Yeast cell-wall polysaccharides regulate ruminal microbial metabolism to enrich lamb with health-promoting fatty...

This study investigated the effects of yeast cell-wall polysaccharides (YCWPs) on lamb meat quality and the mechanisms underlying these effects. Twenty-four lambs were randomly assigned to four groups and were fed a basal diet supplemented with 0 (Control), 0.5 (YCWP 0.5), 1 (YCWP 1), and 2 (YCWP 2) g/day of YCWP, respectively, for 50 days. After a 12-h fast, the animals were slaughtered, and the rumen fluid, rumen digesta, and longissimus lumborum muscles were immediately collected. Fatty acid (FA) composition was analyzed using gas chromatography, and ruminal microbiota was characterized through microbial community sequencing. The results suggested that YCWP 2 supplementation enhanced meat color 45 min postmortem and improved muscle FA profile, as evidenced by the increased redness-greenness value and health-promoting FA levels, respectively. Moreover, microbial diversity analysis showed that YCWP altered rumen bacterial diversity to varying degrees at different doses. At the phylum level, YCWP 1 increased Proteobacteria, Verrucomicrobia, and Tenericutes abundance, whereas YCWP 2 increased Proteobacteria abundance but reduced that of Tenericutes. At the genus level, YCWP 1 increased unclassified Ruminococcaceae, Clostridium, Coprococcus, Succiniclasticum, and Anaerovibrio abundance, whereas YCWP 2 increased those of unclassified Bacteroidales, unclassified Veillonellaceae, and CF231. Furthermore, YCWP 2 modified rumen FA profile by enhancing unsaturated FA production by modulating ruminal biohydrogenation. Correlation analysis showed that changes in rumen bacterial composition correlated with rumen FA profiles, and these FA profiles in turn correlated with the FA composition of lamb meat. These findings provide novel insights into diet-induced regulation of FA composition in ruminant meat.