Jamun fruit extract enhances growth performance, mucosal immunity, disease resistance, and immune- and antioxidant-related gene expression of Cyprinus carpio juveniles

This study evaluated the effects of Jamun fruit extract (JFE) on the growth, immunity, and health of juvenile Cyprinus carpio (average weight: 9.08±0.47 g). Diets containing five different JFE concentrations, that is, 0 (control), 2 (JFE2), 3 (JFE3), 4 (JFE4), and 5 g Kg−1 (JFE5) were fed to five fish groups (maintained in triplicate) for eight weeks. Growth parameters were examined at 4 and 8 weeks post-feeding; whereas, immune and antioxidant-related parameters were measured at 8 weeks post-feeding. Fish were challenged with Aeromonas hydrophila at the end of the feeding trial and mortalities were recorded over 14 days post-infection. Weight gain rate (%) was significantly higher in JFE3, compared to the control. RBC and WBC counts, hemoglobin, total protein level, albumin, and phagocytic activity were significantly enhanced in JFE3 than in control; whereas, there was no significant effect on hematocrit, and blood glucose level. Skin mucosal lysozyme and peroxidase levels were significantly higher in JFE2 ̶ JFE4 than in the control. Significantly higher mucosal total immunoglobulin, alkaline phosphatase, and protein levels were recorded in JFE3. Serum MDA and AST levels were significantly lower in JFE2 ̶ JFE4 than in the control; however, the MPO level was highest in JFE3. Liver antioxidant enzymatic activities were strongly enhanced in JFE3. Further, JFE supplementation upregulated the expression of antioxidant-related genes in the liver. The mRNA expression of TNF-α and IL-1β was upregulated in the kidney and intestine in JFE3. Kaplan–Meier survival curves revealed that the probability of survival (64.69%) was highest in JFE3. Quadratic regression analysis followed by optimization showed that the optimal dietary JFE level was estimated to be 2.59 ̶ 2.74 g Kg−1 to maximize the growth performance. Therefore, JFE at appropriate doses could improve the growth, immunity, and disease resistance of C. carpio against A. hydrophila.