Selenium-enriched yeast improves gut health in broilers by modulating the gut microbiota-metabolites-intestinal...

Selenium (Se) is known to improve gut health in animals, yet research on the effects of different dietary Se compounds on the intestinal health of broilers remains limited. Therefore, this study evaluated the effects of sodium selenite (SS), selenium-enriched yeast (SY), selenomethionine (SM), and nano-selenium (NS) on gut microbiota and their metabolites, intestinal antioxidant capacity, immune response, and gut morphology in broilers and investigated the potential molecular mechanisms by which Se influences intestinal function in broilers. A total of 360 1-d-old male yellow-feathered broilers with an average body weight of 37.00 ± 0.17 g were randomly assigned to five treatments, each comprising six replicates with 12 chicks per replicate. Broilers received either a basal diet or a basal diet supplemented with SS, SM, SY, and NS at 0.5 mg Se/kg for 56 d. Data were analyzed using one-way ANOVA with Tukey's post-hoc test for multi-group comparisons, and statistical significance was set at P < 0.05. Supplementation with SY increased ileal concentrations of secretory immunoglobulin A by 74.87% and interleukin-10 (IL-10) by 54.90%, enhanced ileal activities of total superoxide dismutase (T-SOD) by 123.55% and catalase by 197.20%, and elevated cecal acetate by 35.67% and total short-chain fatty acids (SCFAs) by 28.78%, as well as ileal ursodeoxycholic acid concentration by 154.05% (P < 0.05). Dietary SS elevated ileal IL-10 concentration by 44.72% and glutathione peroxidase activity by 93.74% while reducing tumor necrosis factor-alpha level by 26.46% (P < 0.05). Supplemental NS increased cecal concentrations of acetate by 45.56%, propionate by 85.94%, and total SCFAs by 39.68% (P < 0.05). Compared with the SS, SY supplementation improved jejunal total antioxidant capacity by 81.08% and ileal T-SOD activity by 84.22% (P < 0.05). Additionally, dietary Se supplementation increased the abundances of potentially beneficial bacteria, including Lactobacillus, Parabacteroides, Akkermansia, and UCG_005 (P < 0.05). Genes such as CCR9, CD28, MUC2, HTR6, KCNK5, and SLC9A3 were up-regulated, while GIP, SSTR2, SST1, and CRHR1 were down-regulated by SS or SY supplementation, indicating involvement in intestinal function. In summary, SS and SY improved intestinal antioxidant and immune functions in broilers, whereas SY and NS enhanced cecal SCFAs production. Moreover, Se supplementation modulated the cecal microbial community in broilers.