The effects of dietary astaxanthin on the intestinal microbiota and metabolites, antioxidant capacity, and resistance to Decapod iridescent virus 1 in Macrobrachium rosenbergii

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BACKGROUND: The appearance and cross-border dissemination of numerous pathogenic microorganisms have substantially hindered the sustainable growth of the prawn's farming industry. Nutritional regulation is considered a key strategy for improving disease resistance in aquatic animals. AIMS: A feeding trial was conducted to evaluate the effects of dietary astaxanthin on growth performance, intestinal microbiota and metabolites, antioxidant capacity, immune response, and resistance to decapod iridescent virus 1 (DIV1) in Macrobrachium rosenbergii. METHODS: Dietary supplementation with astaxanthin at doses of 0, 100 mg/kg, 500 mg/kg, and 1000 mg/kg was administered to prawns for 8 weeks, followed by a DIV1 challenge test. The effects were evaluated by analyzing the cumulative survival rate, intestinal microbiota and metabolites, plasma antioxidant indices, hepatopancreatic histology, and the expression levels of immune-related genes. RESULTS: The levels of astaxanthin were significantly increased in the intestine and hepatopancreas (P < 0.05). The relative abundance of Lactococcus garvieae decreased and 5-hydroxy-L-tryptophan level significantly increased in dietary astaxanthin groups (P < 0.05). Following the DIV1 challenge test, the cumulative survival rate was significantly increased in 500 mg/kg dietary astaxanthin group (P < 0.05). Plasma SOD and CAT activities were significantly increased in dietary astaxanthin groups (P < 0.05). Plasma MDA levels and apoptosis rate in hepatopancreas were significantly reduced in dietary astaxanthin groups (P < 0.05). The relative expression levels of toll, myd88, and irf4 genes were significantly increased in astaxanthin supplemented groups (P < 0.05). Dietary astaxanthin did not significantly affect the growth performance of prawns. CONCLUSION: Dietary astaxanthin has the potential to improve intestinal microbiota and metabolites, enhance antioxidant capacity, and strengthen MyD88-dependent Toll-signaling pathways for defense against DIV1. Overall, 500 mg/kg dietary astaxanthin was recommended to achieve the optimal health benefits for M. rosenbergii.