Ileal endogenous response in nitrogen and lysine to dietary protein and cellulose in the chicken : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Animal Science at Massey University

(1)Copyright is owned by the Author of the thesis. Permission is given for a copy to be downloaded by an individual for the purpose of research and private study only. The thesis may not be reproduced elsewhere without the permission of the Author..

(2) ILEAL ENDOGENOUS RESPONSE IN NITROGEN AND LYSINE TO DIETARY PROTEIN AND CELLULOSE IN THE CHICKEN. A THESIS PRESENTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF AGRICULTURAL SCIENCE IN ANIMAL SCIENCE AT MASSEY UNIVERSITY. EKO WIDODO 1994.

(3) Dedi cated t o. Edina Cahyaningsih.

(4) ABS'l'RAC'l'. F o u r expe r iment s were unde rt aken . The f i r s t e x amined t he s we l l i ng prope rt i e s of f a e c e s and the s t o r ag e modulus (G' ). o r e l as t i c prope rt i e s of i l e a l dige s t a to det e rmine. whe t h e r t hey were s u i t ab l e indices f o r de s c r ib i ng feeds on t he b a s i s mai z e ,. of dige s t ive. barley ,. c on s i s t e d s o rghum. of. response .. One. set. of. feeds we re ,. meat and bone me a l and p e a s . A s e c ond set feeds. a ddit i on. of. in. 1. set. the. but. rat io. in of. e ach. case The. 1:1.. invo lve d. t h i rd. set. i nvo l v e d c e l l u l o s e and a med i c inal bu l k i ng agent , Grano c o l , int r o du c e d in increas ing proport i on . The s e c ond and fourth e xp e r iment s were undertaken to quant i fy endogeno u s n i t rogen ( N). r e sponse ( experiment 2 ) and endogenous l y s i n e re spon s e. ( expe r iment 4 ) a t the t e rmi n a l i l eum t o i n c re a s ing diet ary i nt ak e o f c e l l u l o s e ( e xp e r i me nt 2 ) and guan i dinat e d ge l a t i n ( expe r iment. 4) .. Expe r i ment. 3. exp l o re d. p r o ce du r e s. and. r e s p on s e to the feeding o f wet diet s o f the form that were emp l o y e d in e xperiment 4 . I n e xpe r i ment 1 ,. s we l l ing index var i e d ove r a narrow. range between 4 t o 8 cc e x c r e t a / g e x c r e t a. ( DM) . B a r l e y and. meat and bone meal d i f f e red s i gni f i cant l y , but t h e addi t i on o f s o rghum t o e ach caused l i t t l e change in s we l l ing index . The. a ddit i on t o c e l l u l o s e o f Grano c o l. rat i o s. to. 5:0. 3.5:1.5. a l t e red. s i gn i f i c ant l y or l inear l y .. ove r t h e. swe l l ing. index. range o f but. not. The narrow range w i t h i n whi ch. s we l l i ng index varied s ugge s t s i t s app l i c at i on i s l imited . S t o rage. modulus. between 2 . 7 and 7 6 and. mai z e. othe r. plus. d i e t a ry. add i t i on. K. e st imat i o n s. y i e l de d. a. wide. range. P a . Meat and bone me a l p l u s s o rghum. s o rghum. d i f fe red. t re atment s. except. s ign i f i c ant l y the. ma i z e. from diet .. all The. of Grano c o l t o c e l l u l o s e and o f s o rghum to the. i.

(5) cereal s ,. meat. and bone mea l and p e a s p roduced respons e s. t hat we re i n c on s i st ent i n both di rect ion a n d magn i t ut e . The l a c k o f cont r o l ove r c o l l o idal c on s i st en c y of the l iquid and s o l i d phas e s o f t he i le a l dige s t a s ugge s t s t h i s form o f mea surement i s o f l imited u s e . I n exp e r iment 2 , t he c oncent rat i o n s o f N and c hromium (Cr). in. t he. i leal. dige s t a. were. c o n s i st ent. with. the. dige s t i b i l i t y propert i e s o f the dietary c omponent s and the rat i o. of. the. c omp r i s ing. t he. c omponent s , test. diet s .. cel lulose The. and. endogenous. c o rn s t arch e x c ret i on. N. r e s p o n s e t o increas ing dietary intake o f c e l lul o s e was 1 . 1 5 mg N for e a ch g int ake o f c e l l u l o s e. (P<0 . 0 1 ) .. I n exp e r iment 3 , t he concent rat i on o f N in t he i l eal dige s t a i n c r e a s ed with i n c re a s ing c oncent rat ion o f ge l at in i n t he t e s t diet s . F o r e a ch gram int ake o f ge l at i n , of. ileal. was. N. p a s s aged. (P<0 . 0 1 ) .. The. 34 mg. apparent. N. dige st ibi l i t y o f ge l at in was e s t imat ed a s 5 4 percent . I n exp e r iment 4, guan idinat ion of ge l at in r e s u l t e d in an. 8 6%. c onve r s ion. of. lys ine. to. homo arg i n i ne .. The. c o n c ent rat i on of chromium in the i l e a l d i g e s t a was l ow and dimini shed ge l at i n .. with. The. incre a s ing. e st imate. of. c oncent r at i on. the. i leal. of. e x c ret i on. diet ary of. N. in. r e s p o n s e to increas ing int ake of guan i d i n ated ge l a t i n was e xt reme. and. unt enab l e .. con c entrat i on s. we re. e x a ggerated values fed) .. I leal. The. l ow. ileal. c on s i dered to be o f dige s t a. l y s ine. response. f l ow to. dige s t a. er. g i vi ng ext reme. and. ( g dige s t a DM/ g food inc r e a s ing. l eve l s. of. guan idinat ed g e l at in was e s t imated a s 3 4 m g l y s ine p e r g i nt ake o f guan idinat ed ge l at i n .. ii.

(6) ACKNOWLEDGEMENTS. I wou l d l i ke t o a cknowledge my c h i e f supe rvi s o r , R.D.. King. for. his. va luab l e. gu i dan c e ,. pat ience. Mr and. a s s i st ance in both t he p l anning of t he experiment and in p reparat i on o f the written t ext . advi ce ,. His expert i s e ,. c ri t i c a l. and attent i on have been inval u ab l e in making t h i s. study a wortwhi l e l e arn ing expe rienc e , grat e fu l .. and f o r that I am. I wou l d l ike t o rec o rd my thanks to P ro fe s s o r. P . J . Moughan f o r h i s advi ce o n the work . I. wou l d. l i ke. to. thank. Mi s s. R.A.. Wat s on ,. Mr. D .A.. Ham i l t on , Ms F . Jacks on , Mr S . H . Vo on and Mr . S . Rut her f o r d for the i r a s s i st an c e in l aborat ory ana l y s e s . Spe c i a l thanks a re. also. due. to. Mr. D.. Thoma s ,. Mr. G.. McCrae. and Mr. D.. Hart l e y who a s s i s t ed in the running o f the e xper iment s , and in t he c o l l e ct ion of the dat a . The c ompan i onship and advi ce o f other p o s t -graduate student s. and s t a f f. members. o f the. Department. o f An ima l. S c ience are grat e fu l l y acknowl edged . F in a l l y , I wou l d l i ke to. t hank to my f ami l y. for a l l. the i r. support b e f o re. and. du r i ng my studi e s in New Z e a l and, and thank a l l my f r i ends who supported and encouraged me to obt a i n thi s degree .. iii.

(7) TABLE OF CONTENTS. ABS TRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i ACK NOW LEGDEME NTS . . . . . . . . iii TABLE OF CO NTE NTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv LIS T OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V LIS T OF FIGURES viii .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. CHAPTER 1 INTRODUCTIO N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1. CHAPTER 2 PR OTEIN DIG ESTIO N A ND ABSORPTIO N I N THE FOWL. . . . . . . . .. 5. 2 . 1 . MOUTH, PHAR Y NX, OESOPHAGUS A ND CROP . . . . . . . . . . . . 2 . 1 . 1 . MO RPHOLOGY A ND FUNCTIO N . . . . . . . . . . . . . . . . .. 5 5. 2 . 2 . PROVENTRICULUS A ND GIZZARD . . . . . . . . . .. . . . . . . . . . 2 . 2 . 1 . MO RPHOLOGY A ND FUNCTIO N . . . . . . . . . . . . . . . . .. 7 7. .. 2 . 3 . THE SMALL I NTESTINE . . . . . . . . . . . . . . . . . . . 2 . 3 . 1 . MO RPHOLOGY A ND FUNC TIO N . . . . . . . . 2 . 3 . 1 . 1 . PA NCREATIC SEC RETIO NS . . . 2 . 3 . 1 . 2 . PROTEOLYTIC ENZYMES OF THE PA NCREAS . . . . . . . . . . . 2 . 3 . 1 . 3 . REGULATIO N OF PANCREATIC PROTEOLYTIC ENZYMES . . . . 2 . 3 . 1 . 4 . BILE . . . . . . . . . . . . . . . . . . . . 2 . 3 . 1 . 5 . INTESTINAL SEC RETIO NS . . .. . ... .. . . . . . . . . . ... . . . . .. 10 10 12. . . . . . . . .. 12. . . . . . . . . . . . . . . . . . . . . . . . .. 14 15 16. 2 . 4 . CAECA, COLO N A ND CLOACA ......... . . . . . . . . . . . . . . 2 . 4 . 1 . MORPHOLOGY A ND FUNC TIO N . . . . . . . . . . . . . . . .. 18 18. 2 . 5 . MICROBIA L E FF ECTS. 20. .. .. .. . ... . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . . . . . . . . .. 22. .. . . . . . . . .. 26. CH APTER 3 NITROGE N A ND AMINO ACID DIGESTIBILITY . . . . . . . . . . . . . .. 29. 3 . 1 . DIGESTIBILITY IN VITRO ......................... 30. 3 . 2 . DIGESTIBILITY IN VIVO ......................... 3 . 2 . 1 . TOTA L COLLECTIO N METHOD S . . . . . . . . . . . . . . . 3 . 2 . 1 . 1 . FREE-ACCESS METHOD S . . . . . . . . . . . 3 . 2 . 1 . 2 . INTUBATIO N . . . . . . . . . . . . . . . . . . . . . . 3 . 2 . 1 . 3 . RAPID ASSAYS . . . . . . . . . . . . . . . . . . . .. 32 33 34 35 36. 2 . 6 . E NDOGE NOUS PROTEI N SECRETIO N. 2 . 7 . DIGESTIO N AND ABSORPTIO N OF PROTEINS. .. 3 . 2 . 2 . ILEAL COLLECTIO N METHODS 3 . 2 . 3 . S URGICAL METHODS iv. .. .. .. .. .. .. .. .. . . . . . . . .. 37 38.

