Agriculture, Forestry, and Other Land Use (AFOLU) is unique among the sectors considered in this volume, since the mitigation potential is derived from both an enhancement of removals of greenhouse gases (GHG), as well as reduction of emissions through management of land and livestock (robust evidence; high agreement). The land provides food that feeds the Earth’s human population of ca. 7 billion, fibre for a variety of purposes, livelihoods for billions of people worldwide, and is a critical resource for sustainable development in many regions. Agriculture is frequently central to the livelihoods of many social groups, especially in developing countries where it often accounts for a significant share of production. In addition to food and fibre, the land provides a multitude of ecosystem services; climate change mitigation is just one of many that are vital to human well-being (robust evidence; high agreement). Mitigation options in the AFOLU sector, therefore, need to be assessed, as far as possible, for their potential impact on all other services provided by land. [Section 11.1]

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Agriculture, Forestry and Other Land Use (AFOLU)

The goal of this review was to analyze published data related to mitigation of enteric methane (CH 4 ) emissions from ruminant animals to document the most effective and sustainable strategies. Increas- ing forage digestibility and digestible forage intake was one of the major recommended CH 4 mitigation practices. Although responses vary, CH 4 emissions can be reduced when corn silage replaces grass silage in the diet. Feeding legume silages could also lower CH 4 emissions compared to grass silage due to their lower fiber concentration. Dietary lipids can be effec- tive in reducing CH 4 emissions, but their applicabil- ity will depend on effects on feed intake, fiber digest- ibility, production, and milk composition. Inclusion of concentrate feeds in the diet of ruminants will likely decrease CH 4 emission intensity (Ei; CH 4 per unit animal product), particularly when inclusion is above 40% of dietary dry matter and rumen function is not impaired. Supplementation of diets containing medium to poor quality forages with small amounts of concen- trate feed will typically decrease CH 4 Ei. Nitrates show promise as CH 4 mitigation agents, but more studies are needed to fully understand their impact on whole-farm greenhouse gas emissions, animal productivity, and animal health. Through their effect on feed efficiency and rumen stoichiometry, ionophores are likely to have a moderate CH 4 mitigating effect in ruminants fed high-grain or mixed grain-forage diets. Tannins may also reduce CH 4 emissions although in some situations intake and milk production may be compromised. Some direct-fed microbials, such as yeast-based products, might have a moderate CH 4 -mitigating effect through increasing animal productivity and feed efficiency, but the effect is likely to be inconsistent. Vaccines against rumen archaea may offer mitigation opportunities in the future although the extent of CH 4 reduction is like- ly to be small and adaptation by ruminal microbes and persistence of the effect is unknown. Overall, improv- ing forage quality and the overall efficiency of dietary nutrient use is an effective way of decreasing CH 4 Ei. Several feed supplements have a potential to reduce CH 4 emission from ruminants although their long-term effect has not been well established and some are toxic or may not be economically feasible.

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Special topics--Mitigation of methane and nitrous oxide emissions from animal operations: I. A review of enteric methane mitigation options.

The livestock sector supports about 1.3 billion producers and retailers, and contributes 40-50% of agricultural GDP. We estimated that between 1995 and 2005, the livestock sector was responsible for greenhouse gas emissions of 5.6-7.5GtCO(2)e yr(-1). Livestock accounts for up to half of the technical mitigation potential of the agriculture, forestry and land-use sectors, through management options that sustainably intensify livestock production, promote carbon sequestration in rangelands and reduce emissions from manures, and through reductions in the demand for livestock products. The economic potential of these management alternatives is less than 10% of what is technically possible because of adoption constraints, costs and numerous trade-offs. The mitigation potential of reductions in livestock product consumption is large, but their economic potential is unknown at present. More research and investment are needed to increase the affordability and adoption of mitigation practices, to moderate consumption of livestock products where appropriate, and to avoid negative impacts on livelihoods, economic activities and the environment.

Greenhouse gas mitigation potentials in the livestock sector

Escalating anthelmintic resistance has made it essential to develop alternative ways of worm management for reducing selection for worm resistance, and one of the most promising approaches is to treat only those animals unable to cope with worm challenge, thus favouring unselected worms originating from untreated animals. Only clinical evaluation of anaemia (FAMACHA system) and the body condition score are regarded as being of practical value or having potential, respectively, for repeatedly examining flocks or herds and identifying individuals for treatment. Only the FAMACHA system has been tested well enough for use under practical farming conditions. However, further investigation is needed on its effect on animal production, and methods to reduce labour. Trials over several seasons showed that most sheep under severe Haemonchus contortus challenge required no, or only one treatment over a full summer season. A small minority (usually 80%) and treatment costs dropped by approximately 58%. The heritability of FAMACHA values obtained by clinical evaluation was high at 0.55 +/- 0.17% in a Merino stud with +/- 550 young rams and ewes which were the progeny of 21 sires. The FAMACHA system may not be as applicable to goats as to sheep, but further work is necessary. The main benefits of the system are the reduction in treatments, its use for discriminating between animals of varying ability to cope with infection (thus allowing genetic selection), and its lowering of selection pressure on H. contortus for anthelmintic resistance.

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The FAMACHA system for managing haemonchosis in sheep and goats by clinically identifying individual animals for treatment.

By Alain F. Zuur, Elena N. Ieno and Graham M. Smith, New York, Springer, 2007, xxvi + 672 pp., £54.00 or US$84.95 (hardback), ISBN 978-0-387-45967-7 As stated in the preface, finding a suitable and...

