Chandan Debnath
This study investigated the immunomodulatory effects of dietary pineapple peel powder (PPP) supplementation in Labeo rohita fingerlings (15.2 ± 0.3 g) through a 60 d feeding trial followed by a 15 d Aeromonas veronii infection challenge. Processing 1 kg of pineapple fruit generates approximately 30-35% waste, primarily peels, containing bioactive compounds including bromelain enzyme. Using a completely randomized design, 300 fingerlings were distributed into 5 treatment groups in triplicate: Control (0%), T1 (2%), T2 (4%), T3 (6%), and T4 (8%) PPP supplementation. Immunological, haematological, biochemical, and antioxidant parameters were assessed at 0, 15, 30, and 60 d, with bacterial challenge conducted on Day 61 and post-infection (PI) sampling at 7 and 15 d PI. Fish fed 6% PPP (T3) exhibited significantly enhanced immunological parameters, with serum lysozyme activity reaching 185.6 ± 8.4 unit ml-1 compared to 112.3 ± 5.7 unit ml-1 in control. Significant improvements occurred in haematological indices (red blood cells, white blood cells, hemoglobin, hematocrit), serum proteins (total protein, albumin, globulin), and antioxidant enzyme activities (superoxide dismutase, catalase, glutathione peroxidase). Following A. veronii challenge (1×107 CFU ml-1; 0.1 ml fish-1), T3 demonstrated the highest survival rate (82.5 ± 3.4%) compared to control (45.6 ± 2.7%). Growth performance also improved significantly, with specific growth rate (2.84 ± 0.12% vs. 2.15 ± 0.09% d-1) and feed conversion ratio (1.42 ± 0.06 vs. 1.85 ± 0.08) both enhanced in T3 compared to control. These results demonstrate that 6% PPP supplementation optimally enhances immunophysiological parameters, disease resistance, and growth performance in L. rohita, highlighting its potential as a natural immunostimulant in sustainable aquaculture health management.