Use of Mg-L-ascorbyl-2-phosphate as a vitamin C source in shrimp diets

To overcome the lability of vitamin C (L-ascorbic acid or L-AsA), an essential nutrient of shrimp diets, the efficacy of Mg-L-ascorbyl-2-phosphate (MAP), a relatively stable derivative of L-AsA, was examined. Groups of juvenile Penaeus japonicus were fed five different test diets containing different amounts of MAP for 100 days, to determine if MAP could be utilized by shrimp. Normal growth was observed on test groups fed diets containing 1,078, 430 and 215 mg MAP per kg, whereas mass mortality occurred in populations fed diets containing 43 and 0 mg MAP per kg. The dead shrimp found in the latter two treatments exhibited blackened lesions underneath the exoskeleton. The symptom looked similar to what was reported in previous papers as L-AsA deficiency syndrome. The feeding experiment suggests that MAP can be utilized by P.japonicus as a suitable replacement for L-AsA, and a supplement of 215 to 430 mg in 1 kg is sufficient to prevent clinical signs of vitamin C deficiency. Repeated measurements of remaining L-AsA and MAP, made after diet processing and storage, demonstrated that MAP was significantly more stable than L-AsA and was less prone to leaching in sea water.