Effects of dietary live or heat-inactivated autochthonous Bacillus pumilus SE5 on growth performance, immune responses and immune gene expression in grouper Epinephelus coioides.

To evaluate the possible dietary application of live and heat-inactivated probiotic Bacillus pumilus SE5 in grouper Epinephelus coioides, juveniles (14.6 ± 0.2 g) were fed either a basal control diet (without probiotic) or the basal diet supplemented with 1.0 × 108 CFU g−1 live (T1) and heat-inactivated B. pumilus SE5 (T2). The heat-inactivated probiotic significantly improved the final weight, weight gain ( WG) and specific growth rate ( SGR) at day 60 and significantly decreased the feed conversion ratio ( FCR) at day 30 and 60, while the viable probiotic significantly decreased the FCR at day 60 ( P < 0.05). Phagocytic activity, serum complement C3 and IgM levels as well as SOD activity elevated significantly in fish fed the heat-inactivated probiotic for 60 days ( P < 0.05). Furthermore, the heat-inactivated probiotic remarkably up-regulated expression of TLR2 and pro-inflammatory cytokines ( IL-8 and IL-1β) in head kidney ( P < 0.05), but the viable probiotic failed to do so. These results indicated that heat-inactivated B. pumilus SE5 can effectively improve the growth performance and immune responses of E. coioides. [ABSTRACT FROM AUTHOR]