Comparison of L-ascorbyl-2-polyphosphate with L-ascorbyl-2-sulfate in meeting vitamin C requirements of juvenile grass shrimp Penaeus monodon

A growth experiment was conducted to compare the relative efficacy of L-ascorbyl-2-polyphosphate (C2PP) and L-ascorbyl-2-sulfate (C2S) in supplying the dietary vitamin C requirement for juvenile grass shrimp Penaeus monodon. Purified diets with 6 levels of either supplemental C2PP (0, 120, 200, 800, 2000 and 4000 mg/kg diet) or C2S (0, 30, 50, 200, 500 and 1000 mg/kg diet) were fed to P. monodon (mean weight 0.79+/-0.08 g) for 8 weeks. Each diet was fed to three replicate groups of shrimp. Results indicated that shrimp fed diets containing greater than or equal to 22.81 mg of C2PP/kg or greater than or equal to 72.41 mg of C2S/kg diet had significantly (p<0.05) higher weight gain than shrimp fed the unsupplemented control diet. Feed conversion ratio (FCR) was poor in shrimp fed the diet lacking supplementary vitamin C. Shrimp fed diets supplemented with 126.90 and 292.84 mg of C2PP/kg or greater than or equal to 72.41 mg of C2S/kg diet had a higher survival than shrimp fed the unsupplemented control diet. Ascorbic acid concentration in hepatopancreas was higher in shrimp fed diets supplemented with C2PP and C2S than those fed the unsupplemented control diet, and the concentrations were generally proportional to the level of ascorbic acid supplementation in the diet. Weight gain analyzed by broken-line regression indicated that the dietary level of ascorbic acid from each source for juvenile P. monodon is 29.27 mg of ascorbic acid/kg diet for C2PP and 73.83 mg of ascorbic acid/kg diet for C2S suggesting that C2S is about 40% as effective as C2PP in meeting the vitamin C requirements.