Effects of dietary selenium polysaccharide on growth performance, oxidative stress and tissue selenium accumulation of juvenile black sea bream, Acanthopagrus schlegelii

Selenium (Se) plays an important role in the immune system and is essential for growth. An 8-week growth trial was conducted to determine the dietary Se requirement of juvenile black sea bream, Acanthopagrus schlegelii. A basal diet was supplemented with Se polysaccharide at levels of 0.34, 0.52, 0.68, 0.91, 1.08 and 3.06 mg Se/kg. Triplicates of black sea bream (13.00 +/- 0.20 g) were each hand fed one of the diets. Abnormal fish behavior was not observed, and mortality was not influenced by dietary treatment. Increased levels of Se significantly increased the weight gain in fish fed <= 0.91 mg Se/kg diets, while higher inclusion levels showed a slightly decreasing trend for growth performance. The activities of superoxide dismutase, glutathione peroxidase, catalase and glutathione reductase in the serum and liver significantly increased and levelled off in the fish fed >= 1.08 mg Se/kg diets, while the liver and serum malonaldehyde contents significantly decreased with increasing Se levels. The liver and muscle Se contents linearly increased with increasing dietary Se levels. On the basis of the obtained results, it can be concluded that the dietary Se requirement for juvenile black sea bream appears to be 0.86 mg/kg based on weight gain.