通过饲养试验和氮代谢试验,观测饲粮粗蛋白质水平对22~42日龄肉仔鸡生长性能、胴体性能及肉品质、血清生化指标、免疫功能、氮排放及氮表观利用率的影响,研究22~42日龄肉仔鸡玉米-豆粕型饲粮中粗蛋白质的最低需要量。采用单因子完全随机试验设计,将360只22日龄AA肉公雏按体重随机分成6个组,每个组10个重复笼,每个重复笼6只鸡,分别饲喂粗蛋白质实测水平为19.87%(对照组)、18.84%、17.63%、16.81%、15.75%和14.88% 的玉米-豆粕型饲粮21 d。38~42日龄进行氮代谢试验。结果表明:耗料/增重、腹脂率、胸肌滴水损失和红度(a^*)值、腿肌a^*和黄度(b^*)值、血清总胆固醇含量、甘油三酯含量、尿酸含量和氮表观利用率随饲粮粗蛋白质水平降低而显著提高(P<0.05),而平均日增重、胸肌亮度(L^*)值、新城疫抗体效价和氮排放随饲粮粗蛋白质水平降低而显著降低(P<0.05)。与对照组相比,当饲粮粗蛋白质水平由19.87%降至17.63%时,上述指标无显著差异(P>0.05),但显著降低粪便氮排放(P<0.05);当饲粮粗蛋白质水平进一步降低至16.81%及以下时,肉鸡的平均日增重显著降低(P<0.05),而耗料/增重显著提高(P<0.05),腹脂率、胸肌滴水损失、血清总胆固醇和甘油三酯含量显著增加(P<0.05),新城疫抗体效价显著降低(P<0.05)。因此,22~42日龄肉仔鸡玉米-豆粕型饲粮中粗蛋白质最低需要量以17.63%为宜。

An experiment was conducted to investigate the effect of dietary crude protein (CP) level on growth performance, carcass quality, serum biochemical parameters, immune indexes, nitrogen emission and nitrogen apparent availability in broilers, so as to estimate the minimum CP requirement of broilers fed corn-soybean diet from 22 to 42 days of age. A total of 360 22-day-old male broilers were randomly assigned to 5 groups with 10 replicates per group and 6 birds each replicate.The birds were fed the diet containing CP 19.87% (control), 18.84%, 17.63%, 16.81%, 15.75% or 14.88% for 21 days. The nitrogen metabolism test was conducted from 38 to 42 days of age. The results showed as follows:broilers fed lower CP level diets had significantly higher values of ratio of feed to gain, percentage of abdominal fat, drip loss and a^* values of breast meat, a^* and b^* values of thigh meat, serum contents of total cholesterol, triglyceride and uric acid, as well as nitrogen apparent availability (P<0.05). Average daily gain, L^* of breast meat, serum ND antibody titer and fecal nitrogen were significantly increased as the dietary CP level decreased, respectively (P<0.05). Compared with the control, no significant differences were observed in the above mentioned indexes for broilers fed diets containing 17.63% of CP (P>0.05), however, nitrogen content in feces was significantly lower (P<0.05). Broilers fed diets containing 16.81% or lower CP had significantly lower average daily gain and ND antibody titer (P<0.05). Ratio of feed intake to body gain, abdominal fat, drip loss of breast meat, serum total cholesterol and triglyceride were significantly higher when chicks were fed diets with lower CP than 16.81%, respectively (P<0.05). Therefore, the minimum dietary CP requirement of broilers from 22 to 42 days of age is suggested as 17.63%.