 2 . 7 2 1 2 + Ba sa l + 18.33 ± 1.95 3 _ + _ 31 .79 ± 4 . 5 5 4 - + • + 19.68 ± 2.89 S t a n d a r d e r r o r o f t h e mean. ( + )» (-)> s i g n i f i e s p r e s e n t , a b s e n t , r e s p e c t i v e l y . 67 3 .3 .4 E x p e r i m e n t 3 - D i s c u s s i o n The h i g h e r body w e i g h t g a i n s o f c h i c k e n s f e d d i e t s d e v o i d o f added c e l l u l o s e i n c o m p a r i s o n t o t h o s e f e d d i e t s i n c o r p o r a t i n g added c e l l u l o s e i n d i c a t e t h a t 11 p e r c e n t added c e l l u l o s e has a d v e r s e e f f e c t s on body w e i g h t g a i n ( T a b l e 1 0 ) . T h i s f i n d i n g i s i n a c c o r d w i t h a l a r g e body o f e v i d e n c e i n t he l i t e r a t u r e . However , i t i s a t v a r i a n c e w i t h t h o s e o f M o r r i s e t al_. ( 1 9 3 2 ) , D a v i s and B r i g g s ( 1947 , 1 9 4 8 ) , and S a i t o e t al_. ( 1 9 5 9 ) , t h a t f e e d i n g mode ra te amounts o f f i b r o u s m a t e r i a l s may i n c r e a s e g rowth and improve t h e u t i l i s a t i o n o f f o o d above t h a t o b t a i n e d on t he low f i b r e b a s a l d i e t . The s i g n i f i c a n t d i f f e r e n c e i n t o t a l body w e i g h t g a i n b e -tween t he c h i c k e n s f e d t h e h i g h - f a t c e l l u l o s e - e x c l u d e d d i e t and t h o s e f e d t he l o w - f a t ( c a r b o h y d r a t e - b a s e d ) , c e l l u l o s e - a d d e d d i e t , appea r s t o c o n f i r m i n p r i n c i p l e t he s t a t e m e n t made by B e g i n (1961) t h a t t he m a j o r e f f e c t o f c e l l u l o s e when i n c l u d e d i n t he d i e t w i t h o u t s u p p l e m e n t a r y ene r g y was a d e p r e s s i o n i n g r o w t h . T h i s appea r s t o s u g g e s t t h a t d i e t s h i g h i n f i b r o u s i n g r e d i e n t s s h o u l d c o n t a i n a h i g h p r o p o r t i o n o f e ne r g y w h i c h c o u l d be u t i -l i s e d f o r g rowth o r p r o d u c t i o n . Corn o i l i s s u p e r i o r t o s t a r c h i n t h a t i t c o n t a i n s t h e much-needed f a t t y a c i d s w h i l e s t a r c h does n o t . T h e r e f o r e c h i c k e n s f e d t h e c o r n o i l - r i c h d i e t s had t h e advan tage o f u t i l i s i n g t h e ene r g y w h i c h w o u l d have been expended i n f a t t y a c i d b i o s y n t h e s i s f o r g r o w t h . Hence , i n c r e a s e i n body w e i g h t o f b i r d s w h i c h were f e d t h e f a t - b a s e d c e l l u l o s e - i n c l u d e d d i e t o v e r t h o s e f e d t h e s t a r c h - b a s e d c e l l u l o s e - i n c l u d e d d i e t , i s u n d e r s t a n d a b l e . The d a t a on f o o d c o n v e r s i o n e f f i c i e n c y ( T a b l e 12) a r e i n l i n e w i t h t h e c o n c e p t as men t i oned e a r l i e r t h a t t h e a d d i t i o n o f h i g h l e v e l s o f f i b r o u s i n g r e d i e n t s t o c h i c k e n d i e t s d e p r e s s e s t h e 68 e f f i c i e n c y o f f o o d u t i l i s a t i o n . The e v i d e n c e shows t h a t w i t h i n t h e s e r i e s r e l a t i n g t o t h e s o u r c e o f d i e t a r y e n e r g y , t h e b i r d s f e d t h e d i e t s i n c o r p o r a t i n g added c e l l u l o s e u t i l i s e d more f o o d f o r a u n i t o f body w e i g h t g a i n i n c ompa r i s on w i t h t h o s e f e d t h e d i e t s c o n t a i n i n g no added c e l l u l o s e . The f a c t t h a t t h e d i f f e r e n c e s e x i s t e d between t h e two mean w e e k l y v a l u e s w i t h i n t h e s t a r c h - b a s e d o r f a t - b a s e d s e r i e s , becomes m a r k e d l y r educed o r p r a c t i c a l l y n o n - e x i s t e n t ( T a b l e 12a) when t he v a l u e s a r e c a l c u l a t e d t o remove t h e e f f e c t s a t t r i b u t a b l e t o t h e added c e l l u l o s e , d e m o n s t r a t e s t h e i n f l u e n c e o f added c e l l u l o s e ( F i g . 4 ) . The mucosa o f t h e g a s t r o i n t e s t i n a l t r a c t a c t s as a b a r r i e r a g a i n s t t h e e n t r y i n t o t h e body o f l a r g e m o l e c u l e s , w h i c h , i f a b s o r b e d , a r e no t w e l l u t i l i s e d (Wh i te e t a l _ . , 1 973 ) . H a l l s w o r t h and Coa te s (1962) r e p o r t e d t h a t h i g h f i b r e d i e t s cau sed g r e a t e r d e s t r u c t i o n o f mucosa l c e l l s . T h i s a c t i o n may e x p l a i n t h e o b s e r v e d s e v e r e d e p r e s s i o n o f m e t a b o l i s a b i l i t y o f ene rgy o b t a i n e d w i t h b i r d s f e d t h e d i e t s i n c o r p o r a t i n g added c e l l u l o s e . As shown by F i g . 5, t h e r e d u c t i o n i n magn i t ude o r e l i m i n a t i o n o f s i g n i f i -c a n t d i f f e r e n c e s between t h e o b s e r v e d ( T a b l e 13) and t h e a d j u s t e d ( T a b l e 14) mean m e t a b o l i s a b l e ene r gy v a l u e s , p r o v i d e s a d d i t i o n a l s u p p o r t f o r t h e v i e w t h a t , a t h i g h e r d i e t a r y l e v e l s added d i e t a r y c e l l u l o s e d e p r e s s e d m e t a b o l i s a b i l i t y o f e n e r g y . T h i s f i n d i n g i s c o n t r a r y t o t h o s e o f S i b b a l d and S l i n g e r ( 1 9 6 0 ) , P o t t e r e t al_. ( 1 9 6 0 ) , and B e g i n (1961) who r e p o r t e d c e l l u l o s e t o be i n e r t i n r e s p e c t o f i t s e f f e c t on m e t a b o l -i s a b l e ene r g y v a l u e s . Tha t added d i e t a r y c e l l u l o s e has a d e p r e s s i n g e f f e c t on a d i p o s e t i s s u e d e p o s i t i o n i s shown by t h e d a t a p r e s e n t e d i n T a b l e 15. A p o s s i b l e e x p l a n a t i o n f o r t h e o b s e r v e d h i g h e r v a l u e s o f mean a d i p o s e t i s s u e w e i g h t 69 o b t a i n e d w i t h b i r d s f e d d i e t s d e v o i d o f added c e l l u l o s e w i t h i n t h e s e r i e s r e l a t i n g t o s u p p l e m e n t a r y ene r g y s o u r c e , appea r s t o be a p o s s i b l e l o w e r e d ene r gy i n t a k e . Ha inan (1930),. R o b e r t s o n e t a l_. ( 1 9 4 8 ) , and W e l l s (1963) a t t r i b u t e d a s i m i l a r o b s e r v a t i o n t o t h e i m p o s i t i o n o f p h y s i c a l l i m i t a t i o n on t h e i n t a k e o f d i g e s t i b l e n u t r i e n t s . 70 3.4 The E f f e c t of Residual Yolk on the Performance of Chicks 3.4.1 Experiments 4 and 5 3.4.1.1 I n t r oduc t i on There i s a wide v a r i a t i o n among metabo l i s ab le energy values assayed w i t h ch i c k s up to th ree weeks o f age. S i bba ld e t al_. (1960) cons idered the i n f l u e n c e o f age on the metabo l i s ab le energy value of corn to be small and n e g l i g i b l e f o r p r a c t i c a l purposes. Bayley et al_. (1974) repor ted the metabo l i s ab le energy values of ten samples of rapeseed meal determined w i th both ch i ck s and mature roos te r s to be equa l . On the other hand, there are repor t s that i n d i c a t e that the metab-o l i s a b l e energy values f o r some feed i ng red i en t s and d i e t s are h igher . f o r mature b i rd s than f o r ch i ck s ( B a l d i n i , 1961; Young, 1961; Carew et a l_ . , 1963; Ze lenka, 1968; Lodhi e t a l_ . , 1 969; March et a l_ . , 1973). An a t t r a c t i v e theory used to e xp l a i n the d i screpancy among reported metabo l i s ab le energy values of d i e t s determined w i th ch ick s i s the one i m p l i c a t i n g the r e s i dua l y o l k . A v a i l a b l e evidence i n d i c a t e s that absor-p t i on of the yo l k sac cont inues u n t i l about the 14th day in the l i f e of the ch i ck (Zelenka, 1968). S i bba ld and STinger (1963) suggested that the r e s i dua l y o l k might f u r n i s h the ch i ck wi th a s i g n i f i c a n t supply of n u t r i e n t s f o r per iods up to 10 days po s t - ha t ch i ng . A s i g n i f i c a n t supply of n u t r i e n t s from the r e s i dua l y o l k would i n d i c a t e that the metabo l i s ab le energy values determined dur ing t h i s per iod would be i n f l uenced in a cco r -dance wi th the magnitude of c o n t r i b u t i o n of n u t r i e n t s by the r e s i dua l y o l k . Zelenka (1968) te s ted t h i s hypothes is and pub l i shed r e s u l t s that i n d i c a t e changes i n the metabo l i s ab le energy values of d i e t s w i t h i n the 71 f i r s t 14 days of the c h i c k ' s l i f e . As the e f f i c i e n c y of u t i l i s a t i o n of metabo l i s ab le energy i s the prime concern of t h i s phase of the s tudy, two experiments were conducted to i n v e s t i g a t e the e f f e c t o f r e s i dua l y o l k on the metabo l i s ab le energy values of a p r a c t i c a l d i e t and on the s u r v i v a l of ch i cken s . 72 3.4.1 Experiment 4 - M a t e r i a l s and Methods Day-old b r o i l e r s were d i s t r i b u t e d at random i n to three groups of twelve ch i ck s each accord ing to treatments which were c o n t r o l , sham-operated and s u r g i c a l l y - a l t e r e d . The sham-operated ch i c k s had t h e i r y o l k sacs brought out s ide the body c a v i t i e s , manipulated and returned to p o s i t i o n i n t a c t wh i l e the s u r g i c a l l y - a l t e r e d ch ick s had t h e i r y o l k sacs ab la ted through the f o l l o w i n g techn ique. Approximately 0.2 ml of pento-barb i tone (nembutal at a concent ra t i on of 60 mg/ml) was i n j e c t e d i n t r a -venously i n t o each ch i c k . The anaes thet i zed ch i ck was p laced back downwards w i th the vent towards the operated and was fastened to an oper-a t i n g board by i t s legs and wings w i th e l a s t i c bands. A f t e r p luck ing the down on the abdomen, the ch i ck was washed w i th an a n t i s e p t i c s o l u t i o n . The y o l k sac was reached through an i n c i s i o n made i n t o the sk in and the under l y ing muscles to the l e f t of the centre l i n e of the abdomen. The yo l k sac was brought out w i th forceps and was l i g a t e d at the s t a l k before s e c t i o n . The y o l k sacs of sham-operated ch i ck s were brought ou t , handled and pushed back. The abdominal w a l l s of both the yo l k sac -ab la ted and sham-operated chicks ' 'were c lo sed by cot ton sutures each pass ing through the s k i n and the muscle l a y e r s . A t o p i c a l a n t i b i o t i c d res s ing was app l i ed to the sutured area. The operated ch i ck s were put in a ba t te r y brooder and no s p e c i a l treatment was necessary a f t e r complete recovery from the anaes the t i c which l a s t ed approx imately two hours. 73 The three groups o f . i n t a c t and operated ch i ck s were housed, a cco r -d ing to t reatments , in e l e c t r i c a l l y - h e a t e d , 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 ba t te r y brooders w i th r a i s ed w i re screen f l o o r s , in a w e l l - v e n t i l a t e d , t empera tu re - con t ro l l ed brooding room. One treatment group cons i s ted o f two r e p l i c a t e s of s i x ch i c k s each. A l l were fed the same experimental d i e t , the compos i t ion of which i s shown in Table 16. Food and water were prov ided ad l i b i t u m . Records were kept on body weight and food con-sumption on weekly ba s i s . Both food and excreta samples were analysed f o r mo i s tu re , n i t rogen and combust ib le energy accord ing to methods as desc r ibed f o r Experiment 3. T a b l e 16. C o m p o s i t i o n o f e x p e r i m e n t a l d i e t - E x p e r i m e n t 4 I n g r e d i e n t s P e r c e n t H e r r i n g meal (72% CP; 3197 k c a l ME/kg) 21 .3 Ground wheat 53.0 Corn s t a r c h 19.2 Corn o i l 3.0 L i m e s t o n e 1.0 C a l c i u m pho spha te 1.5 P r e m i x 1 0 .5 I o d i z e d s a l t 0.5 M i c r o i n g r e d i e n t s as d e s c r i b e d i n T a b l e 1. 75 3 .4 .2 E x p e r i m e n t 4 - R e s u l t s F o r t h e p e r i o d o f 1-21 days p o s t h a t c h i n g , t h e r e were no s i g n i f i c a n t d i f f e r e n c e s i n body w e i g h t g a i n s between t h e t r e a t m e n t g r oup s . T a b l e 17 shows t h a t i n t h e f i r s t week t h e c h i c k s w i t h o u t y o l k s a c s g a i n e d s l i g h t l y more w e i g h t t h a n bo th c h i c k s i n t h e c o n t r o l and t h e s ham-ope r a t ed g roups b u t t h i s f e a t u r e was n o t shown i n t h e second week. The f i n a l body w e i g h t s do n o t show any s i g n i f i c a n t d i f f e r e n c e s between t r e a t m e n t g r o u p s . F i g . 6 g i v e s t he g r a p h i c a l r e p r e s e n t a t i o n o f t h e t r e n d s i n g rowth r a t e . The re was 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 h e o v e r a l l e f f i c i e n c y o f f o o d c o n v e r s i o n between t h e c o n t r o l and s h a m - o p e r a t e d g roups on t he one hand and t h e g roup w i t h y o l k s a c s removed on t he o t h e r ( T a b l e 1 8 ) . T h r o u g h o u t t h e e x p e r i m e n t a l p e r i o d , t h e c h i c k s w i t h o u t r e s i d u a l y o l k u t i l i z e d more f o o d . p e r u n i t g a i n i n body w e i g h t t han e i t h e r t h e c o n t r o l o r t h e s h a m - o p e r a t e d c h i c k s . F i g . 7 shows t h e t r e n d s r e l a t i n g t o e f f i -c i e n c y o f f o o d u t i l i s a t i o n t h a t e x i s t e d among t he t h r e e t r e a t m e n t g r oup s . Data on t h e e f f e c t o f t r e a t m e n t on t he m e t a b o l i s a b l e ene r gy v a l u e s o f t he d i e t a r e p r e s e n t e d i n T a b l e 19. The t r e a t m e n t s employed had no a p p a r e n t e f f e c t on m e t a b o l i s a b i l i t y o f t h e d i e t . The s l i g h t l y h i g h e r m e t a b o l i s a b l e ene r gy v a l u e s o b t a i n e d w i t h b i r d s w i t h o u t r e s i d u a l y o l k s compared w i t h t h o s e o b t a i n e d w i t h t he s h a m - o p e r a t e d b i r d s p r o v i d e s c l e a r e v i d e n c e t h a t t h e s u r g e r y p e r se d i d n o t a f f e c t t h e c h i c k s a b i l i t y t o m e t a b o l i s e e n e r g y . An i n t e r e s t i n g p o i n t b r o u g h t o u t by t h e d a t a ( F i g . 8 ) . i s t h e h i g h e r a p p a r e n t r e t e n t i o n v a l u e ( 2 . 53 g/100 g o f d i e t ) o b t a i n e d w i t h the b i r d s w i t h o u t r e s i d u a l y o l k compared t o t he 2.18 and 2.13 g/100 g 76 Table 17. E f f e c t of r e s i dua l yolk on weekly body weights and t o t a l  body weight ga in . Mean body weight and weight gains (g) Weeks x , , Tota l Treatment . I n i t i a l 1 2 3 Gain Contro l 33a 89a 225a 426a 393a Sham-operated 34a 90a 226a 437a 404a Yolk sac removed 32a 93a 224a 427a 396a Means w i t h i n a column fo l l owed by the same l e t t e r do not d i f f e r s i g n i f i -c a n t l y (P < 0.05). 77 AGE ( WEEKS) FIG. 6 : EFFECT OF RESIDUAL YOLK SAC ON TOTAL BODY WEIGHT. 78 Table 18. E f f e c t of r e s i dua l yo lk on food convers ion e f f i c i e n c y . Un i t s of food per u n i t of body weight gain Weeks Treatment 1 2 3 Ove ra l l Control 1 .24a 1 .28a 1 .47a 1 .33a Sham-operated 1 .18a 1 .31a 1 f 40a 1 .29a Yolk sac removed 1 .37a 1 .49b' 1 .54a 1 .46b Values f o l l owed by d i f f e r e n t l e t t e r 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). 