Vitamin D3 (cholecalciferol), a fat-soluble vitamin and prohormone, is an important micronutrient in aquafeeds. This study aimed to determine the optimal dietary vitamin D3 requirement for Pacific white shrimp, Penaeus vannamei. An eight-week feeding trial was conducted using 400 shrimp (0.07 ± 0.00 g), randomly assigned into 20 tanks with four replicates per treatment. Five diets were prepared by adding 0, 45, 90, 135, and 270 μg/kg of vitamin D3 (designated as VD0, VD45, VD90, VD135, and VD270, respectively) and fed to the shrimp. The determined vitamin D3 levels of experimental diets were 12, 35, 101, 152, and 294 μg/kg, respectively. Growth and feed utilization improved with increasing dietary vitamin D3 levels, peaking at VD135 group (p 0.05). Protein, lipid and dry matter digestibility of the shrimp were significantly increased with increasing dietary vitamin D3 levels up to VD135 group but decreased again in VD270 group (p < 0.05). Shrimp fed VD270 diet showed significantly higher lysozyme and nitro-blue tetrazolium activities than VD0 group (p < 0.05). Hemolymph cholesterol level was significantly lower in VD270 group than that of VD45, VD90, and VD135 groups (p < 0.05). All vitamin D3 supplemented groups showed significantly higher hemolymph triglyceride level than that of VD0 group (p < 0.05). Blasenzellen cell count and diameter in hepatopancreatic tubule were significantly increased with increasing dietary vitamin D3 levels (p < 0.05). Vitamin D3 supplementation promoted lipid droplet accumulation in hepatopancreatic cells, while excessive levels (VD270) impaired lipid metabolism (p < 0.05). The gene expression levels of insulin-like growth factor binding protein and prophenoloxidase were significantly upregulated in VD90 group in comparison to the VD0 group (p < 0.05). The estimated optimum vitamin D3 level for maximum growth for Pacific white shrimp is likely to be 100.9–113.34 μg/kg, based on broken line regression with insulin-like growth factor binding protein gene expression level and final body weight.
Eom et al. (Sun,) studied this question.