Ruminant methane mitigation: microbiological mechanisms and integrated strategies for sustainable livestock production in the context of climate change

Ruminant methane (CH4) emissions not only cause serious environmental problems but also reduce the energy efficiency of animal feed. Rumen microbial fermentation is a major source of CH4 emissions, and understanding the diversity and community structure of rumen microbes, and the relationship between feed efficiency and CH4 emissions, is key to reducing CH4 emissions. Strategies such as feed modification, microbial regulation and additive application have shown some CH4 mitigation. For example, the addition of fats and fatty acids to the diet composition and the use of probiotics and microbial repellents can change the rumen microbial community structure and improve feed digestibility. Meanwhile, specific chemical analogues and plant secondary metabolites as additives can specifically inhibit the growth of methanogenic archaea and reduce CH4 production. Although multiple CH4 mitigation strategies have been evaluated for reducing CH4 emissions from ruminants, there has been no comprehensive discussion in unravelling the molecular mechanisms of microbial fermentation processes and specific CH4 inhibitors targeting metabolic pathways of methanogens. Therefore, this paper discusses the diversity and community structure of microorganisms in the rumen, methanogenic pathways, and the molecular mechanisms underlying the role of various CH4 mitigation strategies in metabolic reactions and CH4 production pathways in ruminants. This in-depth understanding can help develop more effective CH4 mitigation strategies that can improve the productivity and sustainability of livestock operations while reducing greenhouse gas emissions. The article concludes by outlining important prospects and directions for future research targeting rumen microbial CH4 mitigation and livestock sustainability.