Administration of Red Macroalgae (<i>Galaxaura oblongata</i>) in the Diet of the Rainbow Trout (<i>Oncorhynchus mykiss</i>) Improved Immunity and Hepatic Gene Expression

Abstract

This study is designed to evaluate the effects of dietary red macroalgae (Galaxaura oblongata) on growth performance, serum, and skin mucus immunological and antioxidant responses in rainbow trout (Oncorhynchus mykiss). For this, rainbow trout were fed diets containing different levels of G. oblongata (0 (ctrl), 0.5 (G1), and 1 (G2) %) for 8 weeks. Following the feeding trial, there were no significant differences in growth performance between the experimental treatments (p > 0.05). Total immunoglobulin (Ig) content and lysozyme (LYZ) activity in serum were increased in fish fed G. oblongata (p G. oblongata groups (p p > 0.05). All groups fed G. oblongata showed higher serum catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) activities than the control group (p G. oblongata than the other groups (p G. oblongata than in the control (p p > 0.05). G. oblongata up-regulated gpx gene expression with the maximum value at the group fed 1% G. oblongata (p il-6) and tumor necrosis factor-alpha (tnf-α) gene expressions were significantly up-regulated in fish fed 1% compared with the control and 0.5% groups. Based on the results, 0.5–1% G. oblongata can be used in the fish diet and enhance immunity without causing impairment in growth.

Keywords

• seaweed
• immune system
• antioxidant enzyme
• cytokine
• fish liver