Effects of dietary vitamin E on growth, immunity and oxidation resistance related to the Nrf2/Keap1 signalling pathway in juvenile Sillago sihama

Abstract

The influence of dietary vitamin E supplementation on growth, immunity and oxidation resistance related to nuclear factor-erythroid 2-related factor 2 (Nrf2)/Kelch-like epichlorohydrin associating protein 1 (Keap1) signalling molecules in juvenile Sillago sihama (2.14 ± 0.02 g, initial mean weight ± SD) was investigated. Altogether, 720 fish were divided into six groups with four repetitions (30 fish each) and fed six diets containing graded concentrations of vitamin E including 4, 14, 22, 47, 95 and 198 mg/kg respectively for eight weeks. Compared with the control, results suggested that dietary vitamin E had the following effects: increased weight gain rate (WG), protein efficiency ratio (PER) and feed intake (FI), and decreased feed conversion ratio (FCR) (P < 0.05); increased hepatic alkaline phosphatase (AKP) activity, complement 3 (C3) and immunoglobulin M (IgM) concentrations (P < 0.05); increased glutathione-S-transferase (GST), catalase (CAT) and glutathione peroxidase (GPx) activities; decreased malondialdehyde (MDA) concentration in the liver; increased copper-zinc superoxide dismutase (CuZnSOD), GST, CAT and GPx activities in the intestine (P < 0.05); and upregulated Nrf2, Keap1, CAT, GST, GPx, glutathione reductase (GR), CuZnSOD and manganese superoxide dismutase (MnSOD) gene expression in the liver and intestine (P < 0.05). Based on regression analysis for WG, the dietary requirement of vitamin E for juvenile S. sihama was estimated to be 100.37 mg/kg.