Effects of dietary 25-hydroxyvitamin D3 on growth, calcium-phosphorus metabolism, lipid metabolism and immunity of Litopenaeus vannamei at low salinity

25-hydroxyvitamin D3 (25-OH-D3) is often used as an animal feed additive to improve growth and immunity. Here, we demonstrate that 25-hydroxyvitamin D3 (25-OH-D3) has positive affects on growth, metabolism, and immunity in shrimp (Litopenaeus vannamei) at low salinity. Shrimps (initial weight of 4.50 ± 0.11 g) were fed with the experimental diets containing 0, 1056, 2138, 4069, and 8203 IU/kg 25-OH-D3 respectively for 8 weeks. As the results, the weight gain rate of L. vannamei increased when 25-OH-D3 level from 1056 to 2138 IU/kg, then decreased. The feed conversion ratio exhibited the opposed trend. And the cubic regression analysis indicated the optimum 25-OH-D3 level for growth promotion of L. vannamei was 2615 IU/kg. When the dietary 25-OH-D3 level was up to 2138 IU/kg, the calcium-phosphorus content and the expression of calcium-phosphorus-related genes (calcium binding protein, sodium-dependent phosphate transport protein) were also markedly up-regulated. The lipid catabolism-related genes (carnitine-palmitoyltransferase 1, acyl-CoA oxidase) decreased initially and then increased with the increasing dietary 25-OH-D3 level. And the expression of lipid anabolism-related genes (sterol-regulatory element binding protein, fatty-acid synthetase) showed the opposing trend of lipid catabolism. Compared with the control group, 25-OH-D3 added at 4069 IU/kg significantly decreased the contents of triglycerides and total cholesterol, which was the optimal addition to regulate lipolysis. The addition of 2138 IU/kg 25-OH-D3 significantly increased the activity of superoxide dismutase, catalase, phenoloxidase, lysozyme, alkaline phosphatase, acid phosphatase and total antioxidant capacity, as well as the expression of corresponding genes, and decreased malondialdehyde levels in the shrimp. 25-OH-D3 added at 8203 IU/kg produced some inhibitory effects on growth, reduced immunity and increased lipid content. In summary, dietary supplementation of 25-OH-D3 can improve growth, calcium-phosphorus metabolism, lipid metabolism, antioxidant, and immunity of L. vannamei at low salinity, while the best effect was achieved at an additional level of 2138–4069 IU/kg. •Dietary 25-OH-D3 improved the growth and feed utilization of Litopenaeus vannamei at low salinity.•According to the analysis of WGR, the optimum dietary 25-OH-D3 level in the diet of L. vannamei was 2615 IU/kg.•Dietary 25-OH-D3 enhanced calcium-phosphorus deposition in L. vannamei at low salinity.•Dietary 25-OH-D