VITAMIN-C REQUIREMENT OF GRASS SHRIMP, PENAEUS-MONODON, AS DETERMINED WITH L-ASCORBYL-2-MONOPHOSPHATE

A growth experiment was conducted to compare L-ascorbyl-2-sulfate (C2) and L-ascorbyl-2-monophosphate (C3-M) With L-ascorbic acid (C1) for supplying the dietary vitamin C requirement for juvenile grass shrimp, Penaeus monodon. Purified diets with 7 levels (0, 30, 50, 200, 500, 1000, 2000 mg/kg) of either supplemental C1, C2 or C3-M were fed to P. monodon (mean weight 1.06 +/- 0.05 g) for 8 weeks. Each diet was fed to three replicate groups of shrimp. Results indicated that shrimp fed diets supplemented with C1, C2 or C3-M had significantly (P < 0.05) higher weight pin and better feed conversion ratio (FCR) than those fed the unsupplemented control diet. Survival rates were significantly higher (P < 0.05) in shrimp fed diets supplemented with > 261.5, > 386.3 or > 37.6 mg/kg Of C1, C2 or C3-M, respectively than those fed the unsupplemented control diet. Hepatopancreatic ascorbate concentrations were high in shrimp fed C1 followed by C3-M and C2 and generally the concentration increased as the dietary ascorbic acid supplementation level increased. Broken-line regression analysis indicated that the requirement is 40.25 mg C3-M/kg diet or the equivalent of 18.7 mg ascorbic acid/kg diet. It also indicates that L-ascorbyl-2-sulfate was only about 25% as effective as L-ascorbyl-2-monophosphate in meeting the vitamin C requirement.