Application of biotechnology to nutrition of animals in developing countries.docx

8/22/2019 Application of biotechnology to nutrition of animals in developing countries.docx

1/67

FAO ANIMAL PRODUCTION AND HEALTH PAPER 90

Application of biotechnology tonutrition of animals in developing

countries

byR.A. Leng

Professor of Nutritional BiochemistryDirector of the Institute of Biotechnology

University of New EnglandArmidale, NSW

Australia

The designations employed and the presentation of material inthis publication do notimply the expression of any opinionwhatsoever on the part of the Food and Agriculture Organizationof the United Nations concerning the legal status of any country,territory, city or area or of its authorities, or concerning thedelimitation of its frontiers or boundaries.

M-23ISBN 92-5-103035-9

All rights reserved. No part of this publication may be reproduced, stored in aretrieval system, or transmitted in any form or by any means, electronic,


2/67

mechanical, photocopying or otherwise, without the prior permission of thecopyright owner. Applications for such permission, with a statement of thepurpose and extent of the reproduction, should be addressed to the Director,Publications Division, Food and Agriculture Organization of the United Nations,Via delle Terme di Caracalla, 00 100 Rome, Italy.

FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONSRome, FAO 1991

Hyperlinks to non-FAO Internet sites do not imply any official endorsement of or responsibility for the opinions, ideas, data or productspresented at these locations, or guarantee the validity of the information provided. The sole purpose of links to non-FAO sites is to indicate

further information available on related topics.


3/67

Contents

1 Introduction

1.1 Preamble

1.2 Definition of Biotechnology or High Technology

1.3 The Promise of the New Biotechnology

1.4 The Target Animals

2 Background2.1 Conditions of Ruminants in Third World Countries

2.2 Productivity of Livestock in Developing Countries

2.3 The Implication of Low Productivity

2.4 Feed Resources Available to Ruminants

2.5 Chemical Composition of Low Quality Forages

3 Basic Ruminant Nutrition

3.1 The Rumen and its Micro-organisms

3.2 Fermentative Efficiency in the Rumen

3.3 Meeting the Requirements for Efficient Microbial Growth in the Rumen

3.4 Consequences of the Ruminant Mode of Digestion

3.5 Quantitative Aspects of Fermentative Digestion in the Rumen

3.5.1 A Model of Fermentation in the Rumen

3.6 Protein Utilisation by Ruminants

3.6.1 Ensuring a Balanced Nutrition For Ruminants on Forage Based Diets

3.7 Optimising Microbial Growth in the Rumen

3.7.1 Mineral Requirements of Rumen Microbes

3.7.2 Requirements for Ammonia

3.7.3 Timing of Urea Supplements and the Ratio of Sugars and Starches to Fibre in a Diet

3.7.4 Requirements for Amino Acids/ Peptides by Rumen Organisms

3.7.5 Amino Acid Requirements of Microbes Digesting Fibre

3.7.6 The Roles of Small Amounts of Fresh Forage in Straw Based Diets

3.7.7 Elimination of Rumen Protozoa and Preservation of the Fauna-Free State

3.8 Factors Influencing Efficiency of Feed Utilisation

3.9 Climate, Supplementation and Intake of Low Quality Forages

3.10 Feeding Standards and Feed Evaluation3.10.1 Implications of low Productivity of Ruminants in the Tropics

3.11 Some Basic Explanations for the Inefficiency of Ruminants on Forage Diets

3.11.1 Inefficiency of Acetate Utilisation

3.11.2 Requirements for Glucose by Ruminants.

3.11.3 Balancing Nutrition for Reproduction/ Pregnancy and Lactation

3.12 Implication of Parasite/ Disease and Nutrition

3.13 Implications of an Increased Nutrient Requirements for Work

3.14 Conclusions

3.14.1 Implications for Areas of Research

4 Research Areas

4.1 Research Targets

4.2 Priority Ratings

5 Present Knowledge and Priority Research Areas

5.1 Adjusting P/E Ratio in the Nutrients Absorbed by Ruminants with Protein Supplements

5.1.1 General

5.1.2 Bypass Protein Supplements

5.2 Adjusting P/E Ratio by Manipulation of the Rumen

5.2.1 Supplementation of the Rumen Microbial Ecosystem

5.2.2 Chemical Manipulation of Rumen Fermentative Efficiency

5.2.3 Other Manipulations of Rumen Ecosystems
http://www.fao.org/docrep/004/t0423e/T0423E01.htm#ch1http://www.fao.org/docrep/004/t0423e/T0423E01.htm#ch1http://www.fao.org/docrep/004/t0423e/T0423E01.htm#ch1.1http://www.fao.org/docrep/004/t0423e/T0423E01.htm#ch1.2http://www.fao.org/docrep/004/t0423e/T0423E01.htm#ch1.3http://www.fao.org/docrep/004/t0423e/T0423E01.htm#ch1.4http://www.fao.org/docrep/004/t0423e/T0423E02.htm#ch2http://www.fao.org/docrep/004/t0423e/T0423E02.htm#ch2http://www.fao.org/docrep/004/t0423e/T0423E02.htm#ch2.1http://www.fao.org/docrep/004/t0423e/T0423E02.htm#ch2.2http://www.fao.org/docrep/004/t0423e/T0423E02.htm#ch2.3http://www.fao.org/docrep/004/t0423e/T0423E02.htm#ch2.4http://www.fao.org/docrep/004/t0423e/T0423E02.htm#ch2.5http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.1http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.2http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.3http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.4http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.5http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.5.1http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.6http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.6.1http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.7http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.7.1http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.7.2http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.7.3http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.7.4http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.7.5http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.7.6http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.7.7http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.8http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.9http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.9http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.10http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.10.1http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.11http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.11.1http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.11.2http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.11.3http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.12http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.13http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.14http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.14.1http://www.fao.org/docrep/004/t0423e/T0423E04.htm#ch4http://www.fao.org/docrep/004/t0423e/T0423E04.htm#ch4http://www.fao.org/docrep/004/t0423e/T0423E04.htm#ch4.1http://www.fao.org/docrep/004/t0423e/T0423E04.htm#ch4.2http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.1http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.1.1http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.1.2http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.2http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.2.1http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.2.2http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.2.3http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.2.3http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.2.2http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.2.1http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.2http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.1.2http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.1.1http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.1http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5http://www.fao.org/docrep/004/t0423e/T0423E04.htm#ch4.2http://www.fao.org/docrep/004/t0423e/T0423E04.htm#ch4.1http://www.fao.org/docrep/004/t0423e/T0423E04.htm#ch4http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.14.1http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.14http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.13http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.12http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.11.3http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.11.2http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.11.1http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.11http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.10.1http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.10http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.9http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.8http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.7.7http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.7.6http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.7.5http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.7.4http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.7.3http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.7.2http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.7.1http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.7http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.6.1http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.6http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.5.1http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.5http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.4http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.3http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.2http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3.1http://www.fao.org/docrep/004/t0423e/T0423E03.htm#ch3http://www.fao.org/docrep/004/t0423e/T0423E02.htm#ch2.5http://www.fao.org/docrep/004/t0423e/T0423E02.htm#ch2.4http://www.fao.org/docrep/004/t0423e/T0423E02.htm#ch2.3http://www.fao.org/docrep/004/t0423e/T0423E02.htm#ch2.2http://www.fao.org/docrep/004/t0423e/T0423E02.htm#ch2.1http://www.fao.org/docrep/004/t0423e/T0423E02.htm#ch2http://www.fao.org/docrep/004/t0423e/T0423E01.htm#ch1.4http://www.fao.org/docrep/004/t0423e/T0423E01.htm#ch1.3http://www.fao.org/docrep/004/t0423e/T0423E01.htm#ch1.2http://www.fao.org/docrep/004/t0423e/T0423E01.htm#ch1.1http://www.fao.org/docrep/004/t0423e/T0423E01.htm#ch1


4/67

5.2.4 Alteration of Protein and Amino Acid Composition of Rumen MicrobesRecombinant DNA

Technology

5.3 Adjusting P/E Ratios from the Rumen by Manipulating the Feed Base

5.3.1 Feed Technology and Development of Supplements

5.3.2 Supplementation with Naturally Protected Protein: A Case Study in Strategic Supplements

5.3.3 Providing Bypass Protein in Areas Without Protein Resources

5.4 Maximising Digestibility of Fibrous Feeds

5.4.1 Supplementation

5.4.2 Improving the Enzymatic Ability of Rumen Microbes to Degrade Fibre

5.4.3 Potential Targets for Improving Fibre Digestion

5.4.4 State of the Art in Bioengineering of Rumen Organisms

5.4.5 Selection of Anaerobic Fungi for Better Fibre Degradation in the Rumen

5.4.6 Selection of Bacteria for Fibrolytic Activity

5.4.7 Solubilisation of Lignin

5.4.8 Detoxification of Anti-microbial, Toxic and Anti-quality Factors in Plants

5.5 Developing Detoxification Mechanisms in Rumen Organisms

5.6 Treatment to Increase Digestibility

5.6.1 Improving the Digestibility of Crop Residues by Chemical Treatments

5.6.2 Microbial Treatment of Straw and Other Crop Residues to Improve Digestibility

5.6.3 Potential for Increasing the Digestibility of Poor Quality Roughage by Manipulating the

Digestive Physiology of the Animal5.7 Altering the Partitioning of Nutrients Within the Animal