79 .8 r < O U_ O h; or UJ D_ Q O O u. o CO 1.0 0 YOLK SAC REMOVED. _ . INTACT SHAM-OPERATED I 2 AGE (WEEKS) FIG. 7: EFFECT OF RESIDUAL YOLK ON CUMULATIVE FOOD CONVERSION EFFICIENCY. 80 Table 19. E f f e c t o f r e s i dua l yo l k on metabo l i sab le energy va lues . Mean1 ME" values (kcal/kg) Weeks Treatment 1 2 3 Contro l 3402a 3673a 3788a Sham-operated 3348a 3625a 3776a Yolk sac removed 3396a 3635a 3776a Means w i t h i n a column fo l l owed by the same l e t t e r are 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). ME : Metabo l i s ab le energy. 81 wi th the sham-operated b i rd s prov ides c l e a r evidence tha t the surgery per se d id not a f f e c t the ch i ck s a b i l i t y to metabo l i se energy. An i n t e r e s t i n g po i n t brought out by the data on apparent n i t r ogen r e t e n t i o n i s the h igher apparent r e t e n t i o n value (2.53 g/100 g of d i e t ) obta ined w i th the b i r d s without r e s i d u a l y o l k compared to the 2.18 and 2.13 g/100 g obta ined w i th the i n t a c t and the sham-operated b i r d s , r e s -p e c t i v e l y , i n the f i r s t week and the dramatic drop to p r a c t i c a l l y the same l e v e l (2.39 g/100 g of d i e t ) as t ha t of the sham-operated b i rd s i n the second week ( F i g . 8 ) . The value f o r the b i rds without r e s i dua l y o l k s rose as sharp ly as i t had dipped reaching a l e v e l of 2.68 g/100 g of d i e t , the h ighest of the three values in the t h i r d week. Both the i n t a c t and the sham-operated b i r d s showed a gradual r i s e i n apparent n i t rogen r e t e n t i o n from the second week and by the t h i r d week, both groups had reached the same l e v e l of apparent n i t rogen r e t e n t i o n . 82 h-LU Li_ O o> O O CC 2.6 LU 2 4 a. o LU h-LU CC 2 2.2 2.0 YOLK SAC REMOVED ±0 .04 s v ± 0 ^ ±0.03 / / / ±0.02 .-'•±0.02 SHAM-OPERATED JL J 0 1 2 3 AGE (WEEKS) FIG. 8 : EFFECT OF RESIDUAL YOLK ON APPARENT NITROGEN RETENTION 83 3.4.3 Experiment 4 - D i scus s ion The data on body weight gain reported here (Table 17) i n d i c a t e c l e a r l y that r e s i d u a l ' y o l k has no e f f e c t on the growth ra te of ch ickens to 21 days of age. S ince the higher mean body weiqht gain of the ch i ck s w i thout y o l k sacs d i d not d i f f e r s i g n i f i c a n t l y from the mean body weight gains of the other treatments i n the f i r s t week and s i nce the lead in weight gain was l o s t in subsequent weeks, f u r t h e r d i s cu s s i on on t h i s observat ion does not appear warranted. The l ack of s i g n i f i c a n t d i f f e r -ences in mean o v e r a l l body weight gain j u s t i f i e s the above c o n c l u s i o n . The c loseness of the mean body weight values of each of the three treatment groups i s i l l u s t r a t e d in F i g . 6. Residual y o l k appears to have e f f e c t on the e f f i c i e n c y o f food convers ion as demonstrated by the c o n s i s t e n t l y poorer food convers ion values obta ined w i th b i rd s wi thout r e s i dua l yo l k s and the c o n s i s t e n t l ack of s i g n i f i c a n t d i f f e r e n c e s between the i n t a c t and the sham-operated b i r d s , the yo l k sacs of which groups were not removed. I t i s s u r p r i s i n g that the d i f f e r e n c e s i n food con-ve r s i on e f f i c i e n c y among the treatment groups in the f i r s t week d id not reach the f i v e percent s t a t i s t i c a l s i g n i f i c a n c e l e v e l . There i s no obvious exp lanat ion f o r the b e t t e r food convers ion e f f i c i e n c y va lues obta ined w i th the sham-operated ch ickens over those of the i n t a c t groups. However, i t appears the s u r g i c a l treatment must have s t imu la ted some growth in the f i r s t week. Evidence to support t h i s suggest ion i s pro-v ided by the f a c t that the b i rd s which had undergone s u r g i c a l treatment gained a s l i g h t l y -higher average weight than the i n t a c t b i rd s (Table 17). 84 This s t imu l a ted growth which can l o g i c a l l y be expected to be compen-satory in nature must have been accompanied by a rap id turnover o f n u t r i e n t s i n the f i r s t week, the sham-operated, wi thout l o s s of t i s s u e compared to those w i th yo l k sacs removed, under such s t i m u l a t i o n may have u t i l i s e d food more e f f i c i e n t l y . A s i m i l a r response could have been shown by the b i rd s w i th yo l k sacs removed but the l o s s of t i s s u e would m i l i t a t e aga in s t ach iev ing the same r a t i o obta ined by the sham-operated group. The narrowing o f the gap in food convers ion r a t i o s between the b i rd s w i th yo l k sacs removed and the i n t a c t b i rd s ( F i g . 7) appears to i n d i c a t e a trend towards " n o r m a l i s a t i o n " of p h y s i o l o g i c a l processes. The observed higher apparent n i t rogen r e t e n t i o n value ( F i g . 8) obta ined w i th the group of ch ick s wi thout r e s i dua l yo l k s and which a l s o had the h ighest body weight gain in the f i r s t week i s c on s i s t en t w i th the f a c t that there i s a p o s i t i v e c o r r e l a t i o n between r ap i d growth r a te and n i t rogen r e t e n t i o n . The d i f f e r e n c e in the apparent n i t rogen r e t e n -t i o n between the i n t a c t b i rd s and those w i th yo l k sacs- removed could probably be exp la ined on the f o l l o w i n g ba s i s . There i s evidence that although the yo l k sac i s connected d i r e c t l y w i th the i n t e s t i n e , there i s l i t t l e or no movement of mate r i a l v i a t h i s route even a f t e r hatching and tha t the r e s i dua l y o l k i s absorbed through the yo l k sac membrane and t ranspor ted to the t i s s ue s by the omphalomesenteric ves se l s ( F r i t z , 1961). The r e s i dua l y o l k i s r a p i d l y u t i l i s e d by the b i r d w i t h i n f i v e days (Freeman, 1965). In the absence of i n fo rmat ion on the u t i l i s a t i o n of n u t r i e n t s d e r i v a b l e from the r e s i dua l y o l k q u a l i t a t i v e l y and q u a n t i t -a t i v e l y , the p o s s i b i l i t y should be cons idered that the end-products may 85 be h i gh l y n i trogenous in nature and t h i s cou ld add to the normal n itrogenous e x c re t i on to b r ing down, the value of apparent n i t rogen r e t e n t i o n . Zelenka (1968) found the metabo l i s ab le energy values o f the d i e t to i nc rease r a p i d l y dur ing the f i r s t days a f t e r hatch ing , s t a b i l i s e about one week of age and inc rease again u n t i l two weeks o f age; a f i n d i n g which the data o f t h i s experiment (Table 1.9) would g ene r a l l y tend to support . However, i t does not agree w i t h the observat ion of S ibba ld et al_. (1960) who, a f t e r a s e r i e s of experiments designed to p ro -v ide f u r t h e r i n fo rmat ion on the age of b i rd s on metabo l i s ab le energy values of c o r n , concluded that there were no s i g n i f i c a n t d i f f e r e n c e s between, ages (2 weeks to 16 months) w i t h i n d i e t s and suggested that i f age d i f f e r e n c e s e x i s t , they are n e g l i g i b l e f o r a l l p r a c t i c a l purposes. I t i s worthy of note that t h e i r determinat ions d id not cover the metab-o l i s a b l e energy values f o r one week ' po s t -ha tch ing . Removal a t hatching of the r e s i dua 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 ch i ck s a b i l i t y to metabo l i ze energy, an important observat ion in view of the f a c t that d i s c repanc i e s in metabo l i s ab le energy values in the f i r s t seven to ten days pos t -hatch ing have been exp la ined on the assumption that the r e s i d u a l y o l k s upp l i e s n u t r i e n t s i n amounts s i g n i f i c a n t enough to a f f e c t metabo l i s ab le energy values ( S ibba ld and S l i n g e r , 1963; and Ze lenka, 1968). 86 3.5 E f f e c t of Res idual Yolk on Su r v i va l o f Chicks 3.5.1 Experiment 5 - I n t roduc t i on The purpose of t h i s experiment was to t e s t the hypothes is that the r e s i dua l y o l k f u rn i she s ch i ck s w i th a s i g n i f i c a n t amount of n u t r i e n t s f o r a per iod as much as 10 days a f t e r hatch ing . I f t h i s assumption were t r u e , ch i c k s whose y o l k sacs had been removed w i t h i n a day o f hatching and without access to food, would be expected to d i e i n a s i g n i f i c a n t l y s ho r te r t ime as compared to those w i th i n t a c t y o l k sacs but a l s o depr ived food. 3.5.2 M a t e r i a l s and Methods The exper imental procedure was the same as i n Experiment 4. The on ly d i f f e r e n c e s were that White Leghorn males were used and that the ch i ck s were not fed throughout the t e s t which l a s t e d e i gh t days. A l l the ch i ck s had access to water a t a l l t imes. 3.5.3 Resu l t s Ta'ble 20 summarizes the r e s u l t s of the e f f e c t of yo l k sac on the l i v a b i l i t y of s tarved c h i c k s . There was no m o r t a l i t y in the i n t a c t c on t r o l group i n the f i r s t f i v e days of the experimental p e r i o d . Two-t h i r d s of the c o n t r o l group d ied on the seventh day. The r e s t d ied on the e i gh th day. Most of the m o r t a l i t y among the sham-operated group occurred on the s i x t h day when 23 out of a t o t a l of 32 d i ed . The longest per iod reached by ch i ck s f o r t h i s group was 8 days as i t occurred in the 87 Table 20. E f f e c t of yo l k sac on the s u r v i v a l of c h i c k s . Days m o r t a l i t y occurred Treatment 1 1 2 3 4 5 6 7 8 Contro l no. of b i rd s 3 1 6 5 Sham-operated no. of b i rd s 1 2 23 5 1 Yol k sac removed no. of b i rd s 2 2 2 - 3 17 2 -Tota l number of ch i ck s on each treatment: Contro l - 24 Sham-operated - 32 Yolk sac removed - 28 88 c a s e o f t h e c o n t r o l c h i c k s . W i t h t h e e x c e p t i o n o f t h e f o u r t h d a y , m o r t a l i t y o c c u r r e d on each day f o r t h e seven days t h a t v/as t h e d u r a t i o n f o r t h e g roup w i t h o u t y o l k s a c s . Seven teen o f t h e t o t a l o f 28 c h i c k s w i t h o u t y o l k s a c s d i e d on t h e s i x t h day . F i g . 9 r e p r e s e n t s t h e t r e n d o f m o r t a l i t y among t h e t h r e e t r e a t m e n t g r o u p s . FIG. 9= EFFECT OF RESIDUAL YOLK ON THE LI VABILITY OF STARVED CHICKS . 89 FIG. 9= EFFECT OF RESIDUAL YOLK ON THE LIVABILITY OF STARVED CHICKS . 90 3 .5 .4 E x p e r i m e n t 4 - D i s c u s s i o n The o b s e r v a t i o n t h a t m o r t a l i t y was s e v e r e s t on t h e s i x t h and s e v e n t h days f o r t h e s u r g i c a l l y - m a n i p u l a t e d and t h e i n t a c t b i r d s r e s p e c t i v e l y a rgues a g a i n s t a m a j o r r o l e f o r t he r e s i d u a l y o l k i n s u p p l y i n g s i g n i f i c a n t amounts o f n u t r i e n t s i n t h e f i r s t few days a f t e r h a t c h i n g . The o b s e r v e d h e a v i e s t m o r t a l i t y o c c u r r i n g on t h e same day ( t h e f i f t h day ) f o r t h e s u r g i c a l l y - a l t e r e d b i r d s ( F i g . 9) m i g h t be a s s o c i a t e d w i t h t he e f f e c t o f s u r g e r y . I t i s d i f f i c u l t t o r e c o n c i l e t he f i n d i n g i n t h e p r e s e n t paper t h a t r e s i d u a l y o l k does no t f u r n i s h c h i c k s w i t h a s i g n i f i -c a n t amount o f n u t r i e n t s d u r i n g t he f i r s t week a f t e r h a t c h i n g t o t h e o b s e r v a t i o n o f Z e l e n k a (1968) t h a t by t h e f i f t h day p o s t - h a t c h i n g t he y o l k sac had l o s t 13.1 k c a l r e p r e s e n t i n g abou t 85 p e r c e n t o f i t s 15.4 k c a l o f ene rgy a t h a t c h . The c o n c e p t t h a t t h e r e s i d u a l y o l k s u p p l i e s s i g n i f i c a n t amounts o f n u t r i e n t s d u r i n g t h e e a r l y days has been based upon an. o b s e r v e d f l u c t u a t i o n i n m e t a b o l i s a b l e energy v a l u e s i n t he f i r s t week. I n t e r p r e t a t i o n o f r e s u l t s o f s t u d i e s on n u t r i e n t u t i l i s a t i o n i n t h e n e w l y - h a t c h e d c h i c k has t o t a k e i n t o a c c o u n t t h e f a c t t h a t a t h a t c h t h e c h i c k s a b i l i t y t o d i g e s t f o o d i s no t f u l l y d e v e l o p e d and ' t h a t s ub sequen t deve l opment o f t h e a b i l i t y t o d i g e s t f o o d and a b s o r b n u t r i e n t s i s l a r g e l y a c c o u n t a b l e f o r t h e r i s e and s t a b i l i s a t i o n o f n u t r i e n t u t i l i s a t i o n f rom t h e second week onward s . 91 3. PART 2 THE AVIAN CAECA AND EFFICIENCY OF UTILISATION OF DIETARY ENERGY AND PROTEIN 3.6 The Role of the Caeca i n Energy and P ro te i n Metabolism 3.6.1 Experiment 6 - I n t r oduc t i on The presence of a l a rge b a c t e r i a l popu la t ion in the avian caeca and e x t r a p o l a t i o n of the fea tu re s a s soc ia ted wi th b a c t e r i a - ho s t symbiosis in ruminants and other animals to the domestic ch icken cont inue to prompt sporad ic i n v e s t i g a t i o n s i n to the r o l e of the av ian caeca i n the u t i l i s -a t i o n of d i e t a r y n u t r i e n t s . These i n v e s t i g a t i o n s have f a i l e d to e s tab -l i s h a c h a r a c t e r i s t i c f u n c t i o n f o r the caeca o f the domestic ch i cken . There i s s t ronger evidence to support the hypothes is o f c e l l u l o l y t i c or p r o t e o l y t i c f unc t i on s f o r w i l d b i rd s than there i s f o r domestic ch i ckens . Recent s tud ie s by Thompson and Boag (1975) of the u t i l i s a t i o n of d i e t a r y energy by i n t a c t and caecectomized Japanese qua i l showed that the caeca con t r i bu ted 5.7% of the d a i l y energy requirement. In a previous study, Fenna and Boag (1974) concluded tha t the major f unc t i on of the caeca i s to r e t a i n n u t r i e n t - r i c h ingesta f o r f u r t h e r d i g e s t i o n and absorp-t i o n wh i l e a l l ow ing the b u l k i e r c e l l u l o s e mate r i a l to be excreted more r a p i d l y from the gut. The theory which suggests that microorganisms in the caeca of the domestic ch icken are a source of c e l l u l o l y t i c . enzymes which would enable the ch i cken to ob ta i n some n u t r i t i o n a l va lue from d i e t a r y f i b r e (N i t san and Alumot, 1963; Thornburn and Kh'll.cox, 1964) has not gained wide 92 acceptance. McNab (1973) doubts whether such a process , i f i t occu r s , would be of any n u t r i t i o n a l s i g n i f i c a n c e to the ch i c ken . Mitsan and Alumot (1963) repor ted t ha t caeca l p r o t e o l y s i s compensated i n some degree f o r i n h i b i t e d p r o t e o l y s i s i n the small i n t e s t i n e when raw soy-bean meal was fed to i n t a c t and caecectomized b i r d s . There was no d i f -f e rence , however, in n i t rogen u t i l i s a t i o n when heated soybean meal was f ed . Caecectomy d id not appear to a f f e c t the n i t rogen excreted in the experiments of N i t san and Alumot (1963). Barnes and Impey (1972, 1974) have reported that many d i f f e r e n t types of caecal anaerobes are capable of breaking down u r i c a c i d . What t h i s may have on the n i t rogen economy of the b i r d i s unknown. The absence o f a w e l l - e s t a b l i s h e d f u n c t i o n f o r the caeca o f the domestic ch i cken under l i ne s the need f o r research in t h i s area as i t i s absurd, from the t e l e o l o g i c a l v i ewpo in t , f o r the domestic ch icken to possess an organ of t h i s s i z e that has no c h a r a c t e r i s t i c f u n c t i o n . This view supports Mattocks ' (1971) content ion that s e l e c t i o n pressure aga in s t possess ion of an organ w i th no f u n c t i o n might be expected to cause the o rgan ' s e x t i n c t i o n and that an organ wi th a b l i n d end such as the caecum would be p a r t i c u l a r l y s u s c e p t i b l e to p a r a s i t i c i nva s i on r e s u l t i n g in a f a t a l p e r i t o n i t i s . The pauc i t y o f i n fo rmat i on as i n d i c a t e d above and the re levance of the concept of caeca-mediated n u t r i e n t u t i l i s a t i o n to the t o p i c under i n v e s t i g a t i o n prompted the f o l l o w i n g experiment using i n t a c t and caecec-tomized ch ickens to i n v e s t i g a t e the e f f e c t of the e x c i s i o n of the caeca on the u t i l i s a t i o n o f d i e t a r y energy and p r o t e i n . 