Bacillus subtilis and Saccharomyces cerevisiae as Potential Modulators of Hemato-Biochemical Indices, Digestive Enzymes and Disease Resistance in Labeo rohita

The present study evaluates the effect of the probiotic bacterium Bacillus subtilis and the baker’s yeast Saccharomyces cerevisiae, either single or in combination, on hemato-immunological indices, digestive enzyme activities and disease resistance in Indian major carp, Labeo rohita (Hamilton 1822). Fish (22 ± 1.0 g) were administered three doses of probiotics on alternate days by oral and intraperitoneal injection at 1 × 10⁶ cfu/mL concentration. The specified parameters were examined on the 10th and 20th day after administration in all the groups. Further, the control and treatment groups were both challenged with a lethal strain of Aeromonas veronii intraperitoneally at 1 × 10⁸ cfu/mL concentration after 20 days, following which the clinical signs and survivability rate were documented in all the groups regularly. Overall, an improvement in hematological indices, enzymatic activity and immunological parameters was observed in groups supplemented with probiotics as compared to the control group. Furthermore, when challenged with A. veronii, groups that received oral and injection [CI (B. subtilis + S. cerevisiae I/P injection) and CO (B. subtilis + S. cerevisiae oral)] had the best survivability (85.7%) followed by BS-I (B. subtilis I/P injection) and SC-O (S. cerevisiae oral) with 71.4% and lastly by SC-I (S. cerevisiae I/P injection) and BS-O (B. subtilis oral) with 57.1%. The findings suggest that supplementation of B. subtilis and S. cerevisiae can help to enhance fish health and increase aquaculture production.