Effects of different dietary selenium sources on growth performance, liver and muscle composition, antioxidant status, stress response and expression of related genes in gilthead seabream (Sparus aurata)

Abstract

The present study aimed to determine the effects of dietary inclusion of selenium (Se) in the form of either inorganic Se (sodium selenite, NaSe) or organic Se (hydroxy-selenomethionine, OH-SeMet) on gilthead seabream (Sparus aurata). Triplicate groups of 150 fish each (6.2 ± 0.04 g initial body weight) were distributed in 15 tanks and fed one of five experimental diets for 63 days. A control diet (C) without Se supplementation (0.8 mg Se/kg diet), was formulated and served as a basal diet for the other 4 experimental feeds, supplemented with either 0.2 or 0.5 mg Se/kg supplied in the form of NaSe or OH-SeMet. Fish growth performance, biochemical composition of liver and muscle and Se content, malondialdehyde (MDA) concentration in muscle and hepatopancreas, hepatocyte morphology and lysozyme activity in the serum were studied. Furthermore, expression of related hepatic genes, such as manganese superoxide dismutase (Mn-sod), catalase (cat), heat shock protein 70 (hsp70), and glutathione peroxidase (gpx) was also analyzed. After the trial, fish were exposed to an acute and chronic confinement stress. Blood samples for cortisol analysis were taken at 0 and 2 h after the acute stress and after 7 days of chronic stress. The highest growth rate was observed in fish fed OH-SeMet at a level of 0.2 mg/kg, but with no significant difference with fish fed the control diet with no-added Se. The lowest growth was observed in fish fed NaSe up to 0.5 mg/kg. Increase in dietary Se, particularly in the form of OH-SeMet, led to an increase in Se contents in liver and muscle. Furthermore, dietary inclusion of OH-SeMet, led to a significant (p