93 3.6.1 E x p e r i m e n t 6 - M a t e r i a l s and Methods N i n e - w e e k - o l d New Hampsh i re c h i c k e n s each w e i g h i n g a p p r o x i m a t e l y 800 g were c a e c e c t o m i z e d . Food was w i t h d r a w n f rom them a t l e a s t 18 hours b e f o r e t he o p e r a t i o n . The c h i c k e n was t i e d t o t h e o p e r a t i o n board w i t h e l a s t i c s t r a p s so t h a t i t s v e n t r a l p a r t was up and toward t h e o p e r a t o r . S u r -g i c a l a n a e s t h e s i a was i n d u c e d w i t h p e n t o b a r b i t o l sod ium (Nembuta l ) and e t h e r . An a v e r a g e o f 0.4 ml o f Nembutal (60 mg/ml) was s l o w l y i n j e c t e d i n t o t h e w ing v e i n u n t i l t h e c h i c k e n l o s t c o n s c i o u s n e s s . The 18-gauge n e e d l e used was p o i n t e d t oward t h e body and n e a r l y p a r a l l e l t o t h e w ing as i t was i n s e r t e d . The o p e r a t i o n l a s t e d abou t t w e n t y m i n u t e s pe r c h i c k e n and i n some c a s e s t h e amount o f Nembutal a d m i n i s t e r e d was i n a d e -q u a t e f o r t h i s l e n g t h o f t i m e , t h e r e f o r e e t h e r was used as a s t andby a n a e s t h e t i c . A b o t t l e c o n t a i n i n g e t h e r - s o a k e d c o t t o n wool was p l a c e d a round t h e head o f t h e c h i c k e n f o r a few seconds u n t i l t h e c h i c k e n showed s i g n s o f s e d a t i o n . . The c a e c a were r e a c h e d t h r o u g h a 2.5 cm- l ong l o n g i t u d i n a l i n c i s i o n 2 made i n t o a deplumed a r e a (about 5 cm ) o f t h e s k i n and i n t o t h e abdom-i n a l w a l l m u s c l e s i n t h e l e f t v e n t r a l - l a t e r a l ( p o s t v e n t e r ) r e g i o n 2.5 cm f r om ' t h e m i d l i n e and 2.5 cm a n t e r i o r t o t h e v e n t . The p e r i t o n e u m was t o r n w i t h f o r c e p s and t h e d i s t a l p o r t i o n o f t h e i n t e s t i n e w i t h t h e c aeca was c a r e f u l l y b r o u g h t o u t s i d e t h e body c a v i t y w i t h a b l u n t p robe whereupon t h e c e r v i x o f each caecum was l i g a t e d and h e l d w i t h a haemos ta t b e f o r e e x c i s i o n was made w i t h s c i s s o r s a t t h e i l e o - c o l i c j u n c t i o n l e a v i n g 94 a 5 mm stump f o r s u t u r i n g . One caecum was e x c i s e d and t h e stump s u t u r e d b e f o r e t h e o t h e r was t o u c h e d . A m o d i f i e d p u r s e - s t r i n g s u t u r e was used t o c l o s e t h e c i r c u l a r o p e n i n g o f t h e stump u s i n g a s u r g i c a l s i l k (No. 4/0) and a 3/8 c i r c l e r ound body s u r g i c a l n e e d l e . The s u t u r e was pa s sed i n and o u t a r ound t he c i r c u l a r o p e n i n g and t h e two ends o f t h e s u t u r e was drawn t i g h t . The n e e d l e was t hen drawn back t h r ough t he stump and t he t h r e a d was wrapped a few t i m e s a round i t b e f o r e t h e n e e d l e was d r i v e n t h r o u g h once more f o r a s u r g i c a l s q u a r e k n o t t o be made. The c a e c a l p a r t o f t h e i n t e s t i n e was t hen put back i n p l a c e and t he wound was s p r a y e d w i t h an a n t i b i o t i c p r e p a r a t i o n , V - S p o r i n * ( t r a d e name f o r a t o p i c a l a n t i b i o t i c m a n u f a c t u r e d by Wel lcome D i v i s i o n o f A g r c o Pharmacy L t d . , L a s a l l e , P . Q . ) . The l a y e r s o f m u s c l e s were s t i t c h e d by a method s i m i l a r t o t h e m a t t r e s s s u t u r e u s i n g a 1/2 c i r c l e c u t t i n g s u r g i c a l n e e d l e . The s u t u r e was c o n t i n u o u s l y a p p l i e d back and f o r t h t h r o u g h both edges o f t h e wound. The m o d i f i c a t i o n was n e c e s s i t a t e d by an o b s e r v a t i o n made p r e v i o u s l y t h a t t h e s t r a i g h t p u r s e - s t r i n g s u t u r e t o r e o f f as a r e s u l t o f p r e s s u r e e x e r t e d by t h e d i g e s t a . The two edges o f t h e s k i n were b r ough t t o g e t h e r and c l i p p e d w i t h 18 mm wound c l i p s . The wound o f t h e m u s c l e and s k i n was s p r a y e d w i t h V - S p o r i n * b e f o r e t h e c h i c k e n s were put back i n t h e i r cage s and g i v e n t h e n e c e s s a r y p o s t - o p e r a t i v e c a r e . The s u t u r e c l i p s were removed seven days a f t e r t h e o p e r a t i o n , e x c e p t i n two c a s e s where remova l was e f f e c t e d t e n days a f t e r t h e o p e r a t i o n . C a e c e c t o m i z e d and i n t a c t c o n t r o l b i r d s were m a i n t a i n e d on a 17% p r o t e i n d i e t f o r t h e e n s u i n g 11 weeks . The a b i l i t y o f t h e b i r d s t o 95 u t i l i z e n u t r i e n t s f r om two d i f f e r e n t d i e t s was then d e t e r m i n e d . The c o m p o s i t i o n o f t h e d i e t s i s shown i n T a b l e 2 1 . D i e t 1 c o n t a i n e d 19 .2% c o r n s t a r c h . D i e t 2 c o n t a i n e d 8% c o r n o i l and 11 .2% g round c e l l u l o s e i n p l a c e o f c o r n s t a r c h and was i s o c a l o r i c and i s o n i t r o g e n o u s w i t h D i e t 1. Each d i e t was f e d t o s i x i n t a c t and s i x c a e c e c t o m i z e d b i r d s d u r i n g s u c c e s s i v e t h r e e - w e e k p e r i o d s . Feed c o n s u m p t i o n and t o t a l e x c r e t a v o i d e d by t he i n d i v i d u a l b i r d s were measured d u r i n g t h e l a s t t h r e e days o f weeks 1, 3, 4 , 5 and 6. M e t a b o l i s a b i l i t y o f t he d i e t s was d e t e r m i n e d f o r each week. The method used i s t he one o f q u a n t i t a t i v e f e e d i n g and c o l l e c t i o n o f e x c r e t a and bomb c a l o r i m e t r y . P r o t e i n u t i l i s -a t i o n was e v a l u a t e d by m e a s u r i n g n i t r o g e n r e t e n t i o n , a p p a r e n t n i t r o g e n a b s o r p t i o n and u r i c a c i d e x c r e t i o n . T o t a l n i t r o g e n was d e t e r m i n e d by t h e m a c r o - K j e l d a h l method . The p r o c e d u r e f o r u r i c a c i d d e t e r m i n a t i o n was a m o d i f i c a t i o n o f t h e method d e s c r i b e d by Pudel k i e w i c z e_t a l_. ( 1 968 ) . Samples o f f i n e l y g round e x c r e t a were e x t r a c t e d w i t h 50 ml o f 0 .5% l i t h i u m c a r b o n a t e , i n a 250 ml v o l u m e t r i c f l a s k f o r 30 m i n u t e s a t room t e m p e r a t u r e w i t h c o n s t a n t s h a k i n g o f t h e f l a s k s . The f l a s k s were then made t o 250 ml w i t h d i s t i l l e d w a t e r and m ixed t h o r o u g h l y . A p p r o x i m a t e l y 10 ml o f t he e x t r a c t was c e n t r i f u g e d f o r abou t t e n m i n u t e s and 0.25 ml o f t he s u p e r n a t a n t was a n a l y z e d f o r u r i c a c i d c o n c e n t r a t i o n u s i n g a m o d i f i c a t i o n o f t h e p r o c e d u r e d e s c r i b e d by P r a c t o r i o u s ( 1 965 ) . F a e c a l e x t r a c t o b t a i n e d as d e s c r i b e d above was used i n s t e a d o f p l a s m a , 0.25 ml o f s u p e r n a t a n t o f t h e e x t r a c t was added t o 2 .75 m l , 0.1 M g l y c i n e b u f f e r (8 .06 g g l y c i n e + 14.2 g sod ium h y d r o x i d e pe r l i t e r » p H 9 . 3 ) . A u r i c a c i d s t a n d a r d was i n c l u d e d t o check a c c u r a c y . U r i c a c i d c o n c e n t r a t i o n was r e a d a t 292 my on an u l t r a v i o l e t s p e c t r o p h o t o m e t e r (Unicam model SP 1 800 ) . 96 Table 21. Composit ion of d i e t s fed to i n t a c t and cacecectomized ch ickens. DIET Ingred ient 1 2 Herr ing meal 21. % ,3 21 . ,3 Ground wheat 53. ,0 53. .0 . Corn o i l 3. .0 n . ,0 Corn s t a r ch 19. ,2 Ground c e l l u l o s e V • .2 Bonemeal 1. .5 I. .5 Limestone . ' !• .0 l . .0 Iodized s a l t 0. .5 0. .5 M i c r o n u t r i e n t s 1 0. .5 0. .5 100. .0 100. .0 % P r o t e i n 2'4. .0 24. .0 M i c r o n u t r i e n t s as l i s t e d in Table 1. 97 C o n s i d e r i n g t h e f a c t t h a t t h e c aeca a r e a r e a s o f h i g h m i c r o -b i a l a c t i v i t y , i t was o f i n t e r e s t to a s c e r t a i n whe the r t h e r e was any d i f f e r e n c e between t h e i n t a c t and- t h e c a e c e c t o m i z e d c h i c k e n s i n t h e p r o p o r t i o n o f t h e e x c r e t a due t o b a c t e r i a . To a c h i e v e t h i s o b j e c -t i v e , t h e b a c t e r i a were s e p a r a t e d m e c h a n i c a l l y u s i n g t h e f o l l o w i n g p r o c e d u r e . F r e s h l y v o i d e d e x c r e t a f r o m i n d i v i d u a l b i r d s was c o l l e c t e d , t h o r o u g h l y m i x e d , and an a v e r a g e o f 0.5 g o f sample was we ighed and p l a c e d i n a 50 ml c e n t r i f u g e t u b e . To t h i s 49 .5 ml o f d i s t i l l e d w a t e r was added and t h e sample was t h o r o u g h l y m i xed and spun i n an MSE A n g l e C e n t r i f u g e a t maximum speed f o r t e n m i n u t e s . The s u p e r n a t a n t was removed and t h e s e d i m e n t was p l a c e d i n a d i l u t i o n b o t t l e c o n t a i n i n g about 60 ml d i s t i l l e d w a t e r . G l a s s beads were added and t h e b o t t l e s were shaken f o r 1 hour on an a g i t a t o r . The m i x t u r e was f i l t e r e d t h r o u g h f o u r l a y e r s o f c h e e s e c l o t h on t o a 50 ml c e n t r i f u g e t u b e . The f i l t r a t e ( about 40 m l ) was spun as men t i oned e a r l i e r . The s u p e r n a t a n t was removed and t h e r e m a i n i n g s o l i d s w h i c h c o n s t i t u t e a c r u d e b a c t e r i a c o n t e n t o f t h e e x c r e t a were we i ghed and d r i e d i n a vacuum d r y e r . The b a c t e r i a c o n t e n t as a p e r c e n t a g e o f a p r e - d r i e d e x c r e t a sample was then c a l c u l a t e d . 98 3.6.2 Resu l t s The metabo l i s ab le energy values obta ined f o r the d i e t s when they were fed to the i n t a c t and caecectomized b i rd s are g iven in Table 22. These values have been co r rec ted f o r n i t rogen r e t e n t i o n . D ie t 1 was u t i l i z e d w i th p r a c t i c a l l y the same e f f i c i e n c y by both groups of b i r d s . A s i m i l a r p i c t u r e emerges f o r D ie t 2 which conta ined added c e l l u l o s e , higher f a t l e v e l and no corn s t a r c h . S i g n i f i c a n t d i f f e r e n c e s in meta-bol i s a b l e energy values between D ie t 1 and D i e t 2 were noted. Higher metabo l i s ab le energy values were obta ined on D ie t 2. The ME values obta ined w i t h i n t a c t ch ickens were always s l i g h t l y h igher than those of caecectomized ch ickens on both d i e t s but the d i f f e r e n c e s 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 . Table 23 summarizes the r e s u l t of u r i c a c i d e x c r e t i on (as measured by u r i c a c i d concen t r a t i on ) i n the faeces . The r e s u l t s in re spec t of D ie t 1 were v a r i a b l e . In the f i r s t week the i n t a c t b i rd s excreted more u r i c a c i d than the caecectomized b i rd s but t h i s s i t u a t i o n changed i n the t h i r d week. The r e s u l t s f o r D i e t 2 were more c o n s i s t e n t . The i n t a c t b i r d s excreted more u r i c a c i d than the caecectomized b i r d s . The d i f f e r -ences, however, 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 . The percentage of ingested n i t rogen as u r i c a c i d (Table 23) a l s o fo l l owed a pat te rn s i m i l a r to tha t of the u r i c a c i d c o n c e n t r a t i o n . The n i t rogen balances of the ch ickens f o r the per iod over which c o l l e c t i o n was made are presented i n Table 24. With the except ion of the t h i r d week, the n i t rogen r e t e n t i o n in the caecectomized chicken was s l i g h t l y higher than that of the i n t a c t ch ickens as was the case f o r u r i c 99 T a b l e 22 . M e t a b o l i s a b l e ene r g y v a l u e s 1 o f d i e t s . ( c o r r e c t e d f o r n i t r o g e n - r e t e n t i o n ) D i e t ' Age o f c h i c k e n s i n weeks I n t a c t k c a l / k g C a e c e c t o m i z e d k c a l / k g 1 ( C o r n s t a r c h ) 21 3345a 3325a 23 3350a 3305 a 2 (Co rn o i l & 24 3535b 3530b C e l 1 u l o s e ) 25 3520b 3515b 26 3520b 3510b V a l u e s n o t f o l l o w e d by t h e same l e t t e r s d i f f e r s i g n i f i c a n t l y (P< 0.05) TOO T a b l e 2 3 . U r i c a c i d c o n c e n t r a t i o n i n e x c r e t a by i n t a c t and c a e c e c t o m i z e d c h i c k e n s . Age o f c h i c k e n s D i e t i n weeks I n t a c t C a e c e c t o m i z e d %2 1? X 2 1 ( C o r n s t a r c h ) 21 8.4 2 2 . 0 a 7.7 20 .0a 23 13.7 36.2b 14.3 38.0b 2 (Co rn o i l & 24 8.4 2 8 . 8c 7.8 2 5 . 0c C e l l u l o s e ) 25 10.3 33 .7d 10.0 32 .6d 26 10.7 34 .9d 9.5 31 . I d % i n e x c r e t a , d r y m a t t e r b a s i s . 2 % o f i n g e s t e d N e x c r e t e d as u r i c a c i d . 3 c o m p a r i s o n s a r e between i n t a c t and c a e c e c t o m i z e d g roups w i t h i n d i e t s and v a l u e s f o l l o w e d by t he same l e t t e r s do no t d i f f e r s i g n i f i c a n t l y (P< 0 .05) 101 T a b l e 24. A p p a r e n t N i t r o g e n a b s o r p t i o n ( e x p r e s s e d as a p e r c e n t a g e o f n i t r o g e n i n g e s t e d ) by i n t a c t and c a e c e c t o m i z e d c h i c k e n s . D i e t I n t a c t Age o f c h i c k e n s i n weeks % a b s o r p t i o n C a e c e c t o m i z e d % a b s o r p t i o n 1 ( C o r n s t a r c h ) 21 23 64 .3 ± 3.42 66 .9 ± 1.89 1 63 .5 ± 2.13 65 .6 ± 1.17 (Co rn o i l & C e l l u l o s e ) 24 70.2 ± 0.47 25 65 .9 ± 2.63 26 70.9 ± 3.24 69 .0 ± 3.14 68.4 ± 5.90 69.2 ± 0.81 1 S t a n d a r d e r r o r o f t h e means. 