Efficacy of silicone-coated ascorbic acid and ascorbyl-2-polyphosphate to fast-growing tiger shrimp (Penaeus monodon )

Abstract

Growth, survival, tissue ascorbate concentration and collagen content were studied in fast-growing Penaeus monodon fed two ascorbic acid (AA) derivatives. Prior to the experimental trial, shrimp (initial body weight: 0.9 ± 0.4 g) were fed on a diet lacking vitamin C for 5 weeks. During the following 13-week experiment, the shrimp (initial body weight: 8.2 ± 0.7 g) were given one of five squid-meal-based diets. The dietary treatments consisted of a diet lacking vitamin C, two diets supplemented with either 500 or 1000 mg AA kg−1 in the form of silicone-coated AA, and two diets supplemented with either 500 or 1000 mg AA kg−1 in the form of ascorbyl-2-polyphosphate. Shrimp gained 18.3 g in 13 weeks. The AA-free diet group exhibited the lowest growth rate, feed intake and survival (26.8%) after 4 weeks. Hepatopancreatic ascorbate and muscle collagen content were significantly (P < 0.05) lower in AA-deprived shrimp. At the end of the feeding trial, growth rate and survival were not significantly (P > 0.05) different among groups fed AA-supplemented diets. Hepatopancreatic and haemolymphatic ascorbate concentrations were significantly (P < 0.05) higher in groups given ascorbyl-2-polyphosphate than in groups given silicone-coated AA. A supplement of 500 mg AA kg−1 diet in the form of either silicone-coated AA or ascorbyl-2-polyphosphate was adequate for optimal growth. But ascorbate concentrations in tissues remained much below saturation levels with a supplement of 1000 mg AA kg−1 diet. It is questionable whether the established vitamin C requirements for P. monodon are adequate to maintain tissue ascorbate in fast-growing juveniles.