Screening and Functional Prediction of Rumen Microbiota Associated with Methane Emissions in Dairy Cows

gricultural greenhouse gas emissions account for 14.5% of global anthropogenicemissions, with beef and dairy cattle contributing 35% and 30% of global livestock emissions, respec-tively. This study focuses on dairy cattle, exploring the relationships between rumen microbiota andmethane emission. Using a laser methane detector (LMD), methane emissions from 968 lactatingcows were measured, and 107 cows were selected for high and low emission groups. The resultsshowed that the abundance ofBacteroidalesandPrevotellaceaein the rumen of high methane-emittingcows was significantly higher than that in the low methane-emitting cows. Additionally, it was foundthat bacterial functions related to biosynthesis and carbohydrate metabolism were more active inthe high methane-emitting cows. These findings provide new insights for developing strategies toreduce methane emissions, supporting the sustainable development of the dairy industry. Agricultural activities are a significant contributor to global greenhouse gas emissions, accounting for 14.5% of total anthropogenic emissions. Specifically, greenhouse gas emissions from beef cattle and dairy cattle constitute 35% and 30% of total global livestock emissions, respectively. This study focuses on dairy cattle, exploring the complex relationships between rumen microbiota and methane emission. The methane emissions of 968 lactating Holstein cows were measured using a laser methane detector (LMD, Shanghai Hesai Technology Co., Ltd., Shanghai, China). Among the measured cows, 107 individuals were further selected into high (HME) and low methane-emitting (LME) groups, including 50 cows in the HME group and 57 in the LME group. This study analyzed differences in rumen microbiota and microbial functions between cows with varying levels of methane emissions. The results showed significant differences in the Simpson and Pielou indices of rumen bacterial communities between the HME and LME groups. Beta diversity analysis revealed significant differences in microbial community structure between the two groups. It was found that the abundance of Bacteroidales and Prevotellaceae in the rumen of cows in the HME group cows was significantly higher than that of cows in the LME group (LDA > 3, p < 0.05). Additionally, bacterial functions related to biosynthesis and carbohydrate metabolism were more active in the HME group. This study revealed distinct differences in the rumen bacterial communities between HME and LME cow in Chinese Holstein cattle, and identified specific bacteria and their functional differences in the HME group. The microbial characteristics and metabolic pathways provide new insights for developing strategies to reduce methane emissions, supporting the sustainable development of the dairy industry.