(8) 3.3.. 3 . 2 . 3 . 1 . I LEAL CANNULAT I ON . . . . . . . . . . . . . . . 3 . 2 . 3 . 2 . C OLOSTOMI SED B I RDS . . . . . . . . . . . . . . 3 . 2 . 3 . 3 . CAECEC TOMI SED B I RDS . . . . . . . . . . . . .. 39 39 40. THE CONTRI BUT I ON OF ENDOGENOUS SOURCES TO AMINO AC I D S AND N I TROGEN EXCRET I ON . . . . . . . . . . . .. 41. 3.3.1. 3 3 3 3. 42 44 45 45 45. . . . .. MEASUREMENTS OF END OGENOUS EXCRET I ON 3 . 1 . 1 . P ROTEI N-FREE MET HOD . . . . . . . . . . 3 . 1 . 2 . FAST ING B I RD METHOD . . . . . . . . . . 3 . 1 . 3 . REGRESSI ON METHOD . . . . . . . . . . . . 3 . 1 . 4 . HOMOARG I N I NE METHOD . . . . . . . . . .. . . . . .. . . . . .. . . . . .. CHAP TER 4 EXP ERI MENTAL. 47 . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. 49 49 50 53 62. . . . . . . . .. . . . .... . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. 64 64 65 67 74. EXP ERI MENT 3 . . . .. . . . . . . . . . . . . . . . . . . .. . . . . .. . . . . . . . . OBJEC T I VE . . . . . . ......................... . .. . .. . . . .. MATERI ALS AND METHOD . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . RESULTS . . . . . . . . . . . . . . . .. . . . . . . . . .. . . . . . . . .. . . . . . . . . D I SCUSSI ON . . . . . . .. . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . .. 77 77 77 80 87. EXP ERI MENT 1 . . . . . .... . ..... . . . OBJECT I VE . . . . . . . . . . . . . . . . . . . . MATERIAL S AND METHOD . . . . . . . . . RESULTS . . . . . . . . . . . . . . . . . . . . . . D I SCUSSI ON . . . . . .. . . . . . . . . . . . .. . ... . . . . . . . . ... . . . . .. EXP ERIMENT 2 . . . . . . . OBJEC T I VE . . . . . . . . . . MATERI AL S AND METHOD RESULTS . . . . . . . . . . . . DISCUSSI ON . . . . . . . . .. . . . . .. . . . . . . . . . . . . . . . . . . . . . .... . . . . .. . . . . .. EXP ERI MENT 4 . . . . . . . . . . . . . . OBJEC T I VE . . . . . . . . . . . . . . . . . MAT ERIALS AND METHOD . . . . . . RESULTS . . . . . . . . .. . . . . . . . . . D I SCUSSI ON ... . ... . . . . . . .. .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. ... . . . . .. . . . . . .. . . . . . . . . . ... . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . . . . . . . . . .... . . . ... . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . .. . . . . . . . . . . . .. . .. . . . . .. . . . . .. . . . . .. 89 89 89 91 101. CHAP TER 5. SUMMARY AND CONCLUSI ONS . . .. . . . .. . . . .. . . . . .. . .. . . . . .. 104. B I BL I OGRAP HY. . . . .. . . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 109. AP P END I X . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 125. V. . . . . . . . . . . . . ... . ... . ...... . . . . .. . . . . . . ... . . . .... . . . . .. . . . . .. . . . . ..

(9) LIST OF TABLES. TABLE. PAGE. 2.1.. M i c r o f l o r a popu l at i on i n di f f e rent s it e s o f t he 2 1 d i ge s t i ve t ract o f pou l t ry ( Adapt ed f rom Jayne­ Wi l l i am s and Coat e s , 1 9 6 9 ) .. 2.2.. D i st ribut i on o f nit rogen in the dige s t i ve t ract 2 3 o f 6 week o l d chi cken s .. 3.1.. Endogenous ex cret ion ( mg / da y ) o f amino a c i d s in 4 3 c h i ckens a s determined by d i f fe rent met h o d s .. 4 . 1 . 1 . The e f fect o f diet and pe r i od o f exc ret a c o l l e c t i on on swe l l ing i ndex ( c c / g) .. 54. 4 . 1 . 2 . The e f fect o f diet on f ae c a l s we l l ing i ndex w i t h i n pe r i od o f c o l l e c t i on , 1 2 hours ( SI . 1 ) and 9 hours ( S I . 2 ) i n c c / g .. 55. 4 . 1 . 3 . The e f fect o f di et on the s t orage modu l u s o f i l e a l dige sta ( K P a ) .. 56. (G' ). 4 . 1 . 4 . D i et a r y t re atment NDF and ADF mea surement s i n i n p e rcent ( DM) .. 57. 4.2 .1.. 68. The e f fect o f feeding l eve l and di e t a ry t yp e ( c e l lu l o se :c o rn s t a rch ) on percent age N i n t he d i ge s t a ( DM ba s i s ) .. 4 . 2 . 2 . The e f fect o f feeding l eve l and dietary t yp e on percent age Cr in t he d i ge s t a ( DM b a s i s ) .. 69. 4 . 3 . 1 . The e f fect o f feeding leve l s and the t yp e o f d i et s on t he percentage o f N i n the i l e a l d i ge s t a ( DM b as i s ) .. 80. 4. 3 . 2 .. 82. The e f fect o f feeding leve l s and the t yp e o f d i e t s on the percent age o f C r i n the i l e a l d i ge s t a ( DM b as i s ) .. 4 . 4 . 1 . Me an o f amino a c i d c ontent s ( dup l i c at e s ) o f i l e a l dige s t a ( % ) and guan i di nated ge l at i n .. 92. 4 . 4 . 2 . The e f fect o f chang ing diet ary rat i o s o f gua n i dinated ge l at i n and b a s e on i l e a l d i ge s t a C r and N concent rat i o n ( DM bas i s ) .. 93. vi.

(10) 4 . 4 . 3 . The e ffect o f i n c re a s ing diet ary c o n cent rat i on o f guan i di nat ed g e l a t i n on i l eal dige s t a l y s ine c oncentrat i o n .. 94. 4 . 4 . 4 . Mu l t i p l i e r s used t o obt ain i l e a l exc ret i on o f n i t r ogen and endogenous l y s ine for s pe c i f ied intakes of dietary c omponent s .. 96. 4 .4.5 .. T o t a l i l e a l N exc ret i on ( mg ) a s s o c i at e d w i t h di fferent guan i dinated ge l at in int ake s at c o n s t ant base int ake s .. 96. 4 . 4 .6.. T o t a l i l e a l l y s ine e x c ret i on ( mg ) a s s o c i ated with d i f f e rent guan i dinated ge l at i n i n t a k e s a t a const ant b a s e intake .. 98. vii.

(11) L I S T OF F I GURES PAGE. F I GURE 4 . 1 . 1 . C o r re l at i on between s we l l ing index o f the 1 st 1 2 hours e x c ret a c o l l e ct i o n ( S I . 1 ) and t he p e r cent age o f die t a ry NDF .. 58. 4 . 1 . 2 . C o rre l at i on between s we l l ing index o f t he 1 st 1 2 hours e x c reta c o l l ec t i on ( S I . 1 ) and t he p e rcent age o f diet ary ADF .. 59. 4 . 1 . 3 . C o r re l at i on between s we l l ing index o f the 2nd ( 9 hours ) excret a c o l l e c t i on ( S I . 2 ) and the p e rcent age o f diet ary NDF .. 59. 4 . 1 . 4 . C o r re l at i on between s we l l ing index o f t he 2nd ( 9 hours ) excret a c o l l e c t ion ( S I . 2 ) and the p e rcent age o f diet ary ADF .. 60. 4 . 1 . 5 . C o r re l at i on between s t o r age modulus t he percent age o f d i e t a r y NDF .. (G' ). and. 60. 4 . 1 . 6 . C o r r e l at i on between s t o rage modu lus the pe rcent age o f d i e t a ry ADF .. (G' ). and. 61. of. 61. 4 . 1 . 7 . C o rre l at i on between s we l l ing index ( S I . 1 ) the 1 st 1 2 hours e x c ret a c o l l e c t i on and s t o rage modulus ( G ' ) . 4 . 2 . 1 . Re l at i onship between %N i n the dige s t a and d i et t ype .. 68. 4 . 2 . 2 . Re l at i onship between %N in the dige s t a and feeding leve l .. 69. 4 . 2 . 3 . Re l at i onship between % C r in the dige s t a and d i et t ype .. 70. 4 . 2 . 4 . Re l at i onship between % C r in the dige s t a and f e e ding l eve l .. 70. 4 . 2 . 5 . Re l at i onship between endogenous N and i n c r e a s ing intake o f d i e t ary c e l lu l o s e .. 73. 4 . 2 . 6 . Regr e s s i on r e l at i on sh i p between endogenous n i t rogen and increas ing int ake o f d i et ary c e l l u l o s e b y feeding leve l .. 74. 4 . 3 . 1 . Re l at inship between % N i n the dige s t a and feeding l eve l s by d i e t a ry t ype . 4 . 3 . 2 . Re l at i onship between % N i n the dige s t a and d i et ary t ype by feeding l eve l .. 81. viii. 81.

(12) 4 . 3 . 3 . Re l at i onship between % C r i n t he dige s t a and feedi ng l e ve l s by d i e t a ry t ype .. 82. 4 . 3 . 4 . Re l at ionship between % C r i n the di ge s t a and d i et ary t ypes by feeding l eve l .. 83. 4 . 3 . 5 . Re l at i onship between N at t he t e rmina l i le um and incre a s e s i n d i e t ary ge l at in .. 85. 4 .3.6.. 86. The regre s s i on re l at i on sh ip between i l e a l N and i ncre a s ing int ake o f ge l a t i n by feeding l eve l .. 4 . 4 . 1 . Re l at ionship between l y s ine concent rat i on i n i l e a l d i ge s t a and d i e t a r y concentrat i on o f guan i dinated ge l at i n .. 95. 4 . 4 . 2 . Re l at i onship between t ot a l i l e a l N and i n c r e a s ing int ake s o f guanidinated ge l at i n at a const ant base int ake .. 97. 4 . 4 . 3 . Re l at ionship between t o t a l i l e a l lys ine and increas ing int ake s o f gu anidinated ge l at i n at a const ant base int ake .. 99. 4 . 4 . 4 . Re l at ionship between t o t a l i l e a l N and i n c r e a s ing int ake s o f guanidinated ge l a t i n a t c const ant base intake .. 100. 4 . 4 . 5 . Re l at ionship between t o t a l i l e a l lys ine and increas ing int ake s o f guanidinated ge l at in at a const ant base int ake .. 100. ix.

(13) CHAPTER 1 INTRODUCTION. The a s s e s sment o f the qua l i ty o f feedstu f f s and diet s f e d t o pou l t ry i s based on b i rd a s s ay s that e s t imate the quant i t y. of. nut r i ent. d i ge st i ve proce s s .. and. food. When the. back t o t he amount fed,. energy. amount. ext r a c t e d. ext racted i s. by. the. re l at e d. a c o e f i c i ent o f d i g e s t i b i l i t y o r. met ab o l i z ab i l it y i s obt a ined . E s t imat e s o f t h e n i t r ogen ( N ) a n d amino. acid. ( AA ). dige s t ib i l ity and the met ab o l i z ab l e. energy ( ME ) o f t he feedstu f f s a r e pub l i shed a n d u s e d b y the f o o d c ompounding indu s t r y i n t he provi s i on o f c omme rc i a l d i et s . the. The a s s a y met hods i nvo l ved t ake var i ou s f o rms ,. p r o c edure s. for. e s t imat i ng. amino. acid. and. and N. d i ge s t ib i l i t y a re revi ewed i n chapter 3 ,. but a l l att empt. d i rect l y. c on t r ibut i on. or. indi rect ly. to. m i n imi s e. the. of. endogen ous excret i on s in t h e re sponse . The app l i c at i on o f a n endo genous c o r rect ion i s a n att empt t o a c c ount for and n egat e the endogenous i n f luence . e s t ab l i s h i n g the. size. of. t he. The methods invo l ved in. co rrect ion. vary. and. the i r. magn i t ude appe a r t o b e i n f l uenced by t he methods emp l oyed . Cent r a l t o the i s sue o f endogen ous correct i on s i n N and AA d i ge st ib i l ity stud i e s i s the determinat i on o f the c omp o s it i on. and. quant i t y. of. endogenou s. e x c ret i ons .. Endogenous AA and N output i s a funct i on of t he c omponent s o f e x c re t i on , the i r proport i on s in the exc ret i o n , t he i r AA and. N. c o mp o s i t i on. excret i on . de squ amated. The. and. t he. c omponent s. cel l s ,. mucus ,. magnitute of. of. endogenous. digest i ve. t he. endogenous. e xcret i ons. e n z yme s ,. bile,. are and. m i c r o f l o r a t oget her with unab s o rbed hydr o l y s i s b y -product s o f the i r p a rt i a l o r c omp l e t e d i ge s t i on .. 1.

