Effects of dietary vitamin C on growth, lipid oxidation, and carapace strength of soft-shelled turtle, Pelodiscus sinensis

A feeding trial was conducted to evaluate the effects of dietary vitamin C level on the growth, liver lipid oxidation, and carapace strength of juvenile soft-shelled turtles, Pelodiscus sinensis. Seven experimental diets containing 0–619mg vitamin C/kg were fed to 140 individually reared soft-shelled turtles with an average weight of 4.3±0.07g for 8weeks. There was no significant difference (p>0.05) in weight gain, feed conversion ratio, protein efficiency ratio, and muscle composition among turtles fed different test diets. Muscle composition was as follows: moisture, 73.5%; crude protein, 18.3%; lipid, 2.82%; and ash, 0.73%. Hepatic vitamin C concentration, liver tissue lipid oxidation, carapace strength, and carapace collagen content in turtles fed the vitamin C-free diet were the lowest among the dietary groups. The highest carapace strength was observed in turtles fed a diet containing approximately 350mg of vitamin C/kg. Although the absence of dietary vitamin C did not impact the growth of the turtles, the supplementation of vitamin C could enhance the carapace strength and collagen content of the soft-shelled turtles. Analyzed by a polynomial regression, the estimated dietary vitamin C level for optimal carapace collagen and strength of the soft-shelled turtles was approximately 370–380mg/kg.