Effects of dietary astaxanthin on growth, antioxidant capacity and gene expression in Pacific white shrimp Litopenaeus vannamei

Pacific white shrimp Litopenaeus vannamei (1050 individuals with initial weight of 1.01 +/- 0.001g) were fed either control diet or one of six dietary astaxanthin (AX) concentration (25, 50, 75, 100, 125 and 150mgkg(-1)) diets for 56days in 35 tanks (30 shrimp per tank). After 56days of culture, shrimp-fed AX125 and AX150 diets had higher (P<0.05) weight gain, specific growth rate, total antioxidant status and lower (P<0.05) superoxide dismutase (SOD), catalase (CAT) than shrimp fed control diet. After low dissolved oxygen stress for 1h, survival rate of shrimp fed AX75, AX100, AX125 and AX150 diets was higher (P<0.05) than that of shrimp fed control diet. Hypoxia inducible factor-1 (HIF-1), cytosolic manganese superoxide dismutase (cMnSOD) and CAT mRNA expression levels of shrimp fed seven diets were significantly down-regulated under hypoxia than under normoxia, but their expression levels were higher under hypoxia in shrimp fed AX-supplemented diets than in shrimp fed control diet. About 70-kDa heat-shock protein (Hsp70) mRNA expression level of shrimp fed seven diets was significantly up-regulated under hypoxia than under normoxia, but its expression level was lower under hypoxia in shrimp fed AX-supplemented diets than in shrimp fed control diet.