Can dietary phytogenic mixture improve performance for growth, digestive enzyme activity, blood parameters, and antioxidant and related gene expressions of Nile tilapia, Oreochromis niloticus?

Abstract

The form of dietary phytogenic inclusion and its physiological causal mechanisms for growth promotion and immune stimulation in fish remain unknown. The study examined the effects of dietary phytogenic mixture extracted from lemon (Citrus limon), onion (Allium cepa), and garlic (Allium sativum) (LOG) on Nile tilapia performance, digestive enzymes, haemato-biochemical indices, oxidative stress, and associated gene expression for 70 days. In this experiment, diets were supplemented with 0, 10, 20, and 30 ml LOG kg−1 in isonitrogenous and isoenergetic diets and fed to tilapia with an average initial body weight (4.23 ± 0.09 g). Compared to the control diet, the dietary LOG at 20 ml kg−1 elicited the highest final body weight (FBW, 35.50 g fish−1), weight gain (WG, 31.2 g fish−1), specific growth rate (SGR, 3.02%, day fish−1), and survival rate (99.33%). Significant quadratic differences in chymotrypsin, trypsin, amylase, and lipase were shown with increasing LOG supplementation. There was a quadratic response in hematology parameters of fish with increasing LOG levels. Significant linear decreases in ALT, AST, cholesterol, and triglyceride were shown with the increased LOG inclusion in the diets. A polynomial correlation in total protein, albumin, and globulin was found under different inclusion levels of LOG while significant quadratic increases in SOD, CAT, and Gpx and significant quadratic decrease in MDA was found with increasing LOG supplementation. The IGM-2, SOD, and CAT gene expressions were quadratically improved; the highest relative expression was obtained by fish received 20 ml LOG kg−1 diet. Growth hormone gene expression was quadratically modulated in the liver and pituitary of fish fed diverse doses of dietary LOG compared with the control. The phytogenic of LOG at 20 ml kg−1 elicited the best tilapia performance and hematological indices, increased antioxidant and digestive enzyme activities, and gene expressions of growth, immunoglobulin and superoxide dismutase.