(14) There i s l ik e l y to be an accumu l at i on o f endogenous s e c ret i o n s Git ler. in t he lowe r i leum.. ( 1 964). and Boorman. I t h a s been s ugge sted by. ( 1 9 7 6 ) t hat endogeno u s proteins. re l e a s ed di s t a l l y t o the st omach wi l l e s c ape the denaturing and part i a l dige s t i ve pro c e s s e s o f the st oma c h and that the fu rthe r down the tract they are s e c reted the l e s s exposure they w i l l have to denaturat i on . Studi e s by Ocho a - S o l ano and 35 Git ler ( 1 9 68 ) u s ing S -Met h i onine in rat s to l ab e l endogenous prot e i n s have s hown the i r a c cumu l at i on in the i l eum and muc i n , the g l y c oprot e in of mucus h a s been shown by. H a s h imot o ,. et. al .. (1963). and. H o s k ins. ( 1 978 ). to. be. re s i s t ant t o enz ymat i c d i ge s t i on . The. medi at o r s. e xcret i o n s. are. det e rm i n ing. under norm a l. the. s i ze. c ondi t i on s. of. endogenous. diet a ry .. F at. and. c a rbohydrate dietary incre a s e s rai sed amy l a s e and l ip a s e act i v i t y o f pancre at i c j u i c e. ( Hu l an and B i r d ,. d i e t a ry. f rom. p r ote i n. was. rai s ed. chymo t ry p s i n act ivity was. 16. to. 1 9 7 2 ) . When. 28%. i n c re a s ed i n the. in. diet s ,. duodenum and. j e j unum and the feeding o f unhe ated s o ybean mea l de c re a sed a my l as e , al . ,. l ip a s e and chymot r yp s in act ivity. 1 9 68 ) . P ou l l a in ,. et. ( 1 98 9 ). al .. p r ot e in produced more rap i d muc o s a l hydr o l y s ed dietary prot e i n dietary. l e ve l s. of. f ibre. or. free. in the. ;. et. showed d i e t a ry who l e growth amino. rat. i n c r e a s e d p ancreat i c sec ret i ons. ( D a l B o rgo , in. rat s than. ac ids .. and p i g. ( Z ebrowska ,. Ra i s ing. r e s u lted et. al . ,. in. 1 98 3. Zebrows k a , 1 98 5 ) and i n c r e a s e d the act ivity o r leve l s o f. s ec r e t e d en zyme s al . ,. 1 98 7 ) .. s t i mu l at ing John s on ,. ( S chneeman ,. D i et ary f ibre has muc o s a l. 1 98 8. ;. growth. Jacob s ,. m i c r ob i a l mas s in faeces It. is. s e cret i o n s. et. c l ear. that. al . ,. 1 98 2. ;. Langl o i s ,. et. a l s o been a s s o c i at e d with ( Vahoun y ,. 1 98 3 ;. 1 98 6 ). ( La r s en ,. 1991) .. d i et ary. et. change. al . ,. and. may. 1 98 5. ;. i n c re a s i ng. i n f luence. int o the gut but the e f fect thi s may have on. 2.

(15) amino a c i d c omp o s it i on o r t o t a l amino a c i d and N e ndogenous e xcret i on i s uncertain . S n o ok and Meyer ( 1 9 6 4 b ). f ound that. approx imat e l y 9 0 % o f endogenous prot e in s o f gut s e c ret i on s a n d s l oughed c e l l s were digested a n d absorbed l e av ing 1 0 % f o r e x c ret i on with feed re s i due s . Boorman ( 1 9 7 6 ) the home o s t a s i s. o f amino. a c i d comp o s i t i on. refers t o. o f endogenous. e x c ret i on s and a number o f report s have sugge s t e d that AA c ompo s it i on may be independent o f diet ary s upp l y and. Ju ,. 1 961. p art i t ioned phys i c a l. ;. N a s s et ,. e x c reta. 1968. by. ;. 1 972 ) .. di f ferent i a l. P ar s on s. s ediment ,. (1981). cent r i fugat i on. s eparat i on techn i qu e s int o fract i o n s. m i c rob i a l. (N a s set or. c omp r i s ing. ins o lub l e mat t e r which e quated with. feed re s i dues and a s o lub l e f r a ct i on compri s ing endogenous mat e r i a l. emanat ing. from. t he. gut. and. urine ,. the. three. f ract i on s showe d remarkab l e s imi l a rity in AA c ompo s i t i on . Othe r s ,. on. the. other. hand. have. noted. an. e f fect. on. endogenous AA patt erns of di f f e rent diet ary prot e in s ource s ( Ho l me s ,. 1974) .. et a l . ,. On b a l ance it seems t hat diet ary change s may i n f luence e ndogenous s e c ret ions int o the gut , digest i on result. and ab sorpt i on m i t i gate. in. c onst ant. t e rminal. in. e x c ret i ons. c ompo s i t i on .. Unde r. but the p r o c e s s e s of against. var i at ion and. that. rem a i n. re l at ive l y. this. prem i s e. endogenous. output o f N and AAs wou l d be a funct i on of the magn itute of. e x c ret i on. c omponent s. and. of. as. diet s. such. that. may. be. i n f luence. ma j o r d i e t a ry c omponent s are prot e i n , The. primary. exper iment a l. purpo s e. s e c t i on. of. of. the. this. respon s i ve excre t a. to. the. vo l ume .. The. f ibre and st arch .. work. de s c r ibed. t he s i s. wa s. to. in. the. quant i fy. endogenous n i t r o gen and l y s ine response to changing intakes of. the. ma j or. cellulose. and. diet ary. c omponent s ,. protein. in. the. f ibre form. in of. the. form. ge l at in. of and. guan i dinated ge l at in . A s e c ondary exerc i s e w a s unde rt aken. 3.

(16) t o c h a ra c t e r i s e feedstu f f s on t he b a s i s o f t h e i r excreta and i l e a l dige s t a character i s t i c s . The e xper iment a l s e ct i on i s p r e faced b y a review o f prot e i n dige s t i o n and abs o rpt ion in the fowl and. a. st udy. of. the. methods. and. is sue s. ( chapt e r 2 ). a s s o c i at ed. with. dige s t ib i l ity a s s a y s ( chapt er 3) . The experiment a l sect i on de s c r ib e s four experiment s . The f i r s t e xp l o r e s two methods for charact e r i s ing feeds t u f f s on the bas i s of the i r e x c re t a or. i leal. i nvo l ve. dige s t a studi e s. ( expe r iment 2 ) 4). charact e r i s t i c s . to. quant i fy. Experiment s. endogenous. a n d endogenous l y s ine re spon s e. N. 2. and. 4. respon s e. ( e xper iment. at the te rmi n a l i leum to incre a s ing di e t a r y int ake o f. c e l lu l o s e. ( expe r iment. guan idinated. ge l at in. 2). and. ( trial. 4). a .. t ran s fo rmed E xperiment. 3. prot e i n , e xp l o red. p r o ce dures and response t o the feeding o f wet diets o f the f o rm t hat were emp l oyed in exper iment 4 .. 4.

(17) CHAPTER 2 P ROTE IN D I GESTION AND ABSORPTION IN THE FOWL. C omponent s o f gut s e c ret i ons , nit rogen , p r o t e in , amino a c ids and energy inf luence va l u e s obt a ined in d i ge s t ib i l it y s t udi e s o f feed nit rogen a n d amino a c ids , and met ab o l i sable ene rgy. det ermina t i ons. of. feedstu f f s .. Var i ou s. de s ign. p r o c e du r e s and c o rrect i o n s are adopted t o le s s en t he e f fect o f endogenous s ources o f b i a s and t o improve the abs o l ut e n ature. and. suc c e s s. of. addit ivity. of. feeds t u f f. the s e procedu r e s. is. coe f f i c i ent s .. d i f f i cu l t. to. gauge .. The The. purp o s e o f t h i s s e ct i on i s t o review proce s s e s o f dige s t ion and ab s o rpt ion a s s o c i ated part i cu l a r l y with d i e t ary prot e in t hat. a ffect. excret ion. of. prot e in. and. its. hydro l y s i s. p r o du c t s from the gastro i nt e st ina l t ract .. 2.1. Mouth, 2 .1.1.. Pharynx,. Morphol ogy. pharynx. are. not. i n c l uding the p a l at e. Oe s ophagus and Crop. and. In. Funct i on :. sharp l y. de l imited. fowl there. and. t he choan a l. the. in. mouth. most. and. spe c i e s. i s no s o ft p a l at e a n d t he hard. c ommun i c a t e s with the nas a l. c onne c t i on ,. b i rds. s l it. c avit i e s b y a medi an. ( Hi l l ,. 1 97 1. ;. Duke ,. 1977) .. Teeth are abs ent and the i r funct i on i s accomp l i shed by a h o rny. be ak ,. a. heav i l y. c o r n i f ied tongue. ante r i o r. t ongue f o l d and the grinding a c t i on of the g i z z ard 1 97 6. ;. S t u rk i e ,. The. 1976. c avity. of. ;. Duke ,. the. s quamous epithe l ium .. the. (Hi l l ,. 1 97 7 ) .. mouth. is. l ined w i t h. s t rat i f ied. T a s t e buds are few in number. t we l ve in t he y oung chi c k ). to. ( about. and are s ituated on t he base o f. t he t ongue and on the f l oo r o f the pharynx. ( Hi l l ,. 1 97 6 ) .. Ande r s on and N a f s t ad ( 1 9 6 8 ) c ited by Hi l l ( 1 9 7 1 ) de s c ribed other. s e n s ory. o rgans. and. free. 5. ne rve. endi ngs. ( po s s ib l y.

(18) p r e s sure s e n s i t i ve ). l o c at e d on the hard p a l a t e and b e ak .. Tubu l a r mucous s e c ret ing s a l ivary g l ands are we l l deve l oped in chi ckens ( Duke , 1 9 8 6 ) . They are w i de l y scattered through the mout h and pharynx and are s imp l e branched or c ompound in form . mouth ) ,. Hill. ( 1 97 1 ). r e f e r s to max i l l ary g l ands. p a l at ine gl ands. ( ad j a cent. s phen o -pt e rygo id gl ands. ( ro o f. posterior. g l ands ,. t ongue ,. submandibu l a r. of. ( ro o f o f. t o the c h o a n a l pharynx ) , l ingu a l. s l it ) ,. ant e r i o r. g l ands. on. and the. c r i c o - arytenoid g l ands near t o the opening of the. l arynx and sma l l gl and at t he ang l e of the mout h . Whi l st t he g l ands of the sparrow contain app r e c i ab l e amount s o f amy l a s e ,. those. of. the. c h i cken. and turkey d o n o t. ( Duke ,. 1 986) . Mast i c at i on qu i ck l y .. does. D eglut i t i on. not is. o c cur. and. food. a c c omp l i s hed by. is. the. s wa l l owed t ongue. and. hyobran c h i o - l ingual mus c l e s and l a rynx with r a i s ing of the head p l ay i ng a s e condary r o l e .. The. food i s mo i st ened by. s e c re t i o n s of the mouth and there i s ref lex c l o sure of the choan a l s l it volume. of. ( Hi l l ,. ;. Duke ,. 1 9 7 7 ) . Est imat e s of the. s a l iva produced emp l oy i ng oesophage a l. t echn iqu e s. range. L ink ,. ;. 1 940. f rom 7. Be lman ,. B e lman and Kare The. 1971. (1961). oes ophagus. to. 1 962. 30. ml / 2 4. hours. c i t e d by Hi l l ,. f i st u l a. ( Le a sure. 1 97 1 ). and. a lthough. sugge s t the vo l ume may be great e r . is. a. distens ible. tube. l ined. by. s t rat i f i e d squ amous ep ithe l ium whi ch i s divided into upper and. l owe r. e nt ry. s e ct i ons by. into. thorax .. cont ra c t i on s. a. divert i cu l um ,. Food. a s s i sted b y. is. the. conveyed. l ubri cat ing. c rop ,. by. at. its. p e r i st a l t i c. secret i on s. from. an. abundanc e of mucous gl ands p r e s ent i n t he upper and l owe r s ect i on s but not in the c rop ( Hi l l , 1 9 7 1 ) though t h i s s eems c ont ent i ou s by-pa s s e s. ( Duke , the. p rovent r i cu l u s .. 1 977 ) .. crop When. When the g i z z ard i s empty food. and t he. move s g i z z ard. 6. di rect l y cont a i n s. into food. the or. is.

