MEASURING METHANE PRODUCTION FROM RUMINANTS

Transcription

1 MEASURING METHANE PRODUCTION FROM RUMINANTS

2 Measuring Methane Production from Ruminants Edited by HARINDER P.S. MAKKAR Animal Production and Health Section, Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture, International Atomic Energy Agency, Vienna, Austria and PHILIP E. VERCOE School of Animal Biology, Faculty of Natural and Agricultural Sciences, University of Western Australia, Crawley, WA, Australia Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture International Atomic Energy Agency, Vienna, Austria

3 A C.I.P. Catalogue record for this book is available from the Library of Congress. ISBN (HB) ISBN (e-book) Published by Springer, P.O. Box 17, 3300 AA Dordrecht, The Netherlands. Printed on acid-free paper All Rights Reserved 2007 IAEA No part of this work may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission from the Publisher, with the exception of any material supplied specifically for the purpose of being entered and executed on a computer system, for exclusive use by the purchaser of the work.

4 CONTENTS Foreword... Introduction... vii ix 1 Analysis of Methane... 1 S. Lopez and C J. Newbold 2 Measuring Methane Emission of Ruminants by In Vitro and In Vivo Techniques C.R. Soliva and H.D. Hess 3 The SF 6 Tracer Technique: Methane Measurement from Ruminants K.A. Johnson, H.H. Westberg, J.J. Michal and M.W. Cossalman 4 Estimation of Ruminal Methane Production from Measurement of Volatile Fatty Acid Production R.S. Hegarty and J.V. Nolan 5 Measurement of Methane Production Rate in the Rumen Using IsotopicTracers R.S. Hegarty, R.A Leng and J.V. Nolan 6 Measurement of Methane from Grazing Animals the Tunnel Method P.J. Murray, D.C. Chadwick, C.J. Newbold and D.R. Lockyer 7 A Protocol for the Operation of Open-Circuit Chambers for Measuring Methane Output in Sheep Y.J. Williams, L. Klein and A.-D.G. Wright v

5 vi CONTENTS 8 Construction and Operation of Ventilated Hood-Type Respiration Calorimeters for In Vivo Measurement of Methane Production and Energy Partition in Ruminants T. Suzuki, G.J. McCrabb, T. Nishida, S. Indramanee and M. Kurihara Index

6 FOREWORD The world s livestock sector is amidst a major transformation, fuelled by high demand for meat and milk, which is likely to double over the next two decades in developing countries. The major driving force behind this demand for livestock products is a combination of population growth, urbanization and income growth, especially in developing countries. The challenge is to enhance animal productivity without adversely affecting the environment. A key to this is reducing methane emissions from ruminants. The major limitation to ruminant production in many tropical regions of Africa, Asia and Latin America, where a large proportion of the global ruminant population is located, is poor nutrition. The productivity of animals is restricted by the low nitrogen and high fibre content of the native grasses and crop residues, which form the basis of the diets in these regions. Animals on these types of diets emit more methane than animals fed better quality temperate forages. These methane emissions represent a loss of digestible energy to the animal (up to 15%) as well as a threat to the environment. Reducing methane production by ruminants could improve their productivity, provided the efficiency of ruminal metabolism is not compromised, and reduce their contribution to greenhouse gas emissions. The challenge is to devise nutritional strategies and identify dietary components, particularly from locally available plant resources, that reduce methane emissions. However, before new strategies can be developed, it is essential to be able to measure methane emissions accurately to establish baseline values for current practices. Without this, there is no way to establish whether specific plants or new management systems improve methane emissions by lowering them under the baseline. This publication stems from a training workshop that was organized as part of an FAO/IAEA Coordinated Research Project entitled Development and use of rumen molecular techniques for predicting and enhancing productivity. It contains a comprehensive account of the key techniques for measuring methane in vivo. These techniques provide a variety of options for measuring methane emissions ranging from respiration chambers to the tunnel method, which can be used with animals in the field. These techniques will allow baseline estimates of methane emissions to be established in Member States and the extent to which ruminants contribute to greenhouse gas emissions in these countries. This information will be of interest to national agricultural research organizations, extension officers and government officers responsible for formulating environmental policy. They also vii

7 viii FOREWORD provide the opportunity to test new plants for their potential to reduce methane emissions and to help design new management and feeding strategies based on these measurements. The aim of the book is to better equip the readers to measure and monitor methane emissions accurately and meet the challenge of improving productivity from ruminants without damaging the environment.

