中文摘要：

为了评价不同饲料蛋氨酸水平对吉富罗非鱼生长、饲料利用率及体成分的影响，实验通过在半精制基础饲料中添加DL-蛋氨酸，配制成蛋氨酸水平分别为0．26％、0．55％、0．85％、1．14％、1．44％和1．73％的6种等氮等能（32．09％粗蛋白质，15．82kJ／g总能）的饲料，以初始体质量（66．76±2．29）g的吉富罗非鱼为实验对象，每种实验饲料设3个重复，每个重复放养实验鱼25尾，养殖系统为室内养殖系统，每天表观饱食投喂3次，养殖时间为60d。结果发现，随饲料蛋氨酸含量的增大，罗非鱼的增重率（WGR）、特定生长率（SGR）、饲料蛋白效率（PER）、饲料蛋白沉积率（PDR）均呈现先上升后下降的趋势，饲料系数（FCR）呈现先下降后上升的趋势。且在蛋氨酸含量为1．14％时WGR、SGR、PER均达到最大（分别为361．91％、2．73％／d和2．53％），FCR达到最低（为1．23），PDR则在蛋氨酸水平为1．44％时达到最大（47．22％）。随饲料蛋氨酸含量的增加，罗非鱼肝体比和脏体比呈明显的先下降后上升的变化趋势，肥满度则无明显的变化；随饲料蛋氨酸含量的增加，罗非鱼肌肉粗蛋白质呈先上升后下降的变化趋势，而全鱼和肌肉粗脂肪呈先升高后稳定的变化趋势。但全鱼粗蛋白、全鱼和肌肉中的水分、灰分的含量差异均不显著，肌肉中组氨酸、丝氨酸和胱氨酸含量差异不显著，但其余各种氨基酸含量及肌肉必需氨基酸总量（EEAA）、肌肉氨基酸总量（ETAA）均呈先上升后下降的趋势。以WGR、SGR、PER、PDR、FCR作为评价指标，通过二次回归分析可知，胱氨酸含量为0．30％时，罗非鱼饲料中适宜的蛋氨酸水平应为1．13％～1．16％，占饲料蛋白质的3．52％～3．61％．

英文摘要：

A feeding trial was conducted to evaluate the effects of dietary methionine levels on growth performance, body composition of GIFT （ Oreochromis niloticus） [ initial body weight of（66.76± 2.29） g 1. Six isonitrogenous（32.09% crude protein）and isoenergetic （17.82 kJ/g gross energy）semipurified diets were formulated with the graded methionine levels （0,0.3% , 0.6% , 0.9% , 1.2% and 1.5% dry diet, respectively） ,using gelatin, fishmeal, peanut meal and crystalline amino acids mixtures as the main dietary protein sources. Amino acid pattern in diet is to simulate the amino acid pattern found in the whole body protein of GIFT except for methionine. The six trial diets were determined to contain methionine of 0.26% , 0.55% ,0.85% , 1. 14% , 1.44% and 1.73% dry diet, respectively. Each diet was randomly assigned to triplicate groups of 25 fish and fed to apparent satiation by hand thrice daily （8：00,13：00 and 16：00） for 60 days. The results showed that the weight gain rate （ WGR）, specific growth rate （ SGR）, protein efficiency ratio （PER）and protein deposition rate （PDR）initially increased with increasing dietary methionine levels, but then decreased. Conversely, the feed conversation ratio （FCR）first decreased and then increased. The WGR, SGR, PER were all the highest （361.91% ,2.73 %/d and 2.53 % respectively） when the dietary methionine level was 1.14%. At the same time,the FCR was the lowest（ 1.23 ）. The PDR was the highest（47.22% ） when the dietary methionine level was 1.44%. The hepatosomatic index （HSI） and viscerosomatic index （VSI） of GIFT first decreased with increasing dietary methionine levels, but then increased （P 〈 0.05 ）, yet the condition factor（CF） had no significant differences（ P 〉 0.05 ）. The tendency of crude protein content in muscle was similar to WGR and SGR with increasing dietary methionine levels（ P 〈0.05 ） ,while the crude lipid in muscle first increased with increasing dietary methionine levels and