Dietary selenium requirement of triploid rainbow trout (Oncorhynchus mykiss) based on selenium yeast supplementation

Selenium(Se) is a biological essential trace element that affects the growth and health of fish. The present study aimed to explore the dietary Se requirement of triploid rainbow trout using Se-yeast supplement. The levels of Se added to the basal diet were 0(Se-0), 0.1(Se-0.1), 0.3(Se-0.3), 0.5(Se-0.5), 1.0(Se-1.0), 4.0(Se-4.0) and 16.0(Se-16.0) mg Se/kg diet respectively. Results showed that the fish fed Se-4.0 diet had significantly higher weight gain and lower oxidative stress compared with the fish fed Se-16.0 and Se-0 diets. The optimal dietary Se requirement of triploid rainbow trout was 3.53 mg/kg based on broken-line regression of growth performance. Dietary Se supplementation significantly increased the expression level of selenoprotein genes both in liver (GPX1a, GPX1b1, GPX1b2, SelK, SelP, SelT1, SelT2, SelWl, TrxR3a, SelU) and in muscle (GPX1a, GPX1b2, SelK, SelP, SelU, SelWl, TrxR3b, SelN, MsrB1Al). The minimum dietary Se level was 2.19 or 1.28 mg/kg when the mRNA level of all these selenoproteins reached a plateau in muscle or liver respectively. In conclusion, based on broken-line regression of growth performance and sigmoidal regression of selenoprotein genes expression in muscle and liver, dietary Se requirement of triploid rainbow trout was 3.53, 2.19 and 1.28 mg/kg respectively.