Effects Of Radix Astragali And Vitamin C Of Stress Of Large Yellow Croaker (Pseudosciaena Crocea R.)

Large yellow croaker (Pseudosciaena crocea R.) is a kind of cluster migratoryfish. Its optimum growth temperature is18~25℃, when the water temperature roseto28℃, the intake will be reduce30%to40%.Every hot season from July toSeptember, large yellow croaker vulnerable to heat stress and pest invasion, it isalways much fish dying in hot season. During breeding large yellow croaker alsovulnerable trawl stress impact. Therefore, how to enhance the ability of large yellowcroaker resistance to heat stress and trawl stress is worth to study.The study aimed at evaluating whether the radix astragali and vitamin C, bysupplementing a basal diet with different doses, would enhance the ability of largeyellow croaker resistance to heat stress and trawl stress.Experiment1: Atotal of360fish of large yellow croaker were randomly dividedinto three groups. The control group was fed with basal diet, the others were treatedgroups fed with basal diet supplemented with1.5%and3.0%raw material powder ofradix astragali, respectively. Two weeks of feeding in July, fish were stressed by hightemperature. The survival of large yellow croaker and the change of serum cortisol,glucose and some enzyme activities in liver after the stress were investigated. Theresults showed that serum cortisol and glucose had no significant difference in allgroups. The survival of the control group is95.8%, but the survival of the groups thatsupplemented with1.5%and3.0%raw material powder of radix astragali wasreduced to45.8%and31.7%, respectively. Activities of glutamate pyruvatetransaminase(GPT) in serum in fish fed diets with supplementation3.0%raw materialpowder of radix astragali was significantly higher than that of control group.These results suggested that dietary3.0%of raw material powder of radixastragali on large yellow croaker caused a certain degree of liver damage. The worstthing is that feeding more than1.5%of raw material powder of radix astragali onlarge yellow croaker caused a large number of fish die. The reason of that is worth to do further research.Experiment2: Atotal of360fish of large yellow croaker were randomly dividedinto three groups. The groups were fed with basal diet supplemented with69mg/kg(control),276mg/kg,552mg/kg vitamin C. Four weeks of feeding from July to August,fish were stressed by high temperature. After four weeks the fish were also stressed bytemperature difference stress and trawl stress. The survival of large yellow croakerand the change of serum cortisol, glucose and some enzyme activities in liver after thestress were investigated. The results showed that it is not significantly difference ofsurvival on the groups. Fish fed with basal diet supplemented with more than276mg/kg vitamin C can help fish keep a significantly higher glucose in serum.Before and after the temperature difference stress and trawl stress the276mg/kgvitamin C group no significant differences in serum cortisol and glucose levels. It isconcluded that ingestion of276mg/kg doses of vitamin C could enhance the ability oflarge yellow croaker resistance to heat stress and trawl stress.