Two experiments were conducted to investigate vitamin C requirements o
f the shrimp Penaeus vannamei using L-ascorbyl-2-polyphosphate (APP) i
n semi-purified diets. Shrimp survival but not growth was significantl
y (P < 0.05) reduced by feeding vitamin C-deficient diets. Whole-body
ascorbic acid (WBAA) content in shrimp increased as dietary vitamin C
increased. After shrimp were fed a vitamin C-free diet for 3 weeks, th
e depletion levels for WBAA of shrimp were found to be 2.6 and 4.8 mug
/g for shrimp with an initial weight of 0.1 and 0.5 g, respectively. M
inimum dietary vitamin C levels required for normal survival of P. van
namei were estimated to be 120 mg ascorbic acid-equivalent (AAE)/kg di
et for shrimp with an initial weight of 0.1 g and 41 mg AAE/kg diet fo
r shrimp with an initial weight of 0.5 g. Dietary vitamin C levels of
120 and 90 mg AAE/kg were required for maintaining a normal WBAA conte
nt in shrimp with an initial weight of 0.1 and 0.5 g, respectively. Th
ese data indicated that dietary vitamin C requirement of P. vannamei d
ecreased with increased size.