Effects of dietary Bacillus subtilis C-3102 on the production, intestinal cytokine expression and autochthonous bacteria of hybrid tilapia Oreochromis niloticus ♀ × Oreochromis aureus ♂

Bacillus spp. are widely used in aquafeeds as probiotics for enhanced growth performance, innate immune responses, and disease resistance. The present study aimed to evaluate the effects of low doses of dietary Bacillus subtilis C-3102 on the production, intestinal cytokine expression and adhesive bacteria of hybrid tilapia Oreochromis niloticus ♀ × Oreochromis aureus ♂. Juvenile hybrid tilapia were fed B. subtilis C-3102 at doses of 0 (CK), 2.5 × 105 (Ta) and 5.0 × 105 (Tb) CFU g− 1 of diets for 56 days. The results showed that different diets had no effects on fish growth performance. The B. subtilis supplement was detected in the gut wall of fish treated with 5.0 × 105 CFU g− 1 at 28 days and 56 days by both plate culture and PCR-DGGE methods, while it was only identified in fish treated with 2.5 × 105 CFU g− 1 at 56 days by PCR-DGGE. Supplementation of dietary B. subtilis C-3102 altered the autochthonous gut bacterial communities, significantly increased (P < 0.05) the total amounts of adhesive viable bacteria, induced upregulation of intestinal cytokine expression (IL-1b, TGF-β and TNF-α) and downregulation of intestinal HSP70. Thus dietary supplement of B. subtilis C-3102 at low dose (105 CFU g− 1) is beneficial to tilapia health.