Evaluation of probiotic potential of Bacillus strains on growth performance and physiological responses in Penaeus vannamei

This study was conducted to exhibit the effectiveness of four different Bacillus sp., that is Bacillus subtilis, B. megaterium, B. cereus and B. infantis on growth performance and physiological response in Penaeus vannamei. Experimental diets were identical in all the aspects except Bacillus incorporation: control (basal diet without probiotic) and four treatment diets T1 (basal diet + B. subtilis), T2 (basal diet + B. megaterium), T3 (basal diet + B. cereus) and T4 (basal diet + B. infantis). Each diet was fed at 10% of animal body weight, four times in a day and reared for 6 weeks in triplicate tanks. Among the treatments, final weight (0.97 +/- 0.06 g), weight gain (0.94 +/- 0.06 g), specific growth rate (7.88 +/- 0.18%/day) and survival rate (64.66 +/- 4.16%) were significantly higher in B. subtilis-treated group. Interestingly, in digestive enzyme activities, protease (3.57 +/- 0.42 U/mg protein), lipase (747.83 +/- 139.03 U/mg protein) and amylase (7.53 +/- 1.27 U/mg protein) were higher in B. subtilis-supplemented diet fed group compared with other treatments. However, cellulase (246.83 +/- 29.77 U/mg protein) activity was greater in group received B. megaterium. Significantly lower activities of superoxide dismutase, phenoloxidase and catalase were found in B. subtilis incorporated diet fed group. Hence, the study revealed that B. subtilis improves the growth performance and digestive enzyme activities. This proved the versatility of B. subtilis as a probiotic in shrimp farming practices. However, further exploration is required to commercialize the B. subtilis before recommending its application in aquaculture.