(19) cont ra c t i ng the o e s ophagea l - ingluvi a l f i s su r a c ontro l l ing entry into the c rop r e l a x e s and bo l i are diver t e d i nt o the crop. ( Sturk i e , 1 9 7 6 ) . Many fact ors may cont r o l the rate o f. c rop evacuat ion inc luding wetne s s o f the food, t h e f o o d , e x c i t ement , of f a s t ing. 2.2.. ( Hi l l ,. fe a r ,. 1971. s t rugg l ing ,. Sturk i e ,. ;. finene s s o f. hunge r and l ength. 1986) .. P roventri culus and Gizzard. 2.2.1.. Morphol ogy. and Functi on:. the p rovent r i cu l u s. Acc ording t o H i l l. o r g l andu l ar s t omach i s. ( 1 97 1 ). l ined with a. g l andu l a r mucous membrane o f s impl e c o l umnar e p i t h e l ium and l ies. between. the. l ower. p rovent r i cu l ar g l ands s ubmuc o s a ,. a l ve o l i. neck on. a re. ( p ep s i n o ge n ) hours. both. of duct s the. g i z z ard .. a l ve o l i via. The. cel l s. ( oxynt i c ). The. in the. l ined w i t h muc ous. l umen. s u r f ace .. acid. s e c re t i n g. m a c r o s c op i c l ining and. the. e n z yme. s e c ret ing and di s charge z ymogen f o r up to 3 a. s ingl e. c it ed by Hi l l. on l y. into. muc o s a l. f o l l owing. ( 1 94 7 ) with. ce l l s ,. the. and the. c omp r i s ing tubu l a r. dra in by a s e r i e s. s e cret ing p ap i l l ae. o e s ophagu s. me a l .. (1971). a propo rt i on. of. The. evide n c e. of. Chodn ik. sugge s t s evacuat i o n is pha s i c ce l l s. di s charging. at. any. one. t ime . The g i z z ard,. the s e c ond s ite o f pept i c p rot e o l y s i s ,. i s a heav i l y mu s c l e d grinding chamber l ined i n t e rna l l y with a. thick. abra s ive-re s i s t ant. coat ,. koi l in ,. hardened s e c ret i ons o f the g i z z ard g l ands . g l andu l a r , s ubmu c o s a .. c rypt. forming ,. mucous. c omp o s ed. of. B e n e ath it i s. membrane. and. a. thin. S imp l e tubu l a r g l ands open into the c rypt s of. the m i c rovi l l i m i c r ovi l l i. are. s e c re t i on s. of. p o l y s ac ch a r i de. and the mai n l y the. l i ning ce l l s of. one. g l and. prot e in. of both g l ands. t ype ,. cel l s. comp l exe s. chi e f ( chi e f. and. ce l l s . cel l s ). result. in. and The a re both. h a rden e d vert i c a l ko i l in rods that form den t a t e proce s s e s. 7.

(20) on the s u r f ace and thick h o r i z ont a l b ands o f k o i l in ( Hi l l , 1971) . The main funct ions o f the provent r i cu l u s and gi z z ard are the product ion o f gast r i c j u i ce , p r opu l s i o n of (1986). prote o l y s i s and the. j u i c e and food into the duodenum .. sugge s t s. avian. cont r o l. of. gastric. Sturk i e. s e cret i on. is. s im i l a r t o that o f mammal s and o c curs i n three pha s e s . A ceph a l i c pha s e in which the b i rd ' s s ense o f the p re sence of food o r feeding act ivity i n i t i a t e s gast r i c s ec ret i on by the vagu s ne rve . A gast r i c phase i n it i ated b y the arrival of food in the st omach and act ivated by di r e c t c ontact of inge s t e d nut r i ent s with the gast r i c muc o s a and indire c t l y b y aut onomic ne rve invo lvement and through the r e l e a s e o f g a s t r i c hormone s . An int e s t i n a l pha s e s t imu l at e d by arriva l o f f o o d in t h e sma l l int e s t ine and invoked by the autonomi c ne rve supp l y and the product i on o f inte s t i n a l h o rmone s . Ce l l s produc ing the ho rmone gastrin have been found in the g l andu l a r and mu s c u l a r stomach of bi rds al . ,. 1 97 4. ; L ar s s on ,. et. al . ,. a r e r e f e rred t o a s G c e l l s. 1 9 7 4b ,. ( Butt s ,. 1986). ( P o l ack , et. and in mamm a l s. 1 9 9 3 ) . G a s t r i n probably. s t imu l at e s s e c ret i ons of HCl and pep s in by c au s ing re l e a s e o f a c et y l chol ine from r e l e a s ing c e l l s in t h e submu c o s a o f the p rovent r i culus whi c h then a c t s direct l y on t h e c h i e f cells .. Vagal. st imu l at i on o f ga s t r i c. se cret i on s. in bi rds. o c c u r s di rect l y without invo lvement of acet y l ch o l ine (Kokue and. H a y ama ,. s t ructures h o rmone ,. 1 975 ) . produc ing. The re the. ent e rogast rin ,. is. no. gast r i c. evidence. in. s ecret ing. s ynthe s i s ed. in. b i rds. of. inh i b i t o ry. mamma l s. ( Hi l l ,. 1 97 1 ) . The hormone avian panc reat i c p o l ypept i de d i s c ove red i n c h i ckens ( Kemme l , et a l . , 1 9 6 8 ; L a r s s on , et a l . , 1 9 7 4 a ) appe a r s t o b e invo lved i n the g a s t r i c pha s e o f s e c ret i on. 8.

(21) and. is. released. from. the. pancr e a s. in. response. to. the. p r e s en c e o f amino a c i ds and HCl in t he upper p o rt i on of the gut. f o l l owing a mea l. ( Duke ,. et. 1 982. al . ,. ;. John s on and. H a z e l wo o d , 1 9 8 2 ) . Acc ording to Ha z e l wo o d , et a l .. ( 1 97 3 ). it. a c t s independent l y o f the vagus ne rve to inc r e a s e s e c ret i on o f peps i nogen and HC l . Cho l ec y s t okinin and s e c ret in are hormo n e s produced in the. upp e r. sma l l. r e gu l at o rs. of. the. ( St u rk i e , 1 9 8 6 ) c h i ckens. but. int e s t ine. .. of b i rds. int e s t i n a l pha s e. and mammal s of gast r i c. and. are. s e c ret i on. Cho l e c y s t ok i nin s t imu l ates H+ s e c ret i on in. un l ike. gastrin. doe s. not. app e a r. to. a f fect. pep s in s e c ret i on ( Burho l , 1 9 7 4 ; 1 9 8 2 ) . Secret i n s t i mu l at e s b o t h H+ a n d pep s in s e c ret i on in bi rds ( Burho l , 1 9 7 4 ; 1 9 8 2 ) whi ch d i f fers from i t s funct i on in mamma l s whe re it has an i nh i b i t o ry. act i on. on. product i on .. W. S turk i e. (1986). p o st u l at e s that the di f f e rence in funct i on s may be re l ated to supp o rt i ng the import ant mechan i c a l role o f the gi z z ard in d i g e s t ion and t o the mix ing o f g a s t r i c and int e s t i n a l c o n t e n t s b y regu l a r l y recurr ing int e s t inal r e f luxes . The. vo l ume. of. gast ric. juice. produ c e d. by. the. provent r i cu l u s var i e s f rom 6 - 2 1 ml / hr during s t a rvat i on and up to 3 8 . 8 ml /hr a fter h i s t amine s t imu l at i on ( Hi l l , Ac c o rding. to. Sturkie. ( 1 9 65. ;. 1986). feeding. 1971) .. increa s e s. g a s t r i c s e c ret i on s , f a s t ing decre a s e s them a n d f o o d a f fect s t hem i n p roport ion t o i t s c ont ent o f protein . G a s t r i c j u i ce is. c ompo sed principa l l y o f wat e r with some hydro c h l o r i c. acid,. peps i n ,. muc in. and. c e rt a i n. salts .. S t u rk i e. ( 1 97 6 ). revi ewed its c omp o s i t i o n and secret i on rat e unde r var i o u s c ondit i on s .. 9.

(22) p r ovent ri c u l u s. The. pepsinogen into. its. change s. inactive. active. form ,. pepsin ,. as. the pH. o f the di ge sta. in t he provent ri cu l u s and gi z z ard . to. h ave. speci fi citi e s c ont ent s. precursor. ( z ymoge n ) whi ch i s aut o catalyti c a l l y conve rted. l e a st 5 chi cken pep s inogens app e a r. the. s e c ret s. di f f e ring ( Boorman ,. change. the. ( Sturkie ,. pH. opt ima. 1 97 6 ) .. en z yme s. 1976. As. become. and the. The re are at ;. 1986) .. in. s ome. pH. of. maxima l l y. They cases. gast r i c. active i n. s e quence a n d c reate an e n z ymati c a l l y active mi xture ove r a. w i de. pH. r ange .. Ac c o rding. to. T a y l or. (1968). the. more. sus ceptib l e pept ide bonds t o pepsin hydro l y s i s a re those invo l ving. t he. aromati c. amino. a ci ds. and. those. invo lving. l e u c i ne and val ine .. 2 .3 .. The Smal l Intestine. 2.3 .1. Morphology and Function. :. The h i s t o l ogy o f the avi an. sma l l i nt e s t ine is comp a r ab l e to that of mamma l s a l though there. are. B o o rman , ( and. s ome d i f ferences 1976) .. c r ypt s. a c c o rding. 1 9 65. ;. Hi l l ,. 197 1. ;. The muc o u s memb rane forms nume rous vi l l i. o f l i ebe rkuhn ). to. ( Tone r ,. speci e s .. In. that vary in f o rm and length c a rn i vo rous. bi rds. they. are. f i nge r l ike and we l l deve l oped but in herbivorous b i rds they are f l at t e red and l e a f l i ke ( Z i s wi l e r and F a rne r , 1 9 7 2 ) . The vi l l i. are. forme d by. pro j ect ing. cores. of. l amina propr i a. covered b y s imp l e co lumn a r muc o s a l epithe l i um c ont a i ning many. goblet. ce l l s .. B runne r s. g l ands. are. ab sent. in. the. chi cken duodenum but in s ome b i rd spe c i e s t ubu l a r gl ands that are homo l ogous with b runner gl ands o f mamma l s may be pre s ent. ( C a l houn ,. 1 954. ;. Z i swi l e r. and. F arne r ,. 1 97 2 ) .. Argent a f f i n c e l l s are in high concent rat i on and li e deep in the ep itheli a l gl ands in the upper duodenum o f bi rds ( Hi l l ,. 1 97 1 ) .. 10.

