Comparison of L-ascorbyl-2-monophosphate Na-Ca and L-ascorbyl-2-phosphate-Mg as Vitamin C sources for Yellowtail Seriola quinqueradiata Juveniles

摘要

Two feeding experiments were conducted to examine the efficiency of two types of vitamin C(L-ascorbic acid,AsA) derivatives,L-ascorbyl-2-monophosphate Na-Ca(AMP-Na/Ca)and L-ascorbyl-2-phosphate-Mg(AMP-Mg) in terms of growth,AsA concentration in tissues,and hematology in yellowtail Seriola quinqueradiata juvenile(1.10 ± 0.01 g).Stress resistance for the yellowtail fed AMP-Na/Ca was also determined.In experiment 1,six dry pellet diets with different levels of AMP-Na/Ca(0,12,43,88,440,and 881 mg AsA/kg diet) and AMP-Mg(0,16,52,106,595,and 1164 mg AsA/kg diet) were used.Each diet was fed to the yellowtail three times per day for 50 days.In both the vitamin C sources,the survival rates of the fish fed diets without supplemental AsA were lower than 50% at day 20,and more than 50% of the fish fed the diet containing 12 or 16 mg AsA/kg died during day 30 to 40,but no significant(P>0.05) differences were detected in survival and growth among the fish groups fed the diets with 43 or 52 mg AsA/kg.Liver and brain AsA concentrations generally increased with increasing dietary AsA level of AMP-Na/Ca or AMP-Mg.In experiment 2,dry pellet diets were formulated to contain 43,88,440,and 881 mg AsA/kg using AMP-Na/Ca and the growth experiment lasted 60 days,and the yellowtails were subjected to low salinity and air dive stress.The fish receiving diets with 440 mg AsA/kg showed significantly(P<0.05) higher tolerance to low salinity stress than those of other groups.The fish receiving diets with 440 mg AsA/kg showed the highest survival rate in air dive stress test among all groups.The present study showed that the juvenile yellowtail could use both AMP-Na/Ca and AMP-Mg as AsA sources.The optimum dietary levels of AMP-Na/Ca and AMP-Mg for the yellowtail juveniles were estimated to be 43-52 mg AsA/kg.Furthermore our results also indicate the necessity of inclusing 440 mg AsA/kg diet for production of yellowtail under stressful conditions.