102 showed no c l e a r t r e n d as T a b l e 24 shows. I t i s i n t e r e s t i n g t o p o i n t o u t t h a t t h e b i r d s were s t i l l g a i n i n g w e i g h t ( T a b l e 2 5 ) . The i n t a c t b i r d s v o i d e d f a e c e s w h i c h c o n t a i n e d s i g n i f i c a n t l y ( P ^ O . O l ) more b a c t e r i a l r e s i d u e t h a n d i d t h e c a e c e c t o m i z e d b i r d s . As can be seen f rom T a b l e 2 6 , t h e range was f rom 15.6 t o 30 .5 (mean:22.5) among t he i n t a c t b i r d s , w h i l e t h e v a l u e s f o r t h e b i r d s w i t h o u t c aeca ranged f r om 9.87 t o 19 .00 ( m e a n : 1 3 . 6 ) . T a b 1 e 2 5 - Body, weight gains of i n d i v i d u a l ch ickens. l n I a c t Caecectomized 9 % gain 1 9 • % gain 551 19.3 . 398 16.8 11 .0.4 408 16.3 739 32.1 531 24.0 310 11.2 424 17.7 187 -7.4 388 14.6 264 10.5 368 17.2 Mean 344 13.7 420 17.7 D i f f e r e n c e s , between body w e i g h t s at.21 and 26 weeks o f age. 104 T a b l e 26. B a c t e r i a l c o n t e n t o f e x c r e t a o f i n d i v i d u a l c h i c k e n s , p e r c e n t on a d r y m a t t e r b a s i s . I n t a c t C a e c e c t o m i z e d 17.9 22.8 30 .5 25 .9 15 .6 Mean 1 2 2 . 5a 13.7 9.9 19.0 11.2 14.3 13.6b Mean v a l u e f o l l o w e d by d i f f e r e n t l e t t e r s d i f f e r s i g n i f i c a n t l y (P< 0.05) 105 3 .6 .3 D i s c u s s i o n The m e t a b o l i s a b l e ene r gy v a l u e s ( T a b l e 22) show t h a t m e t a b o l i s a -b i l i t y o f n e i t h e r d i e t was a l t e r e d by c a e c e c t o m y . The ene rgy r e q u i r e d by t h e c h i c k e n i s d e r i v e d f r om c a r b o h y d r a t e ( m a i n l y amy lo se and a m y l o -p e c t i n ) , l i p i d and p r o t e i n components o f t h e i n g e s t e d f o o d . The d i g e s t i v e t r a c t w i t h o u t t h e c a e c a i s a n a t o m i c a l l y endowed t o c a r r y ou t t he p r o c e s s e s o f d i g e s t i o n and a b s o r p t i o n w h i c h means t h a t t he ab sence o f t h e c aeca w i l l n o t s i g n i f i c a n t l y a l t e r t h i s a t t r i b u t e . The ab sence o f t h e c a e c a may cau se an abnormal p r o l i f e r a t i o n and i n c r e a s e o f m i c r o o r g a n i s m s i n t h e s m a l l i n -t e s t i n e . J a y n e - W i l l i a m s and F u l l e r (1971) s u gge s t ed t h a t t h e p r e s e n c e o f m i c r o o r g a n i s m s and/o r t h e i r m e t a b o l i c p r o d u c t s c au se s i n c r e a s e d t h i c k n e s s o f t h e i n t e s t i n a l w a l l and a r e d u c t i o n i n t h e a b s o r p t i v e e f f i c i e n c y o f t h e s m a l l i n t e s t i n e . On t h i s p r em i s e one wou ld e x p e c t t he c a e c e c t o m i z e d c h i c k e n s t o u t i l i s e n u t r i e n t s l e s s e f f i c i e n t l y . However, t h e r e s u l t s o f t h i s i n v e s t i g a t i o n do no t show t h a t . The l a c k o f s i g n i f i c a n t d i f f e r e n c e between i n t a c t and c a e c e c t o m i z e d c h i c k e n s i n r e s p e c t o f t h e i r a b i l i t y t o m e t a b o l i z e d i e t a r y ene r gy i s an e x p e r i m e n t a l e v i d e n c e w h i c h p r o v i d e s an i n d i r e c t s u p p o r t t o t h e f i n d i n g t h a t t h e p r e s e n c e o f a m i c r o f l o r a has l i t t l e e f f e c t on amy la se a c t i v i t i e s i n d i f f e r e n t s i t e s i n t h e f o w l ' s a l i m e n t a r y t r a c t ( L epkov s k y et_ al_. , 1964 ) . The r e s u l t s o f t h i s e x p e r i m e n t a r e no t i n agreement w i t h t h o s e o b t a i n e d by R a d e f f ( 1 9 2 8 ) , Henn ing (1929) and Tho rnbu rn and W i l l c o x (1965) t h a t t h e r e i s m i c r o b i a l d i g e s t i o n o f f i b r e i n t h e caecum o f t h e d o m e s t i c c h i c k e n . Even i f some b a c t e r i a l d i g e s t i o n o c c u r s i n t h e caecum, i t p r o b a b l y p l a y s an 106 i n s i g n i f i c a n t p a r t i n t h e m e t a b o l i s m o f t h e h o s t c h i c k e n compared t o t h a t o c c u r r i n g i n t h e c a e c a o f t h e w i l d b i r d where i t r e p r e s e n t s 5.7% o f t h e d a i l y ene rgy r e q u i r e m e n t (Thompson and Boag , 1975 ) . The h i g h e r m e t a b o l i s a b l e ene r gy v a l u e s o b t a i n e d f o r t h e d i e t wh i ch c o n t a i n e d c o r n o i l as t he m a j o r s o u r c e o f d i e t a r y ene rgy ( D i e t 2) a g ree w i t h v a l u e s r e p o r t e d by o t h e r w o r k e r s who s u b s t i t u t e d c o r n o i l f o r c a r b o -h y d r a t e ( D o n a l d s o n , 1964, 1966; Dona ld son e t a l _ . , 1957; Rand ejt a l _ . , 1958; Carew and H i l l , 1964; D r o r et^ a l _ . , 1973 ) . The o b s e r v e d h i g h e r v a l u e s f o r D i e t 2 can a l s o be e x p l a i n e d on t h e b a s i s t h a t by t h e t i m e t h i s d i e t was f e d , t h e age o f t h e c h i c k e n s had i n c r e a s e d and t h a t t h e i r d i g e s t i v e t r a c t s had been more d e v e l o p e d t o cope w i t h b u l k y d i g e s t a . Many o f t h e t y p e s o f b a c t e r i a i n h a b i t i n g t h e c a e c a u t i l i z e u r i c a c i d and s i n c e u r i c a c i d i s t h e p r i m a r y n i t r o g e n o u s e x c r e t o r y p r o d u c t formed i n t h e a v i a n s p e c i e s , t he p o s s i b i l i t y was c o n s i d e r e d t h a t remova l o f t h e c a e c a m i gh t i n c r e a s e t he amount o f n i t r o g e n e x c r e t e d as u r i c a c i d . The d a t a shown i n T a b l e 23 show t h a t t h e r e was no a p p r e c i a b l e e f f e c t o f t he remova l o f t he c a e c a on t he amount o f u r i c a c i d e x c r e t e d . T h i s was t r u e whe the r t h e amount e x c r e t e d was c a l c u l a t e d as a p e r c e n t a g e o f t h e e x c r e t a o r r e l a t i v e t o t h e amount o f n i t r o g e n i n g e s t e d . The v a l u e s o f t h e e x c r e t a n i t r o g e n e x p r e s s e d as a p e r c e n t a g e o f t h e n i t r o g e n consumed by t h e c o n t r o l g roup i n t h i s s t u d y ( 20 -36% , mean 31%) a r e ana l o gou s t o t h o s e ( 2 0 - 2 5% , mean 23%) r e p o r t e d by F e a t h e r s t o n and S c h o l z (1968) who f e d a d i e t c o n t a i n i a s i m i l a r l e v e l o f p r o t e i n t o c h i c k s f r om d a y - o l d t o 10 days o f age . The p e r c e n t a g e o f i n g e s t e d n i t r o g e n e x c r e t e d as u r i c a c i d i n c r e a s e s w i t h age ( F e a t h e r s t o n and S c h o l z , 1968) and t h i s may e x p l a i n t h e d i f f e r e n c e between t h e two means. In T a b l e 24 t he a p p a r e n t a b s o r p t i o n o f n i t r o g e n has been 107 e s t i m a t e d as t h e sum o f u r i c a c i d n i t r o g e n and r e t a i n e d n i t r o g e n . I t w i l l be seen t h a t t h e r e was no d i f f e r e n c e between t h e i n t a c t and t h e c a e c e c t o m i z e d c h i c k e n s i n t h e a p p a r e n t a b s o r p t i o n o f d i e t a r y n i t r o g e n . A l t h o u g h t h e c h i c k e n s were 20 weeks o f a g e , t h e y g a i n e d w e i g h t d u r i n g t he t e s t ( T a b l e 2 5 ) . The s i g n i f i c a n t l y r educed a ve rage p e r c e n t a g e o f b a c t e r i a i n t h e e x c r e t a f r om t h e c a e c e c t o m i z e d c h i c k e n s ( T a b l e 26) appea r s t o be o f c on sequence . S i n c e t h e r e was l e s s l o s s o f n u t r i e n t s v i a e x c r e t e d b a c -t e r i a i n t h e c a e c e c t o m i z e d , i t was l o g i c a l t o e x p e c t some.compensato ry i n c r e a s e i n t h e l o s s o f n u t r i e n t s v i a o t h e r r o u t e . S i m i l a r r e s u l t s have been o b t a i n e d w i t h g e r m - f r e e compared w i t h c o n v e n t i o n a l a n i m a l s . I t m i g h t be e x p e c t e d t h a t g e r m - f r e e a n i m a l s wou ld show l e s s e x c r e t i o n o f f a e c a l n i t r o g e n t han do c o n v e n t i o n a l a n i m a l s . The r e v e r s e s i t u a t i o n , however , has been shown t o o c c u r . Under t h e d i e t a r y c o n d i t i o n s o f t h e p r e s e n t e x p e r i m e n t , t h e c a e c a d i d no t appea r t o be e s s e n t i a l f o r maximum u t i l i s a t i o n o f ene rgy and p r o t e i n . I f t h e r e a r e advan tage s a s s o c i a t e d w i t h t h e p r e s e n c e o f t h e c a e c a , t h e y must have been c o u n t e r - b a l a n c e d w i t h some d i s a d v a n t a g e s . I t i s t e n t a t i v e l y s u gge s t ed t h a t t h e b a l a n c e i s between b a c t e r i a l and endog -enous p r o t e i n and amino a c i d s w i t h l i t t l e e f f e c t on a b s o r p t i o n o f i n g e s t e d n u t r i e n t s . 108 3.7 REGROWTH OF THE AVIAN CAECA FOLLOWING CAECECTOMY 3.7.1 Experiment 7 - I n t roduc t i on Caecectomy has been employed e x t e n s i v e l y as a means of s tudy ing the r o l e the caeca may p lay in the n u t r i t i o n and phys io logy of b i r d s , p a r t i c u -l a r l y the domestic ch icken (Sunde et a l_ . , 1950; Bea t t i e and Shr impton, 1958; Nelson and N o r r i s , 1961; N i t san and Alumot, 1963; F i s he r and Gr iminger , 1966; Barnes, 1972; Kese and March, 1975). Although severa l a r t i c l e s appear i n the l i t e r a t u r e concern ing the measurement of va r ious p h y s i o l o g i c a l parameters a f t e r caecectomy, r e l a t i v e l y few d i scus s oper-a t i v e procedure and post-mortem obse rva t i on s . Su rg i ca l a b l a t i o n of the avian caeca i s attended by some problems not the l e a s t of which i s tha t of c e r t a i n t y of completeness o f the e x t i r p a t i v e procedure. Tlie omiss ion of d e s c r i p t i v e of the s u r g i c a l p rocess , p a r t i c u l a r l y the completeness of caecectomy does not a l l ow one a common base f o r v a l i d comparison of s u r g i c a l treatment and da ta . I n te rna l organs r eac t d i f f e r e n t l y to removal of d i f f e r e n t amounts of t h e i r t i s s u e ( L i o zne r , 1974). Studies on adu l t developmental processes po in t to a remarkable a b i l i t y of animals to rep lace po r t i on s of t i s s ue s or organs removed by surgery. There are no t i s s ue s i n the bodies of warm-blooded ve r teb ra te s which are not capable of r e p a i r i n g l o c a l i z e d i n j u r i e s and i n some cases (e.g. f r a c t u r e h e a l i n g , fea ther and ha i r r egene ra t i on , or the r e s t i t u t i o n of the u r i na r y b l adde r ) , the response may i n vo l ve high degrees of h i s t o l o g i c a l morphogenesis (Goss, 1965). Adapt ive morphological and f un c t i o na l changes f o l l o w i n g r e s e c t i on of parts 109 of the a l imentary t r a c t are we l l documented i n s u r g i c a l and medical l i t e r a t u r e (Wickborn e t a l_. , 1 975; McDermott and Roudnew, 1976). The f i n d i n g s , c i t e d p r e v i o u s l y , unde r l i ne the need f o r s tud ie s i n v o l v i n g biopsy and autopsy of caecectomized b i r d s . This s ec t i on of the study i s concerned w i th the major gross and mic roscop ic anatomy observed on autopsy. no 3.7.2 M a t e r i a l s and Methods The m a t e r i a l s and methods are e s s e n t i a l l y as desc r ibed f o r e x p e r i -ment 6 because the chickens invo lved i n t h i s study are the same chickens used to study the r o l e of the av ian caeca i n the u t i l i s a t i o n of d i e t a r y energy and p r o t e i n . 3.7.3 Resu l t s The b i rd s were autops ied 85 weeks a f t e r caecectomy and the a l imenta ry t r a c t was examined. As shown in F i g s . 10 and 11, the four s u r v i v i n g caecectomized b i rd s had regrown t h e i r caeca to vary ing l eng ths . The regrowth ranged from 17 to over 40 percent of the length of the caeca i n the unoperated ch ickens (Table 27). Trunk sec t ions from the midzone of each caecum of both the caecectomized and unoperated chickens showed, on h i s t o l o g i c a l examinat ion, t ha t regenerat ion of the caeca had occurred as evidenced by the presence of most of the elements that c o n s t i t u t e the bas i c s t r u c t u r e o f the caecum, namely, the se ro sa , the muscu la r i s e x te rna , the submucosa, the muscu lar i s mucosae, and some glands ( F i g . 12). I l l 10. Regrown caeca from 85-week-old ch ickens caecectomized a t 9 weeks of age and caeca from unoperated ch ickens of the same age. F i r s t three on the l e f t - caecectomized; the next f i v e - unoperated. 112 Fig. 11. (Left) Regrown caecum from caecectomized chicken, and (r ight) caecum from unoperated chicken. 113 T a b l e 27. Length o f i n t a c t and regrown c a e c a . C o n t r o l C a e c e c t o m i z e d B i r d cm 1 21.6 4 . 0 2 23.4 4.1 3 23.7 8.6 4 24.1 10.5 5 24.5 114 Fig. 12. Transverse section through the mid-caecum, top: regrown caecum; bottom: intact caecum. 115 3.7.4 D i scus s ion Studies on the r o l e of the caeca in av ian n u t r i t i o n or phys io logy have, so f a r , f a i l e d to e s t a b l i s h a f unc t i on f o r t h i s organ. In the l i g h t o f the f a c t that regenerat ion of t i s s ue s or organs i s not a ra re phenomenon, i t i s p e r t i n e n t to make the f o l l o w i n g comments in an attempt to e xp l a i n what cou ld cause some of the d i s c repanc i e s e x i s t i n g in the l i t e r a t u r e on the performance of caecectomized ch i ckens . The absence of p r ec i s e d e s c r i p t i o n s of e x c i s i o n methods in experiments i n vo l v i n g caecectomy a l lows f o r v a r i a t i o n in methods, p a r t i c u l a r l y w i th regard to the amount of r e s i d u a l t i s s u e . The presence or absence of r e s i dua l t i s s u e i s l i k e l y to i n f l uence the hea l i ng of the s u r g i c a l wound or the regenerat ion of the organ. The observed regrowth of the f i v e m i l l i m e t e r s stump in t h i s study (Table 27) under l ines the importance of t h i s p o i n t . F i g s . 