Comparison of selenomethionine and hydroxyselenomethionine on tissue selenium retention, and antioxidative capacity of giant grouper, Epinephelus lanceolatus, fed diet with soybean meal

The study aims to evaluate the effects of two organic selenium (Se) sources, selenomethionine (SeMet) and hydroxyselenomethionine (OH-SeMet), on tissue Se retention, and antioxidative capacity of giant grouper, Epinephelus lanceolatus, fed diets with soybean meal (SBM). The control diet containing 32.92% SBM (replaced 40% fish meal protein) was supplemented with 0.3, 0.6 and 1.0 mg Se/kg of SeMet and OH-SeMet. A reference diet with fish meal (FM) as main protein source was also included for comparison. The eight experimental diets were each fed to triplicate groups of grouper juveniles (initial weight: 25.99 +/- 0.04 g) in a recirculation system with seawater for 8 weeks. The Se concentrations in whole body, muscle and liver were dependent on dietary Se concentrations, but not on its supplemental forms. Higher hepatic glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT), but lower malondialdehyde (MDA) content, were observed in fish fed the reference diet than in fish fed the control diet. The results indicated that dietary FM protein replaced by SBM at 40% depressed growth performance, Se retention and antioxidative capacity of giant grouper. Both Se sources supplementation enhanced Se retention and antioxidative capacity, but not growth performance of the fish.