Dietary Bile Acids Improve Serum Antioxidant Status and Modulate Fecal Microbiota in Culled Ewes

This study aimed to investigate the effects of dietary bile acids (BA) supplementation on serum antioxidant capacity, fecal fermentation characteristics, microbial diversity, and community composition in culled ewes. Twenty 5-year-old culled Hu ewes with similar body weights (42.95 ± 1.07 kg) were randomly allocated to two groups (n = 10 per group). The control group (CON) received a basal diet, while the treatment group (BA400) was fed the same basal diet supplemented with 400 mg/kg BA. Compared with the CON group, the BA400 group showed enhanced serum activities of total antioxidant capacity, superoxide dismutase, and glutathione peroxidase, while also showing reduced concentrations of cortisol, malondialdehyde, and reactive oxygen species (p < 0.05). Fecal pH, ammonia nitrogen, total volatile fatty acids, and the concentrations and proportions of individual volatile fatty acids remained unaffected by BA supplementation (p > 0.05). Microbial analysis revealed that the BA400 group exhibited higher fecal bacterial richness and diversity than the CON group (p < 0.05). Analysis of similarities revealed significant differences between the CON and BA400 groups (R = 1.000, p = 0.007). Specifically, BA supplementation increased the relative abundances of beneficial taxa, including Verrucomicrobiota and Akkermansia, while decreasing potentially pathogenic bacteria such as Campylobacterota and Proteobacteria. These findings indicate that dietary BA supplementation improves serum antioxidant capacity and modulates fecal microbial diversity and community structure in culled ewes, suggesting that hindgut microbiota may contribute to the health benefits of BA supplementation in ruminant production.