Optimal Dietary Vitamin C And Vitamin E Levels For Juvenile Discus Fish Symphysodon Haraldi

In this study,the juvenile discus fish Symphysodon haraldi were fed diets containing 0,40,80,120,160 mg/kg of vitamin C and 0,40,80,120 mg/kgvitamin E in a factorial arrangement to investigate potential nutritional interaction and effects on growth and shape performance,antioxidant function,and digestive enzymes activities,lysozyme activity and body color.The experiment was carried out in a circulatory system that could be fully aerated and oxygenated.The culture conditions of experimental fish: All tanks were supplied with full aerated tap water and air injection,being the experiment carried out about 12 h light / 12 h dark daily(light from 8:00 am to 8:00 pm).The temperature,dissolved oxygen concentration and pH were measured with values from 29.4 to 31.6 ℃,7.27 to 10.34 mg/L and 8.03 to 8.53 for temperature,dissolved oxygen and pH,respectively.Fish were hand-fed three times per day(08:30,12:30 and 16:30)for 56-day at a rate of 4 to 5 % of their mean wet mass carefully.After feed distribution,remaining feed in the bottom of the tanks was collected to correct feed intake.Remove excrement and replace 1/3 volume of water from every tank daily.There are the following results: 1.The results showed that vitamin E significantly increased the final body weight (FW),weight gain rate(WR),specific body weight gain rate(SWR),final body length(FBL),body length rate(LR),specific body length gain rate(SLR),final body height(FBH),feed conversion ratio(FCR)of S.haraldi(P < 0.05).Vitamin C increased the SWR,FBH,FBW significantly(P < 0.05).No significant differences in condition factor(CF),and survival rate(SR)were observed between the control and treatment groups(P > 0.05).Additionally,a significant interaction between vitamin C and vitamin E in WR,SWR,and HSI was observed.No interaction between vitamin C and vitamin E in FBL,FBH,FBW.2.Total antioxidant capacity(T-AOC),total superoxide dismutase(T-SOD),and malondialdehyde(MDA)of the liver were measured for antioxidant function as indicators.In the experimental group,vitamin E significantly increased T-AOC and T-SOD and significantly reduced the MDA of the liver(P < 0.05).Vitamin C significantly improved T-SOD of the liver(P < 0.05).Compared with the control group,the T-AOC,T-SOD and MDA in the treatment group did not show significant differences(P > 0.05).An interaction was observed in the T-AOC and T-SOD between vitamin C and vitamin E(P < 0.05).3.In digestive tract digestive enzymes,protease activity(PA)and lipase activity(LA) were selected as the index.Vitamin E significantly increased the PA and LA in the digestive tract of the S.haraldi(P < 0.05),while vitamin C showed no difference in PA and LA(P > 0.05).Vitamin C and vitamin E showed an interaction in the PA.4.In lysozyme activity(LZM)of liver,both vitamin C and vitamin E significantly increased LZM of the liver(P < 0.05).Vitamin C and vitamin E showed an interaction in LZM(P < 0.05).5.In the effects on body composition of S.haraldi and the vitamin C and vitamin E content in the liver.With the increase of vitamin E content,the crude fat content of the body composition showed an increasing trend,while the moisture,crude protein and ash content showed no difference.With the increase of vitamin C in diets,the content of vitamin C in liver increased gradually,but as the amount of vitamin E in the diet increased,the content of vitamin E in liver tissue increased at first and then at a high level.6.In body color,a*(redness),b*(yellowness),L*(brightness)were selected as the index.vitamin C have a certain influence on L*.While vitamin E have a certain influence on L* and a*.Vitamin C and vitamin E showed significant interaction in L* and b*(P < 0.05),the treatment groups showed little improvement compared with the control group.In this study,these findings indicate that the diet supplemented with moderate dietary vitamin C and vitamin E showed beneficial effect on growth performance,digestive tract proteases,and lysozyme activity in liver of S.haraldi.However,there have limited effects on the antioxidant function and body color.These observations of this experiment suggest the diet supplemented with moderate dietary vitamin C(40 mg/kg)and vitamin E(80 mg/kg)can promote the growth and maintain the health for S. haraldi.