Fox D G, Sniffen C J, O'Connor J D, Russell J B, Van Soest P J
Department of Animal Science, Cornell University, Ithaca, NY 14853.
J Anim Sci. 1992 Nov;70(11):3578-96. doi: 10.2527/1992.70113578x.
The Cornell Net Carbohydrate and Protein System (CNCPS) has equations for predicting nutrient requirements, feed intake, and feed utilization over wide variations in cattle (frame size, body condition, and stage of growth), feed carbohydrate and protein fractions and their digestion and passage rates, and environmental conditions. Independent data were used to validate the ability of the CNCPS to predict responses compared to National Research Council (NRC) systems. With DMI in steers, the CNCPS had a 12% lower standard error of the Y estimate (Sy.x) and three percentage units less bias than the NRC system. For DMI in heifers, both systems had a similar Sy.x but the NRC had four percentage units less bias. With lactating dairy cows' DMI, the CNCPS had a 12% lower Sy.x. Observed NEm requirement averaged 5% under NRC and 6% under CNCPS predicted values at temperatures above 9 degrees C but were 18% over NRC and 9% under CNCPS at temperatures under 9 degrees C. Energy retained was predicted with an R2 of .80 and .95 and a bias of 8 and 4% for the NRC and CNCPS, respectively. Protein retained was predicted with an R2 of .75 and .85 with a bias of 0 and -1% for NRC and CNCPS, respectively. Biases due to frame size, implant, or NEg were small. Body condition scores predicted body fat percentage in dairy cows with an R2 of .93 and a Sy.x of 2.35% body fat. The CNCPS predicted metabolizable protein allowable ADG with a bias of 1.6% with a Sy.x of .07 kg compared to values of -30% and .10 kg, respectively for the NRC system.
康奈尔净碳水化合物与蛋白质体系（CNCPS）有一些方程式，可用于预测牛（体格大小、体况和生长阶段）、饲料碳水化合物和蛋白质组分及其消化率和通过率以及环境条件等存在广泛差异情况下的营养需求、采食量和饲料利用率。与美国国家研究委员会（NRC）体系相比，独立数据被用于验证CNCPS预测反应的能力。对于阉牛的干物质采食量（DMI），CNCPS的Y估计值标准误差（Sy.x）低12%，偏差比NRC体系少三个百分点。对于小母牛的DMI，两个体系的Sy.x相似，但NRC的偏差少四个百分点。对于泌乳奶牛的DMI，CNCPS的Sy.x低12%。在温度高于9摄氏度时，观察到的维持净能（NEm）需求在NRC预测值下平均低5%，在CNCPS预测值下低6%；但在温度低于9摄氏度时，分别比NRC预测值高18%，比CNCPS预测值高9%。能量留存的预测中，NRC和CNCPS的决定系数（R2）分别为0.80和0.95，偏差分别为8%和4%。蛋白质留存的预测中，NRC和CNCPS的R2分别为0.75和0.85，偏差分别为0%和 -1%。由于体格大小、植入物或有效净能（NEg）导致的偏差较小。体况评分预测奶牛体脂百分比的R2为0.93，Sy.x为体脂的2.35%。与NRC体系分别为 -30%和0.10千克的值相比，CNCPS预测可代谢蛋白质允许的平均日增重（ADG）偏差为1.6%，Sy.x为0.07千克。
