Fox D G, Barry M C, Pitt R E, Roseler D K, Stone W C
Department of Animal Science, Cornell University, Ithaca, NY 14853.
J Anim Sci. 1995 Jan;73(1):267-77. doi: 10.2527/1995.731267x.
Accurate prediction of forage biological values and performance with animals fed forages requires accurately accounting for factors that influence animal requirements and feedstuff utilization. The Cornell Net Carbohydrate and Protein System (CNCPS) is an application model that uses a combination of mechanistic and empirical approaches to account for the effects of variation in animal factors and feed carbohydrate and protein fractions on animal performance. Thus, accurate animal and environmental descriptions, DMI, feed carbohydrate, and protein fractions and their digestion rates are required inputs. In 25 growth periods with calves fed high-forage diets, the CNCPS accounted for 74, 81, and 83%, respectively, of the variation in ADG predicted to be supported by the ME, metabolizable protein, and essential amino acid intake, the first-limiting of all three accounting for 81% of the variation with a -1% bias. Thus, the CNCPS can be used to accurately describe forage quality and the effects of changes in forage composition on animal performance. The model was sensitive to variations in NDF, CP, protein solubility, NDF and starch digestion rates, feed and microbial amino acid composition, maintenance protein requirement, body protein amino acid content, and the coefficient of efficiency of use of absorbed protein. Analysis of several trials indicates an improved efficiency of ME use with improved amino acid balances. Uses of the CNCPS discussed include interpreting, planning and applying research, teaching, developing tables of requirements and biological values for feeds, complex nutritional accounting, and predicting performance and profits.
准确预测饲喂草料的动物的草料生物学价值和生产性能，需要精确考虑影响动物需求和饲料利用的因素。康奈尔净碳水化合物和蛋白质系统（CNCPS）是一个应用模型，它结合了机械法和经验法来考虑动物因素以及饲料碳水化合物和蛋白质组分的变化对动物生产性能的影响。因此，准确的动物和环境描述、干物质采食量、饲料碳水化合物和蛋白质组分及其消化率是所需的输入信息。在25个用高草料日粮饲喂犊牛的生长阶段中，CNCPS分别解释了预计由代谢能、可代谢蛋白质和必需氨基酸摄入量所支持的平均日增重变化的74%、81%和83%，其中首项限制因素解释了81%的变化，偏差为-1%。因此，CNCPS可用于准确描述草料质量以及草料组成变化对动物生产性能的影响。该模型对中性洗涤纤维、粗蛋白、蛋白质溶解度、中性洗涤纤维和淀粉消化率、饲料和微生物氨基酸组成、维持蛋白质需求、体蛋白氨基酸含量以及吸收蛋白质的利用效率系数的变化敏感。对多个试验的分析表明，随着氨基酸平衡的改善，代谢能的利用效率提高。所讨论的CNCPS的用途包括解释、规划和应用研究结果、教学、编制饲料需求表和生物学价值表、复杂的营养核算以及预测生产性能和利润。
