Selenium nutrition of hybrid striped bass (Morone chrysops × M. saxatilis) bioavailability, toxicity and interaction with vitamin E

Two concurrent 12-week feeding trials were conducted to evaluate the bioavailability of inorganic sodium selenite and organic seleno-DL-methionine and to investigate the potential interaction between selenium and vitamin E in juvenile hybrid striped bass. In experiment 1, purified diets utilizing casein, gelatin and an amino acid premix as protein sources with a basal selenium concentration of 0.11 mg Se   kg^?1 were supplemented with either Na₂SeO₃ to provide selenium concentrations of 1.19, 2.00, 5.17 and 21.23 mg Se kg^?1 or with seleno-DL-methionine to provide 0.90, 1.26 and 2.55 mg Se kg^?1 and fed to juvenile hybrid striped bass in aquaria. A second experiment evaluated potential interactions by feeding these purified diets with or without supplemental vitamin E or sodium selenite, singularly or in combination. No overt selenium deficiency signs were exhibited by fish in either of the experiments; however, signs of selenium toxicity including retarded weight gain (WG), reduced feed intake and feed efficiency ratio (FER) as well as increased mortality, were observed in fish fed the diet containing more than 20 mg Se kg^?1. Whole-body selenium and whole-body selenium retention were linearly influenced by sodium selenite and selenomethionine. However, there was no significant effect of dietary selenium, vitamin E or their interaction on WG, FER and survival. Slope-ratio analysis showed that bioavailability of seleno-DL-methionine as a selenium source for juvenile hybrid striped bass was significantly ( P  < 0.01) higher (3.3-fold) than sodium selenite.