Anita Bhatnagar and Ritu Lamba
The present communication deal with the identification of probiotic strain isolated from the intestine of Cirrhinus mrigala (Mrigal) on the basis of phylogenetic analysis and nucleotide homology and was found similar to Bacillus cereus strain SL1. The strain was further investigated for its probiotic abilities; acid and bile tolerance, autoaggregation, coaggregation and hydrophobicity. A dietary experiment of 90 days was carried out to examine its effect on the growth, digestive enzyme activity and survival of C. mrigala. Four isonitrogenous and isocaloric diets were prepared and B. cereus was incorporated in the experimental diets; T1, T2 and T3 at three different levels in the proportion of 2 × 104, 2 × 105 and 2 × 106 cells 100 g-1 of feed respectively, along with a control diet TC without probiotic. After 90 days, the group of mrigal fed on probiotic supplemented diets showed significantly (P<0.05) better growth, specific growth rate (SGR), feed conversion ratio (FCR) than those fed with basal diet (control) with best result for diet T2 (P<0.05). Values of digestive enzyme activities (protease, amylase and cellulose) and carcass protein were also significantly (P<0.05) higher and excretion of metabolites (ammonia and phosphate) were lower in groups fed with diet T2. When probiotic supplemented diet fed fish were challenged with pathogenic Aeromonas hydrophila by immersion for 10 days, all probiotic fed groups showed high survival in comparison to group fed on control diet without probiotic supplementation indicating immunostimulating effect
