A NET CARBOHYDRATE AND PROTEIN SYSTEM FOR EVALUATING CATTLE DIETS .2. CARBOHYDRATE AND PROTEIN AVAILABILITY
A NET CARBOHYDRATE AND PROTEIN SYSTEM FOR EVALUATING CATTLE DIETS .2. CARBOHYDRATE AND PROTEIN AVAILABILITY
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DOI：
10.2527/1992.70113562x
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发表时间：
1992-11-01
影响因子：
3.3
通讯作者：
RUSSELL, JB
中科院分区：
文献类型：
--
作者：
SNIFFEN, CJ;OCONNOR, JD;RUSSELL, JB
康奈尔大学净碳水化合物和蛋白质系统（CNCPS）有一个子模型，可预测饲料在瘤胃中的降解率、未降解饲料进入下消化道的通道以及动物可获得的ME和蛋白质的量。在CNCPS中，结构性碳水化合物（SC）和非结构性碳水化合物（NSC）是通过连续的NDF分析来估计的。来自文献的数据用于预测SC和NSC降解的分数率。将粗蛋白质分成五个级分。组分A是NPN，其是三氯乙酸（TCA）酸溶性N。不能利用的或与细胞壁结合的蛋白质（组分C）来源于酸性洗涤剂不溶性氮（ADIP），缓慢降解的真蛋白质（组分B3）是中性洗涤剂不溶性氮（NDIP）减去组分C。快速降解的真蛋白（组分B1）是来自缓冲液可溶性蛋白减去NPN的TCA可沉淀蛋白。具有中间降解速率的真实蛋白质（组分B2）是剩余的N。蛋白质降解率估计在体外的程序，使用灰色链霉菌蛋白酶，和曲线剥离技术用于识别率为每个馏分。在瘤胃中消化的碳水化合物或氮的量由降解和通过的相对速率决定。瘤胃通过率是颗粒大小、颗粒大小、堆积密度和消耗的饲料类型（例如，草料对谷物）。
The Cornell Net Carbohydrate and Protein System (CNCPS) has a submodel that predicts rates of feedstuff degradation in the rumen, the passage of undegraded feed to the lower gut, and the amount of ME and protein that is available to the animal. In the CNCPS, structural carbohydrate (SC) and nonstructural carbohydrate (NSC) axe estimated from sequential NDF analyses of the feed. Data from the literature are used to predict fractional rates of SC and NSC degradation. Crude protein is partitioned into five fractions. Fraction A is NPN, which is trichloroacetic (TCA) acid-soluble N. Unavailable or protein bound to cell wall (Fraction C) is derived from acid detergent insoluble nitrogen (ADIP), and slowly degraded true protein (Fraction B3) is neutral detergent insoluble nitrogen (NDIP) minus Fraction C. Rapidly degraded true protein (Fraction B1) is TCA-precipitable protein from the buffer-soluble protein minus NPN. True protein with an intermediate degradation rate (Fraction B2) is the remaining N. Protein degradation rates are estimated by an in vitro procedure that uses Streptomyces griseus protease, and a curve-peeling technique is used to identify rates for each fraction. The amount of carbohydrate or N that is digested in the rumen is determined by the relative rates of degradation and passage. Ruminal passage rates axe a function of DMI, particle size, bulk density, and the type of feed that is consumed (e.g., forage vs cereal grain).