Dietary Diutina rugosa DZ018 modulates rumen microbiota and fermentation while enhancing antioxidant capacity and immune function in sika deer

This study examined the effects of dietary yeast supplementation on antler production performance, serum biochemical indices, rumen fermentation characteristics, and the rumen bacterial community in sika deer (Cervus nippon) during the antler-growing period. Twelve 3-year-old male sika deer were randomly assigned to one of the three experimental diets: a basal diet supplemented with 0 cfu/kg (CON), 1 × 107 cfu/kg (LD), or 1 × 108 cfu/kg (HD) yeast (Diutina rugosa DZ018). No significant differences were observed in antler production performance among treatments. Serum total protein (TP) was significantly higher in the HD group than in the CON group. Yeast supplementation significantly reduced serum malondialdehyde (MDA) levels and significantly increased IgA concentrations. Compared with the CON group, rumen pH was significantly higher in both the LD and HD group, whereas acetate concentration and the acetate-to-propionate ratio were lower. Additionally, yeast supplementation significantly increased rumen bacterial α-diversity, as indicated by higher Chao1 index and Shannon index. The relative abundance of Firmicutes was significantly lower in the LD and HD group than in the CON group. The relative abundance of Bacteroidota, Rikenellaceae_RC9_gut_group and Christensenellaceae_R-7_group were significantly higher in the LD group compared with the CON group. In conclusion, dietary Diutina rugosa DZ018 supplementation enhanced antioxidant capacity and immune function, modulated the rumen bacteria community, and shifted fermentation patterns toward propionate dominance in sika deer. Practically, an appropriate dose (1 × 107 cfu/kg diet) may benefit sika deer health and farm economics.