Impact of Dietary Vitamin D3 Supplementation on Growth, Molting, Antioxidant Capability, and Immunity of Juvenile Chinese Mitten Crabs (Eriocheir sinensis) by Metabolites and Vitamin D Receptor

Vitamin D-3 (Vit-D-3), as an indispensable and fat-soluble nutrient, is associated with skeletal mineralization and health in mammals. However, such associations have not been well studied in economically important crustaceans. Six levels of vit-D-3 with isonitrogenous and isolipidic diets were used to feed Eriocheir sinensis. The range of optimal vit-D-3 requirements is 5685.43-10,000 IU/kg based on growth. The crabs fed 9000 IU/kg vit-D-3 showed the best growth performance. This vit-D-3 dose significantly increased antioxidant capacity in the hepatopancreas and intestine and was optimal for molting and innate immunity via quantitative polymerase chain reaction analysis. Transcriptomics analyses indicate that vit-D-3 could alter protein processing in the endoplasmic reticulum, steroid biosynthesis, and antigen processing and presentation. As shown by the enzyme-linked immunosorbent assay, vit-D-3 could improve vitamin D receptor, retinoic acid receptor, and C-type lectins concentrations. The 1 alpha,25-dihydroxy vit-D-3 content in serum was significantly higher in 3000-9000 IU/kg vit-D-3. The study suggests that dietary vit-D-3 and its metabolites can regulate molting and innate immunity in crabs.