Abstract:In this study we conducted a 10-week feeding trial to evaluate the effects of dietary selenium on the growth, the physiological status and the body composition of Japanese seabass with initial average weight of (214.5±1.0) g. Six semi-purified diets were supplemented with NaSeO3•H2O and the concentrations of Se were 0.12, 0.36, 0.42, 0.60, 0.78 and 1.10 mg/kg．In seawater floating net cages (1.5 m×1.5 m×2 m), a group of 18 fish was fed with these six diets twice daily and every 3 fish had one type of diet. The survival rate and the feed efficiency were not significantly affected by the increased level of dietary Se (P>0.05). The weight gain and the whole body crude protein were the highest in Japanese seabass fed with 0.60 mg Se/kg (diet) (P<0.05). Hepatopancreas and the level of the whole body selenium were positively correlated to the dietary Se level. The activities of both serum and heaptopancreas glutathione peroxidases (GSH-Px) were increased along with the elevated dietary Se level, and peaked at 0.60 mg Se/kg (diet) (P<0.05). When the dietary Se increased to 0.78 mg/kg, the activity of the serum GSH-Px decreased significantly (P<0.05). The activities of both serum and hepatopancreas glutathione S-tramsferase (GST) initially decreased and then increased along with the elevated dietary Se level. The activity of serum GST was significantly higher in the 0.78 mg/kg group than in the 0.12 mg/kg group (P<0.05). The activity of serum glutathione reductase (GR) was also significantly affected by the dietary selenium level, and was significantly higher in the 0.78 mg/kg group than in the 0.12 mg/kg group (P<0.05). The activity of serum superoxide dismutase (SOD) increased along with the elevated dietary Se level up to 0.60 mg/kg, and then declined (P<0.05). The activity of serum SOD was significantly decreased in the 0.78 mg/kg group compared to the 0.12 mg/kg group (P<0.05). The level of malonaldehyde (MDA) was initially decreased and then increased along with the elevated dietary Se level. Japanese seabass in the 0.60 mg/kg group showed the lowest level of MDA, which was distinct from the control group and the 1.0 mg/kg group (P<0.05). These results indicated that 0.60 mg Se/kg (diet) might promote the growth and the anti-oxidative ability of Japanese seabass. Quadrate broken-line analysis with specific qrowth rate (SGR) showed that 0.63 mg Se/kg (diet) could be optimal for the growth of Japanese seabass.