5.7.1 Anabolic Steroids

5.7.2 Growth Hormone

5.7.3 -Agonists

5.7.4 Injected Growth Promotants versus Supplementation to Balance Nutrition

5.7.5 Conclusions

5.8 Cross Breeding to Improve Partitioning of Nutrients into Milk

5.9 Transgenesis and Embryo Manipulation

6 Biotechnology and Monogastric Nutrition

6.1 Introduction

6.2 Potential Areas for Biotechnology in Pig Nutrition

6.2.1 Overcoming Feed Intake Problems on High Fibre Protein Supplements

6.2.2 Possibility of Modifying the Digestive Function Through Development of Transgenic Animals

6.2.3 Porcine Growth Hormone (PSt.)

6.2.4 Transgenic PigsPorcine Growth Hormone

7 Biotechnology and Environment

7.1 Introduction

7.2 Integrated Farming

8 Some Practical Problems for Biotechnology Research in Developing Countries

8.1 Present Research Priorities and Change

8.2 Real World Problems of Capitalising on Modern Biotechnology in Developing Countries

8.2.1 Secrecy in Industrialised Countries

8.2.2 The Need for Expertise in Developing Countries to Capitalise on Various Developments

9 Conclusions and Recommendations

9.1 Priorities9.2 Overall Conclusions

9.2.1 The Vision of the New Biotechnology

9.2.2 The Future

9.2.3 The Problems

9.2.4 Recommendations

A Methods Involved in Modifying Rumen Bacteria

B Some Comments on Use of Protein Meals for Use as Supplement for Ruminants Fed Forages

C References
http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.2.4http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.2.4http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.2.4http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.2.4http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.3http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.3.1http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.3.2http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.3.2http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.3.3http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.4http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.4.1http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.4.2http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.4.3http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.4.4http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.4.5http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.4.6http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.4.7http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.4.8http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.5http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.6http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.6.1http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.6.2http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.6.3http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.6.3http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.7http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.7.1http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.7.2http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.7.3http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.7.3http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.7.4http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.7.5http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.8http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.9http://www.fao.org/docrep/004/t0423e/T0423E06.htm#ch6http://www.fao.org/docrep/004/t0423e/T0423E06.htm#ch6http://www.fao.org/docrep/004/t0423e/T0423E06.htm#ch6.1http://www.fao.org/docrep/004/t0423e/T0423E06.htm#ch6.2http://www.fao.org/docrep/004/t0423e/T0423E06.htm#ch6.2.1http://www.fao.org/docrep/004/t0423e/T0423E06.htm#ch6.2.2http://www.fao.org/docrep/004/t0423e/T0423E06.htm#ch6.2.3http://www.fao.org/docrep/004/t0423e/T0423E06.htm#ch6.2.4http://www.fao.org/docrep/004/t0423e/T0423E06.htm#ch6.2.4http://www.fao.org/docrep/004/t0423e/T0423E06.htm#ch6.2.4http://www.fao.org/docrep/004/t0423e/T0423E07.htm#ch7http://www.fao.org/docrep/004/t0423e/T0423E07.htm#ch7http://www.fao.org/docrep/004/t0423e/T0423E07.htm#ch7.1http://www.fao.org/docrep/004/t0423e/T0423E07.htm#ch7.2http://www.fao.org/docrep/004/t0423e/T0423E08.htm#ch8http://www.fao.org/docrep/004/t0423e/T0423E08.htm#ch8http://www.fao.org/docrep/004/t0423e/T0423E08.htm#ch8.1http://www.fao.org/docrep/004/t0423e/T0423E08.htm#ch8.2http://www.fao.org/docrep/004/t0423e/T0423E08.htm#ch8.2.1http://www.fao.org/docrep/004/t0423e/T0423E08.htm#ch8.2.2http://www.fao.org/docrep/004/t0423e/T0423E09.htm#ch9http://www.fao.org/docrep/004/t0423e/T0423E09.htm#ch9http://www.fao.org/docrep/004/t0423e/T0423E09.htm#ch9.1http://www.fao.org/docrep/004/t0423e/T0423E09.htm#ch9.2http://www.fao.org/docrep/004/t0423e/T0423E09.htm#ch9.2.1http://www.fao.org/docrep/004/t0423e/T0423E09.htm#ch9.2.2http://www.fao.org/docrep/004/t0423e/T0423E09.htm#ch9.2.3http://www.fao.org/docrep/004/t0423e/T0423E09.htm#ch9.2.4http://www.fao.org/docrep/004/t0423e/T0423E10.htm#appAhttp://www.fao.org/docrep/004/t0423e/T0423E10.htm#appAhttp://www.fao.org/docrep/004/t0423e/T0423E11.htm#appBhttp://www.fao.org/docrep/004/t0423e/T0423E11.htm#appBhttp://www.fao.org/docrep/004/t0423e/T0423E12.htm#appChttp://www.fao.org/docrep/004/t0423e/T0423E12.htm#appChttp://www.fao.org/docrep/004/t0423e/T0423E12.htm#appChttp://www.fao.org/docrep/004/t0423e/T0423E11.htm#appBhttp://www.fao.org/docrep/004/t0423e/T0423E10.htm#appAhttp://www.fao.org/docrep/004/t0423e/T0423E09.htm#ch9.2.4http://www.fao.org/docrep/004/t0423e/T0423E09.htm#ch9.2.3http://www.fao.org/docrep/004/t0423e/T0423E09.htm#ch9.2.2http://www.fao.org/docrep/004/t0423e/T0423E09.htm#ch9.2.1http://www.fao.org/docrep/004/t0423e/T0423E09.htm#ch9.2http://www.fao.org/docrep/004/t0423e/T0423E09.htm#ch9.1http://www.fao.org/docrep/004/t0423e/T0423E09.htm#ch9http://www.fao.org/docrep/004/t0423e/T0423E08.htm#ch8.2.2http://www.fao.org/docrep/004/t0423e/T0423E08.htm#ch8.2.1http://www.fao.org/docrep/004/t0423e/T0423E08.htm#ch8.2http://www.fao.org/docrep/004/t0423e/T0423E08.htm#ch8.1http://www.fao.org/docrep/004/t0423e/T0423E08.htm#ch8http://www.fao.org/docrep/004/t0423e/T0423E07.htm#ch7.2http://www.fao.org/docrep/004/t0423e/T0423E07.htm#ch7.1http://www.fao.org/docrep/004/t0423e/T0423E07.htm#ch7http://www.fao.org/docrep/004/t0423e/T0423E06.htm#ch6.2.4http://www.fao.org/docrep/004/t0423e/T0423E06.htm#ch6.2.3http://www.fao.org/docrep/004/t0423e/T0423E06.htm#ch6.2.2http://www.fao.org/docrep/004/t0423e/T0423E06.htm#ch6.2.1http://www.fao.org/docrep/004/t0423e/T0423E06.htm#ch6.2http://www.fao.org/docrep/004/t0423e/T0423E06.htm#ch6.1http://www.fao.org/docrep/004/t0423e/T0423E06.htm#ch6http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.9http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.8http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.7.5http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.7.4http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.7.3http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.7.2http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.7.1http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.7http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.6.3http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.6.3http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.6.2http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.6.1http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.6http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.5http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.4.8http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.4.7http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.4.6http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.4.5http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.4.4http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.4.3http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.4.2http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.4.1http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.4http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.3.3http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.3.2http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.3.1http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.3http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.2.4http://www.fao.org/docrep/004/t0423e/T0423E05.htm#ch5.2.4


5/67

Chapter 1 Introduction

1.1 Preamble

Livestock production is a function of:

feed availability and quality the incidence of diseases including intestinal parasites, blood and other parasites of living tissues (e.g. protozoa), viral and

bacterial invasive agents

the climatic and environmental conditions that prevail in the particular area the genotype which fits it to a particular production system.

In the context of this report, which examines the prospects and perspectives for the use of high technology or biotechnology in nutrition toincrease animal production, the target animals must be the domestic ruminants that are managed by small farmers in third world countries.

The developing countries, in general, have severe constraints on food availability for humans and are often critically balanced in producingsufficient starch-based carbohydrates and high quality proteins to provide for their human population. Thus, the grains produced aregenerally required for the resident population, which is often increasing at a rate several times that of the populations of the industrialisedcountries. Short term food surpluses due to good seasonal growing conditions and/or application of plant/soil research results, will inevitablybe converted to deficits by the growing population's demand for food.

The only exception to this will be if birth rate is reduced and death rate accelerated in these countries. The impact of the presently

untreatable viral disease HIV (or AIDS) will be significant in this area but no predictions are yet available on its effects on future populationdensities in developing countries.

