Effectiveness of Bacillus subtilis on growth and survival of common carp larva in non-earthen ponds

A feeding experiment was conducted to investigate the effect of Bacillus subtilis bacterium and its suitable level on survival and growth rate of larva Cyprinus carpio Mirzakoochek fisheries education center. B. subtilis bacterium isolated from Cyprinus carpio intestine was added to commercial carp feed as a probiotic. Five diets were prepared by soaking carp feed in to the B. subtilis suspension to achieve 104, 105, 106and 107 levels with a non-treated control. After 28 days, the larva carp fed diet at level 106, showed a higher mean weight gain (1196.43mg). The mean weight gain showed a decreasing trend as the B. subtilis level decreased and increased from 106 in the diets. There were significant differences (P<0.05) in weight gain, daily growth and feed conversion ratio (FCR) among treated and control groups. There were significant differences (P<0.05) among treatments and control in survival rate but no significant differences (P>0.05) in water quality and biochemical composition among treated and control groups. It was concluded that the tested strain may be a promising probiotics for larva C. carpio at a level of 106 B. subtillis in to the carp feed.