Response of rumen methane production and microbial community to different abatement strategies in yaks

Background Developing region-specific dietary strategies is crucial for mitigating methane (CH4 ) emissions from yaks. However, there is a lack of tailored emission reduction strategies for yak production in the Qinghai-Tibet Plateau region. This study utilizes an in vitro rumen fermentation technique (Based on the ANKOMRF gas production measurement system) to investigate the effects of different dietary interventions on CH4 production from regional yaks. The selected strategies-Sodium Nitrate solution, regional Medicago sativa L., and regional Helianthus tuberosus L.-were chosen for their potential to reduce CH4 production through various mechanisms: Sodium Nitrate as a methanogenesis inhibitor, Medicago sativa L. for its high nutritional value and its ability to modulate microbial fermentation, and Helianthus tuberosus L. due to its inulin content, which promotes beneficial microbial activity. These dietary interventions aim not only to reduce CH4 production but also to support rumen health and productivity. In addition, gas chromatography and microbial sequencing techniques were employed to identify the optimal emission reduction strategy for regional yaks and to elucidate the key factors influencing the efficacy of these strategies. Results The results indicate that supplementing the confined feeding ration (FR group) with Sodium Nitrate (12 mmol/L, FRN group), Medicago sativa L. (25%, FRM group), and Helianthus tuberosus L. (3%, FRH group) all have the effect of reducing CH4 production from yak rumen. Among these interventions, the FRM group exhibits the most significant reduction, with a decrease in rumen CH4 production by 42.76% compared to the FR group. The dry matter digestibility, total volatile fatty acids (TVFA), propionate, and butyrate levels in all groups were higher than those in the FR group. However, only the FRM group reached a significant level (P < 0.01). The pH values were significantly lower than those in the FR group (P < 0.01) across all groups. Each group exhibited distinct clustering patterns in bacterial and archaeal communities compared to the FR group (P < 0.05). The alpha diversity of bacterial communities was significantly lower than that of the FR group (P < 0.01), while the alpha diversity of archaeal communities was significantly higher than that of the FR group (P < 0.01). Taxa such as Lachnospiraceae, Clostridium, Treponema, Methanomicrobiaceae, Methanosphaera, and Methanoplanus were enriched in the FR group. Conclusions CH4 production from yak rumen were significantly negatively correlated with substrate crude protein (CP) levels, fermentation fluid TVFA levels, alpha diversity of archaeal communities, and the relative abundance of Selenomonas and Megasphaera in bacterial communities (P < 0.01). Conversely, CH4 production were significantly positively correlated with the relative abundance of Methanoplanus in archaeal communities (P < 0.01). From the perspective of CH4 gas production, the ranking of emission reduction effectiveness for different mitigation strategies is as follows: FRM group > FRH group > FRN group.