The likely small surpluses of grains over and above that needed by humans indicates that the production of monogastric animals whichcompete with humans for the basic feed resources (grain) must have good political and or trade advantages before it can be encouraged.However, production of monogastric animals on sugar based products and various by-products may be a future direction for considerableresearch effort.

There is, of course, a middle class in all developing countries which demands meat from poultry and pigs and can afford to pay the relativelyhigh costs of production. This group of people is expanding in the countries that are rapidly industrialising, and this together with the influx oftourists in such countries will increase demand for these products.

There is a high correlation between meat consumed and cash income or standard of living (see Brumby, 1989 and Figure 1.1)

The husbandry of monogastric animals is already at a very high level and, in general, research on grain-fed domestic animals is probably

best left to the industrialised countries where surplus grains are generally available and their production is subsidised (e.g. approximately40% of the value of grain production throughout the EEC and USA is met by subsidies).

In most developing countries pig and poultry production is either based on a scavenger system, (which is restricted to village farmers), or ahigh cost technology system as used, and transferred from, temperate countries (which is used by the large farmer).

Figure 1.1: Food consumption/percentage of diet for meat, wheat and rice, and coarse grains asper capita income increases (Marks &Yetley, 1987-see Brumby 1989)


6/67

Monogastric nutrition cannot be omitted from consideration, however, as the appropriate integration of monogastric animals with ruminants incropping areas is potentially the most efficient systems that might be (or are being) developed to increase animal production overall. Withinthese systems the production of pig and chicken meats from non-conventional feed sources (e.g. sugar cane, molasses, household swill,tubers, roots and by-products) integrated with such systems as protein production from aquatic plants should be the major consideration inthe future.

The ruminant animal, because it has pre-gastric fermentative digestion of feed, generally does not compete with humans for vital quality-feedresources and must therefore have the focus of the discussions. Ruminant animals (biomass) in developing countries far outnumber all otherdomestic animal not only as a source of high quality human food (meat and milk, with blood in some areas), but of fuel (from dung) anddraught power.

The continuing use of ruminants as domestic animals resides in their ability to:

convert fibrous carbohydrates through fermentative digestion, into nutrients that can be used for growth, and milk synthesis efficiently utilise low protein feeds and non-protein nitrogen in the rumen and synthesise proteins with a high biological value for

human consumption

convert the carbohydrates of fibrous feeds into nutrients that can be used to carry out work-functions (e.g. ploughing) more efficiently use dietary protein for tissue synthesis than monogastric animals provided it is in a form protected from microbial

attack in the rumen but digestible by gastric and intestinal enzymes.

Any biotechnology developments will undoubtedly have to target the improvement of efficiency of these attributes under practical conditionspertaining particularly to the small farmer.

There are five major ways by which any technology may significantly improve livestock production:

by altering the feed base to provide a better quantity and balance of nutrients to the animal by altering the digestibility of the feed base by treatment so that more nutrients are extracted. by manipulating the fermentative, gastric and post-gastric digestive processes to extract more and a better balance of nutrients for

the animal from the basal feed.

by manipulating the efficiency of partitioning of absorbed nutrients into productive processes including those that are involved inlife-time productivity

by removing or ameliorating constraints that are part of the environment (largely disease, but also the effects of temperature andhumidity stress)

Strategies for the future use of animals for work and food production cannot ignore the growing environmental crisis and the need to reducegaseous emissions from farming systems. Some comments will be made on this in later sections of this report.

1.2 Definition of Biotechnology or High TechnologyBiotechnology is a much used in word in research submissions since it conjures up images of research at the cutting edge of science. Italso has an overtone of application, potentially patentable products or processes and therefore returns on investment. The promises havebeen much overrated in recent times and in general the promises for application from, for instance, recombinant DNA technology have failedto materialise in terms of animal production. In general, the results of recombinant DNA technology have been disappointing. For exampletransgenic animals have been produced but failure to control expression of the introduced genes has resulted in adverse effects often of anature that horrifies animal welfare groups. This has been given bad press but it has highlighted the need to study the basic aspects ofcontrol of gene expression and cell physiology.

This does not mean however, that the future for and importance of such work is debatable. In fact, the contrary is true, but it has indicated amajor requirement for basic research to understand gene expression and that more time and funds will be needed before many newconcepts can be applied.

Biotechnology in the context of this report cannot be restricted to recombinant DNA technology. Biotechnology is in reality, a science of greatantiquity having its origins in processes such as brewing and wine making.

The broad definition used here is the application of biological organisms, systems or processes to production of animal products

These include meat, milk, hides, wool or hair and draught power. In particular, biotechnology stresses the integration of microbiology,biochemistry and chemical and process engineering. It is always multi-disciplinary, and its strongest aspect is that it is directed to application.It usually requires disciplinary scientists working together and shepherded by person(s) with major integrative abilities. Young scientists (ordisciplinarians) caught up in biotechnology and working in isolation often lose the direction for application or seek out compromise objectivesto justify their approach which may or may not be rational.

On the tour of institutions prior to the writing of this report, it was an observation that a number of young, newly trained (overseas) scientistsin the less well developed countries, were still working in the area of their overseas training without true recognition of the potential


7/67

application of their work. They were, thus, in some ways competing with their previous supervisors and are therefore unlikely to producenovel innovations.

For the purposes of this report biotechnology research is regarded as a multi-level activity. In animal nutrition this includes research that aimsto improve the efficiency of production through manipulation of:

the feed base the animal's digestive system the animal's metabolism

It must also consider the potential for augmenting the feed base with critically deficient nutrients that may be produced locally, particularlyfrom non-conventional sources (e.g. production of protein meals from aquatic plants (algae) grown on biodigestor effluent). It must alsoconsider the possibility of decreasing protein fermentability of plants consumed by ruminants by genetic engineering of plants and othertechniques applied to the plant, the microbial digestion system and the animal.

The narrower definition will be referred to here as the new biotechnology. This is defined as the application of recombinant DNAtechnology to the improvement of animal production through improving nutrition.

1.3 The Promise of the New Biotechnology

The beginning of recombinant DNA technology arose from the work of Crick and Watson (Watson, 1968) and their colleagues at Cambridge.Research in this area is often seen as being superior to other forms of biological research. However, like all research it is often theacquisition of technology and instrumentation which triggers development or progress in this field. Example of developments which allowed

many groups to begin or progress in their work include the development of techniques to split the ovum, to introduce foreign DNA intochromosomal DNA or to force a plasmid into a cell where it will replicate along with other DNA. This is not meant to be a criticism of modernbiotechnology research but it is stated to point out that the new biotechnology is supported by a large group of normal scientists led largelyby a few highly capable and creative persons in the same way as every other field of research endeavour.

The concept of the new biotechnology as a science for the gifted and the imaginative promises of biotechnology put forward in most reviews,have undermined many other fields of research which have then suffered from financial stringencies. These fields often regain prominencewhen, for example, innovative gene transfer methodology has failed to produce the expected applied technology (e.g. higher productivity indomestic animals expressing genes for growth hormone). In this case there has been little recognition of nutritional principles; an animalcapable of growing say to twice the size and at twice the rate because of the acquisition of a gene for growth hormone may need a totallynew nutritional approach. For example, in order to provide for growth and normal bone growth in such animals it will be perhaps necessary toprovide more calcium and phosphorus in forms more easily absorbed and assimilated; protein to energy ratios in the nutrients absorbed mayhave to be increased substantially as may be the availability of v itamins and other minerals.

The need is for a suitable balance of research which must be maintained. The new biotechnology needs to advance along with thefundamental and applied research that is needed to ensure that the application of molecular genetic research reaches the end user, in thiscase the farmer. It is a major theme of this report that it is imperative that research on nutrition must not compete for limited funds with thenew biotechnology.

It is also a major conclusion that concepts of nutrition transferred from temperate countries have been misleading. Recently developedunderstanding of nutrition, which has massive effects on productivity, is the area with most promise and with potential immediate application.The great need is for research to find ways of applying these concepts in production systems under differing environmental conditions withincountries. With a likely doubling of food requirements of developing countries by the year 2000 the need for research which will result instrategies that can be quickly applied is paramount.

1.4 The Target Animals

This dissertation must deal largely with the economically (in its broadest sense) important ruminants in developing countries. These arelargely cattle, buffaloes, sheep and goats. Other animals that pre-ferment their feed, include camels, alpaca, llama, yak, thimin and certainmonkeys as well as certain deer species, and post-gastric fermenters such as the horse, donkey, guinea pig and rabbit must be kept in mindas they are often of major importance in some areas. However, the latter group have not been targeted because of the predominance of

ruminant herbivores. Research on the use of non-conventional feeds is given a brief mention but the major research requirements here areto develop the systems which depend on locally available resources and particular within an integrated farming systems concept.


