Acetate-based Syntrophy Enhances Methane Production Potential of Ruminant Feces

Jian Liu¹Yujie Sha^1*Run Dang²Lifeng Zhou²Meng Zhou³Yang Tan²Jinming Wang⁴Ge Ran⁴Wei Xie⁴Dong Xia⁵Luotong Wang⁶Xingtang Zhao¹Bok-Min Goi⁶Jiafeng Yu^1*Leilei Xiao²

• ¹Dezhou University, Dezhou, China
• ²Chinese Academy of Sciences Yantai Institute of Coastal Zone Research, Yantai, China
• ³Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Harbin, China
• ⁴Yantai University of Science and Technology, Yantai, China
• ⁵Dezhou Animal Husbandry and Veterinary Career Development Center (Dezhou Animal Disease Prevention and Control Center), Dezhou, China
• ⁶Universiti Tunku Abdul Rahman (UTAR), Kajang, Malaysia

Livestock feces contribute to approximately 32% of global methane emissions. Although ruminants are generally believed to have a higher methane production potential than non-ruminants, the dominant pathways and key regulatory processes underlying methane generation in ruminants remain poorly understood, impeding effective manure management and accurate livestock emission assessments. In this study, metagenomic and carbon isotope techniques were employed to investigate methane production potential and key pathways in sheep, pig, chicken, and duck feces. Methane production potential of ruminant sheep feces were significantly higher (approximately threefold) compared to that of non-ruminants. Isotopic analysis of methane sources revealed that sheep feces primarily produce methane through acetoclastic pathway, whereas the other three likely rely on CO2 reduction. Metagenomic analysis of methanogenic pathways further indicated that the abundance of functional genes associated with acetoclastic methanogenesis is significantly higher in sheep feces compared to the other three. Moreover, the co-occurrence network analysis highlighted a tightly coordinated, cross-species partnership between fermentative acetogenic bacteria and methanogenic archaea in the sheep fecal microbiome. Together, our findings provide insights into some key methanogenic pathways, such as acetoclastic methanogenesis, contributing to high methane production from ruminant feces.