Vitamin C requirement of grass shrimp, Penaeus monodon, as determined with l-ascorbyl-2-monophosphate

Abstract

A growth experiment was conducted to compare l-ascorbyl-2-sulfate (C 2) and l-ascorbyl-2-monophosphate (C 3-M) with l-ascorbic acid (C 1) 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 C 1, C 2 or C 3-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 C 1, C 2 or C 3-M had significantly ( P<0.05) higher weight gain 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 C 1, C 2 or C 3-M, respectively than those fed the unsupplemented control diet. Hepatopancreatic ascorbate concentrations were high in shrimp fed C 1 followed by C 3-M and C 2 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 C 3-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.