Ainslie S J, Fox D G, Perry T C, Ketchen D J, Barry M C
Department of Animal Science, Cornell University, Ithaca, NY 14853.
J Anim Sci. 1993 May;71(5):1312-9. doi: 10.2527/1993.7151312x.
The Cornell Net Carbohydrate and Protein System (CNCPS) and NRC (1985) models were evaluated for accuracy in predicting metabolizable protein (MP) and essential amino acid (EAA) allowable ADG, using chemical body and feed composition data from feeding trials with Holstein steers. Nine Holstein steers (113 to 200 kg) were slaughtered and determined to have the following whole-body essential amino acid composition of (grams/100 grams of protein): arginine, 5.94; histidine, 2.07; isoleucine, 2.28; leucine, 5.72; lysine, 5.81; methionine, 1.99; phenylalanine, 3.04; threonine, 3.52; tryptophan, .57; and valine, 3.32. The NRC and CNCPS were then tested against data from 25 feeding periods, each representing the 56-d growth of 10 Holstein steers (mean BW of 162 kg), to determine their ability to predict the gain allowed by the supply of MP and the first-limiting EAA. The NRC (1985) system accounted for 46% of the variation in MP allowable gain, with an average bias of -30%. The CNCPS accounted for 87 and 73% of the variation in MP and EAA allowable gain, with a bias of 8 and 5%, respectively. The bias was reduced to 3% (R2 of .82) when ADG was predicted by the factor (ME, MP, or EAA) first-limiting ADG.
利用荷斯坦公牛饲养试验中的化学体成分和饲料成分数据，对康奈尔净碳水化合物和蛋白质系统（CNCPS）模型和NRC（1985）模型预测可代谢蛋白质（MP）和必需氨基酸（EAA）允许日增重的准确性进行了评估。屠宰了9头荷斯坦公牛（体重113至200千克），并测定其全身必需氨基酸组成如下（每100克蛋白质中的克数）：精氨酸5.94；组氨酸2.07；异亮氨酸2.28；亮氨酸5.72；赖氨酸5.81；蛋氨酸1.99；苯丙氨酸3.04；苏氨酸3.52；色氨酸0.57；缬氨酸3.32。然后，根据25个饲养期的数据对NRC和CNCPS进行了测试，每个饲养期代表10头荷斯坦公牛（平均体重162千克）56天的生长情况，以确定它们预测MP供应和第一限制性EAA所允许增重的能力。NRC（1985）系统解释了MP允许增重变异的46%，平均偏差为-30%。CNCPS分别解释了MP和EAA允许增重变异的87%和73%，偏差分别为8%和5%。当用第一限制性ADG的因子（代谢能、MP或EAA）预测ADG时，偏差降至3%（R2为0.82）。