10 and 11 i n d i c a t e c l e a r l y t ha t a p iece of t i s s u e or organ i n a d v e r t e n t l y or purposely l e f t in s i t u i s l i k e l y to s t imu l a te some form of regrowth or r e p a r a t i v e r egene ra t i on . Such a s i t u a t i o n i s l i k e l y to d i s t o r t r e s u l t s . A b i l i t y to regenerate l o s t organs has been repor ted to d e c l i n e w i th age. Compensatory regrowth or regenerat ion of an organ, i f they do occur , w i l l be f a s t e r i n younger than in o l de r ch i ckens . Adapt ive morpholog ica l and f un c t i o na l changes w i l l be qu i cker in younger ch ickens than in o l de r ones. This r a i s e s the quest ion regard ing the age a t which the o c c l u s i on of an organ w i l l make the most s i g n i f i c a n t impact. When an organ i s removed very e a r l y i n l i f e , probably before i t begins to . f unc t i on e f f e c t i v e l y , i t i s l i k e l y that i t s ( po s s i b l e ) f unc t i on w i l l be 116 t a k e n o v e r by an o r gan o f homologous t i s s u e s . I f , on t he o t h e r hand , t h e o r gan i s removed l a t e r i n l i f e , i t i s p r o b a b l e t h a t a d i f f e r e n t r e s u l t wou l d be p r o d u c e d . Compar ing p h y s i o l o g i c i n d i c e s o f b i r d s c a e c e c t o m i z e d a t d i f f e r e n t ages i n l i f e appea r s t h e r e f o r e t o be a p r o b a b l e s o u r c e o f v a r i a t i o n i n t h e r e s u l t s . I t i s i m p o r t a n t t o bea r i n mind t h e r a p i d i t y w i t h w h i c h h y p e r t r o p h y and/o r h y p e r p l a s i a w h i c h c h a r a c t e r i z e t h e phenomenon o f t i s s u e r e p a i r o r r e g e n e r a t i o n t a k e s p l a c e . In t h e c h i c k e n , r e g e n e r a t i o n and r e s t o r a t i o n o f f u n c t i o n a l i t y may be c o m p l e t e i n one month ( B e a t t i e and S h r i m p t o n , 1958 ) . N i ne week s , t he age a t w h i c h t h e c h i c k e n s i n v o l v e d i n t h i s s t u d y were c a e c e c t o m i z e d , r e p r e s e n t s a s t a g e a t w h i c h t h e b i r d s a r e i n a c t i v e g rowth ( T a b l e 25) and t h e i r c e l l s were s t i l l v e r y v e r s a t i l e t o undergo a l l t h e d e v e l o p m e n t a l p r o c e s s e s a s s o c i a t e d w i t h t i s s u e r e g r o w t h . Even i n t h e a d u l t s t a g e , t h e a v i a n c a e c a may undergo d e v e l o p m e n t a l a d j u s t m e n t t o meet f u n c t i o n a l r e q u i r e m e n t s . In t h e J apane se q u a i l , f o r e x a m p l e , i t has been w e l l documented (Fenna and Boag , 1974) t h a t changes i n some p h y s i c a l a t t r i b u t e s o f f o o d and i n t h e r a t e s o f f o o d c o n s u m p t i o n r e s u l t e d i n changes o f t h e morpho logy o f t h e c a e c a . L a r g e r vo lumes o f f o o d i n g e s t e d pe r day p roduced s i g n i f i c a n t i n c r e a s e s i n c a e c a l l e n g t h s . I t i s u n f o r t u n a t e t h a t t h e d e s i g n o f t he e x p e r i m e n t b e i n g r e p o r t e d d i d no t o f f e r t h e o p p o r t u n i t y o f o b s e r v i n g t h e o n s e t and t h e r a t e o f r e g r o w t h o f t h e c a e c a . Such i n f o r m a t i o n wou ld h e l p e l u c i d a t e s i m i l a r i t i e s o r d i f f e r e n c e s i n r e s p o n s e c r i t e r i a e x i s t i n g between t he i n t a c t and c a e c e c -t o m i z e d c h i c k e n s o f t h i s s t u d y . In c o n c l u s i o n , i t must be r e s t a t e d t h a t p r o o f o f a p h y s i o l o g i c a l r o l e ( s ) f o r t h e c a e c a o f t he d o m e s t i c c h i c k e n has been e l u s i v e f o r t he 117 f o l l o w i n g r e a s o n s : a) D i f f e r e n c e i n e x p e r i m e n t a l methods - v a r i a b i l i t y i n e x c i s i o n me thod s ; f a i l u r e t o a s c e r t a i n o c c u r r e n c e o r ab sence o f r e g r o w t h , b) P o s s i b i l i t y o f r e s t o r a t i o n o f f u n c t i o n - s h a r i n g o f f u n c t i o n a l l o a d ; f u n c t i o n a l s h i f t s t o c e l l s o f homologous t i s s u e s , and c ) V a r i a t i o n i n age o f b i r d s i n v o l v e d i n t h e d i f f e r e n t s t u d i e s . .118 4 . GENERAL SUMMARY AND CONCLUSIONS The r e s e a r c h w h i c h forms t h e s u b j e c t o f t h i s d i s s e r t a t i o n has c o n s i d e r e d many i m p l i c a t i o n s o f t h e use o f d i e t a r y f a t as a s u p p l e m e n t a r y s o u r c e o f ene rgy f o r b r o i l e r c h i c k e n s . The l e v e l o f d i e t a r y f a t and t he s u b s t i t u t i o n o f f a t f o r c a r b o h y d r a t e c a l o r i e s a t v a r y i n g p r o t e i n l e v e l s , have been e v a l u a t e d i n terms o f g rowth p e r f o r m a n c e , f o o d c o n v e r s i o n e f f i c i e n c y , m e t a b o l i s a b l e ene r gy and n u t r i e n t u t i l i s a t i o n and abdomina l f a t d e p o s i t i o n . Hypo the se s c o n s i d e r e d p e r t i n e n t t o an i n - d e p t h t r e a t m e n t o f t h e t o p i c under i n v e s t i g a t i o n were d e v e l o p e d and/o r t e s t e d . The f i r s t s even weeks i n t he l i f e o f a b r o i l e r c h i c k e n r e p r e s e n t a p e r i o d i n w h i c h t he r e q u i r e m e n t s f o r b a l a n c e d p r o t e i n and o t h e r n u t r i e n t s a r e most c r i t i c a l ( S c o t t e_t a l _ . , 1 969 ) . I t i s r e a s o n a b l e t o e x p e c t t h a t r e s p o n s e s t o s t i m u l i i n d u c e d by d i e t a r y t r e a t m e n t s wou l d be maximal d u r i n g t h i s p e r i o d . These r e s u l t s show t h a t t h e i n c o r p o r a t i o n o f f a t i n t he d i e t d i d n o t have any s p e c i a l e f f e c t on the g rowth o f , o r t he u t i l i s a t i o n o f ene r gy by , b r o i l e r c h i c k e n s . T h i s f i n d i n g i s i n agreement w i t h a number o f o t h e r r e p o r t s on c h i c k e n s ( B e g i n , 1969; V e l u and B a k e r , 1974 ) . B e g i n (1969) r e p o r t e d t h a t c h i c k e n s o f t he t h r e e b reeds w h i c h he s t u d i e d used f a t and c a r b o h y d r a t e c a l o r i e s w i t h e q u a l e f f i c i e n c y and t h a t no bene -f i c i a l ' o r d e l e t e r i o u s e f f e c t was a s s o c i a t e d w i t h t h e r e p l a c e m e n t o f c a r b o h y d r a t e by f a t c a l o r i e s . However , t h e f i n d i n g o f t h i s s t u d y d i f f e r s f r o m o t h e r s i n w h i c h d i e t a r y f a t p_er se_ was f o u n d t o improve t h e e f f i c i e n c y o f ene r gy u t i l i s a t i o n by t u r k e y s . (Touchburn and Nabe r , 1966; H a l l o r a n et a l _ . , 1 972 ) . B r e e d d i f f e r e n c e s have been no ted among c h i c k e n s i n the 119 e f f i c i e n c y o f n i t r o g e n and ene r g y u t i l i s a t i o n r e g a r d l e s s o f t he s o u r c e o f c a l o r i e s ( B e g i n , 1969) a n d , as Sa lmon (1972) p o i n t e d o u t , a s p e c i e s d i f f e r e n c e i n t h e r e l a t i v e e f f i c i e n c y o f u t i l i s a t i o n o f c a r b o h y d r a t e and f a t ene rgy i s c o n c e i v a b l e . Summers e t al_. (1964) c o n s i d e r ene r gy as one o f t he most i m p o r t a n t f a c t o r s t o c o n s i d e r i n t h e e v a l u a t i o n o f n u t r i e n t s on a c c o u n t o f i t s i n f l u e n c e on f o o d i n t a k e . F a c t o r s such as d i e t a r y ene rgy c o n c e n t r a t i o n and b a l a n c e between amino a c i d s a r e p r o b a b l y i n t h e f o r e f r o n t as f a r as f o o d i n t a k e - l i m i t i n g f a c t o r s a r e c o n c e r n e d . The i m p o r t a n c e o f c o n s i d e r -i n g n o t o n l y t h e l e v e l o f ene rgy bu t a l s o the c a l o r i e t o p r o t e i n r a t i o o f a d i e t has been empha s i zed by B i e l y and March ( 1 9 5 4 ) , Dona ldson e t a l . ( 1 9 5 5 ) , S c o t t e t a l . . ( 1 9 6 9 ) . A n o t h e r f a c t o r , o t h e r t h a n t h e l e v e l o f ene r gy o r p r o t e i n o r t h e r a t i o between them, i s t h e b a l a n c e b e t w e e n amino a c i d s . I t has been d e m o n s t r a t e d t h a t an i m b a l a n c e ( H a r p e r and Kumta, 1959; F i s h e r and S h a p i r o , 1 961 ) ; e x c e s s ( A l m q u i s t , 1954) o r d e f i c i e n c y (Ma rch and W a l k e r , 1970; March and B i e l y , 1972) i n amino a c i d s r e s u l t s i n marked d e p r e s s i o n i n f o o d i n t a k e . An e a r l i e r O b s e r v a t i o n t h a t the d e t r i m e n t a l e f f e c t o f i n c o r r e c t e n e r g y - . p r o t e i n r e l a t i o n s h i p c o u l d be a l l e v i a t e d by i m p r o v i n g t he b a l a n c e o f amino a c i d s i n t h e d i e t ( H i l l and Dansky, 1950) e s t a b l i s h e d t h e i m p o r t a n c e o f ene r gy and amino a c i d b a l a n c e i n t h e e v a l u a -t i o n o f n u t r i e n t s o r d i e t s . I t i s i m p o r t a n t t o p o i n t o u t t h a t i n i n t e r p r e t i n g t he r e s u l t s o f t he p r e s e n t s t u d y c o n g n i z a n c e s h o u l d be t a k e n o f t he f a c t t h a t f i s h meal was t h e p r i n c i p a l s o u r c e o f p r o t e i n . As s u ch i t was p o s s i b l e n o t o n l y t o p r o v i d e a good s u p p l y o f e s s e n t i a l amino a c i d s bu t a l s o t o m a i n t a i n a c o n s t a n t b a l a n c e between amino a c i d s as t h e p r o t e i n l e v e l i n c r e a s e d . 120 L i p o g e n e s i s i n t he d o m e s t i c c h i c k e n i n v o l v e s t he c o n v e r s i o n o f a c e t y l CoA t o f a t t y a c i d s i n t h e c y t o p l a s m ( A n n i s o n , 1 9 7 1 ) , b u t t h e p y r u v a t e fo rmed f r om g l u c o s e , a m a j o r f a t p r e c u r s o r i n the b i r d , g i v e s r i s e t o a c e t y l CoA i n the m i t o c h o n d r i a . A c e t y l CoA c a n n o t d i f f u s e i n t o the c y t o p l a s m a t a r a t e commensurate w i t h r e q u i r e m e n t f o r l i p o g e n e s i s and has t o be t r a n s p o r t e d t h r o u g h t h e m i t o c h o n d r i a l membrane as c i t r a t e where i t i s c o n v e r t e d t o o x a l o a c e t a t e and a c e t y l CoA ( P e a r c e , 1974 ) . The s h u n t i n g o f t h i s s u b s t r a t e f r om t h e m i t o c h o n d r i a t o the c y t o p l a s m n e c e s s i t a t e s t h e e x p e n d i t u r e o f e n e r g y . Under c o n d i t i o n s o f i n c r e a s e d b i o s y n t h e t i c a c t i v i t y , t h i s ene r gy e x p e n d i t u r e may r e a c h s i g n i f i c a n t p r o p o r t i o n s . Q u i t e a p a r t f r om t h e f a c t t h a t t he s o - c a l l e d e x t r a - c a l o r i c e f f e c t o f f a t has been o b s e r v e d m o s t l y w i t h t u r k e y s , t h e b e n e f i c i a l e f f e c t a t t r i b u t a b l e t o added d i e t a r y f a t i s l a r g e l y a con sequence o f t he f a c t t h a t d i e t s w i t h o u t added f a t may n o t be adequa te i n terms o f t he s u p p l y o f e s s e n t i a l f a t t y a c i d s . I t i s d o u b t f u l whe the r t h e d i e t s w i t h o u t added d i e t a r y f a t used i n the s t u d i e s o f Touchburn and Naber (1966) and J e n s e n e_t al_. (1970) were adequa te i n m e e t i n g the e s s e n t i a l f a t t y a c i d s r e q u i r e m e n t by t u r k e y b r o i l e r s . The d a t a p r e s e n t e d i n E x p e r i m e n t 3 demons ta te t h a t added d i e t a r y c e l l u l o s e has a d e l e t e r i o u s e f f e c t on m e t a b o l i s a b i 1 i t y o f d i e t s and e f f i c i e n c y o f f o o d u t i l i s a t i o n . T h i s o b s e r v a t i o n i s i n agreement w i t h s e v e r a l o t h e r s r e p o r t e d i n t he l i t e r a t u r e ( P e n q u i t e , 1976, W e l l s , 1963 ) . However , i n c l u s i o n o f c e l l u l o s e i n t h e d i e t a t a l e v e l h i g h e r t h a n t h a t used i n t h e p r e s e n t s t u d y d i d n o t i n t e r f e r e w i t h t h e b i r d s ' a b i l i t y t o consume s u f f i c i e n t ene rgy f o r t h e i r r e q u i r e m e n t s ( S i b b a l d e t a l _ . , 1960 ) . 121 The d i f f e r e n c e between t h e f i n d i n g o f t h e p r e s e n t e x p e r i m e n t and t h e one under r e f e r e n c e may be e x p l a i n e d on t he b a s i s o f d i f f e r e n c e s i n s t r a i n and g rowth r a t e o f t he b i r d s i n v o l v e d i n t he two s t u d i e s . Under normal p h y s i o l o g i c a l c o n d i t i o n s , h i g h d i e t a r y f i b r e may s h o r t e n i n g e s t a t r a n s i t t i m e . The i n c r e a s e d b u l k o f n o n - a s s i m i l a b l e m a t e r i a l i n t he a l i m e n t a r y t r a c t o f t he c h i c k e n may p r e c i p i t a t e p h y s i c o - c h e m i c a l r e a c t i o n s w h i c h may a f f e c t p r o c e s s e s s uch as e n z y m e - s u b s t r a t e b i n d i n g and w a t e r - f a c i 1 i t a t e d movement o f n u t r i e n t s t owa rd s and t h r o u g h t h e a b s o r b i n g mucosa l s u r f a c e . As S o u t h g a t e (1973) e x p l a i n e d , l o s s e s o f endogenous m a t e r i a l w h i c h w i l l u n d o u b t e d l y a f f e c t t h e r e s u l t s o f b a l a n c e s t u d i e s may o c c u r as a r e s u l t o f m e c h a n i c a l e r o s i o n o f t he mucosa l s u r f a c e . P i e k a r s k a (1964) and Rao and S u n d e r a v a l l i (1970) o b s e r v e d i n c r e a s e d f a e c a l n i t r o g e n e x c r e t i o n and c o n s e q u e n t l y d e c r e a s e d a p p a r e n t p r o t e i n d i g e s t i b i l i t y i n r a t s f e d s e m i - p u r i f i e d c a s e i n d i e t s c o n t a i n i n g 10-20 p e r c e n t f i b r e o r c r y s t a l l i n e c e l l u l o s e . S i m i l a r f i n d i n g s have been o b t a i n e d w i t h c h i c k e n s f e d d i e t s c o n t a i n i n g h i g h l e v e l s o f f i b r e ( K i b e e t a j _ . , 1964; V l c e k , 1968; V l c e k and P a z o u r e k , 1 970 ) . C o n t r a r y t o p o p u l a r b e l i e f , t he y o l k s a c does n o t i n f l u e n c e m e t a b o l -i s a b l e ene r gy v a l u e s o f n u t r i e n t s i n t he e a r l y days p o s t h a t c h i n g . I f t h e r e s i d u a l y o l k i n f l u e n c e s t h e p e r f o r m a n c e o f t h e c h i c k i n the f i r s t few days p o s t h a t c h i n g , i t must be a p a r a m e t e r ( s ) o t h e r t han g rowth as measured by body w e i g h t s and m e t a b o l i s a b i 1 i t y o f n u t r i e n t s . D u r i n g i n c u -b a t i o n , t he embryo u t i l i z e s a l l n u t r i e n t s , w i t h t h e e x c e p t i o n o f p r o t e i n , t o a n e a r d e p l e t i o n l e v e l . Through some unknown mechan i sm, t h e r e i s a 122 n o t i c e a b l e i n c r e a s e i n t he c o n c e n t r a t i o n o f t o t a l p r o t e i n s i n t h e y o l k (Romanof f and Romanof f , 1967) and t h e y o l k s ac ( R o l ' n i c k , 1970) compared t o the amount a t t h e m i d p o i n t o f embryo deve l opmen t . In a d d i t i o n , s e v e r a l n i t r o g e n o u s compounds i n c l u d i n g r i b o n u c l e i c a c i d and some twen ty amino a c i d s a r e p r e s e n t (Romanof f and .Romano f f , 1 967 ) . The i n c r e a s e d amount o f n i t r o g e n o u s compounds imposes a d d i t i o n a l p h y s i o l o g i c a l l o a d on t h e baby c h i c k . The i m p l i c a t i o n seems t o be a s t e p p i n g up o f t h e r a t e o f n i t r o g e n e x c r e t i o n . T h i s h y p o t h e s i s wou l d e x p l a i n t he o b s e r v e d l o w e r a p p a r e n t n i t r o g e n r e t e n t i o n v a l u e s o b t a i n e d w i t h c h i c k s w i t h i n t a c t y o l k s ac compared t o t h o s e o b t a i n e d w i t h c h i c k s w i t h o u t r e s i d u a l y o l k . Under t h e c o n d i t i o n s o f t h i s e x p e r i m e n t , i t has been shown t h a t n o t o n l y does the r e s i d u a l y o l k n o t p r o v i d e n u t r i e n t s i n s i g n i f i c a n t amounts , bu t i t s p r e s e n c e may i n t e r f e r e w i t h t h e u t i l i s a t i o n o r t h e e x c r e t i o n o f t h e was te p r o d u c t s o f n u t r i e n t s , p a r t i c u l a r l y t h o s e o f p r o t e i n . The d a t a p r e s e n t e d i n P a r t 2 i n d i c a t e t h a t ene r gy u t i l i s a t i o n as measured by m e t a b o l i s a b l e ene r gy v a l u e s i s n o t i n f l u e n c e d by t h e p r e s e n c e o r ab sence o f t h e c a e c a . The d a t a s u p p o r t t h e o b s e r v a t i o n s o f S c o t t ( 1 9 5 5 ) , McBee (1971) and McNab (1973) among o t h e r s , who d i s p u t e t he c l a i m o f c e l l u l o l y s i s i n t h e a v i a n c a e c a . The d a t a a l s o t e n d t o s u p p o r t t h e f i n d i n g o f F i s h e r and G r i m i n g e r (1966) t h a t t h