本试验旨在研究不同饲养密度和饲粮赖氨酸水平对公母分饲肉鸡生长性能、胴体组成和健康状态的影响。试验采用2×2×3三因子完全随机设计，选用罗斯308商品代肉仔鸡公雏1 314只和母雏1 530只，随机分成12个处理，每个处理6个重复（栏）。试验设高、低2个饲养密度，分别为42（16公/m2或18母/m2）和26 kg/m2（10公/m2或12母/m2），以出栏体重计。饲粮分阶段配制，并设高、中、低3个赖氨酸水平，分别为NRC推荐标准的120%、100%和80%。结果显示，高饲养密度极显著降低肉鸡的平均日增重（P<0.01），极显著增加料重比（P<0.01）。在1~35日龄，高饲养密度极显著降低肉鸡的平均日采食量（P<0.01），但在36~42日龄，结果正好相反。各日龄阶段，公鸡的平均日采食量和平均日增重均极显著高于母鸡（P<0.01），而料重比均极显著低于母鸡（P<0.01）。在1~21、1~42日龄，性别与饲粮赖氨酸水平对肉鸡的平均日增重存在互作效应；在36~42日龄，性别与饲养密度对肉鸡的平均日增重和料重比存在互作效应（P<0.05）。在1~35日龄，高饲养密度对公鸡平均日增重影响较大；在36~42日龄，高饲养密度对母鸡平均日增重和料重比的影响较大。高饲养密度和低赖氨酸饲粮显著或极显著降低肉鸡的胸肌率（P<0.05或P<0.01），公鸡的胸肌率和腹脂率极显著低于母鸡（P<0.01）。高饲养密度极显著提高肉鸡步态和脚垫损伤评分(P<0.01)，公鸡的步态评分显著高于母鸡（P<0.05）。以上研究结果表明，高饲养密度不能改变肉鸡的赖氨酸需求，它对于肉鸡生长的不利影响具有日龄和性别特异性。

The effects of stocking density and dietary lysine level on growth performance, carcass composition and health status of separate-sex reared broilers were investigated. Using a 2×2×3 three-factor completely randomized design, 1 314 male and 1 530 female Ross 308 chicks were divided into 12 treatments with 6 replicates (pens) per treatment, respectively. Two stocking densities were designed in this experiment: 26 (low stocking density, 10 males/m2 or 12 females/m2) and 42 kg market weight/m2 (high stocking density, 16 males/m2 or 18 females/m2), respectively. A series of experimental diets with a 20% difference in lysine level (120%, 100%, and 80% of NRC recommendation standard) were compared in a 3-phase feeding program. The results showed as follows: high stocking density significantly decreased average daily gain (ADG) (P<0.01), and significantly decreased feed to gain ratio (F/G, P<0.01). On 1 to 35 days of age, high stocking density significantly decreased average daily feed intake (ADFI, P<0.01), however, the results were the opposite on 36 to 42 days of age (P<0.01). Male broilers had significantly higher ADFI and ADG, and lower F/G compared with female broilers on all feeding phases (P<0.01). On 1 to 21 and 1 to 42 days of age, sex and dietary lysine level had a significant interaction on ADG (P<0.05); on 36 to 42 days of age, sex and stocking density had a significant interaction on ADG and F/G (P<0.05). On 1 to 21 days of age, the ADG of male broilers was more severely affected by high stocking density. In contrast, female broilers were more severely affected in ADG and F/G by high stocking density from 36 to 42 days of age. The breast muscle ratio of broilers was significantly decreased by high stocking density (P<0.05) and low lysine diet (P<0.01). Female broilers had significantly higher breast muscle ratio and abdominal fat ratio compared with male broilers (P<0.01). High stocking density significantly increased the scores of gait and footpad burn, and the gait score of male broilers were significantly higher than that of female broilers (P<0.05). These results suggest that lysine requirement of broilers is not altered by stocking density, and the deteriorated effects of high stocking density are sex and age dependent.［Chinese Journal of Animal Nutrition，2011，23（4）：578 -588］