(23) 2.3.1.1.. P ancreatic Secretion. There are two c omponent s t o pan creat i c s e c ret i on , the e l ec t ro l yt i c or a qu e o u s pha s e c ont a i ning c a t i on s N a+ , K+ , and Ca 2 + at concent rat i ons in human s c l o s e t o t hat o f p l a sma. ( Wi l l s ,. 1 985). and. b i c arbo n at e. i ons ,. and. the. enz ymat i c pha se c omp r i s ing e n z yme s f o r the degradat i on o f proteins ,. carbohydr a t e s. ( Sturk i e , (H i l l ,. 1986) ,. 1971) .. and. ( amy l a s e s ). r ibonuc l e a s e. and and. fat s. ( l ip a s e s ). de oxyribonu c l e a s e. P an c r e at i c j u i c e i s p a l e ye l l ow in c o l our ,. h a s a pH o f 6 . 4 t o 6 . 8 ( chicken s ) and 7 . 4 - 7 . 8. ( turke y s ) and. c annu l at i on of the main pancreat i c duct of 1 4 - 3 0 week o l d white. l e ghorn chi c kens. m l / day. (Hu l an ,. me a s ured. the. et al . ,. re sulted i n a 1 972. Sturk i e ,. ;. di s t r ibut i on. s e c ret i on o f 1 5 -2 0. of. 1 9 7 6 ) . B i rd. tryp s in. and. ( 1 97 1 ). amy l as e. in. d i f ferent segment s of t he duodenum of 1 4 - 1 6 week o ld male chi ckens and found t ha t mo st o f the e n z yme act ivity and 7 5 % respect ive l y ) the. ent ry. gee s e. t ook p l ace in the l a s t quar t e r near. o f the pancreat i c. the. ( 55%. concent rat ion. duct in. i n t o the duodenum . pancreat i c. t i s sue. In of. c hymotryp s i n was t en t ime s that o f t r yp s i n (N i t z an , e t a l . , 1 973). and Kokue and H a y ama. ( 1 97 2 ). showe d t hat the rate o f. s e c ret i on o f panc reat i c j u i c e per unit o f body we i ght was greater for the c h i c ken than in mamm a l s. 2.3.1.2.. ( Sturkie ,. 1986) .. P roteolyt i c Enzymes of the P ancreas. Ke l l e r e n z ymat i c dige s t i on .. (1968). provide s a c l e a r a c c ount of the broad. pro ce s s e s The. i nvo lved. prot e o l yt i c. c omp r i s e endopept i da se s ,. in. intra l uminal. e n z yme s. of. t h e t ryps i n s ,. prot e i n. panc reat i c. juice. t h e chymo t r yp s i n s. a n d the e l a s t a ses , a n d t he exopept ida s e s , c a rboxypept idase A. and. c a rboxypept i d a s e. B.. They. are. s e c reted. into. the. i n t e s t ine a s z ymoge n s and are act i vated by the p rote a s e ,. 12.

(24) ent e rok i na s e ,. secret e d. by. the. int e s t in a l. c o nvert s the t ryps inogens t o t ryps ins .. wal l. whi ch. The p r oc e s s. once. s t a rt e d i s aut o c at a l yt i c and the t ryps in s fo rmed hydro l y s e bonds in other z ymoge n s t o form act i ve enz yme s whi c h are thems e l ve s aut o c at a l yt i c ( S i lk , et a l . , 1 9 8 5 ) . The t ryps in s a r e t hu s cent ral t o p r ot e o l ys i s a n d the i r i nhibit ion has c o n se quence s that exceed a. s imp l e. hydro l y s i s o f dietary prot e in As. de s c ribed. for. diminut i o n. ( Boorman ,. peps i n ,. o f t rypt i c. 197 6 ) .. each. endopept ida s e. is. probab l y a mi xture of e n z yme spe c i e s . Tryp s i n s c at a l y s e t he hydr o l y s i s l y s ine. o f bonds. or. invo l ving b a s i c amino. a rginine. ( Wi l l s ,. 1985. ;. a c i ds. such a s. B o o rman ,. 1 97 6 ) .. Chymot ryp s i n hydr o l y s i s bonds invo lving aromat i c amino a c i d r e s i du e s whe reas the e l a s t a s e s a r e re l at ive l y n o n spec i f i c . The e x opept ida s e s sp l i t o f f te rmi n a l amino a c ids po s s e s s ing free. c a rboxyl. spe c i f i c i t y a d j a c ent. group s .. s im i l a r. to. Type. A. to. peps in. aromat i c. amino. carboxypept idase sp l i tt ing a c i ds. has. pep t i de. whi l st. a. bonds. t ype. B. c a rboxypept ida s e s att a ck bonds invo lving bas i c amino a c i ds ( Wi l l s ,. 1985). inhibited. in. The. act ivit ies. sequent i a l. of. c a rboxypept ida s e s. hydro l y s i s. by. the. a re. proximity. of. p r o l ine and in the c a s e o f the t ype A , charged s ide cha ins whe r e a s the B requ i r e s c l o s e prox imit y of a c a t i o n i c s i de c h a i n for max imum act ivity. (Boorman ,. 1976) .. The pancre at ic en z yme s are c on s i dered t o be extr ins i c e n z yme s wh i ch a c t in t he l umen and a re ads o rbed ont o the epithe l i a l catalyse contrast g l ands. absorptive. sur face. fragment at i on pept ida s e s. and. cells. of. of. the. produced t he. by. whe re. c ont inue. to. po l ypept i de. cha in .. In. the. ep ithe l i a l. int e s t ine. they. surface are. i n t r i ns i c .. They. cont inue the proteo l yt i c funct i on both on the b rush bo rde r and in the l umen where they occur a s a r e s u l t o f. 13.

(25) de s quama t i on. rather. than. s ecret i on .. Rh ode s. ( 1968). has. revi ewed and c l a s s i f ie d t he s e e n z yme s .. 2.3.1.3.. Regulation of P ancreati c P roteolyti c Enzymes. The sequence of event s in mamma l s l e ading t o the f l ow o f panc reat i c j u i ce has been summa r i sed by Sturk i e ( 1 9 8 6 ) . I n mamm a l s t he eat ing o f a me al re s u l t s init i a l l y in vagal s t i mu l at i on vo l ume s. whi ch. causes. t he. pancreas. to. s ec ret e. of the e n z ym i c c omponent o f pancreat i c. l ow. juice .. If. the me a l i s prevent ed f rom re aching the duodenum a s i n the c a s e o f sham feeding the s e c re t i on s t ops , but i f the food reaches the duodenum , the food and gastric HC l st imu l at e s re l e a s e o f s ec ret in from the int e st ine . Sec ret in c au s e s an init ial. s e c ret i on. pancre a s .. D i e t a ry. reaching. the. int e st inal. of. the. amino. duodenum. c omponent. aqueous. a c ids. pept ide s. or. s t imu l at e. cho l e c y st ok i n i n .. the. from. and. the. fat. p ro duct ion. Cho l e c y s t o k i n i n. on of. produ c e s. a. p r o l onged f l ow o f both a queous and e n z ymat i c c omponent s o f panc reat i c j u i ce . Sturkie. (1986). c o l l e ct i ve l y. c it e s. a. sugge s t s. number. regu l at i on. of of. autho r s. who s e. panc reat i c. wo rk. f l ow. in. b i rds i s s imi l a r t o t hat in mamma l s . P ancreat i c s e c re t i on b e g i n s immedi a t e l y when fasted chi ckens are f e d , but i f the ch i ckens are f i r s t vagot omi s ed there is no i n i t i a l response ( K o kue and Hayama , 1 9 7 2 ) . P an c reat i c s e cret i on may i n c r e a s e from 0 . 4 - 0 . 8 ml /hr t o 3 ml / hr immed i at e l y fo l l owing feeding ( I vanov and Gotev , has. been. ( D o ck r a y ,. 1 97 2 ). increase. in. c omponent pept i de. found. 1 9 6 2 c i t ed by Sturk i e , in. and. the been. i nte st i n a l. i nt r avenous. s e c ret i on. ( He at l e y ,. has. t he. et. al . ,. i s o l at e d. of. 1 9 8 6 ) . S e c ret in. muc o s a. i n j e c t ions the. of. turkeys. produced. panc reat i c. an. aqueous. 1 9 6 5 ) . Va s o act ive inte st i n a l from. 14. t he. chi cken. int e s t ine.

(26) (N i l s s on , 1 9 7 4 ). and h a s a s im i l a r funct i on t o s e c re t i n but. i s more potent. ( Va i l l ant , et a l . , 1 9 8 0 ) . Adm i n i s t rat ion o f. cho l e cy st o k i n i n. to. p igeons. has. been. shown. pancreat i c p r ot e o l yt i c enz yme act ivity. to. increase. ( Web s t e r and T y o r ,. 1966). a n d i n c re a s e pancreat i c s e c ret i ons. ( S abha ,. 1970). a lthough in thi s work the s ynthe s i s o f prot e in s by. et. al . ,. the p ancrea s was not increased . P o r c ine cho l e c y st ok i n i n was shown b y D o ckray. ( 1 97 5 ). to. incre a s e the r a t e. of f l o w of. pancreat i c s e c re t i on s and pancreat i c prot e i n in turkey s . There i s evidence t hat dietary c ompo s i t i on a ff e c t s the c ompo s i t ion. of. pancre at i c. j u i ce .. Incre a s e d. int ake. of. d i e t a ry carbohydrat e s a n d f at increase amy l a s e a n d l ip a s e a c t i v i t y o f pancreat i c Borgo ,. et a l .. (1968). juice. ( Hu l an a n d B i r d ,. 1 972) .. Dal. report ed an increase i n chymotryp s i n. a c t i v i t y in t h e duodenum a n d j e j unum when d i et a ry prot e in i n c r e a s e from 1 6 t o 2 5 % percent .. 2.1.3.4.. Bi l e. The b i l i ary system c omp r i s e s the cyst i c duct bear ing t he ga l l bl adder and dra i n ing b i l e ma inly f rom the r i ght l obe o f the l ive r ,. and the hepat i c duct wh i c h drains the. l e ft l obe . Both duc t s ana s t omo s e on a c ommon pap i l l a with the pancreat i c duct at the c auda l end of the a s c ending l imb o f t he duodenum ( Hi l l , 1 9 7 1 ) . B i l e product ion i s st imu l ated by the pre s ence o f b i l e s a l t s i n t he b l o od , by e at ing and cho l e c y st ok i n i n s e c re t i on. is. ( Sturk i e ,. probab l y. invo lved. in. postprandi a l. 1 9 8 6 ) . F o rmat i on o f b i l e b y the l iver. i s a continuous pro ce s s and s e c retory rat e s of about 1 . 0 ml / hr have been observed in conc ious 1 4 week o l d c o ckere l s and anae sthet i sed 4 t o 6 month-o l d b i rds. 15. ( Hi l l ,. 1971) ..

