Abstract:A feeding trial was conducted to evaluate the effects of vitamin D3 (VD3) on growth performance, body composition, and antioxidant capacity of the juvenile sea cucumber Apostichopus japonicus. Six isonitrogen and isoenergetic diets were formulated by adding 0 (D1), 250 (D2), 500 (D3), 1000 (D4), 2000 (D5), or 3000 (D6) IU/kg VD3 into the basal diet (measured value: 95, 334, 570, 1076, 2063, and 3081 IU/kg). Juvenile sea cucumbers with initial body weights of (15.43±0.14) g were fed for 56 days. Results showed that VD3 had no effect on survival rate (P>0.05) of the sea cucumber. Further, both the weight gain rate and specific growth rate were significantly improved, and those of the D1 group were significantly lower than the other groups (P<0.05). The ratios of intestine weight to body weight of the D3, D4, and D5 groups were significantly higher than that of the other three groups (P<0.05), but there were no differences among them (P>0.05). With increasing VD3, moisture, crude protein, and crude lipid contents of the body wall were not affected significantly (P>0.05), but crude ash contents of the body wall increased and thereafter declined, reaching the maximum in the D5 group. The contents of hydroxyproline of the body wall decreased initially and then increased, reaching the minimum in the D4 group (P<0.05). The deposition amount of VD3 in the body wall increased initially and then decreased. The D4 group showed the highest value. VD3 significantly increased the contents of calcium in the body wall (P < 0.05). Additionally, the phosphorus content increased at first and was maintained. The contents of phosphorus of the D4, D5, and D6 groups were significantly higher than that of the D1 group (P<0.05), but there were no differences among them (P>0.05). The contents of magnesium in the body wall increased in all groups by dietary VD3, and all experimental groups had significantly higher magnesium contents than that in the D1 group (P<0.05). The contents of iron increased initially and then decreased, and the contents in the D5 and D6 groups were significantly lower than those in the other groups (P<0.05). The contents of manganese decreased, but the difference between each group was not significant (P>0.05). With increases in dietary VD3 level, both the activities of alkaline phosphatase and total superoxide dismutase in the intestines of the experimental groups first increased and then declined, while the contents of malondialdehyde decreased. The total antioxidative capacity and catalase activity in the intestines of all groups were not significantly affected (P>0.05) by VD3. In conclusion, analysis by a WGR linear regression equation indicated that the optimal demand for VD3 in the sea cucumber (initial body weight 15.43 g) was 1587.5 IU/kg.