e a v i a n c a e c a do no t p l a y a s i g n i f i -c a n t r o l e i n p r o t e i n u t i l i s a t i o n . The a s s i m i l a t i o n o f p r o t e i n s i s t h e c o n c e r t e d p r o c e s s c l o s e l y r e g u l a t e d by n e u r a l and hormonal mechanisms r a t h e r t h a n a r e s u l t o f c l e a r l y d e f i n e d i n d i v i d u a l s t e p s ( G i t l e r , 1964 ) . The use o f n i t r o g e n b a l a n c e method as a c r i t e r i o n f o r t he e s t i m a t i o n o f n i t r o g e n r e t e n t i o n i n t h e body i s a s e n s i t i v e method , so s e n s i t i v e t h a t 123 the b a l a n c e w i l l v a r y v e r y r a p i d l y w i t h s h i f t s i n p h y s i o l o g i c a l s t a t e s , r e s p o n d i n g t o a l t e r a t i o n s i n d i e t s , e n d o c r i n e s e c r e t i o n s and a b n o r m a l i t i e s o f v a r i o u s k i n d s . One o r more o f t h e a b o v e - m e n t i o n e d f a c t o r s c o u l d be r e s p o n s i b l e f o r t h e o b s e r v e d v a r i a t i o n s i n the a p p a r e n t n i t r o g e n r e t e n t i o n v a l u e s w i t h i n t r e a t m e n t g roups and t h e f l u c t u a t i o n s w i t h i n p e r i o d s . Co s t a ( 1 9 6 0 ) , A l l i s o n and B i r d (1964) have r e p o r t e d l o s s e s o f s i z e a b l e amounts o f d i e t a r y n i t r o g e n t h r o u g h some u n s u s p e c t e d r o u t e , p o s s i b l y as gaseous n i t r o g e n f rom the l u n g s . Neshe im and C a r p e n t e r (1967) r e p o r t e d f e r m e n t a -t i o n o f p r o t e i n and p e p t i d e s w h i c h e s cape breakdown and e n t e r t he c a e c a r e s u l t i n g i n t h e l o s s o f n i t r o g e n i n t he fo rm o f ammonia. The f a c t t h a t u r i c a c i d n i t r o g e n was u sed as a component f o r t h e e s t i m a t i o n o f t h e a p p a r e n t n i t r o g e n a b s o r p t i o n and t h e f a c t t h a t u r i c a c i d d e t e r m i n a t i o n u n d e r e s t i m a t e s t h e t o t a l n i t r o g e n e x c r e t e d s h o u l d be c o n s i d e r e d i n a r r i v i n g a t a c o n c l u s i o n on t he p r o t e i n u t i l i s a t i o n as measured by a p p a r e n t n i t r o g e n a b s o r p t i o n o r r e t e n t i o n . The v i ew i s h e l d by some r e s e a r c h e r s t h a t t he c a e c a may f u n c t i o n a c t i v e l y i n t r a p p i n g p r o t e i n o f endogenous o r i g i n o r d i e t a r y p r o t e i n w h i c h has e s c aped d i g e s t i o n and/o r a b s o r p t i o n i n t he upper g u t . I f t h i s i s t r u e , i t i s l o g i c a l t o e x p e c t t h i s mechanism t o be f u l l y o p e r a t i o n a l i n s i t u a t i o n s o f p r o t e i n i n a d e q u a c y o r d e f i c i e n c y . R e c y c l i n g may r educe t h e amount o f p r o t e i n e x c r e t o r y p r o d u c t s and t h i s may a f f e c t t h e b a l a n c e o f n i t r o g e n i n t he body. The l e v e l o f p r o t e i n used i n t h i s s t u d y was no t l ow enough t o evoke such a mechan i sm. The t e s t i n g o f t h i s h y p o t h e s i s -t h a t t h e c a e c a may r e c y c l e p r o t e i n i n c a s e s o f i n a d e q u a t e d i e t a r y p r o t e i n l e v e l - w i l l y i e l d v a l u a b l e i n f o r m a t i o n . 124 F i n a l l y , i n v i ew o f the ' i n t e g r a t e d n a t u r e o f t h e n u t r i t i o n a l f a c t o r s i n f l u e n c i n g the e x p r e s s i o n o f any p h y s i o l o g i c r e s p o n s e , f u r t h e r r e s e a r c h s h o u l d i n v o l v e t h e i n v e s t i g a t i o n o f t he b road i m p l i c a t i o n s o f as many r e l a t e d f a c t o r s as p o s s i b l e . The s t u d y d e s c r i b e d h e r e i n r e p r e s e n t s an a t t e m p t t o a c h i e v e such an o b j e c t i v e . 125 REFERENCES A h r e n s , R.A., J . E . W i l s o n , J r . and M. Womack. 1966. C a l o r i e and n i t r o g e n s t o r a g e f r om d i e t s c o n t a i n i n g p u r i f i e d c a s e i n v e r s u s a m i x t u r e o f amino a c i d s s i m u l a t i n g a c s e i n . - J . N u t r . , 8 8 : 219 -224 . A i t k e n , J . R . , G.S. L i n d b l a d and W.G. H u n s a k e r . 1954. B e e f t a l l o w as a s o u r c e o f ene r gy i n b r o i l e r r a t i o n s . P o u l t r y S c i . 33 : 1038. Abs . A k e s t e r , A . R . , R.S. A n d e r s o n , K . J . H i l l and G.W. O s b a l d i s t o n , 1967. A r a d i o g r a p h i c s t u d y o f u r i n e f l o w i n t h e d o m e s t i c f o w l . B r . P o u l t . S c i . 8 : 2 0 9 -A l l i s o n , J . B . and J .W.C. B i r d . 1964. E l i m i n a t i o n o f n i t r o g e n f rom t h e body. I n : Mammalian P r o t e i n M e t a b o l i s m . (H.N. Munro and J . B . A l l i s o n , e d s . ) , pp. 4 8 3 - 5 1 2 . Academic P r e s s , New Y o r k , London. A l T r e d , J . B . 1969. R e l a t i o n s h i p s between t h e c o n c e n t r a t i o n o f l i v e r m e t a -b o l i t e s and k e t o g e n e s i s i n c h i c k s f e d " c a r b o h y d r a t e - f r e e " d i e t s . J . N u t r i t i o n 99 : 101 -108 . A l m q u i s t , H . J . 1954. U t i l i s a t i o n o f amino a c i d s by c h i c k s . A r c h . B i ochem. B i o p h y s . 52 : 197 -202 . A l m q u i s t , H . J . 1956. Changes i n f a t e x t r a c t a b i 1 i t y and p r o t e i n d i g e s t i -b i l i t y i n f i s h meal d u r i n g s t o r a g e . J . A g r . Food Chem. 4 : 6 38 - 639 . A n n i s o n , E .F . 1971. " L i p i d and A c e t a t e M e t a b o l i s m " . I n : P h y s i o l o g y and B i o c h e m i s t r y o f t he Domes t i c F o w l . ( D . J . B e l l and B.M. F reeman, e d s . ) , pp. 321 -337 . Academic P r e s s , London , New Y o r k . A s s o c i a t i o n o f O f f i c i a l A g r i c u l t u r a l C h e m i s t s . 1965. O f f i c a l Methods o f A n a l y s i s . 10 th E d i t i o n , W a s h i n g t o n , D.C. B a l d i n i , J . T . 1961. The e f f e c t o f d i e t a r y d e f i c i e n c y on t h e ene r gy m e t a -b o l i s m o f t h e c h i c k . P o u l t r y S c i . 4 0 : 1177 -1183 . B a l d i n i , J . T . and H.R. Ro senbe r g . 1955. The e f f e c t o f p r o d u c t i v e ene r g y l e v e l o f t h e d i e t on t h e m e t h i o n i n e r e q u i r e m e n t o f t h e c h i c k . P o u l t r y 126 S c i . 34: 1301-1307. Barnes, E.M. 1972. The av ian i n t e s t i n a l f l o r a w i th p a r t i c u l a r re fe rence to the po s s i b l e e c o l o g i c a l s i g n i f i c a n c e of the caecal anaerobic b a c t e r i a . Am. J . of C l i n . Nutr. 25: 1475-1479. Barnes, E.M. and C.S. Impey. 1970. The i s o l a t i o n and p rope r t i e s of the p re -dominant anaerobic b a c t e r i a i n the caeca of ch ickens and tu rkey s . Br. Pou l t . S c i . 11: 467-481. Barnes, E.M. and C.S. Impey. 1974. The occurrence and p rope r t i e s of u r i c a c i d decomposing anaerobic b a c t e r i a i n the av ian caecum. J . App l . Bact. 37: 393-409. Barnes, E.M. and C.S. Impey. 1972. Some p r ope r t i e s o f the non-spor ing anaerobes from pou l t r y caeca. J . App l . Bact. 35: 241-251. Barnes, E.M. and D.H. Shrimpton. 1957. A s u r g i c a l and chemical technique f o r the study of the metabo l ic a c t i v i t y of the gut f l o r a i n v i v o . Fourth Int . Congr. Nutr. ( P a r i s ) , Abs. p. 72. Barnes, E.M., G.C. Mead, D.A. Barnum and E.G. Harry. 1972. The i n t e s t i n a l f l o r a of the ch icken dur ing the per iod 2 to 6 weeks of age w i th pa r -t i c u l a r re ference to the anaerobic b a c t e r i a . B r i t . Pou l t - S c i . 13: 311-326. Barnes, R.H. and E. Kwong. 1964. Methionine absorpt ion and u t i l i s a t i o n from soybean p r o t e i n and the e f f e c t o f soybean t r y p s i n i n h i b i t o r - A study of amino a c i d a v a i l a b i l i t y . In: The Role of the G a s t r o i n t e s t i n a l T rac t i n P r o t e i n Metabol ism. (H.N. Munro, ed.) B l a c k w e l l . pp. 41-80. Bar tov, I., S. Bo rns te in and B. L i p s t e i n . 1974. E f f e c t of c a l o r i e to p ro -t e i n r a t i o on the degree of fa tness i n b r o i l e r s fed on p r a c t i c a l d i e t s . Br. Pou l t . S c i . 15: 107-117. 127 Bay ley, H.S., S . J . S l i n g e r , J.D. Summers and G.C. Ashton. 1974. Factors i n f l u e n c i n g the metabo l i s ab le energy value of rapeseed meal: l e v e l in d i e t , e f f e c t s of s t e a m - p e l l e t i n g , age of c h i c k , length of time on d i e t , v a r i e t y of rapeseed and o i l e x t r a c t i o n procedure. Can. J . Anim. S c i . 54: 465-480. B e a t t i e , J . and D.H. Shrimpton. 1958. Su rg i ca l and chemical techniques f o r in v i vo s tud ie s of the metabolism of the i n t e s t i n a l m i c r o f l o r a of dom-e s t i c f ow l s . Quart. J . Exp. P h y s i o l . 43: 399-407. Beg in, J . J . 1961. The e f f e c t of c e l l u l o s e w i th and without supplemental energy i n ch i ck d i e t s . P o u l t r y S c i . 40: 892-900. Beg in, J . J . 1969. The e f f e c t of d i e t and breed of ch icken on the metabol ic e f f i c i e n c y of n i t rogen and energy u t i l i z a t i o n . Pou l t r y S c i . 48: 48-54. B i e l y , J . and B.E. March. 1954. Fat s tud ie s i n p o u l t r y . 2. Fat supplements in ch ick and pou l t r a t i o n s . Pou l t r y S c i . 33: 1220-1227. B i e l y , J . , B.E. March and H.L.A. Ta r r . 1951. The n u t r i t i v e va lue of f i s h meal and condensed f i s h s o l u b l e s . I I I . E f f e c t of heat ing f a t - c o n t a i n i n g and hexane-extracted meal. Progress Report, P a c i f i c Coast S ta . F i s h . Res. Bd. (Canada) No. 89: 79-81. Boge, G . I 9 6 0 . Amino a c i d composit ion of he r r i n g (Clupea harengus) and he r r i ng meal. Des t ruc t i on of amino ac ids dur ing p roces s ing . J . Sc. Food Agr. 11: 362-365. Carew, L.B. J r . and F.W.. H i l l . 1964. E f f e c t of corn o i l on metabol ic e f f i c i e n c y of energy u t i l i z a t i o n by c h i c k s . J . N u t r i t i o n 83: 293-299. Carew, L.B. J r . , D.T. Hopkins and M.C. Nesheim. 1964. In f luence o f amount and type of f a t on metabo l ic e f f i c i e n c y of energy u t i l i z a t i o n by the ch i c k . J . N u t r i t i o n 83: 300-306. 128 Carew, L.B. J r . , M.C. Nesheim and F.W. H i l l . 1963. The r e l a t i o n s h i p of d i e t a r y energy l e v e l and den s i t y to the growth response of ch ick s to f a t s . P o u l t r y S c i . 42: 710-718. Carew, L.B. J r . , R.H. Machemer, J r . , R.W. Sharp and D,C. Foss. 1972. Fat absorpt ion by the very young ch i c k . P o u l t r y S c i . 51: 738-742. C a r r i c k , C.W. and R.E. Roberts . 1947a. Studies on feed e f f i c i e n c y , 1. The r e l a t i v e e f f i c i e n c y of corn and wheat products i n ch i c k r a t i o n s . P o u l t r y S c i . 27: 111-117. C a r r i c k , C.W. and R.E. Roberts . 1947b. Studies on feed e f f i c i e n c y , I I . The r e l a t i v e e f f i c i e n c y of corn and oats i n ch i ck r a t i o n s . P o u l t r y S c i . 27: 213-218. Combs, G.F., E.H. Bosard, G.R. Ch i l d s and D.L. Blamberg. 1964. E f f e c t of p r o t e i n l e ve l and amino a c i d balance on vo lunta ry energy consumption and carcass compos i t ion. P o u l t r y S c i . 43: 1309. Abs. Cos ta , G. 1960. Hypothet i ca l pathway of n i t rogen metabol ism. Nature 188: 549-552. C u l l e n , M.P., O.G. Ramussen and O.H.M. Wi lder . 1962. Metabo l i zab le energy value and u t i l i z a t i o n of d i f f e r e n t types and grades of f a t by the ch i c k . P o u l t r y S c i . 41: 360-367. Davidson, J . , J . Mathieson, R.B. W i l l i ams and A.W. Boyne. 1964. E f f e c t s of animal f a t and of low r a t i o s of p r o t e i n to metabo l i zab le energy on the u t i l i z a t i o n of d i e t a r y energy by medium- and fa s t -g rowing s t r a i n s of p o u l t r y . J . S c i . Fd. A g r i c . 15: 316-325. Dav is , F. and G.M. B r i ggs . 1947. The growth promoting a c t i o n of c e l l u l o s e in p u r i f i e d d i e t s f o r c h i c k s . J . N u t r i t i o n 15: 383-395. Dav i s , F. and G.M. B r i gg s . 1948. Sawdust i n p u r i f i e d ch i ck r a t i o n s . P o u l t r y S c i . 27: 117-118. 129 DeGroote, G., N. Reyntens and J . Am i ch -Ga l i . 1971. Fat s t ud i e s . 2. Metabo l i c e f f i c i e n c y of enerqy u t i l i z a t i o n of g lucose, soybean o i l and d i f f e r e n t animal f a t s by growing c h i c k s . Pou l t r y S c i . 50: 808-819. Donaldson, W.E. 1962. The response of ch ick s to d i e t a r y animal f a t in new and o ld environments. Pou l t r y S c i . 41: 1106-1108. Donaldson, W.E. 1964. Adaptat ion of the ch ick to d i e t a r y energy source. J . N u t r i t i o n 82: 115-120. Donaldson, W.E. 1966. In f luence of d i e t a r y f a t on l i pogene s i s and f a t t y a c i d i n t e r c o n v e r s i o n . Wor ld ' s P o u l t r y Congr. Proc. 13: 196-199. Donaldson, W.E., G.F. Combs and G.L. Romoser. 1956. Studies on energy l e v e l s i n p o u l t r y r a t i o n s . 1. The e f f e c t of c a l o r i e - p r o t e i n r a t i o of the r a t i o n on growth, n u t r i e n t u t i l i s a t i o n and composit ion of c h i c k s . Pou l t r y S c i . 35: 1100-1105. Donaldson, W.E., G.F. Combs and G.L. Romoser. 1958. Studies on the energy l e v e l s in pou l t r y r a t i o n s . 3. E f f e c t of c a l o r i e - p r o t e i n r a t i o on growth, n u t r i e n t u t i l i s a t i o n and body composit ion of p o u l t s . Pou l t r y S c i . 37: 614-619. Donaldson, W.E., G.F. Combs, G.L. Romoser and W.C. Supplee. 1955. Body compos i t ion , energy i n t a k e , feed e f f i c i e n c y , growth r a t e and f ea the r c ond i t i on of growing ch ick s as i n f l uenced by the c a l o r i e / p r o t e i n r a t i o of the r a t i o n . P o u l t r y S c i . 34; 1190, abs. Donaldson, W.E., G.F. Combs, G.L. Romoser and W.C. Supplee. 1957. Studies on energy l e v e l s i n pou l t r y r a t i o n s . 2. To lerance of growing ch ick s to d i e t a r y f a t . P o u l t r y S c i . 36: 807-815. -Dror, Y., H.F. Sassoon, J . J . Watson, D.O. Mack and B.C. Johnson. 1973. Fat versus sucrose as the non p r o t e i n c a l o r i e po r t i on of the d i e t of r a t s . 130 J . N u t r i t i o n 103: 342-346. Dukes, H.H. 1955. The Phys io logy of Domestic Animals. Comstock Pub l i s h i n g Co., New York, N.Y. Edwards, H.M. and P. Hart . 1971. Carcass composit ion of ch ickens fed carbo-hyd ra te - f r ee d i e t s con ta i n i ng var ious l i p i d energy sources. J . Nutr . 101: 989-996. E l -Lakany. 1972. Storage changes i n natura l and model 1 i p i d - p r o t e i n systems. Ph.D. T h e s i s , Univ. B r i t . C o l . F a r r e l l , D.J. 1972. The e f f i c i e n c y of u t i l i s a t i o n of energy by b r o i l e r chickens on d i e t s w i th a range of energy concen t ra t i on s . Proc. Aust. Stock Fd. Mfrs . Ass. Aust. Meat Fedn. 155-159. F a r r e l l , D.J. 1974. E f f e c t s of d i e t a r y energy concent ra t i on on u t i l i s a t i o n of energy b y . b r o i l e r chickens and on body composit ion determined by carcass a n a l y s i s and p red i c t ed using t r i t i u m . Br. Pou l t r y S c i . 15: 25-41. F a r r e l l , D .J . , R.B. Cumming and J .B . Hardaker. 