Multi-Species Probiotics Improve Health Performance and Alleviate Stress Responses of Rohu (Labeo rohita) in Inland...

Probiotics are increasingly recognized for their role in enhancing fish health, strengthening immune responses, and mitigating stress, particularly as rising inland water salinity continues to compromise fish health and reduce aquaculture productivity. To investigate the potential of probiotics as a countermeasure against the health and productivity challenges posed by brackish water, a 9-month feeding trial was conducted to evaluate the hematological and antioxidant responses of Labeo rohita (20.18 ± 0.22 g; Mean ± SD) reared in inland brackish water earthen ponds (mean area: 1.0 acre; depth: 1.5 m; salinity: 6.1 ppt) and fed diets with or without a multi-species probiotic (MSP) containing Bacillus subtilis (1.9 × 10¹⁰ "CFU/g"), Bacillus licheniformis (2 × 10¹⁰ "CFU/g"), and Clostridium butyricum (2.2 × 10⁸ "CFU/g"). A total of 900 fish were randomly distributed into three treatment groups (P I, P II, and P III), each with three replicate ponds. Fish in group pond P I (control) were fed a basal diet without probiotic supplementation, whereas fish in groups P II and P III received the same basal diet supplemented with MSP at 0.5% and 1%, respectively. A significant improvement (p < 0.05) in blood biomarkers was observed in the 1% MSP fed fish, even when reared at inland brackish water. Erythrocyte count, hemoglobin content, hematocrit count, total serum protein, albumin, and globulin were significantly higher (p < 0.05) in the 1% MSP fed fish compared to the non-probiotic-fed fish. A significant effect of rearing time on oxidative stress markers (ROS and TBARS) which increased over time and significant decline in antioxidant enzymes (SOD, CAT, POD, and GSH) were observed in brackish water ponds without probiotics (p < 0.05), however, dietary MSP supplementation significantly mitigated oxidative damage and enhanced antioxidant defenses in liver, kidney, and gills (p < 0.05). Frequency of erythrocytic alterations was also significantly reduced in MSP-supplemented groups compared to non-probiotic groups (p < 0.05). Marked recovery in histoarchitecture of liver, kidneys, and gills in MSP-supplemented groups compared to non-probiotics groups. In conclusion, dietary MSP supplementation effectively improved blood health and antioxidant capacity in L. rohita in inland brackish-water ponds, suggesting its practical potential to enhance health performance under brackish-water farming conditions.