Effects of synthetic astaxanthin and Haematococcus pluvialis on growth, antioxidant capacity, immune response, and hepato-morphology of Oncorhynchus mykiss under cage culture with flowing freshwater

Abstract

A feeding experiment was carried out to compare the effects of dietary synthetic astaxanthin and Haematococcus pluvialis on growth, antioxidant capacity, immune response and hepato-morphology of Oncorhynchus mykiss under cage culture with flowing freshwater. Three isonitrogenous and isolipidic diets were formulated with or without synthetic astaxanthin and H. pluvialis and were administered to O. mykiss for 56 days. The results showed that growth performance and muscle lipid of O. mykiss were significantly improved by diet supplemented with synthetic astaxanthin or H. pluvialis. Feed coefficient ratio of O. mykiss fed the diets supplemented with synthetic astaxanthin or H. pluvialis was lower than that of fish fed the control diet. Besides, dietary synthetic astaxanthin or H. pluvialis supplementation significantly improved dorsal muscle pigmentation of O. mykiss. The beneficial effects on growth performance and pigmentation were more evident in synthetic astaxanthin than that in H. pluvialis. Synthetic astaxanthin or H. pluvialis supplementation activated Nrf2-ARE pathway, enhanced superoxide dismutase activity and decreased MDA content in the liver. Furthermore, synthetic astaxanthin or H. pluvialis improved the non-specific immunity by activating lysozyme and complement system, exerted anti-inflammatory activity by inhibiting the expression of pro-inflammatory cytokines (interleukin 1β, interleukin 8 and tumor necrosis factor-α) and improved the liver morphology. Based on these findings, dietary synthetic astaxanthin and H. pluvialis supplementation have a beneficial effect on the growth performance, antioxidant capacity, innate immune response and liver health of O. mykiss.