Microbial regulatory pathways of methane emission reduction in the rumen of ruminants

<p indent="0mm">The large amount of greenhouse gas emissions produced by human activities is an important cause of global warming. As the second largest greenhouse gas in the atmosphere, methane emissions seriously affect human health, ecosystem and food security. Low-carbon emission reduction is a common goal of the world. Methane emissions from ruminants, more than 90% of which comes from the rumen, contribute about 17% of total methane emissions worldwide. Rumen methanogenesis in ruminants is the result of direct process of microorganisms, and its methane emission reduction methods have been extensively studied. However, the specific mechanism of methane emission reduction strategies is still unclear, which prevents the development of effective and precise approaches. Therefore, from the perspective of rumen microorganisms and methanogenesis mechanism, this paper summarizes the existing methane emission reduction mechanisms and corresponding methods for different rumen microbiota, including reducing the abundance of methanogens or inhibiting methanogenic pathway, reducing hydrogen production or competing for hydrogen by acting on rumen bacteria and fungi, and indirectly affecting methanogens by defaunation. At the same time, this paper proposes three future development directions of methane reduction in ruminants, including phage therapy, anaerobic oxidation of methane, and early regulation of the rumen microbiome, aiming to provide reference for the effective design and comprehensive application of ruminant methane emission reduction measures in the future.