反刍家畜胃肠道甲烷排放与减排策略

反刍家畜胃肠道甲烷排放是重要的温室气体排放源,减少反刍家畜胃肠道甲烷排放有助于缓解全球温室效应和提高家畜饲养效率。本论文从中国反刍家畜胃肠道甲烷排放现状、瘤胃甲烷生成机制、甲烷生成的日粮营养影响因子和甲烷减排策略与潜力4个方面系统综述反刍家畜胃肠道甲烷排放的研究进展。目前,中国反刍家畜甲烷总排放量超过10 Tg,占全球胃肠道甲烷排放的比例超过15%。反刍家畜胃肠道甲烷排放主要来自瘤胃和后肠道,其中瘤胃甲烷占胃肠道甲烷生成总量的80%以上。二氧化碳还原路径利用瘤胃内的氢和二氧化碳合成甲烷,是瘤胃内生成甲烷的主要路径。瘤胃内的氢还可被相关微生物利用,合成挥发性脂肪酸和微生物蛋白等代谢产物,进而被机体利用。减少反刍家畜胃肠道甲烷排放的关键在于促进瘤胃内氢的利用,以及阻断瘤胃内的氢被甲烷菌利用合成甲烷。甲烷减排的日粮营养调控策略包括优化日粮组成、改善饲料品质、提高瘤胃流通速率、添加氢池和甲烷抑制剂等。大多数营养调控策略的甲烷减排效果小于40%,最新研制的3-NOP抑制剂的甲烷减排效果最高可达80%。但是,一些减排策略的产业化应用还受添加剂残留、抗生素禁用、食品安全、产品价格和消费者喜好等因素影响。牧场管理和遗传选育也是降低甲烷排放量的重要手段,过去100年来已实现每千克标准乳的甲烷排放量减排效果为57%。未来反刍家畜胃肠道甲烷研究将主要集中在低排放品种的遗传选育、不同营养调控策略间的组合效果、甲烷减排的经济效益和可持续性、家畜生长性能与健康、食品安全、消费者喜好等方面。

Enteric methane emissions and mitigation strategies in ruminants

Enteric methane emissions from ruminants is an important source of greenhouse gas production. Reducing enteric methane emissions from ruminants helps to alleviate global greenhouse effect and improve livestock feed efficiency. This study will review the latest researches of enteric methane emissions, and includes enteric methane emissions in China, mechanism of ruminal methanogenesis, the nutritional factors that affect methanogenesis, and strategies for methane inhibition. At present, enteric methane emissions exceed 10 Tg in China, which accounting for more than 15% of global enteric methane emissions. The enteric methane is mainly produced in the rumen and hindgut, and the methane from rumen accounts for more than 80% of enteric methane production. The carbon dioxide reduction is the major pathway of ruminal methanogenesis, which uses abundant hydrogen and carbon dioxide to produce methane. Hydrogen can also be used to produce volatile fatty acids and microbial proteins which can be utilized by the livestock. The key to reducing methane emissions is to promote the hydrogen utilization in the rumen and prevent hydrogen utilization from methanogenesis. Nutritional mitigation strategies include optimizing diet composition, improving feed quality, increasing rumen passage rate, adding hydrogen sinks and methane inhibitors. Most nutritional strategies have less than 40% reduction of enteric methane emissions, except the newly developed inhibitor, 3-NOP, which can reduce methane emissions by up to 80%. However, the industrial application of some strategies is also affected by other factors, such as additive residues, antibiotics prohibition, food safety, production prices, and consumer preferences. Farm management and genetic selection are also important strategies to reduce the methane emissions, and can reduce the methane emissions by 57% in terms of g·kg^-1 milk during the recent 100 years. Further studies can be focused on genetic selection of low-emission breeds, the combined effects of different nutritional strategies, the economic benefits and sustainability of methane emissions reduction, livestock growth performance and health, food safety, and customer preferences and other aspects.