8 INTRODUCTION Methane is one of the most important greenhouse gasses and approximately 70% of methane emissions are linked to human activities. Domestic ruminants are responsible for 25% of these emissions, which are derived mainly from their gastrointestinal tract but also from their manure. Importantly, the methane produced by ruminants is an energy loss to production and reducing emissions would benefit ruminant production and the environment. The demand for meat, milk and fibre from ruminants is increasing but there is also pressure from society to reduce the impact our production systems have on the environment. Under these circumstances, developing systems for reducing methane emissions seems an appropriate and logical problem to address. Methane emissions derived from the gastrointestinal tract of ruminants are approximately 10 times higher than the emissions from manure. These emissions are a direct result of fermentation processes performed by ruminal microorganisms and, in particular, the archael methanogens, which scavenge hydrogen and use it to produce methane. The amount of methane that is produced is determined by a number of factors including for example, diet, the number of protozoa in the rumen and the number and type of methanogens present; these are not mutually exclusive. The production of methane is a direct energy loss to the animal as well as a source of pollution. Manipulating any or all of these factors could help to reduce methane emissions and achieve our objective of improving productivity without damaging the environment. However, to establish baseline estimates of methane emissions from current practices and assess the impact of new practices introduced to reduce methane emissions, it is essential to be able to quantify methane accurately under different circumstances. Methane emissions can be measured using both in vitro and in vivo techniques. Using and maintaining animals for experimental purposes is expensive. Consequently, in vitro techniques are often the initial choice for investigating strategies for reducing or inhibiting methane production. The in vitro techniques are relatively inexpensive ways to test many different diets, combinations of diets, potential inhibitors and additives for their effects on methanogenesis, simultaneouslyand ix

9 x INTRODUCTION quickly. In these tests, a sample of rumen fluid is used to help simulate normal rumen fermentation in batch or continuous culture. Methane production can be measured in these simulated systems by sampling the gas and analysing its composition, using for example, gas chromatography. Diets, additives and inhibitors that reduce methane production in vitro can then be examined in more expensive in vivo experiments for their potential to mitigate methane emissions in practical feeding situations. The in vivo experiments involve measuring methane in live animals, either in animal houses or under production conditions. The animals, or the head of the animals, are often enclosed in respiration chambers, where the gases that are emitted can be collected and analysed. There are also systems where methane production is measured using isotopic tracers or by inserting inert tracer gases into the rumen. All of these techniques are addressed in this manual. The chapters in this manual have been written by experts with a keen interest in developing systems for reducing methane emissions to improve livestock production without damaging the environment. The techniques they have described are the best and most up-to-date techniques available for quantifying methane in the laboratory and from animals under both production and experimental conditions. The readers are provided with a variety of alternatives for quantifying methane and will find that one technique may suit their circumstances better than the others. For example, attempting to measure methane emissions from ruminants in an enclosed chamber in the heat and humidity associated with a tropical environment will be different to attempting a similar experiment under European conditions. The head box technique described in Chapter 8 and being used in Thailand is a good example of this. Using this technique, only the head of the animal is contained within a respiration box minimizing the effects of the heat and humidity in comparison to retaining the entire animal in an enclosed chamber. The chapters are written in the detail used normally for standard operating procedures and provide detailed descriptions on the assembly and construction of equipment. Additional photos are provided in some chapters that help the reader to visualize what is described in the text, in easy step-wise guides. All of the chapters include literature that is relevant to the technique. The first two chapters deal mainly with in vitro techniques and the following 6 chapters provide an array of in vivo techniques that are used to quantify methane emissions. This manual will enable researchers in both developed and developing countries to choose and establish the most appropriate techniques for quantifying methane emissions accurately for their situations. It will enable researchers to screen plant resources and by-products for their potential to reduce methane emissions and assess the impact of new strategies for reducing methane under production conditions. It will also enable better feeding practices and management systems to be designed that improve productivity while reducing methane emissions. By encouraging more research institutes around the world to establish accurate methods for quantifying

10 INTRODUCTION xi methane emissions, the inventories of the contribution ruminants make to total methane emissions and the impact our efforts to reduce these emissions are having will improve substantially. Harinder P.S. Makkar Animal Production and Health Section Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture International Atomic Energy Agency Vienna, Austria Philip E. Vercoe School of Animal Biology Faculty of Natural and Agricultural Sciences University of Western Australia Crawley, WA, 6009, Australia