Effects of dietary supplementation of potential probiotic Bacillus subtilis VSGI singularly or in combination with Lactobacillus plantarum VSG3 or/and Pseudomonas aeruginosa VSG2 on the growth, immunity and disease resistance of Labeo rohita

Labeo rohita fingerlings were fed for 60days with basal diet (BD) or one of the following experimental diets: DI (BD+B. subtilis); DII (BD+B. subtilis+L. plantarum); DIII (BD+B. subtilis+P. aeruginosa) and DIV (BD+B. subtilis+P. aeruginosa+L. plantarum). Various growth and immune parameters were examined at 30 and 60days postfeeding. The fish group fed DIV diet had better improvement (P<0.05) in weight gain, specific growth rate (SGR) and feed conversion ratio (FCR) than the control and other treatment groups. The serum lysozyme activities, alternative complement pathway activity, phagocytic activity and respiratory burst activity in head kidney macrophages of L. rohita increased significantly in the experimental groups throughout the trial period. Superoxide dismutase increased significantly in the experimental groups, except DI fed group, after 60days of feeding. A significant improvement in serum IgM level was observed in the treatment groups at 30days of feeding only. Further, fish fed the DIV diet had highest (P<0.05) postchallenge survival rate (86.6%), followed by DII (73.3%) and DIII (66.6%) against A. hydrophila infection. Considering these promising results, we suggest that a multi-species probiotic supplementation in equal proportions for 60days can effectively improve growth and immunity of L. rohita.