本试验研究了1～21日龄肉仔鸡每日摄入不同水平的能量和蛋白质对其生长性能及体组分的影响，旨在确定日粮能蛋比（代谢能/粗蛋白质）与日粮蛋白质沉积为体蛋白质的效率（ep）间的函数关系及日粮能量以蛋白质形式和以脂肪形式沉积的效率。试验选取体重相近的1日龄爱拔益加（AA）肉仔鸡432只，按性别及日粮不同随机分为24个处理，每个处理3个重复，每个重复6只鸡。肉仔鸡每日限量饲喂，饲喂水平分别为正常采食量的95%、80%、65%、50%，每日定量供给肉仔鸡高、中、低3个水平的高蛋白质基础日粮及由饲喂水平决定的定量淀粉，进而使肉仔鸡每日采食能蛋比不同的12种日粮。试验期21 d，试验初和试验末分别进行屠宰试验，以测定肉仔鸡体成分。试验结果显示：1）日粮能量及蛋白质水平显著影响了肉仔鸡试末体重、体蛋白质重及体脂肪重（P<0.05）；高蛋白质摄入水平下，随能量摄入水平的增高，公、母肉仔鸡试末体重、体蛋白质重及体脂肪重显著增高（P<0.05）；中蛋白质摄入水平下，公、母肉仔鸡体脂肪重随能量摄入水平的增高显著增高（P<0.05），试末体重及体蛋白质重在50%～80%限饲水平时，随能量摄入水平的增高显著增高（P<0.05）；低蛋白质摄入水平下，公鸡体脂肪重随能量摄入水平的增高显著增高（P<0.05），公、母肉仔鸡试末体重及母鸡体脂肪重在50%～80%限饲水平时，随能量摄入水平的增高显著增高（P<0.05），而体蛋白质重随能量摄入水平的增高无显著差异（P>0.05）；2）日粮能量水平、蛋白质水平显著影响了肉仔鸡体增重、体蛋白质增重及体脂肪增重（P<0.05），其影响趋势与对肉仔鸡试末体重、体蛋白质重及体脂肪重的影响趋势相似；3）随日粮能蛋比的增加，日粮蛋白质沉积为体蛋白质的效率先线性增加，之后保持稳定，日粮能蛋比达到69.28 MJ/kg时，公、母肉仔鸡ep达到最大值，分别为0.64、0.63；4）公、母肉仔鸡日粮能量沉积为体蛋白质的效率分别为0.72、0.68，沉积为体脂肪的效率分别为0.59、0.65，公、母肉仔鸡平均沉积每克蛋白质分别需要能量32.88、34.82 kJ，沉积每克脂肪分别需要能量66.43、60.12 kJ。上述结果表明日粮能量及蛋白质摄入水平影响了肉仔鸡生产性能、体蛋白质及体脂肪沉积，日粮能蛋比影响了日粮蛋白质沉积为体蛋白质的效率，同时本试验确定了建立肉仔鸡机制性生长预测模型所需要的相关参数。

The effects of different energy and protein levels on the growth performance, body protein and body fat of broilers aged from 1 to 21 days were investigated to identify the relationship between the efficiency of protein utilization for body protein deposition (ep) and energy∶protein ratio and the efficiency of energy utilization for protein and fat deposition. Four hundred and thirty-two one-day-old Arbor Acres (AA) broilers were randomly arranged into 24 treatments with 3 replicates in each treatment and 6 chicks in each replicate by sex and diets. Broilers were fed with 95%, 80%, 65% and 50% restriction of ad libitum intake, respectively. On each day, broilers were supplied with three allowances of high-protein basal diets and appropriate amount of starch which were determined by 4 feeding levels. Thus, 12 diets with different energy∶protein ratios were formed. The trial lasted for 21 days. At the beginning and the end of the trials, broilers were killed, and the body compositions were determined. The results showed as follows: 1) the different energy and protein levels significantly affected the final body weight, body protein and body fat weight of male and female broilers (P<0.05); at high level of protein, the final body weight, body protein and body fat weight of male and female broilers were significantly increased with the increase of energy intake (P<0.05); at middle level of protein, the body fat weight of male and female was significantly increased with the increase of energy intake (P<0.05), and at 50%～80% feed restriction, the final body weight and body protein weight of male and female broilers were significantly increased with the increase of energy intake (P<0.05); at low level of protein, the body fat weight of male broilers was significantly increased with the increase of energy intake (P<0.05), and at 50%～80% feed restriction, the final body weight and body fat weight of male and female broilers and body fat weight of female broilers were significantly increased with the increase of energy intake (P<0.05), but there was no significant difference in body protein weight of broilers (P>0.05); 2) the different energy and protein levels significantly affected the average daily gain of body weight, body protein and body fat (P<0.05), and the effects were the same to those of energy and protein intake on the final body weight, body protein and body fat weight of broilers; 3) with the increase of energy∶protein ratio, ep increased linearly at first, and then kept constant at last; when the energy∶protein ratio reached 69.28 MJ/kg, the ep of male and female broilers attained their maximum values, and was 0.64 and 0.63 respectively; 4) the efficiency of energy utilization for protein deposition in male and female broilers was 0.72 and 0.68, respectively, and the efficiency of energy utilization for fat deposition in male and female broilers was 0.59 and 0.65, respectively; male and female broilers needed 32.88, 34.82 kJ of ME per gram of fat deposition and 66.43, 60.12 kJ of ME per gram of protein deposition, respectively. The results above indicated that the levels of protein and energy affected the growth performance, body protein and fat deposition, the energy∶protein ratio affected the efficiency of protein utilization for body protein deposition; at the same time, some parameters required for broilers growth prediction model based on mechanism research were identified.［Chinese Journal of Animal Nutrition, 2010，22（4）:886-893］