(27) In. mamm al s. bi l e. p i gment s , b i l e a c i ds ,. cont a i n s. wate r ,. cho l e s t e ro l ,. prot e in ,. bile. neut ral f at s , u r e a and. ino rgan i c i on s . B a c t e r i a in the l ower intest ine decon j ug a t e b i l e a c ids and a l t e r them chemi c a l l y by t h e reduct i on o f hydroxyl group s . Decon j ugat ed a n d unal t ered b i le a c i d s are reab s o rbed in t he b l oo d. and. t aken. reconst ituted in. bile. l owe r sma l l. is. up. ( But t s , low,. by. the. l ive r. int o t he p o rt a l whe re. they. are. 1 9 9 3 ) . The c oncentrat i on o f p r o t e in. many. abundant i s a lbumin. int e st ine. are. g l y c o p r o t e ins. ( Butt s ,. and. t he. most. 1993) .. 2 . 3.1.5. Inte stinal Secretions. Evidence for the nature o f s e c re t i ons produced by t he sma l l. int e s t ine h ave been reviewed b y H i l l. ( 1 976) ,. Sturk i e. ( 1 97 6 ;. about. 5.6. to. 7.2. Duke. 1 9 8 6 ) . The sma l l int e s t ine is t he. p r imary s it e o f chem i c a l digest i on . from. (1971) ,. in. tho s e. t e s t ed ( Herp o l and Van Grembergen ,. I nt e s t i n a l pH range s. spe c ie s. that. have. been. 1 9 6 7 ) . The pH inc r e a s e s. from t he o r a l t o abo r a l end and t he p H o f e a c h p o rt i o n o f t he t ract i s regu l at e d b y s e c re t o ry a ct ivi t y within t hat port i on. ( Hurwit z. and. Bar ,. 1 968) .. Vagal. s t imu l at i on. i n c re a s e s t he inhe rent mot i l it y o f t he tract. ( Duke ,. 1 97 6. ; Hi l l , 1 9 7 1 ; S t u rk i e , 1 9 8 6 ) . I nt e s t i n a l s e c ret i on may be increased by duode n a l di st ent ion s t imu l at e s. re l e a se. of. ( Hi l l ,. 1 97 1 ). s t imu l at i on 1967) .. Vagal. st imu l at i on. ( wh i ch probab l y di r e c t l y. inte st i n a l. ho rmone s ). and by s e cret in has. more. an. by. ( Koka s ,. e f fect. vaga l et. on. al . ,. muc o u s. s e c ret i on t han on s e c ret i on o f digest ive en z yme s ( St u rk i e , 1 986). and. recent. s t imu l at e s. duodenal. p re s ent. muc o s a l. in. ( Sturk i e ,. work. sugge s t s. s e c ret i on s cell. there. extract. 1986) .. 16. t hat that. whi l st. are are. s e c re t in. other h o rmone s also. invo l ved.

(28) Intestinal. e n z yme. s e c ret i o n s. inc lude. amy l a s e ,. s accharida se s , p ept idases and l ip a s e . Lactase and t reha l as e whi ch act s o n t he common p l ant c a rb ohydrate t reha l o se a re not. s e c reted. present. but. ( Sturk i e ,. maltase ,. i s oma l t a s e. and. sucrase. are. 1 9 8 6 ) . Gre atest d i s a c char i d a s e a c t i v i t y. i s found in t h e upp e r i leum , w i t h t he duodenum having l e s s and t he l ower i l eum a lmo st none known. to. be. produced. by. ent e rokina se ,. s e c ret in,. ( St u rk i e , 1 9 8 6 ) . Ho rmon e s. the. c h i c ken. cho le c y s t o k i n i n. int e s t ine and. are. va s o ac t ive. int e s t i n a l pept i de . S i l k , et a l . t he presence. of. ( 1 9 8 5 ) c i t e recent s tudies wh i ch indi c at e s o lubi l i sed. int e s t i n a l. cytop l a smi c. int e s t in a l. muc o s a l. i nt e s t i n a l. c ontent s. of. amin o. humans .. bru sh-bo rde r. o l igopept ida s e s They. func t ion. and in as. e xopept idases a n d remove amino a c i d re s i dues from the amino end. of. pept i de. chains .. Duke. ( 197 7 ). pept i da s e s and c a rboxypept ida s e s. report s. inc lude di ,. formed. the. in. sma l l. amino. have been found in t he. duode n a l muc o s a o f chi ckens c it ing DeRycke pept i d a s e s. both. ( 1 9 6 2 ) . Amino. tri and t e t r a pept id a s e s inte s t in a l. muc o s a .. They. and a re. hydr o l y s e. pept i de s t o ami n o a c i ds both a t t he surface o f t he muc o s a before ab sorpt i o n and within t he epithe l i a l c e l l s b e f o re amino The s e. a c ids. ent e r t he blood c i rcu l at i on. enzyme s. ent e r. the. int e s t i n a l. ( La r sen ,. l umen. 1991) .. through. t he. desqu amat i on o f t he muc o s a l ce l l s and a s sume a funct i on a l l y s i gn i f i c ant. role. in. t he. t e rmin a l. dige s t i on i n t h e i l eum ( S i l k ,. et al . ,. s t age s 1 9 85) .. of. prot e i n. I n the i l eum. t he act ivity of l uminal pept ida s e s i s great er t han in the j e j unum. and. t he i r. import ance. r e l at ive. to. proteo l yt i c. a ct ivit i e s on t he sur face o f muc o s a l c e l l s i n the i l eum may be increased . The product s of l umina l proteo l y s i s are free amino a c i ds and sma l l pept ide s having a chain l ength of t wo t o s i x amino a c i d re s idues. ( S i lk ,. 17. et. al . ,. 1 985) ..

(29) 2.4.. Caeca ,. 2.4.1.. Colon and C loaca. Morphology. and. The c ae c a a re a p a i r o f. function:. b l ind ended tube s that a r i s e a t the j un ct i on o f the sma l l and l a rge inte stine ,. e xt end forward f o r about ha l f the i r. l ength and then doub l e b a c k o n them s e l ve s . They are l ined w i t h c o l umna r epithe l ium whi ch in the b a s e region end) is. ( b l ind­. i s re l at ive l y smooth but in the body and neck region s. f o rmed int o vi l lu s - l ike pro j ect i on s whi c h sugge s t s a n. ab s o rpt ive. funct i on .. Lymph o i d. t i s sue. is. s c at t e red. throughout the submu c o s a and o c c a s i on a l gobl et ce l l s are p r e s ent in the l ining epithel ium The c o l on i s i l e o - c ae c o -c o l i c ep ithe l ium. is. short. 1971) .. and narrow and extends. j un c t i on formed. (Hil l ,. to. into. the. c loaca .. short. b road ,. from the. The. muc o s a l. vi l lu s - l ike. p r o j e c t i on s that are l ined with co lumn a r c e l l s and nume rous gob l et ce l l s The. (Hill ,. c loaca. is. 1 97 1 ) . a. spheroida l. chamber. int o. whi ch. the. d i g e s t ive and uro-gen i t a l tracts c onve rge . It is s ep arated from t he c o l on by a mus c u l a r c on s t r i ct i on and opens to the e xt e r i o r at the vent . whi ch. forms. short. It is l i ned with c o l umn a r epithe l ium. v i l l u s - l ike. s t ructure s. ant e r i o r l y. and. wh i ch are mo re f l at t ered and l e a f l i ke t owards the vent whe re it me rge s on the inner a spect of the upper and l owe r l ip s into st rat i f i e d s qu amou s epithel ium. ( Hi l l ,. 1971) .. The digest ive funct i ons o f the avi an c a e c a and c o l on h ave been revi ewed b y H i l l 1986). and. Duke. ( 1 97 6 ) .. ( 1 97 1 ) , There. Sturkie. is. l it t l e. ( 1 9 65 ;. 1 97 6 ;. evidence. of. dige s t i on i n the l arge intest ine o f bi rds other t han i n the c a e c a although there i s evidence of wate r re s o rpt i on in the c o l on and urine and f l u i d re fluxing int o the c a e c a 1971. ;. Sturkie ,. ( C l ement s ,. et. (Hi l l ,. 1 9 7 6 ) . On l y f l u i d port i on s ent e r the c a e c a al . ,. 1 97 5 ). and t h e dige s t a that ent e r s. 18. is.

(30) ret a ined t here up t o four t ime s l onge r than mat e r i a l t hat by-pa s s e s it. ( Sturk i e ,. 1986). with the rat i o of c a e c a l t o. no rma l droppings varying depending o n diet a r y c ompo s it i on from 1 t o 7 for barley diet s t o 1 t o 1 1 f o r whe at di e t s ( Hi l l ,. 1 971) .. The c a e c a appears t o be impo rt ant i n wat e r abs o rpt i on ( Thronburn and Wi l l cox , prot e in. met ab o l i sm. 1 9 65 ). and. and may p l ay a ro l e in non. protein. ut i l i s at i on .. In. Wil l o w. p t a rmiga n s urine refluxing i n t o the c a e c a w a s degraded i n t o. ammon i a. and. incorporat ed. into. amino. a c ids. by. bact e r i a l. act i o n , but o n l y bact e r i a ut i l i sed t h e amino a c ids and none was. ab s o rbed by the host. Howeve r ,. ( Mo rtensen and T inda l l ,. 1981) .. whe r e a s in gee s e urea exc ret i on wa s 5 . 7 % gre a t e r. fo l l owing caecectomy s im i l ar procedu r e s in chi ckens fai l e d t o demon s t rate a n incre a s e i n u r i c a c i d secret i on ( K e s e and Ma rch ,. 1 9 7 5 ) . The feeding of prot e i n s ource s t hat are l e s s. dige s t ib l e. such. as. unhe ated. s oybe ans. may. re s u l t. in. s i gn i f i c ant port i ons o f d i e t a ry prot e i n e s caping i nt e s t i n a l prot e o l y s i s and becoming ava i l ab l e t o degradat i o n b y c a e c a l flora .. Degradat i on. sub s t ant i a l . c h i c kens. by. Ke s s l e r ,. exc reted. caecal. et. 15-3 0. bact e r i a. (1981). al .. percent. to. be. s howed c ae cect omi sed. more. int act bi rds and the s tudi e s of Low. app e a r s. ami n o. ( 1 985). a c ids. t han. s uppo rt the s e. findings . The. cae c a. appear. to. have. an. impo rt ant. role. in. bact e r i a l fe rment at i on of dietary f ibre and t he i r e f fect re s p onds t o diet ary prec ondi t i oning . Sturkie ( 1 9 7 6 ) revi ews e a r l y studies that indi c at e d that the c rude f ibre o f c o rn , oat s and whe at were dige s t e d more p o o r l y by c ae c e ct om i s e d than. by. int a ct. b i rds .. The. c oe f f i c i ent. of. d i ge s t ibi l it y. change f o r c o rn f ibre f rom 1 7 . 1 a n d 1 9 . 7 be f o re c ae c e c t omy to. 0.0. f o l l owing. studi e s which. it .. Sturkie. ( 1 98 6 ). c it e s. a. number. of. show that the c a e c a l bact e r i a o f dome s t i c. 19.

(31) f o w l s digest Duke ,. et. l itt l e o r n o c e l l u l o s e . al. ( 1 9 8 4 ). On the other hand,. demonst rated. in. turk e y s. that. p r e condit i o n ing with h i gh f ibre or h i gh c e l lu l o s e diet s impr oved c e l lu l o s e degradat i on from 2 . 8 per cent i n b i rds not precondit i oned to 1 0 . 4 percent in b i rds p re condit i oned . The gluco s e freed b y c e l l u l o s e breakdown w a s abs o rbed by the. c ae c a. (1983). and used by t he host b i rds .. c o n c l ude. that. precondi t i on ing. Bedbury produce s. and Duke a. caecal. f l o r a more c ap ab l e o f f ibre dige st i on a n d c e l l u l o l y s i s . Sturk i e ( 1 9 8 6 ) c it e s a number o f s t udi e s that indicate wild. gal l i forms. may. ext ract. cons ide r ab l e. energy. from. f e rment at i on by c ae c a l b a cte r i a and there i s evidence that indicates c a e c a l s i z e responds to increas ing c oncent rat i ons of. diet a ry. f ibre. ( Gas away ,. 1 9 7 6). a l though. dietary. rather t han qua l i t y may be caus ing the e f fect. bulk. ( Sturk i e ,. 1 98 6 ) .. 2 .5 .. �crobial Effe cts. The. nut rit i on a l. s i gn i f i c ance. of. popu l at i on s. of. m i c r oorgan i sms i n the digest ive t ract h ave been revi ewed by S a l t e r ( 1 9 7 3 ) for pou l t ry and S avage ( 1 9 8 6 ) f o r mamma l s . In. the. fowl. bact e r i a l. g a s t ro int e s t i n a l t ract. act ivity and. is. occurs. throughout. i l lust r ated. in. T ab l e. the 2.1.. a dapt ed f rom Jayne-Wi l l i ams and Coates ( 1 9 6 9 ) . The dominant b a c t e r i a in t he c rop appears to be l ac t obac i l l i and we ak l y acid. or. we ak l y. i n c r e a s ingly. a lk a l ine. ana e r ob i c. envi ronment s condit ions ,. (pH. t he. 6.5. to. 7 . 5) ,. c ompo s i t i on. of. d i ge s t a , t h e nut r it i on a l status o f the h o st a n d t h e qua l it y o f t he prot e in f e d a l l appe a r t o nature Ful ler, the. o f the bact e r i a l. i n f l uence t h e s i z e and. popu l a t i ons. ( Jayne -Wi l l i ams. and. 1 9 7 1 ) . Although bact e r i a a re more c oncentrated in. c a e c a there may be. a. greater turnove r. 20. of b a c t e r i a l.