8/67

Chapter 2 Background

2.1 Conditions of Ruminants in Third World Countries

The reasons for keeping ruminants in developing countries are not always easily understood by the outsider. They are kept for a number ofreasons, which change in priority depending on their location and owners including the following:

for food (e.g. meat, milk and blood or any of these combinations) and also as a reliable food store for years of drought as status symbols of wealth as a means of accumulation of wealth to be cashed for a number of purposes (e.g. life threatening events; to meet marriage costs;

to provide for pay-back etc.)

as an edge against inflation for fuel (dung for sale or to provide for household cooking) for fertiliser production (e.g. dung) drought power for religious purposes and/or entertainment (e.g. the fighting rams of Indonesia) work purposes (ploughing, puddling of soil for rice etc.) transport hides for leather as investment by city business men to create a stake in agriculture which is often motivated by the possibility of tax relief to make use of poor lands which would not otherwise be used for agricultural purposes.

The desire of the farmer to increase productivity of his animals, is highly dependent on the purpose for keeping the livestock. It is sometimesan advantage to maintain a low level of productivity. For example, if animal numbers are more important than production per animal, it isadvantageous to have stunted, thin animals which require low management inputs.

In this presentation the target animals are the animals in the herds of small farmers where meat, milk, work, or any combination of these(meat/work, meat/milk, milk/work) are the major objectives as these are the major owners of livestock in developing countries and the targetfor many of the aid-sponsored projects.

2.2 Productivity of Livestock in Developing Countries

Few developing countries have surplus tracts of land that can be regarded as fertile and therefore produce high quality fodder. In general,human population pressures and the primary need to supply human food ensures that livestock are restricted to:

poor quality (often overgrazed) pasture lands, either infertile or with terrain that makes them impossible to utilise for crops orwhere erosion has made them unusable.

Table 2.1: Average meat production (kg) per animal of total population of cattle/buffaloes in Europe (representative of the concentrate/foragefeeding systems) and in Asia/Pacific (1986)


9/67

Cattle Buffalo

Europe 68 50

Asia/Pacific 5 7

standing crop residues or weeds following cropping when environmental conditions are poor for plant growth and a further crop inthat year cannot be taken.

crop residues (cut and stored) agro-industrial by-products extensive pastures of poor quality and otherwise sparse (e.g. The Llanos of Colombia and Venezuela).

The net result is in general an extremely low rate of productivity with animals often at 5 years of age at maturity and productivity at 0.10.25of that of ruminants in temperate countries grazing fertilised pastures or fed high quality feeds based on grain and immature pasture plants. Acomparison of the levels of production of cattle between developed and developing countries is shown in Tables 2.1, 2.2 and 2.3.

Table 2.2: Average carcass weight (kg) per animal slaughtered (Jasiorowski, 1988) (1986 statistics)

Cattle Buffalo

Europe 185 206

Asia/Pacific 120 161

Table 2.3: The change in the average milk yield per cow in industrialised and third world countries

Country/Region

Average yield/cow(kg/year)

Percentage increase (%)

1976 1986 (1976 to 1986)

North America 3,250 5,200 60

EEC Countries 2,900 4,100 35

Asia 620 700 13

Africa 322 354 7

2.3 The Implication of Low Productivity

Biotechnology research in industrialised countries is not generally aimed at low yielding animals. In addition to poor nutrition, adverse climateand disease, other stresses are also generally high, particularly in those countries situated in the tropics. These additional constraints arelikely to affect and often remove any advantage of biotechnology transferred from developed countries.

The considerable differences in feed resources available in developing countries compared to developed countries (where mostbiotechnology research is presently centered) and the low cost of production systems employed in the developing world as compared withthe industrialised world (where subsidies on agricultural production are often in excess of 40% of the value of the product) indicates thatdirect technology transfer is unlikely to be successful.

2.4 Feed Resources Available to Ruminants

The feeds that are available to ruminants in developing countries are fibrous and relatively high in ligno-cellulose. They are usually of lowdigestibility and they are often deficient in critical nutrients, including protein, non-protein nitrogen and minerals.

As a generalisation, the forages consumed by ruminants in developing countries are almost always below 55% (usually 4045%) digestibilityand are often less than 8% crude protein and this protein level is more often around 3 5%, e.g. cereal straws. The only exception to this is inthe early growth phase of pasture and when stocking rates are extremely low and the animals are able to select for leaf material. The lowlevels of production per head and per acre of most grazing systems are indicated by the summary of data given by Walker (1987) (seeFigure 2.1). Without supplements, these low levels of production lead to a highly inefficient use of the available feed, with a possibility that upto 30% of the feed consumed is dissipated as heat. This heat has at times great effects on feed intake particularly in the tropics (see Chapter3).


10/67

It is necessary, therefore in discussing the nutrition of ruminants, to appreciate the digestion of forage based diets and the constraints to theutilisation of nutrients that arise largely from a fermentative digestion system, since this knowledge must considerably influence researchpriorities.

2.5 Chemical Composition of Low Quality Forages

In the literature concerned with the nutritional value of forages, considerable emphasis is placed on the crude chemical composition of theforage. Although analyses that indicate cell solubles and cell wall materials are highly useful for studying the fermentative characteristics of aforage, they bear little relationship to its feeding value to the animal (see later). Considerable efforts is often put into feed analysis which is

often totally unwarranted particularly in the developing countries. In this report the overriding effects of a balanced nutrient approach tofeeding are emphasised. It is suggested that in most production systems for ruminants based on a poor quality forage, it is the balance ofthose nutrients providing the major building blocks for tissue synthesis and milk production, that should be the primary concern. With mostforages and contrary to the assertations in the past that energy deficiency is the primary constraint to ruminant production on low qualityfeeds, the efficiency of feed utilisation is the major determinant of the production levels achieved. Therefore in reviewing the need forbiotechnology research, this is the area for most consideration.

Recent evaluation of data from studies in tropical countries has indicated that medium to high levels of production at very high feedconversion efficiencies can be achieved by ruminants on poor quality forages adequately supplemented with critical nutrients (see Preston &Leng (1987) for review). Of more importance is that the efficiency of utilisation of the metabolizable energy of a straw based dietappropriately supplemented can be higher than that of grain based diets (Leng, 1989b). This suggests that the efficiency of utilisation ofmetabolisable energy of a forage can be markedly improved simply by supplementation (by up to 10 fold). It also discounts theories that thedigestible nutrients from such feeds are less efficiently utilised than from grain based diets.

Figure 2.1: Cattle growth on pasture is a function of pasture type, fertiliser applications and legume content. Productivity per unit area ismaximised for the different pastures at different stocking rates: 89 kg/ha for native pastures, 223 kg/ha for tropical grass with legume, 682

kg/ha for tropical grass with fertiliser and on temperate pasture (clover) 105 kg/ha. (Source: Walker 1987)


11/67

Chapter 3 Basic Ruminant Nutrition

3.1 The Rumen and its Micro-organisms

As the utilisation of forages by ruminants depends on microbial fermentative digestion, the principles of digestion in the rumen are discussedas a framework to view the requirements for biotechnology innovations in nutrition.

The rumen is the dominant feature of the digestive tract of cattle. This maintains a medium that supports a dense and varied population ofmicroorganisms. These organisms ferment feed materials to produce mainly shortchain organic acids or volatile fatty acids (VFAs), methaneand carbon dioxide and the process provides substrate (the feed) and ATP (energy) for the growth of micro-organisms.

The microbial mix in the rumen is complex and highly dependent on diet. The main agents that break down fibre, sugars, starches andproteins in the rumen are all anaerobic and include bacteria, protozoa and fungi.

The bacteria are the principal organisms that ferment plant cell-wall carbohydrates (Hungate, 1966) but the anaerobic phycomycetous fungimay at times be extremely important (see Bauchop, 1981).

Protozoa are now recognised as having an overall negative effect in the rumen, particularly where ruminants are fed forage diets low in true-protein (Bird et al. 1990). Protozoa ingest and digest bacteria and reduce the bacterial biomass in the rumen (Coleman, 1975) andconsequently the protein supply to the animal. Thus, they decrease the protein to energy ratio in the nutrients absorbed (see later) andincrease the requirement of animals for true protein. The net result of the presence of protozoa is an increased requirement for dietarybypass protein and on low protein diets a decreased efficiency of utilisation of feed for growth and milk production (see later) (Bird etal. 1990).

The presence of protozoa in the rumen may also reduce the rate at which bacteria colonise and degrade the ingested feed particles. Instudies with sheep fed straw based diets, it has been found that the apparent digestibility of dry matter was increased by 18% after protozoahad been removed from the rumen (i.e. defaunated) (Bird & Leng, 1984; Soetanto, 1986). This research indicates that large increases inproductivity may be achieved with ruminants fed fibrous diets, particularly those low in true protein by controlling or removing protozoa fromthe rumen. Other workers have not seen the differences in digestibility and in some instances removal of protozoa from the rumen has led todecreased digestibility of mixed, starch containing diets (Jouany & Ushida, 1990).

3.2 Fermentative Efficiency in the Rumen

A deficiency of a nutrient needed by rumen micro-organisms reduces microbial growth efficiency which reduces microbial biomass andeventually reduces digestibility and feed intake, particularly of fibrous feeds.

