Impact of dietary astaxanthin sources on growth performance, antioxidant status, immune response, and intestinal morphology in rainbow trout (Oncorhynchus mykiss)

This research examined the impact of different sources of astaxanthin on the growth performance, antioxidant capacity, immune status, and intestinal morphology of rainbow trout (Oncorhynchus mykiss). A total of 360 fish were randomly assigned to 12 tanks and fed experimental diets containing 0 mg/kg (control), 100 mg/kg astaxanthin derived from wall-broken Haematococcus pluvialis (WBHPA), wall-unbroken H. pluvialis (WUHPA), and chemically synthesized astaxanthin (CSA). Dietary supplementation with WUHPA significantly reduced growth performance, whereas the inclusion of WBHPA or CSA had no effect. Dietary inclusion of CSA significantly reduced intestinal lipase and alkaline phosphatase activities, while intestinal lipase activity was also reduced by dietary WUHPA supplementation. Dietary supplementation with different sources of astaxanthin improved intestinal mucosal barrier function (decreased plasma endothelin-1 level and increased intestinal mucosal resistance). However, no significant changes were observed in intestinal morphology. Although the antioxidant capacity of fish improved with astaxanthin supplementation, the effects varied across the different sources. Plasma antioxidant indices showed minimal differences across the three astaxanthin groups, whereas CSA and WBHPA exhibited more pronounced antioxidant effects in liver and intestine, respectively. In conclusion, dietary astaxanthin, particularly from WBHPA, positively influenced intestinal digestion and absorption capacities as well as intestinal mucosal barrier function in rainbow trout, suggesting its applicability as a functional feed additive in aquaculture.