Effects of dietary astaxanthin supplementation on growth performance, antioxidant status, immune response, and intestinal health of rainbow trout(Oncorhynchus mykiss)

A feeding trial was conducted to assess the impacts of dietary astaxanthin from wall-broken Haematococcus pluvialis(WBHPA) on the growth performance, antioxidant status, immune response, and intestinal health of rainbow trout(Oncorhynchus mykiss). Six experimental diets were formulated with various concentrations of WBHPA, ranging from 0 to 8.4 g/kg(containing 0 to 125 mg/kg astaxanthin). Each diet was fed to triplicate groups of rainbow trout(mean initial weight of 561 g) twice daily for 9 consecutive weeks. The survival rate and feed intake of fish exhibited no significant differences among the dietary groups(P > 0.05). Similarly, dietary inclusion of 25 to 100 mg/kg astaxanthin did not significantly affect the weight gain and daily growth coefficient(P > 0.05), but excessive inclusion of astaxanthin(125 mg/kg) slightly depressed these parameters(P < 0.05). Dietary inclusion of 25 to 50 mg/kg astaxanthin increased the activities of intestinal digestion and absorption enzymes(lipase, creatine kinase, and alkaline phosphatase), while the inclusion of 25 to 75 mg/kg astaxanthin improved the immune response of fish. Furthermore, regardless of inclusion level(25 to 125 mg/kg), dietary astaxanthin supplementation strengthened the intestinal mucosal barrier function and improved antioxidant activity,thereby promoting intestinal development. Conclusively, 25 to 75 mg/kg astaxanthin from WBHPA was recommended to be included in diets for rainbow trout.