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

Transcription

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 THE PRODUCTIGN OP VOLATILE FATTY ACIDS IN SHE!-;}) ON DIFFERENT PASTURE 'l'ypes A thesis presented 1n partial tultilment ot requirements tor tbe degree ot Maeter ot Agricultural Science in Antmal Science a t Maase)' Uu1vers1 t7 JAJJ.ES BRUCE MACKINTOSH 1970 the

3 AODOWLEDGEMEirfS I wlab to ank my supervisors, Dr. M.J.Ulyatt end Proteasor D.s.nux, tor tbetr conti nu a l Interest, guidance and asslatance thro gbout tn1 project. I ind ebted the following tor their valuable and w1111ds aaa1atanoe: 1lr P.Vlleg and tbe tecbn1cal atatt ot the Applied Btoob let Dlvialon, D.S.I.R. tor tbe prep ration 101d care ot the anlm8la; Mr B.A.Tbomaon and Mr A.S.D.KlDg tor technical aaslatance durldg the experimot; Mr J.A.Raven, Kr aaeistance wl tb I.D.Sbelton and Mr N.J.Cbandler tor obemical anal7als ot pasture; The atatf ot the Herbage Laboraloey, Gr aalmda Dlvlalon, D.S.I.R. tor tbe botanical anal7aea; M bera ot the Sheep and Dalr,r Huabandr7 Departmenta tor belptul dlacu.. lon. Special tbanka are due to Kre M.D.Bew\b tor t7p1db tb1a theala.

4 PREPACE 'rhe New Zealand economy depends largely on the ettlclent conversion ot pasture to exportable animal products. The current emphasis on higher stocking rates increases the need tor pastures best suited to animal production. Pasture species used 1D New Zealand are recognised as ditter1ng in their ettects on animal production, these differences being loosely attributed to Yariation 1n asture quality". It the level ot oatput ot saleable product la the accepted measure ot pasture quality, thea the principal factors governing this are the quantity ot teed consumed and its subsequent ut111aat1on. A number of studlea hrve shown that dltterences ln food intake alone cannot account tor the observed differences ln antmal performance. It baa thus been considered important to investigate the factors attectlng the utlliaatlon ot pasture by the animal. Volatile tatty acids (VFA) produced ln the rumen are generally considered to account tor 10 to 80 per cent ot the net energy requlrementa ot ruminants, and their production must be a Jor dete lnant ot teed utlllaation. Dltterences 1D tbe ruminal oonoentrationa and proportloaa ot VPA have ott.en ben obaeryecl wl'tb pasture teedldg and have been otted aa poaalble reaaona tor dltterenoea 1D pasture qual1t,-. Tbe lnveat1sat1oa deaor1bed bere waa undertaken a a prellm1d&r7 atudy ot tbe role ot VPA production ld determining tbe quall ot Zealand p sture speolea.

5 TABLE OF CONTENTS CHAPTER ONE REVIEW OP LITERATUHE Introduction The Quality ot M Jor New Zealand Paature Speolea The Nutritional Slgn1t1canoe ot Volatile Patty Acid Teobnlquea tor the eaeurement ot VPA Production Rete Sampling trom th e : umen ot Sb ep 36 CHAPTER TWO the MAT :al\ls AND MF.THODS Animal a Paatures Experimental Dea lgn Peed Organ1aat1on Apparent Dtg at1b111ty Determination Intu ton Techn1qu V.A Sampllng Proo dure ADalyttcal 2.9. St ethoda 51 tt tloal AD l7a1a ot Dat 59

6 CHAPTER THREE 3.2. RESULTS lxper1mentel Me thod 60 Animal 66 Pastures 67 Dige tibl Energy Intake VFA Infusion 71 VFA Sampling and VFA An lyeia Production Rotee The Contribution of VJA ProduotloD to Digestible Energv Intake CHAPTER FOUR n DISCUSSION VFA Produotion RBtee 78 The Rel tionehlp between V?A Conoentr tion nd VPA Production 1n tb Rumen 82 of V?A Production 1n tbe Rumen ot Graslng Sbe p 84 The Mea urement SUMUARY 87 REFlm.ENCES 89 APPJmDICBS

7 LIST OF' T.I\BI.ES T a ble following Live Weight Gains of Sheep on Different Pasture Species 2 Rumen Characteristics ot Sheep on Different Pasture Species 3 Published Estimates of VFA Production in Sheep 7 Theoretical Ktfic1ency of Utilisation ot Various Subatrates Intercon version of VFA in the General 2.2. Analysts of Total Soluble Sugars Rumen ot Sheep Plan ot the F periment 51 Analysis uf Regression of VFA Proportions in D1alysstcs on Proportions in Prepared Solutions 60 Molar Proportions ot VFA in Rumen Samples 61 Analysts ot Regression ot VP.A. Proportions in Dialysates on Proportions in Direct Samples Recovery of 14c Label after Preparation tor Counting Live Weights and Live eigh t Changes ov er the Experimental Period Botanical Composition ot Pastures 3.6. Chemical Composition and Content ot Herbage 3.7. Soluble Carbohydrate Content ot Cut Feeds Energy

8 3.8. Mean D lly Intakes and D1geet1b111ty ot Pest res. Period I 68 Mean Daily Intakes end D1gest1b111ty ot Paaturee. Period II Digestible Energy Intakes Molar Proportion D1alyaatea or VFA in Percentages ot Total oh Hum n Acld c 1n 72 _ Recovery of Rad1oact1v1ty VFA during Intrarum1nal ot Labelled n Rumen Infusion Acetic Acid Interoonvers1on Rumen ot VFA 69 in 73 the 73 Uetes VPA Production Contr1bli tion ot V A Production DE Intake 75 to 77

9 LIST OF FIGURES following Figure 1.1. Metabolic Pathways ot VFA Production Metabolic Pathways of VFA Utilisation 13 Relationship between Channels Retio and Counting Efficiency

10 LIST OF PLA'l'ES following Plate I Plate II Plate III Infusion and Sampling Apparatus in Operation 47 Diagrammat1o Representation ot Dialysis Probe Relative Positions ot D i e ly is Probe and Intus1on Outlet 48

11 APPENDICES Appendix I Appendix II Live Weight Changes - AD ly s is ot Variance Dig stible Ver1anoe ergy Intake - Analysis of Appendix III Append ix IV Rate ot Infusion ot 14c-Labelled VFA Measurement o f Specific Act1v1ty ot Solutions Analy 1s of Infusion Variance - ot Rumen VFA Appendix V Specific Aot1v1t1es Samples Appendix VI Measurement ot S p ecific Activity ot Rumen VFA trom separated Acids - Analysis ot V ariance Appendix VII Measurement Total Rumen Appendix VIII Appendix IX of Spec1tic Activi ty ot VFA - Analy is ot Variance Elimination of Spurious R es u lts Example Calculation ot VFA Prod uction Rete and Contribution to DE Intake VFA.Analy la Appendix X Production Rates ot Variance Appendix XI Contribution ot VPA Production to DE Intake - ADaly i or Variance ot -