Effects of dietary selenium supplementation on physiological parameters, tissue fatty acid composition, and fatty acid-metabolism relative gene expression of grouper (Epinephelus coioides) fed high plant protein diets
摘要
The present study evaluated the effects of dietary selenium (Se) supplementation on growth performance, physiological responses, tissue fatty acid profiles, and the expression of genes related to fatty acid metabolism in juvenile grouper (Epinephelus coioides). A control diet based on soy protein concentrate, replacing 40% of the fish meal protein, was supplemented with graded levels of Se at 0, 0.3, 0.6, and 1.0 mg Se kg−1. A fish meal-based reference diet was also included for comparison. The five test feeds were assigned to three groups of fish with an average weight of 13.14 ± 0.03 g, and cultured in a recirculating aquaculture system for 56 days. No significant differences (p > 0.05) were observed among dietary treatments in terms of weight gain, feed efficiency, survival, and whole-body proximate composition of grouper. Tissue Se concentrations in whole body, liver, and muscle, hepatic glutathione peroxidase activity, and proportions of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) increased proportionally with dietary Se levels. Whole-body EPA retention was highest in fish fed the reference diet and 1.0 mg Se kg−1, intermediate in the 0.6 mg Se kg−1 group, and lowest in the 0 and 0.3 mg Se kg−1 groups. Similarly, DHA retention was elevated in fish fed the reference diet and 1.0 mg Se kg−1 diet. Furthermore, hepatic mRNA expression levels of fatty acid desaturase 2 (FAD2), elongase 5 (FAD5), and peroxisome proliferator-activated receptor gamma (PPAR-γ) were upregulated in a dose-dependent manner in response to dietary Se. These findings demonstrate that Se supplementation can enhance antioxidant defense mechanisms, tissue Se deposition, and the hepatic accumulation of EPA and DHA.