Exploring the impact of rumen microbiome on ovine flavor-related compounds and comparing flavor profiles between Tibetan sheep and Small-tail Han sheep.

The characteristic 'mutton flavor', primarily attributed to branched-chain fatty acids (BCFAs), is influenced by various factors including rumen microbes. This study aims to elucidate the disparities in meat flavor compounds and their underlying regulatory mechanisms mediated by rumen microbes between two important sheep breeds on the Qinghai-Tibetan Plateau. We used LC-MS/MS to analyze BCFAs and rumen short-chain fatty acids (SCFAs), along with metagenomic sequencing to characterize the rumen microbiome. Compared to Tibetan sheep, Small Tail Han sheep exhibited significantly higher concentrations of BCFAs, including 4-ethyloctanoic acid (EOA) and 4-methyloctanoic acid (MOA), as well as SCFAs such as pentanoate, glutarate, and propionate. In contrast, acetate levels were inversely correlated with these fatty acids. Metagenomics revealed a predominance of Bacteroidota (formerly Bacteroidetes) and Bacillota (formerly Firmicutes) in sheep. Furthermore, random forest and LEfSe analyses identified seven bacterial biomarkers, including Lactobacillus, Ligilactobacillus, Blautia, Anaerovibrio, Selenomonas, Phocaeicola, Sodaliphilus. Functional analysis indicated differences in carbohydrate degradation capabilities of two breeds. Likewise, strong positive correlations of propionate with MOA, and glutarate with EOA were observed, respectively. The findings are expected to provide critical insights into the potential for modulating meat flavor through nutritional strategies targeting rumen microbes.