The present study examined the effect of Bacillus subtilis on growth performance, digestive enzyme activity, and immune response of juvenile white-leg shrimp (Litopenaeus vannamei) in 100 m2 lined ponds. Control (without B. subtilis) and experimental (with B. subtilis) diets were fed at 10% of animal body weight, four times daily for 6 weeks in duplicate ponds. Significantly increased final weight, weight gain, specific growth rate, average daily growth, and survival rate were observed in the B. subtilis treated group (P < 0.05). Significantly higher (P < 0.05) digestive enzyme activities of protease, lipase, amylase, and cellulase were found in the B. subtilis supplemented diet fed group. At the end of trial, a challenge study, using Vibrio alginolyticus, found lower (15.00 ± 2.88%) cumulative mortality in the B. subtilis treated group compared to control (73.33 ± 3.33%). Activities of immune and antioxidant enzymes (phenoloxidase, SOD, and catalase) were significantly higher (P < 0.05) in the B. subtilis-incorporated diet fed group. Interestingly, histopathology of the hepatopancreas and intestine revealed that the B. subtilis-supplemented group showed no deformity. Overall, the study found inclusion of B. subtilis in P. vannamei diet improves growth, physiometabolic activities, and immunity, indicating B. subtilis as a potential probiotic for shrimp feed.
Keywords: Digestive enzymes; Histopathology; Immunity; Probiotics; White-leg shrimp.
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