Effect of dietary selenium in rainbow trout (Oncorhynchus mykiss) broodstock on antioxidant status, its parental transfer and oxidative status in the progeny

We studied the effects of supplementing a plant-ingredient based rainbow trout broodstock diet with different forms of selenium (Se) on reproductive performance, parental Se transfer and antioxidant metabolism in their progeny before first-feeding. Three groups of rainbow trout were fed a diet either without selenium supplementation (NC, basal Se level: 0.3 ppm) or supplemented with 0.3 ppm Se either in the form of sodium selenite (SS) or as hydroxy-selenomethionine (SO, dietary Se level: 0.7 ppm) over a 6-month period prior to spawning. In Se-supplemented groups, the total number of females spawning was significantly higher compared to the negative control group and the females fed SO began to spawn earlier compared to females fed SS or NC. Total Se concentrations were significantly higher in female muscle of SO group. Higher Se concentrations in the oocytes of both Se-supplemented groups confirmed a maternal transfer of Se, while total Se concentrations in milt samples were not significantly different between dietary groups. There was no effect on glutathione peroxidase (GPX) or other antioxidant enzyme activity in the liver of female or male broodstock, whereas in the swim-up fry, GPX activity was significantly higher in both Se-supplemented treatments with the highest activity in the SO group. Se-supplementation enhanced the expression of hepatic SelPa in broodstock males and females along with MsrB1, GPx1a, GPx4a2, CAT, Gclc, Keap1 and MsrB2 in male liver. In swim-up fry, only organic Se-supplementation led to a higher gene expression for SelPa, GPX1a, GPX1b2, CAT and MsrB2. An improvement of the oxidative status in whole-body of swim-up fry could not be confirmed in this study as the GSH/GSSG was even lower in swim-up fry of Se-supplemented groups, whereas the 8-isoprostane levels were lower in the SS group and no effect on protein carbonyl levels could be detected. Organic Se-supplementation led to a significant increase in the a-tocopherol and vitamin C levels in the progeny. These results show that dietary Se in broodstock nutrition influences spawning occurrence and along with the parental transfer, several traits in the progeny are affected.