The effects of dietary selenium on growth performances, oxidative stress and tissue selenium concentration of gibel carp (Carassius auratus gibelio)

A 100-day growth trial was executed to determine the dietary selenium (Se) requirement of juvenile gibel carp (Carassius auratus gibelio). Selenomethionine was supplemented to casein-gelatin diets at 0, 0.1, 0.25, 0.5, 1.0, 2.5 and 5 mg Se kg(-1), respectively. Each of these seven semi-purified diets containing 0.34, 0.47, 0.66, 0.82, 1.23, 2.77 and 5.13 mg Se kg(-1) was fed to triplicate groups of gibel carp (2.74 +/- 0.02 g) in a flow-through system. No behaviour abnormalities and no mortality were found in fish exposed to dietary Se concentrations. With the increasing dietary Se supplemented concentrations, weight gain of fish remarkably increased at the levels of <= 1 mg Se kg(-1) diet and then showed no significant difference above 1 mg Se kg(-1) levels. Although growth performances (weight gain, hepatosomatic index, condition factor and survival) were not impaired in gibel carp fed at above the levels of 2.5 mg Se kg(-1), indicators of oxidative stress were changed significantly. Serum superoxide dismutase (SOD) activities significantly declined, hepatic glutathione peroxidase (GPx) activities significantly increased and the tissue Se concentrations significantly raised at the highest supplemented level of 5 mg Se kg(-1). A clear linear relationship between Se-depended GPx activities and hepatic Se concentrations was observed. The present results indicated that the dietary Se requirement for gibel carp is 1.18 mg Se kg(-1) diet based on weight gain, GPx activities and tissue accumulation