Effects of different dietary levels of L-ascorbyl-2-polyphosphate on growth and tissue vitamin C concentrations in juvenile olive flounder, Paralichthys olivaceus (Temminck et Schlegel)

Abstract

This experiment was conducted to study the effects of different dietary levels of vitamin C, L-ascorbyl-2-polyphosphate (ASPP), on growth and tissue vitamin C concentrations in juvenile olive flounder, Paralichthys olivaceus (Temminck et Schlegel). Fish were fed one of six semi-purified diets containing an equivalent of 0, 25, 50, 75, 150, or 1500 mg ascorbic acid (AA) kg−1 diet (C0, C25, C50, C75, C150 or C1500) in the form of ASPP for 12 weeks. Weight gain (WG) and protein efficiency ratio (PER) of fish fed the C0 diet were significantly lower than those of fish fed the other diets (P < 0.05), and WG and PER of fish fed the C25, C50 and C75 diets were significantly lower than those of fish fed the C1500 diet (P < 0.05). Fish fed the C0 diet exhibited vitamin C deficiency symptoms such as anorexia, scoliosis, cataract, exophthalmia and fin hemorrhage at the end of the 12-week test. After 12 weeks of the feeding trial, AA concentrations from gill, kidney, and liver of fish fed the C0, C25, C50 and C75 diets were significantly lower than those of fish fed the C150 and C1500 diets (P < 0.05). Based on broken line analyses for WG and PER, the optimum dietary levels of vitamin C were 91 and 93 mg AA kg−1 diet respectively. These findings suggest that the dietary vitamin C requirement could be 93 mg AA kg−1 diet to support reasonable growth, and greater than 150 mg AA kg−1 diet may be required for AA saturation of major tissues for juvenile olive flounder under experimental conditions.