Attenuation of salinity-induced stress and improvement of brackish water aquaculture of Labeo rohita through dietary interventions of multi-species probiotics

The present investigation was targeted to determine the attenuating role of multi-species probiotics (MSP) of Bacillus subtilis (1.9 × 10¹⁰ CFU/g), Bacillus licheniformis (2 × 10¹⁰ CFU/g), and Clostridium butyricum (2.2 × 10⁸ CFU/g), against salinity-induced stress and dietary influence on physiological indices of aquaria reared Labeo rohita fingerlings. Three hundred and twenty-four fish (weighed = 60 ± 2.35 g initially) were divided into nine equal groups, each with three replicates for a duration of 60 days. These experimental groups were represented as follows: (S0/NS) salinity-free group fed with basal diet, (S6/NS) 6.00 ppt salinity stress group fed with basal diet, (S12/NS) 12.00 ppt salinity stress group fed with basal diet, (S0/MSP1) salinity-free group fed with 1% MSP, (S6/MSP1) 6.00 ppt salinity stress group fed with 1% MSP, (S12/MSP1) 12.00 ppt salinity stress group fed with 1% MSP, (S0/MSP2) salinity-free group fed with 2% MSP, (S6/MSP2) 6.00 ppt salinity stress group fed with 2% MSP, and (S12/MSP2) 12.00 ppt salinity stress group fed with 2% MSP. Probiotics supplemented fish exhibited positively improved growth, digestive enzymes, nutrient utilization, hematobiochemical traits, and antioxidant capacity under different levels of salinity compared to non-supplemented fish (p < 0.05). Stress indices in terms of oxidative stress, cortisol and glucose and osmoregulatory responses under salinity stress improved significantly in fish nurtured on probiotic added diet over time compared to non-probiotic diet groups (p < 0.05). The histomorphology of hepato-renal, intestine and gills structures was observed with improved histoarchitecture in terms of cellular integrity and functionality in MSP diet groups compared to non-probiotics ones. Studies of erythrocytes structures and intestinal histometric indices revealed significant improvement across MSP feeding in salinity test groups, compared to non-probiotic salinity groups (p < 0.05). Consequently, we find that dietary administration of these multi-species probiotics enhanced stress coping capacity and yielding improvements in physiology of reared Labeo rohita under salinity stress conditions, resulting in a significant enhancement in brackish fish culture production.