The first priority in feeding ruminants is to ensure no deficiencies in the diet of nutrients for microbial growth in the rumen. Of major

importance is that the efficiency of microbial growth (that is, the amount of microbial biomass available for digestion in the intestines per unitof digestible carbohydrate entering the rumen) also determines the proportion of digested feed that is converted to methane and VFA.Methane production accompanies the formation of acetate or butyrate, whereas methane and VFA production are inversely related tomicrobial cell production.

3.3 Meeting the Requirements for Efficient Microbial Growth in theRumen

On most diets based on crop residues and low-digestibility forages, the primary limitation to the growth of rumen micro-organisms is probablythe concentration of ammonia in rumen fluid The second consideration is deficiencies of minerals, particularly sulphur, phosphorus,magnesium and certain trace minerals.

Ammonia in the rumen must be above a critical level for a considerable period of the day to ensure a high rate of microbial growth anddigestion and therefore feed intake. The level of ammonia that supports the optimal population of micro-organisms in the rumen the highest

protein to energy ration in the nutrients absorbed, and therefore maximum digestion, will vary among diets. In general on forage based dietsthe ammonia level should be above 200 mg nitrogen/litre (see Leng, 1991).

It must be stressed, however, that any nutrient, (including many minerals required in the growth of micro-organisms), that is deficient in a dietwill result in low microbial cell yield relative to VFA and lead to a low protein (from microbes) to energy (from VFA) in the nutrients absorbed(this is discussed under quantitative aspects of fermentation digestion below).

The ratio of protein digested and absorbed from the intestines to the VFA produced in and absorbed from the rumen is termed the P/E ratio.


12/67

3.4 Consequences of the Ruminant Mode of Digestion

One of the consequences of the ruminant mode of digestion is that fermentation results in up to 20% of the digestible energy intake beinglost as heat and methane. A second major disadvantage is that proteins that are fermented in the rumen are not then sources of amino acidsfor the animal because they are hydrolysed and their constituent amino acids deaminated by microbes.

In general, where ruminants are fed forage based diets typical of that available in tropical developing countries, small amounts of extranutrients are needed to balance nutrient availability to requirements. Proteins which are directly available to the animals and are protectedfrom degradation increase the efficiency of anabolism of the absorbed nutrients in growth, pregnancy, lactation or work. (see Leng, 1991).

3.5 Quantitative Aspects of Fermentative Digestion in the Rumen

The end products of rumen fermentative digestion are governed by the feed, the rate of consumption of feed, the balance of nutrients in thefeed for microbial growth and the balance of micro-organisms that develop in the rumen (bacteria, protozoa and fungi).

In general, a proportion of the digestible feed dry matter is converted to VFA, methane and carbon dioxide and the balance is assimilated intomicrobial cells. The pathways of these reactions are well known and a schematic outline is shown in Figure 3.1.

Microbial cells, that are synthesised from the feed resource use the ATP that is generated in the formation of VFA from the feed to providethe energy for synthesis. The microbes are lost from the rumen pool either by passage out of the rumen to be partially digested in theintestine or by death and breakdown within the rumen (with formation of VFA, CO 2 and methane). Lysis and degradation in the rumen isinefficient as it makes the protein of microbes unavailable as such to the animal.

Because microbial cells are more reduced than the substrate fermented, the quantity of microbial cells leaving the rumen per unit ofcarbohydrate consumed is related to methane production. The efficiency of microbial growth is then a primary determinate of the quantity ofmethane produced.

Figure 3.1: Energetics of rumen fermentation (Leng, 1982)

3.5.1 A Model of Fermentation in the Rumen

For the purposes of the present discussion and to demonstrate the underlying principles of the concepts developed, a model for a 200 kgsteer will be used to illustrate the quantitative availability of nutrients from rumen fermentation. The steer consumes 4 kg which represents 25Mole anhydroglucose or organic matter which is completely fermented in the rumen.

It is assumed:

that the fermentation of 1 mole of carbohydrate gives rise to either 2 mole acetate, 2 mole of propionate or 1 mole of butyrate,according to the following stoichiometry:

Hexose Pyruvate + 2ATP+ H2

2Pyruvate +2H2O

2HAc+ 2CO2 + 2H2 +2ATP

2Pyruvate + 2HPro + 2H2O + 2ATP


13/67

8H2O

2Pyruvate +4H2O

H Bu + 2H2 + 2CO2 +2ATP

CO2 + H2 CH4 + 2H2O + 2ATP

In the stoichiometry, H2 indicates reduced co-enzymes, HAc is acetic acid, HPro is propionic acid and HBu is butyricacid

that the animal's rumen is functioning at normal level of fermentative efficiency in which one-third of the organic matterfermented is converted to microbial cells and the rest to VFA, CO 2 and CH4.

that the moles ATP generated per mole of end-product are for acetate 2, butyrate 3, propionate 3, and methane 1 (Isaacson etal. 1975).

On chemical principles, the equation of substrate use and end products from fermentation of 4 kg of carbohydrate is:

Carbohydrate to VFA16.7 CHO 21HAc+ 6HPro + 3HBu + 7.5CH4 + 78ATP

Carbohydrate to microbial cell precursors8.3CHO 1.4polysaccharide + 13.8pyruvate + 2CH4 + 17ATP

Overall:25CHO 21HAc+ 6HPro + 3HBu+9.5CH4 + 1300 g dry cells.

In the example, one-third of the carbohydrate provides the substrate for microbial cell synthesis 1300 g dry microbial cells are produced at aYATPof about 14.5 (YATPis a measure of the efficiency of utilisation of ATP generated in fermentation of carbohydrates to VFA; it is defined

as the g dry cells produced per mole ATP available.)

The upper level of efficiency (or the theoretical highest level of cell production) has a YATPof 26. On the other hand the lowest efficiency of amicrobial growth in the rumen that is deficient in, say, ammonia, is possibly below a YATPof 4.

The relationship between the efficiency of cell synthesis and fermentative end products produced are shown in Figure 3.2. These valueswere arrived at by similar calculations as that given above.

Figure 3.2: Relationship between the production of microbial cells and volatile fatty acids and methane in fermentative digestion in ruminants

The relative efficiency of the system (indicated as YATP) is governed largely by the availability of essential nutrients for microorganisms (afterLeng, 1982). The ranges of YATPare shown for:

A. a relatively inefficient rumen (i.e. ammonia deficient)B. a normal rumen with no deficient nutrient for microbial growth

C. a rumen free of protozoa with no deficient nutrient for microbial growthD. the theoretical optimum microbial growth efficiency.


14/67

Table 3.1: The effect of different efficiencies of microbial growth on the ratio of protein to VFA energy (P/E ratio) available from the rumen ofa steer consuming 4 kg of organic matter which is totally fermentable.

YATP

8 14 19 25

Microbial

protein*synthesised

(g/d)

500 800 1010 1212

VFA produced (MJ/d) 41 34 30 26

Methane produced

(MJ/d)9.4 8.5 8.0 7.6

Heat (MJ/d) 6.4 5.1 4.3 3.1

P/E ratio (g protein/MJ) 12 25 34 47

* Microbial protein may be only 7585% digestible and this will change the P/E ratio markedly in the animal.

Based on this model, but assuming a varying efficiency, the microbial cells produced relative to VFA and methane production change areshown in Table 3.1. The main point to emphasise is that, depending on the efficiency of utilization of ATP, the amount of carbohydrateconverted to microbial cells can be highly variable. It is the efficiency of microbial growth that largely controls the amount of methaneproduced by an animal (see Figure 3.2).

Ensuring a high ratio of microbial cells (protein) produced relative to VFA (energy) or a high P/E ratio is critical for efficient feed utilisation(see Section 3.10) and mechanisms for manipulating this ratio are discussed in the next section.
http://www.fao.org/docrep/004/t0423e/T0423E03.htm#note1http://www.fao.org/docrep/004/t0423e/T0423E03.htm#note1http://www.fao.org/docrep/004/t0423e/T0423E03.htm#note1


15/67

3.6 Protein Utilisation by Ruminants

Protein that is fermented in the rumen is largely wasted as a source of amino acids to the animal because:

dietary protein is degraded and essential amino acids are deaminated to form ammonia and VFA fermentation of 1 g of protein generates only half the ATP that would be produced from 1 g of carbohydrate and therefore

anaerobic microbial growth on protein is approximately half that on carbohydrate.

In combination these effects result in only 30 to 60 g of microbial protein becoming available to the animal for digestion for every kilogram ofdietary protein that is fermented in the rumen. The fermentation of protein is, however, associated with relatively small amounts of methaneproduction. On the other hand methane is not generated when protein bypasses the rumen.

Protein that is insoluble, or has a high component of disulphide bonds or is associated with tannins tends to bypass rumen fermentation butis digested in the intestines and in this way it augments the microbial protein and alters the ratio of protein to energy (P/E) in the nutrientsabsorbed. The better the balance of nutrients for microbial growth the higher the ratio of P/E in the nutrients produced in fermentation. Thehigher the content of bypass protein in the diet the higher the P/E ratio in the absorbed nutrients.

