中文摘要：

本试验旨在应用康奈尔净碳水化合物一蛋白质体系（CNCPS）评定我国北方奶牛常用粗饲料的营养价值。分别从北京、山东、河南、河北、内蒙古等地采集奶牛常用粗饲料共3类7种33个样品，应用CNCPS中碳水化合物和含氮化合物的分类方法，测定粗饲料的营养成分，计算其碳水化合物和蛋白质组分，并进行分类分析。结果表明：粗饲料的可溶性粗蛋白质主要是非蛋白氮，真蛋白质含量相对较少；苜蓿粗蛋白质含量高，不可利用蛋白质含量较低，非结构碳水化合物含量高，是优质的粗饲料；小麦秸的不可利用纤维和不可利用蛋白质含量较高，营养价值较差；玉米青贮类饲料不可利用纤维和不可利用蛋白质含量较低，营养价值优于秸秆类饲料；糯玉米秸秆的粗蛋白质含量较高，不可利用纤维和不可利用蛋白质含量均较低，营养价值优于玉米秸和玉米秸青贮饲料。结果提示，CNCPS测定的指标较多，可一定程度上反映动物对饲料利用的情况，对饲料营养价值的评价更精确。

英文摘要：

The objective of this study was to evaluate the nutrient values of roughages for dairy cattle in north ern China using Cornell net carbohydrate and protein system （CNCPS）. A total of 33 roughage samples in 3 classes and 7 types were collected from Beijing, Shandong, Henan, Hebei and Inner Mongolia, etc. The basic nutrient contents were analyzed, and the carbohydrate and protein fraction were calculated respectively accord ing to the CNCPS method. The roughage samples were analyzed by category. The results showed that the solu ble crude protein in roughage was mainly nonprotein nitrogen, and true protein content was relatively less; al falfa was a kind of high quality roughage with high protein content, low unavailable protein content and high nonstructural carbohydrate content; the nutrient value of wheat straw was low for the high unavailable fiber and protein ; the corn silage feed had a higher nutrient value than the straw class feeds for the lower content of una vailable fiber and protein; the nutrient value of waxy maize stalk was higher than that of corn stalk and corn stalk silage feeds for higher crude protein and lower unavailable fiber and unavailable protein. The results indi cate that the analytical methods of CNCPS includes more component items of feed samples, and this system can reflect feed utilization better and evaluate nutrient values of feeds more accurately.