Fermented rice water enhances disease resistance against Aeromonas hydrophila infection in Labeo rohita fingerlings by modulating immune response.

This study investigated the immunomodulatory potential of dietary fermented rice water (FRW) in enhancing resistance to Aeromonas hydrophila infection in Labeo rohita fingerlings. Using a completely randomized design, 360 fingerlings (11.87 ± 0.24 g) were distributed across 12 tanks with three replicates per treatment. Fish received commercial diets supplemented with 0 % (control), 1 %, 2 %, or 3 % FRW for 45 days, followed by bacterial challenge at 1 × 10 CFU/fish. FRW supplementation significantly enhanced hematological parameters compared to controls (P < 0.05). Red blood cell counts increased from 3.05 × 10 cells/μL in controls to 3.76-3.79 × 10 cells/μL in the 2 % and 3 % treatments. White blood cell counts rose from 9.18 × 10 to 12.34-12.51 × 10 cells/μL, while hemoglobin concentrations improved from 8.34 to 10.28-10.35 g/dL in supplemented groups (P < 0.05). Serum biochemical markers demonstrated substantial improvements, with total protein levels reaching 4.47-4.52 g/dL versus 3.53 g/dL in controls (P < 0.05). Non-specific immune responses, antioxidant enzyme activities, and gene expression were significantly enhanced in FRW groups (P < 0.05). Gene expression analysis revealed upregulation of TLR21, MyD88, IL-10, and TGF-β1, while TNF-α was downregulated compared to controls (P < 0.05). Growth performance improved significantly, with specific growth rates increasing from 1.65 %/day in controls to 1.92-1.94 %/day in the 2 % and 3 % groups (P < 0.05). Following bacterial challenge, survival rates were significantly higher in FRW-supplemented groups (66.67-84.44 %) compared to controls (46.67 %) (P < 0.001). The 2 % and 3 % treatments showed equivalent protective efficacy (P > 0.05), indicating optimal protection at 2 % inclusion level. However, careful concentration optimization remains critical as suboptimal dosing may compromise therapeutic benefits. These findings demonstrate FRW's potential as a sustainable immunostimulant for aquaculture disease management.