Salvianolic Acid C Inhibits Methane Emissions in Dairy Cows by Targeting MCR and Reshaping the Rumen Microbial Community

Background Methane (CH₄) emissions from ruminants significantly contribute to greenhouse gas effects and energy loss in livestock production. Methyl-coenzyme M reductase (MCR) is the key enzyme in methanogenesis, making it a promising target for CH₄ mitigation. This study aimed to identify and validate plant-derived inhibitors by employing molecular docking to screen compounds with strong binding affinity to the F430 active site of MCR and assessing their efficacy in reducing CH₄ emissions. Results Molecular docking analysis identified Salvianolic acid C (SAC) as a potent inhibitor of MCR, exhibiting a strong binding affinity to the F430 active site (binding energy: −8.2 kcal/mol). Enzymatic inhibition assays confirmed its inhibitory effect, with a half-maximal inhibitory concentration (IC₅₀) of 692.3 µM. In vitro rumen fermentation experiments demonstrated that SAC supplementation (1.5 mg/g DM) significantly reduced CH₄ production ( P  < 0.01) without negatively affecting key fermentation parameters. Microbial community analysis using 16S rRNA sequencing and metagenomics revealed that SAC selectively altered the rumen microbiota, increasing the relative abundance of Bacteroidota while significantly reducing Methanobrevibacter ( P  = 0.04). Additionally, metagenomic analysis indicated the downregulation of key methanogenesis-related genes ( mcrA , rnfC ), suggesting a dual mechanism involving direct enzymatic inhibition and microbial community modulation. Conclusions These findings indicate that SAC effectively reduces CH₄ production by inhibiting MCR activity and reshaping the rumen microbial community. As a plant-derived compound with strong inhibitory effects on methanogenesis, SAC presents a promising and sustainable alternative to synthetic methane inhibitors, offering potential applications in mitigating CH₄ emissions in livestock production.