Analysing ecological data

In Australia, agriculture is responsible for ~17% of total greenhouse gas emissions with ruminants being the largest single source. However, agriculture is likely to be shielded from the full impact of any future price on carbon. In this review, strategies for reducing ruminant methane output are considered in relation to rumen ecology and biochemistry, animal breeding and management options at an animal, farm, or national level. Nutritional management strategies have the greatest short-term impact. Methanogenic microorganisms remove H2 produced during fermentation of organic matter in the rumen and hind gut. Cost-effective ways to change the microbial ecology to reduce H2 production, to re-partition H2 into products other than methane, or to promote methanotrophic microbes with the ability to oxidise methane still need to be found. Methods of inhibiting methanogens include: use of antibiotics; promoting viruses/bacteriophages; use of feed additives such as fats and oils, or nitrate salts, or dicarboxylic acids; defaunation; and vaccination against methanogens. Methods of enhancing alternative H2 using microbial species include: inoculating with acetogenic species; feeding highly digestible feed components favouring ‘propionate fermentations’; and modifying rumen conditions. Conditions that sustain acetogen populations in kangaroos and termites, for example, are poorly understood but might be extended to ruminants. Mitigation strategies are not in common use in extensive grazing systems but dietary management or use of growth promotants can reduce methane output per unit of product. New, natural compounds that reduce rumen methane output may yet be found. Smaller but more permanent benefits are possible using genetic approaches. The indirect selection criterion, residual feed intake, when measured on ad libitum grain diets, has limited relevance for grazing cattle. There are few published estimates of genetic parameters for feed intake and methane production. Methane-related single nucleotide polymorphisms have yet to be used commercially. As a breeding objective, the use of methane/kg product rather than methane/head is recommended. Indirect selection via feed intake may be more cost-effective than via direct measurement of methane emissions. Life cycle analyses indicate that intensification is likely to reduce total greenhouse gas output but emissions and sequestration from vegetation and soil need to be addressed. Bio-economic modelling suggests most mitigation options are currently not cost-effective.

Ruminant enteric methane mitigation: a review

Australian sheep and wool handbook.

Nitrate may serve as a non-protein nitrogen (NPN) source in ruminant diets while also reducing enteric methane emissions. A study was undertaken to quantify methane emissions of cattle when nitrate replaced urea in a high concentrate diet. Twenty Angus steers were allocated to two treatment groups and acclimated to one of two iso-energetic and iso-nitrogenous finisher rations (containing NPN as urea or as calcium nitrate), with all individual feeding events recorded. A single methane measurement device (C-lock Inc., Rapid City, SD, USA) was exchanged weekly between treatments (2 × 1-week periods per treatment) to provide estimations of daily methane production (DMP; g CH4/day). A 17% reduction in estimated DMP (P = 0.071) resulted from nitrate feeding, attributed to both a tendency for reduced dry matter intake (DMI; P = 0.088) and H2 capture by the consumed nitrate. NO3-fed cattle consumed a larger number of meals (14.69 vs 7.39 meals/day; P < 0.05) of smaller size (0.770 vs 1.820 kg/meal) each day, so the average interval between a feeding event and methane measurement was less in NO3-fed cattle (3.44 vs 5.15 h; P < 0.05). This difference could potentially have skewed the estimated DMP and contributed to the tendency (P = 0.06) for NO3-fed cattle to have a higher methane yield (g CH4/kg DMI) than urea-fed cattle. This study found short-term methane emission measurements made over 2 weeks (per treatment group) were adequate to show dietary nitrate tended to reduce emission and change the feeding pattern of feedlot cattle. Changes in feeding frequency may have confounded the ability of short-term methane measurements to provide data suitable for accurately estimating methane per unit feed intake.

Methane emissions and feeding behaviour of feedlot cattle supplemented with nitrate or urea

The present paper reviews estimation methods for measuring pasture intake of individual grazing animals, in particular, the use of indigestible plant markers. Natural alkanes and alcohols function essentially as an internal marker and thus accommodate differences in forage digestibility among individuals and those arising from interactions between supplement and forage. An estimate of diet composition partitions total intake into its component plant species. Estimates of diet composition require correction for incomplete faecal marker recovery, where relative recoveries (i.e. the recovery of the alkanes relative to each other) suffice. If estimates of whole-diet digestibility are also wanted, actual faecal alkane recoveries must be used. Using known labelled supplement intakes as a means of estimating the intake of all other diet components avoids the need to dose animals separately with synthetic alkanes. The results, problems and possible workarounds for a commercial system under development to estimate individual animal pasture intakes using known labelled-supplement intakes are outlined. A prototype bin system was trialled and, despite many initial technological problems, it showed enough promise for Sapien Technology to continue to develop the system with Proway Livestock.

The trials and tribulations of estimating the pasture intake of grazing animals

This book covers a broad range of topics relevant to the sheep and wool industry in all the main regions of the world. Despite the importance of the sheep industry to Australia, the previous edition was the first publication to have brought together a comprehensive treatment of these topics. This revised book significantly expands on the earlier edition, containing 11 new chapters with all previous chapters updated and expanded. This book is fully international in scope, future developments in all areas are discussed and the sheep meat aspects of the industry are covered in more depth. The contributing authors are influential in the industry through their employment in international Universities, Departments of Primary Industry, research organisations and private companies. The book is designed as a text for tertiary undergraduate and postgraduate students in all years of their courses. It describes the principles upon which various activities in the sheep and wool industry are based, together with the practical implications of these principles. This comprehensive book will also be of interest and benefit to all those involved in the sheep and wool industry, including producers, wool classers, shearers, brokers, traders, exporters and processors. It covers all aspects of the international sheep and wool industry from paddock to plate and from farm to fabric.

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David Cottle

Papers

Ruminant enteric methane mitigation: a review

Australian sheep and wool handbook.

Methane emissions and feeding behaviour of feedlot cattle supplemented with nitrate or urea

The trials and tribulations of estimating the pasture intake of grazing animals

International sheep and wool handbook