日粮非植酸磷和基因工程酵母菌植酸酶水平对22～42日龄黄羽肉鸡生长和胫骨发育的影响

 【目的】研究确定22～42日龄黄羽肉鸡非植酸磷（NPP）的需要量及毕赤酵母基因工程菌植酸酶（PHY A）的磷当量值。【方法】选用22日龄岭南黄羽肉公鸡1 320只,随机分为11个处理,每处理4个重复,每重复30只鸡。处理1为基础日粮（NPP水平为0.08%）,不添加磷酸氢钙和植酸酶;处理2～7在基础日粮中分别添加不同水平化学纯磷酸氢钙,日粮NPP水平分别为0.16%、0.24%、0.32%、0.40%、0.48%、0.56%;处理8～11在基础日粮中分别添加200、400、600 U•kg-1PHY A、400 U•kg-1美国进口植酸酶产品（PHY B）。【结果】肉鸡日增重随日粮NPP水平升高而增加,0.32%～0.56%组平均日增重显著高于对照组和0.16%组（P＜0.05）,0.48%组日增重最大;添加磷组肉鸡采食量显著高于对照组（P＜0.05）;0.40%组料重比最低,显著低于对照组（P＜0.05）;随日粮NPP水平升高肉鸡胫骨脱脂干骨重、干骨中磷含量和灰分中磷含量均显著升高,0.48%组达到最高,显著高于对照组、0.16%和0.24%组（P＜0.05）,添加磷组干骨中钙含量与灰分含量显著高于对照组（P＜0.05）。添加400、600 U•kg-1 PHY A和400 U•kg-1 PHY B显著提高了日增重、采食量和胫骨脱脂干骨重（P＜0.05）,添加2种植酸酶均显著提高了胫骨干骨中钙、磷含量与灰分中磷含量（P＜0.05）,添加600 U•kg-1 PHY A显著提高了干骨中灰分含量（P＜0.05）。【结论】22～42日龄满足黄羽肉鸡最佳生长和骨骼发育的NPP需要量为0.40%,PHY A的磷当量为685 U•kg-1。

Nonphytate Phosphorus Requirement and Efficacy of a Genetically Engineered Yeast Phytase on Yellow Broilers at 22-42-Day-Old of Age

Objective] An experiment was conducted to investigate the requirement of nonphytate phosphorus (NPP) and efficacy of a genetically engineered yeast phytase (PHY A) by Lingnan yellow broilers from 22 d to 42 d. Method] A total of 1320 one-day-old male chicks were randomly divided into eleven dietary treatment groups, which consisted of four replicate floor pens with 30 birds per pen. The control group (Treatment 1) was fed with basal diet of NPP 0.08% without dicalcium phosphate or phytase supplementation. Dietary levels of NPP were 0.16, 0.24, 0.32, 0.40, 0.48, and 0.56%, respectively, for treatments 2 to 7, through addition of dicalcium phosphate (chemistry grade) to the basal diet. Diets of treatments 8 to 11 were supplemented with PHY A at 200, 400 and 600 U·kg~(-1), a commercial phytase product (PHY B) at 400 U·kg~(-1) level, respectively. Result] The birds in 0.32%-0.56% NPP groups gained more than those of the other groups (P<0.05). The NPP supplementation significantly improved feed intake (P<0.05). The feed gain ratio was significantly decreased by 0.40% NPP diet compared to the control birds (P<0.05). The level of 0.48% NPP was required for optimum tibia development. The additions of PHY A at 400 U·kg~(-1) and 600 U·kg~(-1) level and PHY B all significantly improved ADG (P<0.05), ADFI (P<0.05), and dry defatted tibia weight (P<0.05). And the percentage of tibia ash was increased by 600 U·kg~(-1) PHY A supplementation (P<0.05). Conclusion] The requirements of NPP for maximal ADG and highest percentage tibia ash both are 0.40%. The phosphorus equivalency value of PHY A is estimated at 685 U·kg~(-1) for male yellow broilers of 22-42 day old.