3.6.1 Ensuring a Balanced Nutrition For Ruminants on Forage Based Diets

From the above discussion the first priority for improving the utilisation of a low digestibility forage by ruminants is to optimise the availabilityof nutrients from fermentative digestion by:

ensuring that there are no deficiencies of microbial nutrients in the rumen and therefore the microbes in the rumen grow efficientlyand, through fermentative activity, extract the maximum possible amounts of nutrients from the forage (i.e. the ratio of microbialcells to VFA produced is high as are production rates of these end products)

ensuring that the microbial cells (which provide most of the protein to the animal) synthesised in the rumen are not lysed andfermented in the rumen but are available for digestion and absorption as amino acids from the intestines.

The second objective of a feeding strategy should be to optimise the efficiency of partitioning of absorbed nutrients into product by:

supplementation with critical nutrients that escape or bypass rumen fermentation to augment and balance the nutrients absorbedto those required for maintenance of homeostasis, maintenance of body temperature, exercise (or work), and the particularphysiological or productive function.

As the nutrients needed for different functions differ in priority, supplementation strategies will need to vary according to climate,environment, management and production targets in any one location.

3.7 Optimising Microbial Growth in the Rumen

3.7.1 Mineral Requirements of Rumen Microbes

The rumen microbes have specific requirements for both macro and micro minerals to meet the needs of structural components of cells andfor components of enzymes and co-factors. Little is known about the requirements of the microbial milieu for trace elements and as a rule ofthumb it is accepted that if the animal is not deficient then it is unlikely that the rumen microbes will be deficient.

As Suttle (1987) has so aptly put the situation, it will rarely be possible to approach a suspected mineral deficiency situation with a table ofminor nutrient requirements or biochemical criteria in the hand, and define a scale of the animal health (microbial health) problems. Inpractice, either no mineral supplements are used or a shot gun mixture is given as a salt licks (McDowellet al. 1984) or as molasses (whichis concentrated plant juice rich in minerals) suitably fortified with minerals (Kunju, 1986).

As with any deficiency of a nutrient the likely scenario of a mineral deficiency for rumen organisms is first a reduced growth efficiency ofmicrobes (lowered ratio of cells to VFA produced) with or without a decrease in digestibility. As the deficiencies become more extreme thedigestibility of forage must decrease along with the decrease in microbial pool size and it is only then that feed intake will decrease. Feedintake however, will be decreased as P/E ratio decreases if the animal is heat stressed (see later). Correction of deficiency will obviouslyreverse these effects.

3.7.2 Requirements for Ammonia

Ensuring adequate ammonia N in the rumen to supply the majority of nitrogen for microbial growth is the first priority in optimisingfermentative digestion of forage. Satter & Slyter (1974) suggested that 5080 mg NH3-N/1 of rumen fluid was the optimum for maximising


16/67

microbial growth yield and this has been widely accepted. However, recent studies from two laboratories in Australia have clearly indicatedthat the minimum level of ruminal fluid ammonia for optimum voluntary intake of low N, low digestibility forage by cattle is about 200 mg N/1,even though the digestibility of the forage (in nylon bags) was optimised below 100 mg NH3-N/1 (Krebs & Leng, 1984; Boniface et al. 1986;Perdok et al. 1988). All these studies were carried out in hot environments and the effects on feed intake are possibly explained by animproving P/E ratio in the nutrients absorbed, which reduces the metabolic heat load.

The effects of increasing ruminal fluid ammonia by infusion of urea into the rumen of steers on the intake of rice straw and its digestibility innylon bags in the rumen are shown in Figure 3.3.

Figure 3.3: The effects of the level of ammonia in the rumen on the intake and in sacco digestibility of straw by cattle. The ammonia levels

were adjusted by infusing urea in the rumen (Perdok et al., 1988)


17/67

3.7.3 Timing of Urea Supplements and the Ratio of Sugars and Starches to

Fibre in a Diet

Supplements must provide adequate levels of ammonia in the rumen for continuous growth of both fibrolytic and saccharolytic organisms.The only satisfactory approach to meeting these changing requirements for ammonia is to provide ammonia continuously. One way of doingthis is to provide salt/urea or molasses/urea licks and allow the animal to take these as needed. There are indications that cattle andbuffaloes given continuous access to multi-nutrient blocks based on molasses/urea are able to control fairly closely their intake of urea. Oncebuffaloes were accustomed to molasses/urea blocks they adjusted their intake according to the N content of the basal diet (NDDB

unpublished data). Lambs given wheat straw and molasses/urea blocks also had similar abilities and consistently maintained their rumenammonia levels above 200 mg N/1 (Sudana & Leng, 1986).

3.7.4 Requirements for Amino Acids/ Peptides by Rumen Organisms

There has been considerable controversy concerning the requirements for peptides/amino acids by rumen microbes for efficient growth. Anumber of studies, however, have reported results ofin vivo studies which appear to have indicated no apparent requirement for amino acidsfor efficient growth of rumen organisms (see Leng & Nolan, 1984). The results of studies by Maeng et al. (1989) may explain some of thecontradictory results. The studies of these researchers indicated that rumen microbes growing on different carbohydrate substrates haverequirements for different N-substrates; celluloytic organisms may not require amino acids to the same extent as organisms growing onstarches or sugar as the major substrate. For microbes utilising sugars growing on starches there was an apparently high requirement forpreformed amino acids/peptides but this was not so for cellulolytic organisms.

Maeng et al. (1989) also showed an increase in efficiency of microbial growth on fibrous carbohydrates with decreasing dilution rate of rumencontents. If true this may be advantageous to ruminants given low quality forages that must be retained in the rumen for a considerable

period to allow digestibility to be optimised. At the same time the improved ratio of cells: VFA yielded (i.e. P/E ratio) along with the increasedavailability of the total nutrients are both advantageous. Such a mechanism would advantage an animal with (1) a comparatively slowturnover rate of rumen contents (i.e. buffalo vs. cow or goat vs. sheep; see Devendra, 1989) or (2) fauna-free vs. faunated animal (see Bird &Leng, 1985) or animals at high environmental conditions versus cold stressed animals (see Young, 1983).

3.7.5 Amino Acid Requirements of Microbes Digesting Fibre

The organisms in the rumen that are largely responsible for the fermentation of cellulose (Ruminococcus albus, Ruminococcusflavefaciensand Fibrobacter succinogenes (previously called Bacteroides succinogenes) appear to have minimal requirements for aminoacids and grow on ammonia (see Leng, 1991 for discussion). Conversely, organisms important in starch hydrolysis (Butyrivibrio fibrisolvens,Bacteroides ruminicola, Selenomonas ruminantium, Streptococcus bovis and Ruminobacter (Bacteroides) amylophilus (Hobson et al. 1988)readily incorporate amino acid N and in many cases peptides (see Leng, 1991).

Supplementation of sheep fed a poor quality forage with branched chain VFA has been reported to increase the apparent flow of microbial-Nto the duodenum. The apparent stimulation of microbial growth with branched chain VFA has also been shown to increase feed intake on

occasions (Hemsley & Moir, 1963). This together with the suggested requirements for peptides/amino acids by rumen organisms (which onthe basis of the results of Maeng et al. (1989) must now be questioned) has tempted many scientists to explain the increased feed intake ofruminants, on poor quality forages that are supplemented with bypass protein, to the slow release of amino acids, peptides and branchedchain fatty acids to the rumen milieu from the protected protein (see Hunter, 1988; Silva & rskov, 1988a), even though in most studies therewas no evidence of increased digestibility with such supplements in predominately fibre based diets.

The above discussion indicates that the cellulolytic organisms in the rumen even of cattle on straw based diets, are rarely if ever deficient inamino acids, peptides or branched chain VFA in the rumen (see also Maeng et al. 1989). This is not to deny that these organisms may stillneed these nutrients in catalytic amounts but that they are rarely if ever at such low concentrations in rumen fluid to bring about adeficiency.

3.7.6 The Roles of Small Amounts of Fresh Forage in Straw Based Diets

Farmers in developing countries have generally recognised the benefits to cattle of adding a small amount of fresh green herbage to strawbased diets. These practices, which have evolved through trial and error, may have a number of beneficial effects which include the supply of

vitamin A, essential minerals, ammonia, peptides/amino acids in an otherwise unsupplemented diet.

Recently it has been shown that where the supplemental forage in a straw based diet given to sheep is of high digestibility a boost todigestibility of the basal diet occurs even at relatively small levels of supplementation (Juul-Nielsen, 1981; Silva & rskov, 1988a; Ndlovu &Buchanan-Smith, 1985). The rate of digestibility of straw depends on the rate and extent of colonisation of fibre and the biomass of adherentorganisms (Cheng et al. 1989) and the high digestibility forage supplement may act to seed microbes onto the less digestible straw.

On the other hand, other influences cannot be ruled out. For example, in the studies of Silva & rskov (1988a) in the absence of an effect ofsupplemental forage on digestibility, the rumen ammonia levels were often not significantly below 200 mg NH 3-N/1. Where increases indigestibility of the basal forage occurred to supplemental forage the ammonia levels in the rumen were significantly below 200 mg N/1 andthe supplement apparently improved the concentration to above the critical level (see Leng 1991).


