Dietary Syzygium cumini leaf extract influences growth performance, immunological responses and gene expression in pathogen-challenged Cyprinus carpio

Abstract

This study evaluated the effects of jamun leaf extract (JLE) as a feed supplement on growth performance, haemato-immunological, oxidative stress-related parameters, and cytokine gene expression in Cyprinus carpio challenged with Aeromonas hydrophila.. Diets containing four different JLE concentrations, that is, 0 (basal diet), 5 (JLE5), 10 (JLE10), and 15 g kg-1 (JLE15), were fed to carp (6.17 & PLUSMN; 0.43 g) for eight weeks. Growth per-formance was significantly higher in JLE10. Haemato-immunological and antioxidant parameters were deter-mined in fish at 48 h post-challenge with A. hydrohila. The cumulative survival was highest in JLE10 (69.69%) 14 days post-challenge. Serum protein (2.18 & PLUSMN; 0.06 g dL-1), lysozyme (32.38 & PLUSMN; 1.2 U mL-1), alternative com-plement pathway (70.43 & PLUSMN; 1.61 U mL-1), phagocytic activity (21.18 & PLUSMN; 0.48%), respiratory burst activity (0.289 & PLUSMN; 0.09 OD630nm), and immunoglobulin levels (6.67 & PLUSMN; 0.36 U mg mL-1) were significantly higher in JLE10 than in the control. Serum alanine aminotransferase (44.06 & PLUSMN; 1.62 Unit mL-1), aspartate aminotransferase (31.58 & PLUSMN; 1.82 Unit mL-1), and malondialdehyde (2.57 & PLUSMN; 0.26 nmol mL-1) levels were lower in JLE10 than in the control (p < 0.05), whereas myeloperoxidase activity was significantly higher in JLE5 and JLE10 than in the control. Superoxide dismutase levels in the serum were higher (p < 0.05) in JLE5 and JLE10 than in the other groups. Gene expression analysis revealed that the mRNA expression of pro-inflammatory cytokines TNF-& alpha; and IL-1 & beta; was upregulated (p < 0.05) in the liver, head-kidney, and intestine of challenged carp in JLE10. The signalling molecule NF-& kappa;B p65 was upregulated in lymphoid organs in JLE10 but not in the liver. The anti-inflammatory cytokine IL-10 was significantly downregulated in challenged carp in JLE10 compared with that in the con-trol. Quadratic regression analysis showed that optimal dietary JLE was estimated to be 9.03-10.15 g kg-1 to maximize the growth performance. Results of the present study revealed that dietary JLE at 10 g kg-1 can significantly improve the immunity and disease resistance of C. carpio. Thus, JLE is a promising food additive for carp aquaculture.