Dietary Supplementation of Archaeal Carotenoids Improved Antioxidative Capacity and Regulated Immune‐related Gene Expression of Golden Trout Oncorhynchus Mykiss Against Challenge

Archaeal carotenoids, as novel bioactive compound, are stronger free radical scavenger. The effects of archaea Halorubrum carotenoids on skin coloration, antioxidative status and immune-related genes expression of golden trout Oncorhynchus mykiss were investigated. In total, 420 fish (10.90 +/- 0.06 g) were divided into three groups with four replicates, and fed with commercial diets containing 0 (Ctrl), 25 mg/kg (P25) and 50 mg archaeal carotenoids/kg feed (P50) for 8 weeks. Although no significant difference was observed on growth, the fish fed archaeal carotenoids had significantly higher yellowness and carotenoid content (p < 0.05) in skin. Compared with the Ctrl group, the total antioxidant capacity (T-AOC) in serum was significantly enhanced in the P25 and P50 groups (p < 0.05), but no significant difference on lysozyme activity was obtained (p > 0.05). In liver, the catalase activity significantly decreased in the P50 group (p < 0.05), but T-AOC and superoxide dismutase activity was not significantly regulated by archaeal carotenoids (p > 0.05). The significant improvement of liver glutathione peroxidase in P50 group was observed, while malondialdehyde content significantly decreased (p < 0.05). After ammonia exposure and Aeromonas hydrophilia challenge, higher survival was observed in the P25 and P50 groups, associating with reducing the expression of pro-inflammation cytokines il-1 beta, but enhancing the expression of anti-inflammation cytokines tgf-beta and hsp70. However, ammonia stress and pathogenic challenge caused opposite trends in the expression of tnf-alpha. Our study confirmed the beneficial role of archaeal carotenoids on skin coloration, antioxidative and immune systems of golden trout, and provided evidence for the potential application of this novel carotenoid in health management of aquaculture.