18/67

3.7.7 Elimination of Rumen Protozoa and Preservation of the Fauna-Free

State

The physiological research which has shown that there is an increased availability of microbial protein for digestion in fauna-free ascompared to faunated ruminant (see Jouany & Ushida, 1990) has supported the feeding trials with large numbers of animals which hasdemonstrated significantly high feed conversion efficiencies and wool growth rate in sheep without rumen protozoa as compared to controlanimals.

Fauna free cattle on the same intake of a low protein, molasses/urea based diet grew at a 43% greater rate than faunated cattle on the samefeed intake. The improved production was therefore an effect of a higher efficiency of feed utilisation (Bird & Leng, 1978).

The discussion to follow, on the implications of environmental temperature/humidity for the nutrition of ruminants, will indicate why a majorchange in P/E ratio in the nutrients absorbed (i.e. the major difference between faunated and fauna-free ruminants) will be more effective inimproving ruminant production in the tropics as compared to temperate/cold countries. In the tropical areas the available forages used tofeed to ruminants are generally lower in digestibility, lower in true protein and animals are rarely cold, but heat stress at times may be severe.It should also be noted that animals brought into animals houses from fairly could environments may at times suffer severe heat stressthrough a combination of a well insulated fleece or coat and an imbalanced diet.

3.8 Factors Influencing Efficiency of Feed Utilisation

The efficiency with which absorbed nutrients are converted to ruminant products (liveweight, milk etc.) is dependent on precisely meeting theanimal's requirements above maintenance for individual nutrients required for the particular function (see Preston & Leng, 1987). These, attimes, are influenced by body condition as affected by previous health and nutritional history (see Leng, 1989b), the demands for body

temperature control (Blaxter, 1962) and the requirements for substrate oxidation in exercise (or work).

Graham et al. (1959) (see also Blaxter, 1962) showed that the quantitative oxidation of individual nutrients (largely fat) depended on thedegree of heat/cold stress of the animal. A cetogenic substrate was largely used to keep an animal warm when it was required to increase itsmetabolic rate in cold stress. In this report it is assumed that a cold stressed animal will oxidise acetogenic substrate for heat production untilsurplus acetogenic substrate is totally utilised, after which fat mobilisation provides an extra and often the major source of metabolic fuel.The apparently preferential oxidation of circulating acetate leaves a higher ratio of amino acids (and glucose) in the nutrients available forproduction than would be available to an animal in its zone of thermoneutrality. Conversely, an animal that is not cold has more acetogenicsubstrates available for anabolic purposes.

The environment can, thus, alter the partitioning of nutrients into productive functions and therefore affect the efficiencies of feed utilisation.The design of supplements, to balance diets for ruminants, needs to account for the varying demands for nutrients brought about by thethermal environment of the animal.

It is recognised that cold stress in animals often increases voluntary feed intake and rumen turnover rate. And in this way on some diets itincreases microbial cells moving to the lower tract and this has been suggested to increase the P/E ratio in the nutrients available formaintenance or production (see Kennedy et al. 1986).

As an example of how environmental factors can change the nutrient balance available to ruminants for anabolism and maintenance, amodel used previously to predict the relative availability of specific nutrients to a standard steer (see Leng, 1982) has been modified to usewith sheep and includes the effects of cold stress. The model is based on the sheep (closely shorn) used in the studies of Graham etal. (1959) which were fed on a daily basis 600, 1200, or 1800 g of a dried grass pellets and subjected to short periods at environmentaltemperatures ranging from 8 to 40C at a relative humidity of 50%.

The data in Table 3.2 indicate that the need to maintain body temperature may require a considerable proportion of the available acetogenicnutrients to be oxidised. In the absence of a cold stress considerably more of digestible nutrients (and in particular more acetogenicsubstrate) is available for maintenance and synthesis. If in thermoneutral conditions the acetogenic substrate cannot be utilised for synthesisof tissue component because of a low availability of essential amino acids and/or glucose (i.e. imbalance in P/E or G/E) (see Preston & Leng,1987) then acetate must be dissipated as heat. If the animal is able to oxidise the excess substrate but cannot dissipate the heat-generatedbecause environmental temperature and humidity are high then it could allow its body temperature to increase to some extent but eventuallyit must reduce its feed intake. If the animal's body temperature rises, metabolic rate increases through the oxidation of protein (Blaxter, 1962)which may have implications for protein requirements of ruminants in the tropics and differential responses to supplementation in the tropics

as compared to temperate areas.

it means that in hot . The requirements of are high.

Table 3.2: A theoretical assessment of the effects of environmental temperature on the balance of nutrients available for anabolism (Theexample used is from Graham et al. (1959), in which closely shorn sheep were subjected to temperatures from 8 to 40C)

Ration (g dried


19/67

grass/d)

600 1200 1800

Minimal heat production (MHP) 5.8 8.3 10.5

Temperature at MHP (C) 40 33 24

Metabolizable energy intake (MJ) at MHP 5.1 9.8 13.7

Heat production required to combat 5C below

critical temperature (MJ)*2.2 2.2 2.2

Nutrients available (MJ)**from:

Acetic acid

Butyric acid

Propionic acid (G)

Total Volatile Fatty Acids (E)

1.90

0.27

0.54

2.71

3.80

0.54

1.08

5.42

4.75

0.74

1.49

6.98

Microbial protein available (g/d) 72 148 198

P:E ratio (G/MJ)++ 26:1 27:1 28:1

Available P:E ratio (g/MJ) 118:1 45:1 40:1

G:E ratio (MJ/MJ)II 0.25 0.24 0.27

Available G:E ratio 7.71 0.48 0.43

* The heat production for each degree lowering of environmental temperature below the critical temperature was assumed to

increase by 0.44 MJ/24 h (Grahamet al.1959).** The available nutrients are calculated assuming that all the digestible dry matter is digested in the rumen, that the rumen

microbes have a YATP14 and that microbial cell synthesis and VFA production are stoichiometrically related as described by Leng(1982). No allowance was made for a possible increase in dilution rate with increasing feed intake.++ Calulated microbial protein available (g) for digestion relative to VFA (MJ).II Propionate (MJ): acetate plus butyrate (MJ) available; the glucogenic energy ratio The available P:E and G:E ratios are defined as the nutrient ratios after the acetogenic nutrients have been used for bodytemperature control at 5C below the critical temperature. They are calculated assuming that the energy for heat production arises

from the oxidation of acetate and/or butyrate. Grahamet al.(1959) showed fat was the major source of heat and that metabolism ofglucogenic or aminogenic substrate is unaffected by cold stress whereas fat (acetogenic substrate) oxidation accounted for the heat

produced.

The temperature/humidity at which ruminants are cold stressed depends greatly on the level of feed intake, the insulation provided by thehair or wool coat and the environmental conditions prevailing, e.g. wind, rain and availability of shelter. Thus, the environmental temperaturesat which minimum extra heat production to combat the cold stress occurs will probably move through a range of from around 10C to 40C.

3.9 Climate, Supplementation and Intake of Low Quality Forages

There has been vigorous debate on whether supplementation of sheep and cattle on low quality forage based diets with urea and/or bypassprotein increases intake of the basal feed resource (see Leng, 1989b). The differences in results may be hypothesised to be a result of an
http://www.fao.org/docrep/004/t0423e/T0423E03.htm#note2http://www.fao.org/docrep/004/t0423e/T0423E03.htm#note2http://www.fao.org/docrep/004/t0423e/T0423E03.htm#note2http://www.fao.org/docrep/004/t0423e/T0423E03.htm#note3http://www.fao.org/docrep/004/t0423e/T0423E03.htm#note3http://www.fao.org/docrep/004/t0423e/T0423E03.htm#note3http://www.fao.org/docrep/004/t0423e/T0423E03.htm#note4http://www.fao.org/docrep/004/t0423e/T0423E03.htm#note4http://www.fao.org/docrep/004/t0423e/T0423E03.htm#note4http://www.fao.org/docrep/004/t0423e/T0423E03.htm#note6http://www.fao.org/docrep/004/t0423e/T0423E03.htm#note6http://www.fao.org/docrep/004/t0423e/T0423E03.htm#note6http://www.fao.org/docrep/004/t0423e/T0423E03.htm#note5http://www.fao.org/docrep/004/t0423e/T0423E03.htm#note5http://www.fao.org/docrep/004/t0423e/T0423E03.htm#note5http://www.fao.org/docrep/004/t0423e/T0423E03.htm#note6http://www.fao.org/docrep/004/t0423e/T0423E03.htm#note6http://www.fao.org/docrep/004/t0423e/T0423E03.htm#note6http://www.fao.org/docrep/004/t0423e/T0423E03.htm#note5http://www.fao.org/docrep/004/t0423e/T0423E03.htm#note6http://www.fao.org/docrep/004/t0423e/T0423E03.htm#note4http://www.fao.org/docrep/004/t0423e/T0423E03.htm#note3http://www.fao.org/docrep/004/t0423e/T0423E03.htm#note2


20/67

interaction between climate and the balance of nutrients available from a diet. When research results (Australian) on the effects ofsupplementation to balance nutrition of cattle on low quality forages are grouped according to climatic zones a pattern emerges (Figure 3.4).

