中文摘要：

实验通过评价斜带石斑鱼幼鱼生长性能、血清指标和相关酶活性的变化,探讨斜带石斑鱼获得最大生长的饲料蛋氨酸（Met）水平与Met代谢关键酶活性和氧化损伤的关系。添加DL-Met使实验饲料中Met的含量分别为0.71%、0.98%、1.26%、1.57%、1.86%和2.18%（Diet1-Diet6）,配制6组等氮等脂的饲料。选择健康实验鱼[初重（9.75±0.05）g]随机分为6组,每天分别于8：00和17：00投喂实验饲料,养殖8周。结果表明,Diet3组鱼体增重率和特定生长率显著高于Diet1和Diet6组（P〈0.05）;Diet4斜带石斑鱼幼鱼的肥满度显著高于Diet1、Diet5和Diet6（P〈0.05）;Diet2和Diet3组血清总蛋白含量显著高于Diet5组（P〈0.05）,Diet3组幼鱼血糖含量显著低于Diet1组和Diet2组（P〈0.05）,血清总胆固醇含量在Diet3组逐渐降低,Diet4—6组显著低于Diet2组（P〈0.05）;Diet3组肝脏超氧化物歧化酶（SOD）和过氧化氢酶（CAT）活性最高,显著高于其他各组（P〈0.05）,Diet 4组肝脏磷酸烯醇式丙酮酸羧激酶（PEPCK）活性与Diet 3相比差异不显著,但是显著低于其余各组（P〈0.05）。综合以上结果,以特定生长率为判据,经二次曲线模型拟合可得斜带石斑鱼幼鱼若获得最大特定生长率,其饲料中Met的最适含量为1.42%（占饲料蛋白3.16%）。在该水平下,鱼体血糖、血清总胆固醇含量和PEPCK活性较低,有利于改善鱼体对能量的利用;SOD和CAT活性升高有利于改善鱼体的氧化损伤。

英文摘要：

In this study, we investigated the effects of dietary methionine（Met） on the growth performance, the serum index, the activities of key enzymes in Met metabolism, and the oxidation of juvenile groupers（Epinephelus coioides）. Six iso-nitrogen and iso-lipid diets were prepared with DL-Met supplement at different concentrations, 0.71%, 0.98%, 1.26%, 1.57%, 1.86%, and 2.18%（Diet1-Diet6）. Each treatment was randomly assigned to a triplicate of 30 fish [initial weight（9.75±0.05） g] per aquarium. Fish were fed at 8： 00 and 17： 00 every day and were maintained in a flow- through aquaria for eight weeks. The results showed that the weight gain and the specific growth rate of the Diet3 group were significantly higher than those of the Diet1 and Diet6 groups（P〈0.05）. The condition factor of the Diet4 group was significantly higher than that of the Diet1, Diet5 and Diet6 groups（P〈0.05）. The levels of serum total proteins of the Diet2 and Diet3 groups were significantly higher than that of the Diet5 group（P〈0.05）. The level of blood glucose of the Diet3 group was significantly lower than that of the Diet1 and Diet2 groups（P〈0.05）. The level of serum total cholesterol was gradually reduced in the Diet3 group, and it was significantly decreased in the Diet4 and Diet6 groups compared to the Diet2 group（P〈0.05）. The activities of superoxide dismutase（SOD） and catalase（CAT） in the liver of the Diet3 group were the highest（P〈0.05）. There was no significant difference in the activity of phosphoenolpyruvate carboxylase kinase（PEPCK） between the Diet3 and the Diet4 groups, but it was significantly lower than that in the other groups（P〈0.05）. Quadratic regression analysis of the specific growth rate corresponding to the level of dietary methionine indicated that the optimal concentration of dietary methionine for the growth of juvenile groupers was 1.42% of dry diet in the presence of 0.46% cystine（corresponding to 3.16% of dietary protein on a dry weight basi