Knapp J R, Laur G L, Vadas P A, Weiss W P, Tricarico J M
Fox Hollow Consulting LLC, Columbus, OH 43201.
Gwinn-Sawyer Veterinary Clinic, Gwinn, MI 49841.
J Dairy Sci. 2014;97(6):3231-61. doi: 10.3168/jds.2013-7234. Epub 2014 Apr 18.
Many opportunities exist to reduce enteric methane (CH4) and other greenhouse gas (GHG) emissions per unit of product from ruminant livestock. Research over the past century in genetics, animal health, microbiology, nutrition, and physiology has led to improvements in dairy production where intensively managed farms have GHG emissions as low as 1 kg of CO2 equivalents (CO2e)/kg of energy-corrected milk (ECM), compared with >7 kg of CO2 e/kg of ECM in extensive systems. The objectives of this review are to evaluate options that have been demonstrated to mitigate enteric CH4 emissions per unit of ECM (CH4/ECM) from dairy cattle on a quantitative basis and in a sustained manner and to integrate approaches in genetics, feeding and nutrition, physiology, and health to emphasize why herd productivity, not individual animal productivity, is important to environmental sustainability. A nutrition model based on carbohydrate digestion was used to evaluate the effect of feeding and nutrition strategies on CH4/ECM, and a meta-analysis was conducted to quantify the effects of lipid supplementation on CH4/ECM. A second model combining herd structure dynamics and production level was used to estimate the effect of genetic and management strategies that increase milk yield and reduce culling on CH4/ECM. Some of these approaches discussed require further research, but many could be implemented now. Past efforts in CH4 mitigation have largely focused on identifying and evaluating CH4 mitigation approaches based on nutrition, feeding, and modifications of rumen function. Nutrition and feeding approaches may be able to reduce CH4/ECM by 2.5 to 15%, whereas rumen modifiers have had very little success in terms of sustained CH4 reductions without compromising milk production. More significant reductions of 15 to 30% CH4/ECM can be achieved by combinations of genetic and management approaches, including improvements in heat abatement, disease and fertility management, performance-enhancing technologies, and facility design to increase feed efficiency and life-time productivity of individual animals and herds. Many of the approaches discussed are only partially additive, and all approaches to reducing enteric CH4 emissions should consider the economic impacts on farm profitability and the relationships between enteric CH4 and other GHG.
减少反刍家畜单位产品的肠道甲烷（CH₄）和其他温室气体（GHG）排放存在诸多机会。过去一个世纪在遗传学、动物健康、微生物学、营养和生理学方面的研究推动了奶牛生产的进步，在集约化管理的农场中，温室气体排放量低至1千克二氧化碳当量（CO₂e）/千克能量校正奶（ECM），而粗放型养殖系统中这一数值超过7千克CO₂e/千克ECM。本综述的目的是定量且持续地评估已被证明可减轻奶牛单位ECM肠道CH₄排放（CH₄/ECM）的方法，并整合遗传学、饲养与营养、生理学和健康方面的方法，以强调为何畜群生产力而非个体动物生产力对环境可持续性至关重要。基于碳水化合物消化的营养模型用于评估饲养和营养策略对CH₄/ECM的影响，并进行了荟萃分析以量化补充脂质对CH₄/ECM的影响。第二个结合畜群结构动态和生产水平的模型用于估计提高产奶量和减少淘汰的遗传和管理策略对CH₄/ECM的影响。这里讨论的一些方法需要进一步研究，但许多方法现在就可以实施。过去在甲烷减排方面的努力主要集中在基于营养、饲养和瘤胃功能改变来识别和评估甲烷减排方法。营养和饲养方法或许能够将CH₄/ECM降低2.5%至15%，而瘤胃调节剂在不影响产奶量的情况下持续减少甲烷排放方面收效甚微。通过遗传和管理方法的组合，包括改善防暑、疾病和繁殖管理、性能提升技术以及设施设计以提高个体动物和畜群的饲料效率和终身生产力，可以实现CH₄/ECM更显著的降低，降幅达15%至30%。这里讨论的许多方法只是部分相加，所有减少肠道甲烷排放的方法都应考虑对农场盈利能力的经济影响以及肠道甲烷与其他温室气体之间的关系。
