An 8‐wk experiment was conducted to evaluate the effects of dietary protein on the growth performance, body composition, and serum biochemical indices of large male genetically improved farmed tilapia (GIFT), Oreochromis niloticus, reared in fertilized freshwater cages. Six semi‐purified diets were formulated, containing 18.05, 22.39, 25.97, 31.62, 35.97, and 39.89% protein (designated as P18, P22, P26, P30, P34, and P38, respectively). Each diet was fed to randomly selected fish (initial mean weight 216.7 g) in four cages. At the end of the experiment, the final body weights varied significantly (P < 0.05), ranging from 520 to 580 g. Fish receiving the P30 diet had the highest final weight value (580.5 ± 5.4 g). Weight gains of fish fed the P26 and P30 diets were significantly higher (P < 0.05) than those fed the P18 and P38 diets. The apparent feed efficiency of fish fed the P18 diet was significantly lower (P < 0.05) than that of fish in the other groups except the P22 group (P > 0.05). The apparent protein efficiency ratio decreased gradually with increasing dietary protein. Whole‐body moisture and ash showed no significant difference (P > 0.05), but protein and fat content were significantly affected by dietary protein level (P < 0.05). No significant differences were found for serum total protein, triglyceride, total cholesterol, glutamic‐oxaloacetic transaminase, and glutamic‐pyruvic transaminase levels among different diets (P > 0.05); only serum glucose level was affected by dietary protein levels (P < 0.05). Second‐order polynomial regression of weight gain suggested 29.3% dietary protein is adequate content for maximum growth of large male GIFT, O. niloticus.

中文翻译：

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日粮蛋白质水平影响在肥育的淡水笼养的大型男性转基因养殖罗非鱼，尼罗罗非鱼的生长性能

进行了为期8周的实验，以评估饮食蛋白对大型男性转基因养殖罗非鱼（GIFT），尼罗罗非鱼（Oreochromis niloticus）生长在受精淡水网箱中的生长性能，身体组成和血清生化指标的影响。配制了六种半纯化饮食，分别含有18.05％，22.39％，25.97％，31.62％，35.97％和39.89％的蛋白质（分别指定为P18，P22，P26，P30，P34和P38）。将每种饮食喂入四个笼子中随机选择的鱼（平均平均体重216.7 g）。在实验结束时，最终体重差异很大（P<0.05），范围从520到580 g。接受P30饮食的鱼的最终体重最高（580.5±5.4克）。饲喂P26和P30日粮的鱼的增重明显高于饲喂P18和P38日粮的鱼（P <0.05）。饲喂P18日粮的鱼的表观饲料效率显着低于P22组（P > 0.05）（P <0.05），而其他各组的鱼的表观饲料效率均显着低于P18 。表观蛋白质效率比随着日粮蛋白质的增加而逐渐降低。全身水分和灰分没有显着差异（P > 0.05），但蛋白质和脂肪含量受饮食蛋白质水平显着影响（P<0.05）。不同饮食之间的血清总蛋白，甘油三酸酯，总胆固醇，谷氨酸-草酰乙酸转氨酶和谷氨酸-丙酮酸转氨酶水平没有显着差异（P > 0.05）；膳食蛋白水平仅影响血清葡萄糖水平（P <0.05）。体重增加的二阶多项式回归表明，29.3％的膳食蛋白质足以满足大型男性GIFT尼罗罗非鱼的最大生长需求。