Effect of dietary selenium level on growth performance, body composition and hepatic glutathione peroxidase activities of largemouth bass<i>Micropterus salmoide</i>

Abstract

An 8-week growth trial was conducted to determine the effect of dietary selenium (Se) level on growth performance, body composition and hepatic glutathione peroxidase (GPx) activities of largemouth bass. Sodium selenite was added to the fish meal basal diet at 0, 0.2, 0.4, 0.6, 0.8 and 1.0 mg kg−1 Se providing 0.97, 1.17, 1.42, 1.60, 1.85 and 2.06 mg Se kg−1 diet respectively. Each diet was fed to triplicate groups of fish (initial mean body weight: 4.95 ± 0.03 g) in a closed indoor recirculating system. The Se concentration in the rearing water was not detectable during the whole experimental period. The highest weight gain was obtained in fish fed diets with 1.60 mg Se kg−1, which was significant higher (P < 0.05) than the basal diet with 0.97 mg Se kg−1 and did not differ significantly (P > 0.05) with the other treatments. Feed conversion ratio, protein efficiency ratio, protein productive value, apparent digestibility coefficients of dry matter and muscle composition were not significantly impacted (P > 0.05) by dietary treatments. Fish fed diets with ≥1.42 mg Se kg−1 obtained higher liver lipid contents than treatments with lower dietary Se levels. Hepatic malondialdehyde (MDA) was unchanged (P > 0.05) in relation to dietary Se concentration. Hepatic GPx and glutathione reductase (GR) activities markedly increased and decreased (P < 0.05) with increasing dietary Se concentration, respectively, and both reached a plateau with ≥1.85 mg Se kg−1. Based on growth performance, hepatic MDA and enzymatic responses of GPx and GR, the highest Se concentration (2.06 mg kg−1) employed in our study was not harmful for largemouth bass, and the optimal dietary level should be 1.60–1.85 mg Se kg−1 from sodium selenite, at a dietary vitamin E level of 400 IU kg−1.