(32) cells. and. a. great e r. e ffect. of. bacterial. act i v i t y. on. dige st i on in other part s of the t ra c t a s a re s u l t of the d i f f e rent eva c u at i on rate s of t he c a e c a , and c o l on. ( Ma cN ab ,. sma l l i n t e s t ine. 1 97 3 ) .. T ab l e 2 . 1 . M i c r o f l ora popu l at i on in d i f f e rent s i t e s o f the dige s t ive tract o f pou l t r y ( Adapt ed from Jayne­ Wi l l i ams and Coat e s , 1 9 6 9 ) . Organ i sms. Organi sms / g in c ontent s o f Duodenum I l eum Crop. St reptococci. 0 - 1 09. St rep . St rep . St rep . St rep .. fa e c a l is l iqu e fa e c a l is zym o gen e s fa e cium. C a e cum. Lactobaci l l i L. L. L.. l a ctis a cidoph il u s s a l ivarius. Coli forms. E. A.. coli a e rogen es. 0 - 1 05 not det ermined. C l o stridi a. Cl .. we l chii. 0. Bacteroide s. 0. 0. Other organisms Cl. sporogenes, Cl. Eubacterium sp., aerobic sporeformers, micrococci, moulds and yeasts.. paraputrificum, Cl. tertium, coryneforms, anaerobic cocci,. Mason ( 1 9 8 4 ) , D r a s e r and H i l l ( 1 9 7 4 ) and Wrong , e t a l . (1981). provide. mamma l i an. gut. met ab o l i s e d. are. evidence flora . amino. of. Among. the. digest ive. the. a c ids ,. act i v i t y. nit rogenous. ma i l l ard. of. c ompounds. c ompounds. ( amino. a c i d- sugar comp lexes ) , muc o s a l res i due s , muc ogl y c oprote i n s , uric. acid. and. amine s .. The. most. s i gni f i c ant. react i ons. invo lve the f o rmat i on of short chain fatty a c i ds through the. reduc t i on. of. amino. acids. 21. with. the. l iberat i on. of.

(33) ammon i a . Othe r react i on s invo l ve the o x i dat i ve deaminat i on of. amino. acids. with. t he. produc t i o n. of. a l dehyde s. and. f o rmat ion of succinat e , fumarat e , indo l e prop i onat e , indo le p yruvat e a s we l l a s othe r pheno l i c a c ids . The a c ids l owe r t he pH o f the cont ent s o f the l arge i nt e st ine and l ower s t h e a c t i vi t y o f the deami nase-produ c i n g bact e r i a whi ch are f avoured by a l k a l ine pH c ondit i ons . Gut. bact e r i a. may. also. met abo l i z e. de c a rb o x y l at i on and f i s s i on react i on s .. amino. a c i ds. by. F i s s ion react i on s. r e s u l t in t he format i on o f other amino a c ids , a-keto a c i ds , c yc l i c c ompounds and amine s and dec a rb o xy l as e s are known t o be produced by s ome bacteri a . The p roduct s. int e s t i n a l of. the i r. m i c r o f l ora act i vi t i e s. may to. use. t he. s ynthe s i s e. breakdown the i r. own. p r o t e ins . Thi s ma i n l y involve s the a s s im i l at i on o f ammon i a b u t t he ut i l i s at i on o f amino a c ids h a s a l s o been repo rted by P ayne. ( 1 975). as c it e d by Lar sen. ( 1 9 9 1 ) . B o o rman. (1976). doe s not d i s c ount t he p o s s ib i l ity that ami n o a c ids f reed by b a ct e r i a l a c t i v i t y may a l s o be abs o rbe d . The c on s i stency of. f ae c a l. amino a c i d c ompo s it i on ove r a variety of diet. t yp e s noted by P a r s ons. ( 1981). ;. Boorman. ( 1 976). and Larsen. ( 1 9 9 1 ) may re f l ect the m i c rob i a l comp o s i t ion ( Ma s on , 1 9 8 0 ) and c ons i stency o f t e rminal endogenous s e c ret i on s o f the gut. ( B oorman ,. 2 . 6.. 1976) .. Endogenous prote in s ecretions. P rote inaceou s. gast roint e st in a l. s e c ret i on s have. f our. p r imary s ources: t he enz yme s secreted a l ong the t r a ct and those. a r i s ing. from. ep i t he l i a l. c e ll s ,. s e c re t i on s .. The. t he. panc reas. p l a sma prot e in n ature. and. 22. and. bile,. s e c ret ions ,. funct i on. of. de s quamated and mucous the. e n z yme s.

(34) s e c re t i on s have been covered in e a r l i e r sect i on s . T ab l e 2 . 2 .. drawn from Hi l l. (1971). demo n s t r at e s t hat. as dige s t a p a s s e s from the gi z z ard into the duodenum t he re i s an approximate 3 f o l d di lut i o n o f e xogenous n i t r o gen by endogenous fold). s ou r c e s .. S omewhat. s im i l a r re l at i onships. have been report ed by B o o rman. ( 1 976). ( four. of studi e s o f. the dog and t he rat and sugge st t hat c o n s i derab l e dige s t i on and abs o rpt i o n. o f endogenous prot e in mu st. t ake p l ac e. in. more dist a l s e gment s of the gut . Tab l e 2 . 2 . D i st r ibut i on o f nit r o gen in the dige s t i ve t ract of 6 week old chicken s . Food o r int e s t in a l segment. % N. %Cr 2 03. N / C r 2 03. Food Crop P rovent r i c u l u s Gi z z ard Upper duodenum Lower duodenum Upper j e j unum Lower j e j unum Uppe r i l eum Lower i l eum. 3 . 55 3 . 55 3 . 13 2 . 74 8 . 33 8 . 55 6 . 00 5 . 23 4 . 54 4 . 30. 0 . 458 0 . 352 0 . 1 92 0 . 189 0 . 230 0 . 2 82 0. 700 1 . 437 1 . 274 0. 811. 7 . 75 10 . 03 1 6 . 30 14 . 50 3 6 . 25 30 . 37 8 . 58 3 . 64 3 . 65 5 . 30. The. s e c re t i on. of. p l a sma. p r ot e i n. int o. the. int e s t inal t ract has been reviewed b y Freeman Rot h s ch i l d ,. et. al .. (1970). and. t he i r. role. in. g a s t ro­. (1964). and. mamma l i an. digest ive s e c re t i ons summari sed by But t s ( 1 9 9 3 ) . E s t ima t e s o f t he amount o f p l a sma prot e i n. l o s s into t h e d i g e s t ive. t ract range between 1 0 percent f o r p l a sma albumin ( F re eman , 1964. ;. Je f f r i e s. and. S l e i senge r ,. 1968). and. up. to. 20%. ( Cuthbe rt s on and T i l st one , 1 9 7 2 ) a l though ear l ie r e s t imat e s imp l ied c at ab o l i s m by way o f the gut might be even greater ( B o o rman ,. 1976) .. With the exc ept i on. 23. of. immunoglobu l in A.

(35) whi c h i s secreted b y the muc o s a and a dh e r e s t o and prot e ct s the. muc o s a l. prot e i n s. s u r f a ce ,. are. there. is. no. a c t i ve l y t ransported. evidence. that. a c r o s s the. p l a sma. epithe l i a l. s u r f a c e . A carr i e r me chan i sm prop o s e d i s t hat l ymph a r i s ing from c ap i l l a r i e s i n t he l amina prop r i a is carried into the l umen. a l ong. with. de squamat ing. ep i t he l i a l. ce l l s. ( But t s ,. 1 993) . Ce l l u l a r e x fo l i at i on from the muc o s a l s u r f a c e o f the g a s t r o - intest i n a l t r act invo lve s c e l l s originat ing i n t he c rypt s migrat ing up the epithe l i a l. s u r f ace. o f t he vi l l i. whe re t hey are shed a t the ap i c a l s u r f a c e ( B o o rman , 1 9 7 6 ) . T he s i z e and s hape o f the vi l lu s i s governed by the rate of c e l l loss and rep l acement and to ret a in s i z e and shape a. cont r o l mus t. e x i s t that. c oo rdinate s. rat e s. of shedding. with rates o f s ynthe s i s in the crypt s ( Creame r , 1 9 7 4 ) . E ach cell. is. repl aced. in. ( Imondi a n d B i rd ,. approx imat e l y. 1 966). and is. 48. hou rs. i n t he. fowl. s im i l a r to e s t ima t e s. for. rep l a c ement t ime o f the t ot a l gut ce l l p opu l at ion in dogs and humans. of. 4-6. days. and in. rat s. of. 3-7. days. ( Butt s ,. 1 993) . But t s t he. ( 1 9 9 3 ) notes a number o f fact ors that in fluence. growt h. st imu l at e s. of. t he. muc o s a l. muc o s a growth. and. ( Jacobs. and. supp l y ,. whether who l e prot e i n ,. amin o. a c i ds. ( P ou l l ai n ,. Lupt on ,. in. have et. al .. 1984) .. mamma l s . int e s t inal. Forms. i n fluenced 1989) .. of. D i e t a ry ce l l. diet ary. f ibre. turn ove r. amino. acid. hydr o l y sed prot e i n o r free muc o s a l. The. growth. c omp o s i t ion. in of. the. rat. t he. gut. m i c r o f l o ra and phy s i c al and chemi c a l t rauma may incre a s e c e l l l o s s ( Badawy , e t a l . , 1 9 5 7 ) a n d t h e presence o f no rma l bact e r i a l f l o r a s horters t he ave rage l i fe of a c e l l t o h a l f that. unde r. Gu i l f o r d ,. b a ct e r i al. free. 1990) .. 24. condit i on s. ( St rornbeck. and.