1973. The e f f e c t s of d i e t a r y energy concent ra t i on on growth r a te and convers ion of energy to weight gain i n b r o i l e r ch ickens . Br. P o u l t . S c i . 14: 329-340. Feather s ton , W.R. and R.W. Scho l z . 1968. Changes i n l i v e r xanth ine dehydro-genase and u r i c a c i d e x c r e t i o n in ch i ck s dur ing adaptat ion to a high p r o t e i n d i e t . J . N u t r i t i o n 95: 393-398. Fenner, L. and D.A. Boag. 1974. Adapt ive s i g n i f i c a n c e i n Japanese qua i l and spruce grouse ( G a l l i f o r m e s ) . Can. J . Zoo l . 52: 1577-1584. F i s h e r , H. and P. Gr iminger. 1966. Raw soybean u t i l i s a t i o n by caecectomized c h i c k s . Pou l t r y S c i . 45: 848-849. F i s h e r , H. and R. Shap i ro. 1961. Amino a c i d imbalance: Rations low in t ryptophane, methionine or l y s i n e and the e f f i c i e n c y of u t i l i s a t i o n 131 o f n i t r o g e n i n i m b a l a n c e d r a t i o n s . J . N u t r i t i o n 75: 395 -401 . F o r b e s , E.B. and R.W. S w i f t , w i t h t he t e c h n i c a l c o l l a b o r a t i o n o f A. Greenwood-Buckman, J . E . S c h o p f e r and M.T. D a v e n p o r t . 1944. A s s o c i a t i v e • •• dynamic e f f e c t s o f p r o t e i n , c a r b o h y d r a t e and f a t . J . N u t r i t i o n 27: 453 -468 . F o r b e s , E .B . , R.W. S w i f t , R.F. E l l i o t t and W.H. James. 1946. R e l a t i o n o f f a t t o economy o f f ood u t i l i z a t i o n . I. By t he g row ing a l b i n o r a t . J . N u t r i t i o n 31 : 203 -212 . F r a p s , G.S. 1943. R e l a t i o n o f p r o t e i n , f a t and ene r gy o f t h e r a t i o n s t o t he c o m p o s i t i o n o f c h i c k e n s . P o u l t r y S c i . 22: 421 -424 . F r a p s , G.S. 1946. C o m p o s i t i o n and p r o d u c t i v e ene r gy o f p o u l t r y f e e d s and r a t i o n s . Texas A g r . Exp. S t a . B u l l . 678. F reeman, B.M. 1965. The r e l a t i o n s h i p between oxygen c o n s u m p t i o n , body, t e m -p e r a t u r e and s u r f a c e a r e a i n t h e h a t c h i n g and young c h i c k . B r . P o u l t . S c i . 6: 6 7 - 72 . F r e n c h , C . E . , A. B l a c k and R.W. S w i f t . 1948. F u r t h e r e x p e r i m e n t s on t h e r e l a t i o n o f f a t t o economy o f f o o d . u t i l i z a t i o n . 3. Low p r o t e i n i n t a k e . J . N u t r i t i o n 35: 8 3 - 88 . F r i t z , E. 1961. D o t t e r r e s o r p t i o n und h i s t o l o g i s c h e verc lnderungen des d o t t e r s a c k s nach dem s c h l u p f e n des kOkens. W i l h e l m Roux* A r c h . E n t w i c k l . - M e c h . O r g . , 153: 93 - 119 . G a r d i n e r , E.E. 1971 . R e l a t i o n s h i p o f e n e r g y , phosphorus and b reed o f c h i c k e n t o g r owth and f ood e f f i c i e n c y . B r . P o u l t . S c i . 12: 3 1 - 39 . G i t l e r , C. 1964. P r o t e i n d i g e s t i o n and a b s o r p t i o n i n n o n r u m i n a n t s . Mammalian P r o t e i n M e t a b o l i s m . (H.N. Munro and J . B . A l l i s o n , e d s . ) . Academic P r e s s , New Y o r k . 132 Goodridge, A.G. 1968. Metabolism of glucose U- C in v i t ro in adipose t issue from embryonic and growing chicks. Am. J . Phys io l . 214: 897-901. Goss, R.J. 1965. Mammalian regeneration and i t s phylogenetic re lat ionsh ip. Proc. Regeneration in Animals. North-Holl. Publ. Co., Amsterdam. Griminger, P. 1957. On the vitamin K requirement of turkey poults. Poultry Sc i . 36: 1227-1235. Halloran, H.R., J.B. Lyle and W.T. Trana'. 1972. "Extra c a l o r i c " e f fect of a blended animal and vegetable feeding f a t . Poultry Sc i . 51: 1814. Abs. Hallsworth, E.G. and J . I . Coates. 1962. The growth of the alimentary t ract of the fowl and the goose. J . Agr. Sc i . 58: 153-163. Hainan, E.T. 1930. The ro le of f i b re in poultry feeding. Proc. Fourth World's Poultry Congress, 221-228. Hainan, E.T. 1949. The architecture of the avian gut and tolerance of crude f i b r e . B r i t . J . Nutr i t ion 3: 245-253. Harper, A.E. and U.S. Kumta. 1959. Amino acid balance and protein require-ment. Fed. Proc. 18: 1136-1142. Henning, H. 1929. Die verdaul ichkeit der Rohfaser beis Huhn. Landurn. Vers Stnen 108: 253. Cited by McNab. 1973. Herstad, 0. 1970. Effekt av f e i t t - t i l s k o t t t i l b r o i l e r f o r . (Effect of f a t -supplements in b ro i l e r feed). Meldinger fra Norges Landbrukshogskole 49: 1-55. Cited by Salmon, 1972. Heuser, G.F., L.C. Norr i s , H.T. Peeler and M.L. Scott. 1945. Further studies on the apparent e f fect of d i g e s t i b i l i t y upon growth, weight-maintenance and egg production. Poultry S c i . 24: 142-145. H i l l , F.W. and L.M. Dansky. 1950. Studies on the protein requirements of chicks and i t s re la t ion to dietary energy l e v e l . Poultry S c i . 29: 763. Abs. 133 H i l l , F.W. and L.M. Dansky. 1954. S t u d i e s o f t h e ene rgy r e q u i r e m e n t s o f c h i c k e n s . 1. The e f f e c t o f d i e t a r y ene r gy l e v e l on g rowth and f e e d c o n s u m p t i o n . P o u l t r y S c i . 33: 112 -119 . H i l l , F.W. and S. B r a m b i l a . 1955. P r o p e r t i e s o f h i g h l i p i d d i e t s based on f r e e f a t t y a c i d s . F e d . . P r o c . 24. Ab s . 2066. H i l l , F.W. and S. B r a m b i l a . 1965. N u t r i t i o n a l p r o p e r t i e s o f r e c o n s t i t u t e d t r i g l y c e r i d e s f o r t h e c h i c k . F e d . P r o c . 24: Ab s . 2067. H o r a n i , F. and N . J . D a g h i r . 1975. M e t a b o l i s a b l e ene rgy (M.E. ) v a l u e s o f t h r e e p r o t e i n s upp l emen t s as d e t e r m i n e d w i t h c h i c k s and l a y i n g hens . P o u l t r y S c i . 54: 1886 -1889 . H u n t e r , J . E . , A . J . Du ran t and A . G . Hogan. 1930. S t u d i e s on p a t h o l o g y and p h y s i o l o g y o f c a e c a l pouches o f t u r k e y s . 2. U t i l i s a t i o n o f f o o d by t u r k e y s w i t h a b l a t e d c a e c a . U n i v . M i s s o u r i A g r i c . Exp. S t a . Res . B u l l . 136. I s a a k s , R .E . , R.E. D a v i e s , R. R e i s e r and C R . Couch . 1963. Growth s t i m u -l a t i n g e f f e c t s o f h i g h l e v e l s o f v e g e t a b l e o i l s . J . Am. O i l Chem. S o c . 40: 747 -749 . J a y n e - W i 1 1 i a m s , D . J . and R. F u l l e r . 1971. The i n f l u e n c e o f t h e i n t e s t i n a l m i c r o f l o r a on n u t r i t i o n . I n : P h y s i o l o g y and B i o c h e m i s t r y o f t h e Domes t i c F o w l . ( D . J . B e l l and B.M. F reeman, e d s . ) , Academic P r e s s , New Y o r k , N.Y. J e n s e n , L . S . , G.W. S chuma ie r and J . D . La t shaw. 1970. " E x t r a c a l o r i c " e f f e c t o f d i e t a r y f a t f o r d e v e l o p i n g t u r k e y s as i n f l u e n c e d by c a l o r i e : p r o t e i n r a t i o . P o u l t r y S c i . 49: 1697-1704. Kaupp, B.F. and J . E . I v e y . 1922. D i g e s t i b l e n u t r i e n t s o f p o u l t r y f e e d s as 134 d e t e r m i n e d by l a b o r a t o r y f e e d i n g t e s t s . P o u l t r y S c i . 2: 1-9. Ke se , A . G . and B.E. Ma r ch . 1975. The r o l e o f t h e a v i a n c a e c a i n ene r g y and p r o t e i n m e t a b o l i s m . P o u l t r y ' S c i . 54: 1781 . Ab s . K i b e , K., I. T a s a k i and M. S a i t o . 1964. E f f e c t s o f f i b r e on t he b i o l o g i c a l v a l u e and t r u e d i g e s t i b i l i t y o f d i e t a r y p r o t e i n and on t h e deve l opment o f i n t e r n a l o r gan s o f c h i c k s . J a p . J . Z o o t e c h . S c . 35: 159 -166 . K j e l d a h l , J . 1883. Neue Methode z u r Bestimmung des S t i c k s t o f f s i n o r g a n i s c h e n K t i r p e r n . Z. A n a l . Chem. 22: 366 -382 . As d e t a i l e d i n A . O . A . C . Kubena, L . F . , B.D. L o t t , J.W. D e a t o n , F .N . F r e e c e and J . O . May. 1972. Body c o m p o s i t i o n o f c h i c k s as i n f l u e n c e d by e n v i r o n m e n t a l t e m p e r a t u r e and s e l e c t e d d i e t a r y f a c t o r s . P o u l t r y S c i . 51: 517 -522 . L a k s e v e l a , B. 1958. P r o t e i n v a l u e and amino a c i d b a l a n c e o f condensed h e r r i n g s o l u b l e s and s p o n t a n e o u s l y hea ted h e r r i n g m e a l , c h i c k e x p e r i m e n t s . J . A g r . S c i . 51 : 164 -176 . L e a , C H . and R.S. Hannan. 1950. S t u d i e s o f t h e r e a c t i o n between p r o t e i n s and r e d u c i n g s u ga r s i n t h e " d r y " s t a t e . 111 . N a t u r e o f t h e p r o t e i n g roups r e a c t i n g . B i ochem. B i o p h y s . A c t a 5: 433 -454 . L e a , C . H . , L . J . P a r r and K . J . C a r p e n t e r . 1958. Chemica l and n u t r i t i o n a l changes i n s t o r e d h e r r i n g m e a l . B r . J . N u t r . 12: 297 -312 . L e a , C . H . , L . J . P a r r and K . J . C a r p e n t e r . 1960. C h e m i c a l and n u t r i t i o n a l changes i n s t o r e d h e r r i n g m e a l . B r . J . N u t r . 14: 91 - 113 . L e e s o n , S., K.N. Boorman, D. L e w i s and D.H. S h r i m p t o n . 1974. M e t a b o l i s a b l e ene r g y s t u d i e s w i t h t u r k e y s : m e t a b o l i s a b l e ene r gy o f d i e t a r y i n g r e d i e n t s . B r . P o u l t . S c i . 15: 183 -189 . L e p k o v s k y , S., M. Wagner, F. F u r u t a , K. Ozone and T. K o i k e . 1964. The p r o t e a s e s , amy l a se and l i p a s e o f t h e i n t e s t i n a l c o n t e n t s o f g e r m f r e e and c o n v e n t i o n a l c h i c k e n s . P o u l t r y S c i . 43 : 722 -726 . 135 L i o z n e r , L.D. 1974. Organ Regenerat ion: A Study of Developmental B io logy i n Mammals. (B.M. Ca r l s on , e d . ) , Consu l tants Bureau, New York, N.Y. Lodh i , G.N., R. Renner and D.R. C l a n d i n i n . 1969. Stud ies on the metabo l -i z a b l e energy of rapeseed meal f o r growing ch i ck s and l a y i n g hens. P o u l t r y S c i . 48: 964-970. L o o i , S.H. and R. Renner. 1974a. E f f e c t of feed ing " c a rbohyd ra te - f r ee " d i e t s on the c h i c k ' s requirement f o r v i tamin B-12. J . N u t r i t i o n 104: 394-399. L o o i , S.H. and R. Renner. 1974b. E f f e c t of feed ing " c a rbohyd ra te - f r ee " d i e t s on the c h i c k ' s requirement f o r meth ion ine. J . N u t r i t i o n 104: 400-404. Maas, W. 1934. Metabolism experiments on fowls w i th a r t i f i c i a l anus. Nutr . Ab s t r . Rev. 3: 949. Mangold;, E. 1934. D i ge s t i on and u t i l i s a t i o n of crude f i b r e . Nutr. Ab s t r . Rev. 3: 647-656. March, B.E. and J . B i e l y . 1955. Fat s tud ie s in p o u l t r y . 3. F o l i c a c i d and f a t t o l e r ance in the ch i c k . Pou l t r y S c i . 34: 39-44. March, B.E. and J . B i e l y . 1956. Fat s tud ie s i n p o u l t r y . 5. The e f f e c t of d i e t a r y f a t l e v e l on the c ho l i n e requirement of the ch i c k . Pou l t r y S c i . 35: 545-549. March, B.E. and J . B i e l y . 1972. The e f f e c t o f energy supp l i ed from the d i e t and from environment head on the response of ch i ck s to d i f f e r e n t l e v e l s v o f d i e t a r y l y s i n e . Pou l t r y S c i . 21 (51): 665-668. March, B.E. and R.O. Walker. 1970. The e f f e c t of s h i f t s i n the d i e t a r y amino a c i d pa t te rn on feed consumption i n the ch i c k . Can. J . PhysioT. Pharmacol. 48: 265-268. March, B.E., J . B i e l y , C. Goudie, F.E. C lagget t and H.L.A. Ta r r . 1961. The e f f e c t of storage temperature and a n t i o x i d a n t treatment on the chemical 136 and n u t r i t i v e c h a r a c t e r i s t i c s of he r r i ng meal. J . Amer. Chem. Soc. 33: 80-84. March, B.E., T. Smith and S. E l -Lakany. 1973. V a r i a t i o n s i n est imates of metabo l i zab le energy va lue of rapeseed meal determined w i th ch ickens of d i f f e r e n t ages. Pou l t r y S c i . 52: 614-618. Mar ion, J . E . and H.M. Edwards, J r . 1963. E f f e c t of d i e t on the uptake of c a r b o n - 1 4 - l a b e l l e d a c e t a t e , g lucose and l e u c i ne i n t o l i p i d s o f the ch i c k . J . N u t r i t i o n 81: 55-59. Masson, M.J. 1954. M i c ro scop i c s tud ie s of the gut f l o r a of the hen w i th s pec i a l re fe rence to the breakdown of s ta rches . Proc. 10th Wor ld ' s P o u l t r y Congress, Edinburgh, 105-111.-Mattocks , J .G . 1971. Goose feed ing and c e l l u l o s e d i g e s t i o n . Wildfowl 22: 107. Mattson, F.H. 1967. D i e ta r y compos i t i on , as r e l a t e d to the f a t e of d i e t a r y l i p i d s . Proc. 1967 Devel . Conf. on L i p i d s on the Fate of D i e ta r y L i p i d s . (G. Cowg i l l and L.W. K i n s e l l , ed s . ) . U.S. Govt. P r i n t i n g O f f i c e , Washington. Maumus, J . 1902. Les caecums des o i seaux. Ann. S c i . N a t l . VI I I Ser. Z oo l . 15: 1. Maumus, J . and L. Launoy. 1901. La d i g e s t i o n caeca le chez l e s o i seaux. B u l l . Mus. Natn. H i s t . Nat . , P a r i s , 7: 361. McBee, R.M. 1971. S i g n i f i c a n c e of i n t e s t i n a l m i c r o f l o r a in he rb i vo ry . Annu. Rev. E c o l . Syst . 2: 165-176. McDermott, F.T. and B. Roundness. 1976. I l e a l c r yp t c e l l popu la t ion k i n e t i c s a f t e r 40% small bowel r e s e c t i o n . Gast roentero logy 70: 707-711. McNab, J.M. 1973. The av ian caeca: A rev iew. Wor ld ' s P ou l t . S c i . J . 29: 251-263. 137 Mead, G.C. and B.W. Adams. 1975. Some observat ions on the caecal m i c r o f l o r a of the ch i c k dur ing the f i r s t two weeks of l i f e . Br. Pou l t . S c i . 16: 169-176. M i l l e r , D.S. 1955. The n u t r i t i v e value of f i s h p r o t e i n s . Chem. & Ind. (Lond.) 18: 501-502. M o r r i s , L., R.B. Thompson and V.G. H e l l e r . 1932. Crude f i b r e i n ch icken r a t i o n s . Pou l t r y S c i . IT: 219-225. Mraz, F.R., R.V. Boucher and M.G. McCartney. 1956. The i n f l uence of d i e t a r y p roduct i ve energy and f i b r e on growth response i n ch i ckens . Pou l t r y S c i . 35: 1335-1340. Munro, H.N. and T.W. Wikramanayake. 1954. Absence o f a time f a c t o r i n the r e l a t i o n s h i p between l e v e l o f energy i n t ake and p r o t e i n metabol ism. J . N u t r i t i o n 52: 99-114. Munro, H.N., J .G . Black and W.S.J. Thomson. 1959. The mode of a c t i o n of d i e t a r y carbohydrate on p r o t e i n metabol ism. B r i t . J . Nutr. 13: 475-485. Ne l son, T.S. and L.C. N o r r i s . 1961. Stud ies on the v i t amin K requirement of the c h i c k . P o u l t r y S c i . 40: 392-395. Nesheim, M.C. 1965. Amino a c i d a v a i l a b i l i t y i n processed p r o t e i n s . P ro -ceedings 1965 Co rne l l N u t r i t i o n Conference f o r feed manufacturers , pp. 112-118. Nesheim, M.C. and K . J . Carpenter. 1967. The d i g e s t i o n of heat damaged p r o t e i n Br. J . Nutr. 21: 399-411. N i t s a n , Z. and E. Alumot. 1963. The r o l e of the caecum i n the u t i l i s a t i o n o f raw soybean i n c h i c k s . J . N u t r i t i o n 80: 299-304. ' 1 Nowland, W.J . , R.A.E. Pym and P . J . McMahon. 1971. The 1971 random sample b r o i l e r t e s t . P o u l t r y Notes, pp. 6-11 N.S.W. Department of A g r i c u l t u r e . C i t ed by D.J. F a r r e l l , 1974. Br. P o u l t . S c i . 15: 25-41. 138 O ' D e l l , B.L., W.D. Woods, O.A. L a e r d a l , A.M. J e f f a y and J . E . Savage. 