Dietary emulsifier and antioxidant improved astaxanthin utilization and antioxidant capacity of rainbow trout ( Oncorhynchus mykiss )

This study investigated the effects of dietary emulsifiers and antioxidants on astaxanthin utilization and antioxidant capacity of rainbow trout. First, 50 and 100 mg kg−1 of synthetic astaxanthin (AST-50 and AST-100) were added to the control diet (Con), then 400 mg kg−1 sodium taurocholate (ST), 100 mg kg−1 tea polyphenols (TP) and 100 mg kg−1 surfactin (SUR) were added to the AST-50 diet. The six diets were fed to rainbow trout (6.69 ± 0.02) g for 6 weeks. No significant differences were found in weight gain and feed conversion ratio among all the diets (p > .05). The flesh redness (a*), yellowness (b*) and the astaxanthin content in flesh and liver were significantly increased in fish fed with ST, TP and SUR diets compared with the CON fish, but these values were lower than that in fish fed with AST-100 diet (p < .05). Diets involving TP and SUR significantly enhanced T-AOC in flesh, serum and liver, whereas T-SOD was decreased than those of AST-50 and ST diets (p < .05). In conclusion, the supplementation of tea polyphenols and surfactant in the diet effectively improved the astaxanthin deposition and antioxidant capacity of rainbow trout, and sodium taurocholate promoted the deposition of astaxanthin, rather than the antioxidant capacity.