AbstractTo investigate the supplemental effects of Bacillus subtilis C‐3102 on the production, hatching performance, egg quality, serum antioxidant capacity and immune response of laying breeders, a total of 480 Xuefeng black‐bone (25‐week‐old) hens were randomly assigned into four treatment groups: Hens fed the basal diets with 0 (CON), 3.0×105 (BS‐1), 6.0×105cfu/g (BS‐2) and 9.0×105 (BS‐3) cfu/g of B.subtilis C‐3102. As the B.subtilis C‐3102 level increased, egg weight (linear, p<0.01; quadratic, p=0.003), fertility (linear, p=...