1960. D i s t r i b u t i o n of the major nitrogenous, compounds and amino ac id s i n ch icken u r i n e . Pou l t r y S c i . 39: 426-432. O'Hea, E.K. and G.A. L e v e i l l e . 1969. L i p i d b i o s yn the s i s and t r an spo r t i n the domestic ch i ck (Ga l lu s domest icus ) . Comp. Biochem. P h y s i o l . 30: 149-159. O l s son, N. 1948. The r o l e o f ' f i b r e i n the food of hens and c h i c k s . Proc. E ighth Wor ld ' s P o u l t r y Congress, 162-167. • Panda, J .N . and G.F. Combs. 1950. Stud ies on the energy requirements of the ch ick f o r r ap id growth. Pou l t r y S c i . 29: 774-775. Payne, G.C. and D. Lewis. 1964, Nu t r i en t den s i t y i n ch i ck d i e t s . 13th Wor ld ' s P o u l t . Congr. K iev , 182-186. Payne, W.L., R.R. K i f e r , D.G. Snyder and G.F. Combs. 1971. Stud ies of p ro -t e i n d i g e s t i o n i n the ch i c ken . 1. I n v e s t i g a t i o n of apparent amino a c i d d i g e s t i b i l i t y of f i s h meal p r o t e i n us ing caecectomized, adu l t male ch i ckens . Pou l t r y S c i . 50: 143-150. Pearce, J . 1974. The i n t e r r e l a t i o n s h i p s of carbohydrate and l i p i d metabol ism. Wor ld ' s Pou l t r y S c i . 30: 115-128. Penqu i te, R. 1936. Over 10 percent f i b r e apparent ly i s undes i r ab le . Oklahoma Agr. Exp. S ta . Annual Report, 156-157. Pete r son , D.W., C R . Grau and N.F, Peek. 1954. Growth and food consumption i n r e l a t i o n to d i e t a r y l e v e l s of p r o t e i n and f i b r ou s bu lk. J . N u t r i t i o n 52: 241-257. P i e ka r s k a , J . 1964. E f f e c t of chemical compos i t ion of crude f i b r e on some f u n c t i o n and weight of the d i g e s t i v e t r a c t . Rocz. Pantstowowego. Z a k l . H ig . 15: 471-480 (Nutr. Abs. Rev. 35: 3845). P o t t e r , L.M., L.D. Matter son, A,W. A r n o l d , W.J. Pude lk iewicz and E.P. S ingsen. 1960. S tud ies i n e va l ua t i ng energy content of feeds f o r the ch i c k . 1. 139 The eva l ua t i on of the metabo l i s ab le and p roduct i ve energy of alpha c e l l u l o s e . P o u l t r y S c i . 39: 1166-1177. P r a c t o r i u s , E. 1965. U r i c a c i d . In: Methods of enzymatic a n a l y s i s . (H.W. Bermeyer, ed . ) . Academic P res s , New York, N.Y. pp. 500-501. Pude l k i ew i c z , W.J . , M.W. S tutz and L.D. Matterson. 1968. Determinat ion of u r i c a c i d i n av ian exc re ta by the use of u r i c a se and d i f f e r e n t i a l spec-trophotometry. P o u l t r y S c i . 47: 1274-1277. Radeff , T. 1928. Uber d i e Rohfaserverdaureng beim Huhm und d i e h i e r be i dem Bl inddarm zukommende Bedeutung. Biochem. Z. 193: 192-196. Rand, N.T. , F.A. Kummerow and H.M. Scott-. 1957. The r e l a t i o n s h i p of d i e t a r y p r o t e i n , f a t and energy on the amount, compos i t ion and o r i g i n of carcass f a t . Pou l t r y S c i . 36: 1151-1152. Abs. Rand, N.T., H.M. Scot t and F.A. Kummerow. 1958. D ie ta ry f a t i n the n u t r i t i o n of the growing c h i c k . P o u l t r y S c i . 37: 1075-1085. Rao, M.N. and O.E. S u n d e r a v a l l i . 1970. Extraneous c e l l u l o s e : e f f e c t on p ro te i n u t i l i s a t i o n . Stud ies w i th weanl ing r a t s . J . Am. D i e t e t i c Assoc. 57: 517-519. Record, P.R. 1943. A f a c t o r i n oat h u l l s e s s e n t i a l f o r growth of c h i c k s . Iowa Research Bu i . 312. Renner, R. 1964. Factors a f f e c t i n g the u t i l i z a t i o n of " c a r bohyd r a t e - f r ee " d i e t s by the c h i c k . 1. Level of p r o t e i n . J . N u t r i t i o n 84: 322-326. Renner, R. and A.M. Elcombe. 1964. Factors a f f e c t i n g the u t i l i s a t i o n of " c a r bohyd r a t e - f r ee " d i e t s by the ch i c k . 2. Level of g l y c e r o l . J . N u t r i t i o n 84: 327-330. Renner, R. and F.W. H i l l . 1960. The u t i l i z a t i o n of corn o i l , l a r d and t a l l o w by ch ickens of var ious ages. Pou l t r y S c i . 39: 849-854, 140 R ichardson, C.E., A.B. Watts and E.A. Epps. 1956. Energy s tud ie s w i th b r o i l e r s : The e f f e c t of us ing va r ious f i b r ou s f e e d s t u f f s w i th and w i thout added f a t i n a p r a c t i c a l b r o i l e r r a t i o n . P o u l t r y S c i . 35: 1167-1168. Robertson, E.I., R.F. M i l l e r and G.F. Heuser. 1948. The r e l a t i o n of energy to f i b r e i n ch i ck r a t i o n s . P o u l t r y S c i . 27: 736-741. R o l ' n i k , V.V. 1970. "Withdrawal of the y o l k sac and i t s importance in po s t -embryonic development". In: B i r d Embryology, pp. 98-99. I s r ae l Program f o r S c i e n t i f i c T r a n s l a t i o n s , Jerusa lem, 1970. Romanoff, A.L. and A . J . Romanoff. 1967. "Chemistry of the nonembryonic po r t i on s of the egg". In: B iochemist ry of the Avian Embryo. John Wi ley and Sons, New York, London, Sydney, p. 187. S a i t o , M. I. T a s a k i , K. K ihe, H. Yamada and T. I ga ra sh i . 1959. E f f e c t of var ious c e l l u l o s e l e v e l s i n the d i e t on the ch i ck growth. P o u l t r y S c i . 38: 373-376. Salmon, R.E. 1972. The e f f e c t of d i e t a r y f a t on the performance, carcass q u a l i t y , f a t t y a c i d composit ion and storage s t a b i l i t y of tu rkey s . Ph.D. The s i s , Univ. of Saskatchewan, Canada. Salmon, R.E. 1974. E f f e c t of d i e t a r y f a t concen t ra t i on and energy to p r o t e i n r a t i o on the performance, y i e l d of carcass components and composit ion of s k i n and meat of turkeys as r e l a t e d to age. Br. P o u l t . S c i . 1.5: 543-560. S a l t e r , D.N. and M.E. Coates. 1971. The i n f l uence of the m i c r o f l o r a of the a l imenta ry t r a c t on p r o t e i n d i g e s t i o n i n the c h i c k . Br. J . Nutr. 26: 55-69. Schwartz, H.G., M.W. Tay lo r and H. F i s h e r . 1958. The e f f e c t of d i e t a r y energy concen t ra t i on and age on the l y s i n e requirement of growing c h i c k s . J . N u t r i t i o n 65: 25-37. 141 S c o t t , H.M. 1955. V i tamin K as r e l a t e d to the haemorrhagic c o n d i t i o n . Feed Age 5, No. 3: 40. S c o t t , H.M., L.D. Matterson and E.P. S ingsen. 1947. N u t r i t i o n a l f a c t o r s i n f l u e n c i n g growth and feed e f f i c i e n c y . 1. E f f e c t of the source of carbohydrate. Pou l t r y S c i . 26: 554. Abs. S c o t t , M.L., M.C. Nesheim and R.J. Young. 1969. N u t r i t i o n of the Ch icken, p.50. M.L. S co t t & A s s o c i a t e s , I t haca , New York. Shap i ro , S.K. and W.B. S a r l e s . 1949. Microorganisms i n the i n t e s t i n a l t r a c t of normal ch i ckens . J . Bact. 58: 531-544. Sheeny, E .J . 1939. E f f e c t of f i b r e and bulk i n the d i e t of ch ickens on t h e i r growth and on the prevent ion of f ea the r p i c k i n g and cann iba l i sm. Proc. , Seventh Wor ld ' s P o u l t r y Congress, 205-209. S i b b a l d , I.R. and S . J . S l i n g e r . 1960. The metabo l i zab le energy content of a ch i c k s t a r t e r d i e t d i l u t e d w i t h c e l l u l o s e and k a o l i n . P o u l t r y S c i . 39: 1294. Abs. S i b b a l d , I.R. and S . J . S l i n g e r . 1963. A b i o l o g i c a l assay f o r metabo l i zab le energy i n p ou l t r y feed i ng red i en t s together w i th f i n d i n g s which demon-s t r a t e some of the problems a s soc i a ted w i th the e va l ua t i on of f a t s . P o u l t r y S c i . 42: 313-325. S i b b a l d , I.R., J.D. Summers and S . J . S l i n g e r . 1960. Factors a f f e c t i n g the me tabo l i z ab l e energy content of p o u l t r y feeds. P o u l t r y S c i . 39: 544-556. S l i n g e r , S . J . , I.R. S ibba ld and W.F. Pepper. 1964. The r e l a t i v e a b i l i t i e s of two breeds of ch ickens and two v a r i e t i e s of turkeys to metabo l i zab le d i e t a r y energy and d i e t a r y n i t r o g e n . Pou l t r y S c i . 43: 329-333. S l i n g e r , S . J . , J.D. McConnachie and W.F. Pepper. 1955. The value of- animal f a t f o r d i f f e r e n t s t r a i n s and crosses of b r o i l e r s . P o u l t r y S c i . 34: 789-794. 142 Southgate, D.A.T. 1973. Fibre and the other unavailable carbohydrates and the i r effects on the energy value of d ie t s . Proc. Nutr. Soc. 32: 131-136. Spring, J.L. and W.G. Wilkinson. 1957. The influence of dietary protein and energy level on body composition of b ro i l e r s . Poultry Sc i . 36: 1159. Abs. Stansby, M.E. 1948. Report on fat in f i sh meal. J . Assoc. O f f i c . Agr. Chem. 31: 606-610. Sugden, L.G. 1974. Energy metabolized by bantam chickens and blue-winged t e a l . Poultry S c i . 53: 2227-2228. Summers, J.D., S.J. Sl inger and G.C. Ashton. 1965. The ef fect of dietary energy and protein on carcass composition with a note on a method for estimating carcass composition. Poultry Sc i . 44: 501-509. Summers, J.D., S.J. S l inger, J.R. Sibbald and W.F. Pepper. 1964. Influence of protein and energy on growth and protein u t i l i z a t i o n in the growing chicken. J . of Nutr i t ion 82: 463-468. Sunde, M.L., W.W. Cravens, C A . Elvehjem and J.G. Hal p in. 1950. The ef fect of d iet and caecectomy on the i n te s t i na l synthesis of b iot in in the mature fowl. Poultry Sc i . 29: 10-14. Supplee, W.C. 1960. The ef fect of an t i b i o t i c supplementation on the response of poults to d ietary corn o i l . Poultry Sc i . 39: 227-229. Swift, R.W. and A. Black. 1949. Fats in re la t ion to ca lo r i c e f f i c i ency . J . Am. Oi l Chem. Soc. 26: 171-176. Tasaki, I. and H. Sakurai. 1969. Studies on the energy metabolism in the fowl. Mem. Lab. Anim. Nutr., Nagoya Univ., 4. Cited by Fa r re l l et a l . (1973) Br. Poult. Sc i . 14: 329-340. Thomas, O.P. and P.V. Twining. 1971. Bro i le r nut r i t i on during the wi th-drawal period (7-8% weeks). Proc. Md. Nutr. Conf., 87-90. 143 Thompson, D.C. and D.A. Boag. 1975. Role of the caeca i n Japanese qua i l e n e r g e t i c s . Can. J . Zoology 53: 166-170. Thomson, W.S.T. and H.N. Munro. 1955. The r e l a t i o n s h i p of carbohydrate metabolism to p ro te i n metabol ism. IV. The e f f e c t of s u b s t i t u t i n g f a t f o r d i e t a r y carbohydrate. J . Nutr. 56: 139-150. Thornburn, C C . and J . S . W i l l c o x . 1964. The caeca of the domestic fowl and d i g e s t i o n of the crude f i b r e complex. 11. Experiments in v ivo wi th f i s t u l a t e d b i r d s , and the a r t i f i c i a l and i s o l a t e d caecum in v i t r o . B r i t . Pou l t . S c i . 5: 33-43. Thornburn, C C and J . S . Wi l cox . 1965a. The caeca of the domestic fowl and d i g e s t i o n of the crude f i b r e complex. 1. D i g e s t i b i l i t y t r i a l s w i th normal and caecectomized b i r d s . B r i t . Pou l t . S c i . 6: 23-31. Thornburn, C C . and J . S . Wi lcox . 1965b. The caeca of the domestic fowl and d i g e s t i o n of the crude f i b r e complex. I I . Experiments in v i vo w i th f i s t u l a t e d b i r d s and the a r t i f i c i a l and i s o l a t e d caecum in v i t r o . B r i t . Pou l t S c i . 6: 33-43. Touchburn, S.P. and E .C Naber. 1966. The energy va lue of f a t s f o r growing tu rkey s . Proc. 13th Wor ld ' s P o u l t r y Congress. 190-195. Vanschoubroek, F., G. Vermeersch and R. De S c h r i j v e r . 1971. A comparison of e f f e c t o f l a r d and soyabean o i l on food and water i n t a k e , body weight, food convers ion e f f i c i e n c y and m o r t a l i t y of b r o i l e r c h i c k s . P o u l t r y S c i . 50: 495-501. Ve l u , J .G . and D.H. Baker. 1974. Body composit ion and p r o t e i n u t i l i s a t i o n of ch i ck s fed graded l e v e l s o f f a t . P o u l t r y S c i . 53: 1831-1838. Vermeersch, G. and F. Vanschoubroek. 1968. The q u a n t i f i c a t i o n of the e f f e c t of i n c r ea s i n g l e v e l s of va r ious f a t s on body weight g a i n , e f f i c i e n c y of food convers ion and food i n take of growing c h i c k s . B r i t . P o u l t . S c i . 144 9: 13-30. V l cek , A. 1968. In f luence of increased amounts of crude f i b r e i n feeds on weight gains and consumption of feeds by b r o i l e r s . Sborn. ved. P rac i Vyzk. Ustavukrmivar Poho re l i ce 7: 87-96. (Nutr. Abs. & Rev. 1970: 6444). V lcek , A. and M. Pazourek. 1970. In f luence of amount and q u a l i t y of crude f i b r e i n feeds f o r cocke re l s and p u l l e t s on N balance and d i g e s t i b i l i t y of feeds . Sbornik Ved. P rac i Vyz. Ustav.u Vyz ivy Z o i r a t . P o h o r e l i c e , 8: 169-183. (Nutr. Abs. Rev. 42: 10025). Vogtmann, H., H.P. P f i r t e r and A.L. P rabuck i . 1975. A new method of determin ing m e t a b o l i s a b i l i t y of energy and d i g e s t i b i l i t y of f a t t y ac id s in b r o i l e r d i e t s . Br. P o u l t . S c i . 16: 531-534. Vohra, P. 1972. Eva luat ion of metabo l i zab le energy f o r p o u l t r y . Wor ld ' s P o u l t r y S c i . J . 29: 204-214. Waibe l , P.E. 1958. E f f e c t i v e n e s s of unknown growth f a c t o r s , a n t i b i o t i c s , and animal f a t i n turkey pou l t r a t i o n s . Pou l t r y S c i . 37: 1144-1149. We l l s , R.G. 1963. The r e l a t i o n s h i p between d i e t a r y energy l e v e l , food con-sumption and growth i n b r o i l e r c h i c k s . Br. P o u l t . S c i . 4: 161-168. Whitehead, C.C. and C. F i s h e r . 1975. The u t i l i s a t i o n of var ious f a t s by turkeys of d i f f e r e n t ages. Br. P o u l t . S c i . 16: 481-485. White, A . , P. Handler and E.L. Smith. 1973. P r i n c i p l e s of B iochemis t ry (5th e d . ) , McGraw-Hil l Book Company, New York, N.Y. Wickbom, G., J .H . L a n d o r . F . L . Bushkin and J . E . McHuiqan. 1975. Changes i n canine g a s t r i c output and serum g a s t r i n l e v e l s f o l l o w i n g massive small i n t e s t i n e r e s e c t i o n . Gast roentero logy 60: 448-452. W i l cke , H.L. and J . C . Hammond. 1940. Fea the r i ng , growth, feed consumption 145 and rachi-togenesis in chicks as influenced by kinds of grain in the d ie t . J . Agr. Research 61: 369-380. Yacowitz, H., R.D. Carter, J . Wyne and M.G. McCartney. 1956. Effects of varying protein and fat levels in a f i n i sh ing rat ion for turkey b ro i l e r s . Poultry Sc i . 35: 227-229. Yoshida, M. and H. Morimoto. 1970a. Interrelat ionship between dietary pro-tein level and carcass composition of chicks. Agr ic. B i o l . Chem. 34: 414-422. Yoshida, M. and H. Morimoto. 1970b. Periodical change in the carcass com-posit ion of chicks a f te r switching over the d iet to l ipogenic or l i p o l y t i c d ie t . Agr ic. B i o l . Chem. 34: 423-431. Yoshida, M., H. Hoshii and H. Morimoto. 1966. L i po l y t i c d iet to control ' carcass fa t deposition of growing chicks. World's Poultry Congr. Proc. 13: 200-202. Yoshida, M., H. Hoshii and H. Morimoto. 1970. Lypolyt ic d iet to control carcass f a t deposition of growing chicks. Abs. Nutr. Abs. & Revs. (1971) 41: 8622. Young, R.J. 1961. The energy value of fats and fa t ty acids for chicks. I. Metabolizable energy. Poultry Sc i . 40: 1225-1233. Young, R.J., R.L. Garrett and M. G r i f f i t h . 1963. Factors af fect ing the absorbabi l i ty of fa t ty acid mixtures high in saturated f a t t y acids. Poultry S c i . 42: 1146-1154. Zelenka, J . 1968. Influence of age of chicken on the metabolizable energy value of poultry d ie t s . B r i t . Poult. S c i . 9: 135-142. 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0094218/manifest

Comment

Related Items