Dietary Vitamin D3 Modulates Antioxidant Responses, Immune-Related Gene Expression, and Flesh Quality in Giant Freshwater Prawn (Macrobrachium rosenbergii) Under Pathogenic Vibrio Challenge

The giant freshwater prawn (Macrobrachium rosenbergii) is a commercially pivotal crustacean species in global freshwater aquaculture, while vibriosis caused by non-O1 Vibrio cholerae has become the primary bottleneck restricting its sustainable intensive farming. Vitamin D3 (VD3) is a biologically active fat-soluble nutrient involved in mineral metabolism and immune regulation in animals, yet its effects on the physiological responses of M. rosenbergii under a pathogenic bacterial challenge remain largely unelucidated. In this study, six experimental diets were formulated with graded dietary VD3 concentrations (0.10, 0.18, 0.28, 0.48, 0.68, and 0.88 mg/kg) to feed juvenile M. rosenbergii (initial body weight: 2.06 ± 0.07 g) for 70 d, followed by a 72 h non-O1 Vibrio cholerae challenge test. The results showed that dietary VD3 supplementation alleviated the non-O1 Vibrio cholerae-induced histopathological damage in the intestine and hepatopancreas of prawns. VD3 supplementation significantly modulated antioxidant enzyme activities in a tissue-specific manner: SOD activity increased in the intestine, while CAT and GSH-PX activities increased in the hepatopancreas. However, the MDA, T-AOC, and GSH-PX (intestine) or SOD (hepatopancreas) showed no significant responses, indicating that VD3’s antioxidant effects were selective rather than comprehensive. Meanwhile, an appropriate amount of VD3 markedly upregulated the mRNA expression of multiple immune-related genes (pattern recognition receptors, antimicrobial peptides and immune effectors) in a tissue-specific pattern. However, some antioxidant indices and immune-related genes showed no significant responses. Furthermore, VD3 supplementation significantly modulated certain muscle physicochemical parameters of prawns, including altered redness, cooking loss, and textural characteristics. Based on the evaluated physiological indicators, 0.48–0.68 mg/kg VD3 appeared to produce the most favorable overall response. These findings suggest that dietary VD3 may modulate the physiological responses associated with host defense during a bacterial challenge in M. rosenbergii, potentially through modulation of antioxidant capacity and immune-related gene expression, while benefiting the flesh quality. VD3 is thus a potential nutritional approach for improving health status during a bacterial challenge in freshwater crustacean farming.