It appears to be in the tropics and subtropics where poor quality forage intake by cattle is low without supplementation and where significantresponses in feed intake occurs when a non-protein nitrogen deficiency is corrected and extra protein that escapes rumen fermentation isprovided in the diet. It is strongly stressed that supplementation with urea and proteinmeals increases voluntary intake of poor quality foragesby cattle under tropical conditions to approximately the same level of intake as unsupplemented cattle under temperate conditions (Leng,1989b). In this situation the supplement is only correcting a depressed intake back to normal intake.

Figure 3.4: Intake of low digestibility forages by cattle either unsupplemented or supplemented with bypass protein or bypass protein and

urea (Lindsay & Loxton, 1981; Lindsay et al., 1982a,b; Lee et al., 1984; Hennessy, 1984; Perdok, 1987; Kellaway & Leibholz, 1981)

The conclusion that can be drawn from this is that supplements which improve the P/E ratio in nutrients absorbed by cattle fed low qualityforage reduces metabolic heat production. Where metabolic heat production in unsupplemented cattle fed low quality forages would increasebody temperature then the animal reduces its feed intake. This reduction in voluntary feed intake is ameliorated by the supplement whichallows the acetogenic substrate which would otherwise have to be oxidised to be partitioned into synthetic reactions with a resultantdecrease in heat production.

The concept of small increases in P/E ratio being able to reduce metabolic heat and at times therefore allow an animal to consume morefood might explain the effects of increasing levels of urea in a diet on forage intake (when digestibility is no longer increased) and also theoccasional effects on feed intake of branched chain VFA supplements. The concept is that it is a supplement that improves microbial growthefficiency which has an effect on feed intake and this is only seen in the hot conditions when feed intake is depressed.

The interaction of nutrition and climate may explain why there is a stubborn disbelief by some researchers from developed countries (largelyin the temperate areas) of research carried out in developing countries in the tropics. Many of the results of supplementation indicate that aprotein that escapes rumen fermentation stimulates both the level and efficiency of production of milk (or live-weight gain) in ruminants fed oncrop residues (see Figure 3.5).


21/67

The discussion above indicates that ruminants in hot countries have an advantage of not having to oxidise much acetogenic substrate (orbody fat) to keep warm. By balancing the diet with supplements, this acetogenic substrate may be captured in products or oxidised to provide

ATP for assimilation of the additional nutrients into products. In cold/cool countries supplementation with protein is less necessary, as theutilisation of surplus acetate for heat, decreases the need to balance nutrients. As long as feed intake is high (i.e. the diet is highly digestibleand perhaps cold stress stimulates intake) production remains relatively high as the nutrients for heat production are extracted and thebalance used in synthetic reactions. Nevertheless, increases in the efficiency of utilisation are obtained when low protein diets aresupplemented with a bypass protein even in temperate countries (see rskov, 1970; Silva et al. 1989; Leng et al. 1977) and at times feedintake is also stimulated but it is unknown whether the animals in such studies were actually subjected to hot conditions.

Figure 3.5: Schematic relationship between diet quality (metabolisable energy MJ/kg dry matter) and food conversion efficiency (g liveweight

gain/MJ ME) (- - -) (from Webster, 1989). The relationships found in practice with cattle fed on straw or ammoniated straw with increasinglevel of supplementation. Australia (, o,) (Perdok et al., 1988), Thailand () (Wanapat et al., 1986) and Bangladesh () (Saadullah, 1984).Recent relationships developed for cattle fed silages supplemented with fish proteins (Olafsson & Gudmundsson, 1990) (o) and tropical

pastures supplemented with cottonseed meal (Godoy & Chicco, 1990) (*) are also shown. This illustrates the marked differences that resultwhen supplements high in protein are given to cattle on diets of low ME/kg DM

It can be concluded that ruminants in the tropics that are adequately supplemented with small quantities of essential nutrients may produceat the same rate on a lower digestibility feed as an animal on higher digestibility feed in a cold environment.

To emphasise the differences in potential thermal stress of animals under different conditions the average temperature humidity index (THI)(which is an index of potential heat stress conditions for ruminants (see Johnson, 1987) on a monthly basis for Cambridge (England),Chittagong (Bangladesh), Bangkok (Thailand) and Armidale (Australia) are shown in Figure 3.6. The critical THI (72) for high milk producingcows as determined by Johnson (1987) is included in the figure. However, it must be emphasised that in addition to temperature/humidities,the critical THI will depend on the insulation provided by the animal's coat and its behaviour in seeking shelter, as well as the incidence ofwind and rain in addition to level and quality of feed intake.

Many studies have shown that at the same forage intake by ruminants with an already efficient digestion that a supplement of protein thatreaches the small intestine increases the efficiency of feed or metabolisable energy utilisation for growth. This is positive proof that wastefuloxidation of nutrients can occurs (See Figure 3.5). It seems reasonable that, because Blaxter (1962) and his colleagues showed thatacetogenic substrate are largely burned off that the inefficiency of ruminants on forage based diets is a result of acetate being oxidisedwastefully. This points to a major difference in considering the nutrition of ruminants in the tropics as compared with temperate countries.

do e nutrition guideline at the end, at the Nicourguious conditious.


22/67

3.10 Feeding Standards and Feed Evaluation

Most forages consumed by livestock in developing countries have a low digestibility which rarely exceeds 55% and is mostly in the range of4045%. The calculated metabolisable energy in the dry matter (ME/DM), thus, ranges from 7.5 MJ down to 4.8 MJ. Feeding standardsindicate that feeds with a metabolisable energy content, of 7.5 MJ will support growth rates of cattle of approximately 2 g/MJ of ME intake.On a forage at the lowest level of ME, cattle would be in negative energy balance (see ARC, 1980) (also for reference see Webster, 1989).

Figure 3.6: Temperature humidity index (THI) of climates in temperate countries as indicated by Cambridge (U.K.) and Armidale (Australia)as compared to tropical countries as indicated by Bangkok (Thailand) and Mymensingh (Bangladesh). The THI is calculated on the mean of

the maximum-minimum temperatures and humidities

THI(C) = Temp. (dry bulb) + 0.36 Temp. (dew point) + 41.2C

Contrast this with results of supplementary feeding trials based on balancing the nutrition of animals with urea/minerals and bypass protein,where cattle growth rates equivalent to 18 g/MJ of ME intake have been achieved in cattle fed straw (see Figure 3.6). Obviously the presentlyaccepted feeding standards (see ARC, 1980) have been very misleading and can not be used as a means of predicting animal performance.Of vital importance however, is that the application of the concept of balanced nutrition can improve animal growth by 23 fold and theefficiency of animal growth by as much as six fold over previous estimates (a range of 210 fold).

In addition it also shows that although growth rates of cattle are below those on grain based diets cattle on forage based diets can highlyefficiently convert feed to product.

3.10.1 Implications of low Productivity of Ruminants in the Tropics

Low productivity of ruminant livestock has been accepted in developing countries as an inevitable result of the poor feed base and a low feedconversion efficiency. The concept being that there is a large heat production (energy requirement) associated with the ingestion, movement

of digesta along the tract in animals on forages as compared to concentrates (see rskov & Macleod, 1990). This conclusion is contrary tothe conclusions of Leng (1990) and the concept of balanced nutrition presented here.

3.11 Some Basic Explanations for the Inefficiency of Ruminants onForage Diets


23/67

3.11.1 Inefficiency of Acetate Utilisation

The original calorimetric studies of Graham and his colleagues (see Blaxter, 1962) indicated that infused acetate or butyrate were utilised bysheep with low efficiencies, i.e. there was a high heat increment when acetate was given compared with propionate. Considerable effort hassince been expended on testing the hypothesis (or disproving it) that acetogenic substrate is used wastefully. Blaxter and his colleagues(Graham et al. 1959) used diets based on dried grass which was chopped and cubed. It had a metabolisable energy content (M/D) of about8.5 MJ/kg dry matter. As most of the protein in the diet could have been highly soluble, the P/E ratio in absorbed nutrients would have beenrelatively low.

The controversy concerning the efficiency with which acetogenic substrate is utilised may be rationalised at least to some extent byconsidering the balances of nutrients available to the ruminants in the various experiments and the ability or otherwise of the animals tosynthesise fat, dissipate heat or to oxidise substrate to keep warm. For example the presence of small amounts of fish meal, that has aconsiderable amount of protein that escapes the rumen, in a concentrate diet (see rskov & Allen, 1966) provides an explanation for thedifferences between these authors' results and those summarised by Blaxter (1962) where sheep were fed dried grass which may havecontained a highly soluble source of protein.

3.11.2 Requirements for Glucose by Ruminants

The need to manipulate or supplement diets for ruminants in order to

Application of biotechnology to nutrition of animals in developing countries.docx

Documents

Transcript of Application of biotechnology to nutrition of animals in developing countries.docx