Abstract

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.