O'Connor J D, Sniffen C J, Fox D G, Chalupa W
Department of Animal Science, Cornell University, Ithaca, NY 14853.
J Anim Sci. 1993 May;71(5):1298-311. doi: 10.2527/1993.7151298x.
The Cornell Net Carbohydrate and Protein System was modified to include an amino acid submodel for predicting the adequacy of absorbed essential amino acids in cattle diets. Equations for predicting the supply of and requirements for absorbed essential amino acids are described and presented. The model was evaluated for its ability to predict observed duodenal flows of nitrogen, nonammonia nitrogen, bacterial nitrogen, dietary nonammonia nitrogen, and individual essential amino acids. Model-predicted nitrogen, nonammonia nitrogen, bacterial nitrogen, and dietary nonammonia nitrogen explained 93.2, 94.6, 76.4, and 79.3% of the observed duodenal flows, respectively, based on R2 values from predicted vs observed regression analysis. Based on slopes of regression lines, model-predicted duodenal nitrogen and nonammonia nitrogen were different from observed duodenal flows (P < .05), whereas model-predicted bacterial nitrogen and dietary nonammonia nitrogen were not different from observed duodenal flows (P < .05). Model-predicted duodenal flows of individual essential amino acids explained 81 to 90% of variation in observed duodenal amino acid flows. Based on slopes of regression lines, model-predicted duodenal threonine, leucine, and arginine were the only amino acids different from observed duodenal flows (P < .05). Ideas for further model improvements and research in amino acid metabolism were also presented.
康奈尔净碳水化合物和蛋白质系统被修改，纳入了一个氨基酸子模型，用于预测牛日粮中吸收的必需氨基酸的充足程度。文中描述并给出了预测吸收的必需氨基酸供应和需求的方程式。对该模型预测十二指肠氮、非氨氮、细菌氮、日粮非氨氮和单个必需氨基酸流量的能力进行了评估。基于预测值与观测值回归分析的R2值，模型预测的氮、非氨氮、细菌氮和日粮非氨氮分别解释了观测到的十二指肠流量的93.2%、94.6%、76.4%和79.3%。基于回归线的斜率，模型预测的十二指肠氮和非氨氮与观测到的十二指肠流量不同（P < 0.05），而模型预测的细菌氮和日粮非氨氮与观测到的十二指肠流量无差异（P < 0.05）。模型预测的单个必需氨基酸的十二指肠流量解释了观测到的十二指肠氨基酸流量变化的81%至90%。基于回归线的斜率，模型预测的十二指肠苏氨酸、亮氨酸和精氨酸是与观测到的十二指肠流量不同的仅有的氨基酸（P < 0.05）。文中还提出了进一步改进模型以及开展氨基酸代谢研究的思路。
