Comparison of l-ascorbyl-2-monophosphate-Ca with l-ascorbyl-2-monophosphate-Na/Ca on growth and tissue ascorbic acid concentrations in Korean rockfish ( Sebastes schlegeli)

Abstract

This experiment was conducted to compare l-ascorbyl-2-monophosphate-Ca (AMP-Ca) with l-ascorbyl-2-monophosphate-Na/Ca (AMP-Na/Ca) for supplying the dietary vitamin C for juvenile Korean rockfish ( Sebastes schlegeli). Fish were fed 1 of 11 semi-purified diets containing equivalent of 0, 50, 100, 200, 400, and 800 mg ascorbic acid (AA)/kg diet in the form of AMP-Ca or AMP-Na/Ca for 12 weeks. After 12 weeks of the feeding trial, weight gain (WG), feed efficiency (FE) of fish fed with the control diet (vitamin C-deficient diet) were significantly lower than those of fish fed with the vitamin C-supplemented diets in either form ( P<0.05). WG of fish fed with AMP-Na/Ca 400, AMP-Na/Ca 800, AMP-Ca 400 and AMP-Ca 800 diets were significantly higher than those of fish fed with the control diet, AMP-Na/Ca 50, AMP-Ca 50 and AMP-Ca 100 diets ( P<0.05). In general, there was no significant difference between AMP-Ca diets and AMP-Na/Ca diets at the same supplementation levels. By the end of the 9th week, fish fed with the control diet began to show the initial vitamin C deficiency signs such as anorexia, erratic swimming behavior, darkening in skin color and reduced growth. The ascorbic acid concentrations in fish muscle and liver increased with the increase of the vitamin C supplementation levels in fish diets regardless of which kind of vitamin C source used. There were no significant differences in ascorbic acid concentrations in liver and muscle of fish between the two vitamin C sources at the same supplementation level. These results indicate that AMP-Ca is a bioavailable form of vitamin C source for Korean rockfish and it has the antiscorbutic activity equal to AMP-Na/Ca. Broken-line analysis of weight gain indicated that the dietary vitamin C requirement of Korean rockfish was 106 mg AA/kg diet based on the pooled WG of fish fed with the AMP-Na/Ca and AMP-Ca diets. However, based on the different forms of ascorbic acid, the vitamin C requirements were 101 and 112 mg AA/kg diet with the forms of AMP-Na/Ca and AMP-Ca, respectively.