Effects of dietary supplementation of astaxanthin (Ast) on growth performance, activities of digestive enzymes, antioxidant capacity and lipid metabolism of large yellow croaker (Larimichthys crocea) larvae

A 30-day feeding experiment was operated to evaluate the impact of astaxanthin (Ast) on growth performance, activities of digestive enzymes, antioxidant responses and lipid metabolism of large yellow croaker (Larimichthys crocea) larvae. Four micro-diets (isonitrogenous and isolipidic) were formulated with graded Ast levels (0, 20, 40 and 80 mg/kg) in form of Haematococcus pluvialis powder (0, 0.4, 0.8 and 1.6 g/kg). Results showed that the specific growth rate of larvae was significantly enhanced by supplementation of 80 mg/kg Ast compared to the control group. Meanwhile, the Ast supplementation could significantly improve the digestive capacity of larvae through increasing activities of digestive enzymes, including trypsin in larvae pancreas segments (PS) and intestinal segments (IS), lipase, and alkaline phosphatase in brush border membranes compared to the control group. In terms of antioxidants, Ast supplementation significantly advanced the antioxidant capacity through increasing the activity of total antioxidant capacity and catalase, and reducing content of malondialdehyde. The activity of lysozyme and nitric oxide content of larvae were significantly increased by Ast supplementation compared to the control group. Furthermore, the triglyceride content in visceral mass was significantly reduced by Ast supplementation probably through up-regulating expression of lipid catabolism-related genes (cpt1, lpl, hl, aco, and ppar-alpha), and down-regulating expression of lipogenesis-related genes (fas, dgat2, and srebp1) and lipid transport-related genes (fabp11, apoB100, and mtp). In summary, appropriate supplementation of Ast (40-80 mg/kg) could improve the growth performance of large yellow croaker larvae through enhancing of digestive enzymes activities, antioxidant capacity and promoting lipid utilization.