(36) The c ompo s it i on and func t i o n o f muc u s s e creted in the g a s t o - int e s t inal t ra c t has been revi ewed b y. ( Al l en ,. ;. its. 1984). and. Mant l e. and. Al l en. ( 1 989). and. 1981. role. in. mamma l i an digest ive phy s i o l ogy summar i s ed by But t s ( 1 9 9 3 ) . Muc u s. is. a wat er and mucus. glycoprot e in. ( mu c i n ). mixture. that occurs in two f o rms , a s a wat er ins o l ub l e ge l adhe r ing t o the muc o s a l sur f a c e of the ent i re gut and as a s o l ub l e f r a c t i on that mixe s with �uminal ge l .. Mucus. is. condi t i on s c o l umnar. by. c ont i nuous l y simp l e. epithe l i a l and. released. exocyt o s i s. ce l l s. t hrough c e l l exfo l i at i on . e n z yme s. j u i c e s a n d ove r l i e s the. de squ amated. found It ,. unde r. from. mucus. throughout. rest ing s e c ret ing. the. gut. and. t ogethe r with the digest ive. epithe l i a l. cells. represent. the. ma j o r source of endogenous prot e in in the s e c r e t i ons of the gut .. Spec i a l i s ed st ructures. i n c l u de the cells. of. invo lved. in mucus. s a l ivary and oesophage a l. the. provent r i culus ,. g l ands ,. brunn e r ' s. s e c ret ion mucus neck. g l ands. of. the. du odenum , gob l et c e l l s and the c rypt s o f l i eberkuhn of the int e s t ine . epithel ium. I t funct i on s to protect the unde r l y ing muc o s a l from. t rauma. of. a. mechan i c a l ,. chem i c a l. or. path o l og i c a l nature and a ct s a s a b a r r i e r sepa rat ing gut f lora. and. pathogen s. from. cont act. with. the. l ini ng. e p i t h e l ium . It i s permeable to l ow mo l e c u l a r we ight s o l ut e s ( < 1 0 0 0 DA) but not t o l a rge mo l e cu l e s s u c h a s prot e in s and w i t h i n i t s l ayers it may c ont a i n dietary prot e ins , pept ide s and. amino. acids ,. m i c ro o rgan i sms ,. e n z yme s ,. s l oughed. p l a sma. ce l l s ,. prot e ins ,. immunoglobu l in. bile , A. and. dige s t a f ragment s and s o lut e s and ions . In. vitro. mamma l i an. studi e s have shown that puri f i ed muc i n s o f. origin. are. suscept ible. to. prot e o l y s i s. by. d i g e s t ive enzyme s with t he re l e a s e of degraded g l y c oprotein s ubun i t s muc u s. ( Mant l e and Al l e n ,. may. also. arise. from. 1 9 8 9 ) . Lo s s o r degradat i on of the. abra s ive. act i on. of. the. p a s s age o f dige sta and f rom the mot i l e f o r c e s o f digest i on .. 25.

(37) C a s sidy , bran. ( 1 981). et a l .. s upp l emente d. c on c luded that c e l lu l o s e and wheat. diets. increased. s e cret i o n. w ithin. the. l arge int est ine . I t i s appa rent that a dynam i c e qu i librium mu s t. exist. that. maint a i n s. the. integrity. of. the. mucus. b a r r i e r against cont inuous e ro s i on of the muc u s l ay e r s .. 2.7.. D igestion and Absorption of P roteins. Reviews on the phys i o l ogy of dige st i on in p o u l t ry have been pub l i shed by Sturk i e ( 1 9 6 5 , B o o rman. and. F reeman. ( 1 97 6 ) ,. extens ive coverage by Snook D avenpo rt (1990) , (1 993) a. (1982) ,. Larsen. Wi l l s. (1991) ,. 1 9 7 6 , 1 9 8 6 ) , Hi l l. Duke. ( 1 97 7 ). (1973) ,. ( 1 985) , Re rat. and. i n mamma l s. Re rat ,. et a l .. S t r ombeck. and. and Corring. (1971) , (1976) , Gu i l ford. (1991) ,. But t s. and f o r p i gs L o w and Z ebrows k a ( 1 9 8 9 ) . D ige st i on i s. l um i n a l proce s s i n i t s e a r l y st age s that. i nvo lve s the. hydro l y s i s of macromo l e c u l e s into shorter s ub-un it s . T h i s i s f o l l owed b y a rap i d degradat ion into l e s s e r un i t s. (by. a proce s s. the. int e st ine ). ope rat ing o n t he brush bo rde r sma l l. enough to. surface. ent er the m i c r o s c op i c. of. spa c e s. between the vi l li and be ab s orbed i n t o epi t he li a l ce l l s . Thi s f in a l st age o r membrane dige s t i on i s brought about by e n z yme s nat ive t o ( in t r i n s i c ) or ads o rbed ont o ( ext rins i c ) the muc o s a l surface . The pancre at i c e n z yme s are ext r ins i c f a c t o r s that a c t both in t he lumen and a t ads o rpt ion s it e s on the digest ive-abs o rpt ive surface . The int r i n s i c. e n z ymes. are t he pept i d a s e s of the sma l l int e s t ine wh i ch act on the bru s h bo rde r o f the ce l l and in the lumen when they arrive through. the. pro c e s s. of. di ge s t i on and absorpti on. c e l lu l a r. e x fo l i at i on .. of res idu a l. Further. dige s t a may r e s u l t. from bacte r i a l proteo l y s i s whi ch in the f o w l i s m o s t act ive in. the. caeca. ( Boorman ,. 197 6) .. P rot ein. dige s t i on. occurs. predominant l y in the st omach and prox ima l sma l l int e s tine and the ma in s ite of ab s o rpti on is the sma l l intestine .. 26.

(38) P rot e i n mo l e c u l e s are denatured i n it i a l l y b y a c i di c e n z ymat i c hydr o ly s i s in the provent r i cu l u s and gi z z ard . I n mamma l s amino. absence o f t h i s st age re s u l t s i n a reduct i on o f acid. abs o rpt ion. dige s t i b i l ity duodenum. ( Butt s ,. whe re. it. and. a. reduct i on. in. prot ein. 1 9 9 3 ) . Ac i d i c c hyme pa s s e s into the is. sub j ect. to. a lkal ine. pancreat i c. s e c ret i on s that r a i s e lumi n a l cont ent s t o near a lk a l ine pH t o provide opt ima l c ondit i on s for degradat ive act ivit i e s o f panc reat ic. and brush borde r prot e o l yt i c en z yme s .. The. brush b o rder cont a in s pept i da s e act i v i t y against pept i de s 3 - 6 r e s idues i n the length whi l e the dipept i da s e s app e a r to. be. pre sent. predominant l y. in. the. cyt o s o l. of. the. epithe l i a l cel l s but with s ome pre s ent in the brush borde r . Some o f the pept i da s e s from the bru s h b o rder and cyt op l a sm o f t he ce l l s are s o lubi l i s ed in the lume n , in part from t he breakdown. of. e x fo l i ated. epithe l i a l. l uminal hydro l yt i c activity Ab s o rpt ion throughout. the. of. amino. sma l l. ( Butt s ,. a c i ds. cells,. and. a. 1993) .. and pept ide s. int e s t ine. a s s ume. but. t akes p l a c e. with. p redominant. a c t i v i t y o ccur ing in the j e j unum . T ran sport of amino a c i ds by intest inal ent e rocyt e s o c curs by s i mp l e and f ac i l it ated di f fu s i on s y st ems. and a re. pre f e rence .. a c t i ve. t ransport .. c l a s s i f ied Sturk i e. on. (1986). ab so rpt ive proces s .. the. reviews. Amino. acid. basis in. some. t ransport. of. subst rate. det a i l. avi an. Abs o rpt ion occurs b y a t t a c hment to a. spe c i f i c s i te on the muc o s a l epithe l i a l membr ane . Learner ( 1 97 1 ). c i ted by H i l l. ( 1 971 ). c onc luded t hat in t he c h i cken. there we re at l e a s t t hree separate abs o rpt ive p athways for neut r a l amino a c i ds :. a s y st em for met h i onine and r e l a t e d. a l iphat i c compounds ,. one for glyc ine a n d o n e f o r p r o l i ne. and. re l ated. amino. a c ids .. He. also. reco gni s e d. pathway f o r b a s i c amino a c i ds . Among members. a. d i s t inct. o f a group. there i s c ompet i t i on in the ab s orpt i ve proce s s a l t hough t he abs o rpt i on. s it e s. exhibit. 27. p r e f e rence. rather. t han.

(39) e x c lus i vene s s . arginine ,. L - l y s ine. absorpt ion. L -phenyl a l an ine. or. with. g l y c ine s it e. l it t l e. ( Gou s ,. Endogenous. et al. ,. prot e i n. e x o genous. prote in .. intest inal. t ract. or. no. not. more. may p l ay. and. by. L-leucine. L - i s o l euc ine ,. compet it ion. L­. or L­. ob s e rved. for. 1 977 ) .. is. The. inhib i t e d. L -h i s t i dine. ab s o rpt i on i s inhib i t e d by L-va l ine , methion ine ,. is. dige s t ed di s t a l. a more. as. rap i dl y. segment s. imp o rt ant. of. ro l e. abs orpt i on o f amino a c i ds o f endogenous prot e i n. as t he. in. t he. ( Crampt on. and Ne sheim, 1 9 6 9 ) . B o o rman ( 1 9 7 6 ) sugge s t s in expl anat i on t hat. endogenou s. prote ins. are. not. sub j ected. to. the. denat u r ing and p a rt i a l digest ive proce s se s o f t he s t omach . Howeve r ,. Nas set. ( 1 972 ). has po inted out that t he rat i o o f. endogenous t o exogenous prot e i n dec r e a s e s a l ong t he sma l l i nt e st ine ,. a. phenomenon. endogenous. prot e i n. be ing. t hat. is. re s i s t ant. incon s i stent to. dige s t ion. with and. abs o rpt ion . I nt e s t inal muc o s a l upt ake o f pept ides i s mediated b y a spe c i f i c carr i e r s y s t em and i s re s t r i ct e d t o t h e upt ake of dipept ides and t r ipept ide s . The upt ake of pept ides i s genera l l y faster than the ab s orpt i on o f free amino ac ids and. such. upt ake. c onfers. enhanced. e f f i c iency. to. the. digest ive proce s s by enab l ing intra c e l l u l a r hydro l y s i s o f dipept i de s and t r ipept ide s ( But t s , 1 9 9 3 ) . Some pept ides and p r o t e i n s are abs o rbed int act int o the b l ood p l a sma and are p robab l y ( Webb ,. t ransported. 1 990. ;. But t s ,. to. and. 1993) .. 28. hydro l y s e d. in. t i s sue. cel l s.

(40) CHAPTER 3 NI TROGEN AND AMINO ACID D I GE STIBI LITY. 3.. D I GESTIBI LITY. D i ges t ib i l it y i s a me a sure o f t he amount that h a s been ext racted from a f o od through the p r o c e s s o f dige s t i on and ab s o rpt i on .. It. may be e s t imat ed by measuring the amount. exc reted and s ubst racting it from t he amount fed . E x c re t e d mat e r i a l. may. c ont a in. deb r i s , mucu s , c o rrect ion. of. endo genous. o r i gi n ,. cell. digest ive e n z yme s , b i l e and m i c ro f l or a and. o f met abol i c o r i g i n , a. waste. is. urine ,. app l ied. a s we l l as food re s i due s . to. negate. the. i n fluence. If of. endogenous and met abo l i c s ource s t h e e st imat e s de r ived a re " t rue " rather than " apparent " . The mo s t common l y unde rt aken me a surement s. are. tho se. on. nit rogen. (N). and. amino. a c ids. ( AA ) . P apadop o u l u s dige s t ib i l i t y. as. ( 1 985). de f i n e d. apparent. amino. " the di ffe rence between t he. acid. amount s. of. amino acid int ake i n the diet and i n the excreta o r i l e a l dige s t a " food .. as. a proport ion. Expre s s i o n s. digest ibi l it i e s. as. of the. de s c r ib ing. amount. consumed. apparent. adapt ed from B o lt on. and. (1969). in. the. t ru e. AA. are. g i ven. be l ow. App a rent digest ibi l it y. T rue d i g e s t ib i l it y. D i et ary AA - E x c r e t a AA =. D i et ary AA. D i et ary AA -. ( Ex c ret a AA ( Endogenous + Met ab o l i c AA ) ). =. D i et a ry AA. 29.