Traxler M J, Fox D G, Van Soest P J, Pell A N, Lascano C E, Lanna D P, Moore J E, Lana R P, Vélez M, Flores A
Department of Animal Science, Cornell University, Ithaca, NY 14853, USA.
J Anim Sci. 1998 May;76(5):1469-80. doi: 10.2527/1998.7651469x.
We used chemical composition and in vitro digestibility data from temperate and tropical forages to develop relationships between indices of lignification and forage indigestible NDF. Neutral detergent fiber indigestibility increased nonlinearly as the lignin concentration of the NDF increased. Differences in estimated indigestible NDF using equations developed for a specific forage class (C3 and C4 grasses and legumes) were small and are probably not biologically significant when compared to those estimated from a common equation. Selected equations were compared with the Cornell Net Carbohydrate and Protein System (CNCPS) for the prediction of ADG. The linear equation (2.4 times NDF lignin content) used by the CNCPS and the Beef NRC had some of the largest errors due to mean bias. A log-log model [4.37 x (lignin/NDF)(.84)] provided the best combination of low total prediction error, low mean bias, and minimal error due to regression bias when permanganate lignin was used. A similar equation based on sulfuric acid lignin [6.17 x (lignin/NDF)(.77)] also met the above criteria. These equations then were evaluated with the CNCPS model against animal growth data from diets ranging in forage quality. Regardless of the equation used for predicting unavailable fiber, the CNCPS underpredicted daily gain, with mean biases ranging from -.10 to -.22 kg/d. Regression bias ranged from .13 to .14 kg/d and the coefficients differed from unity (P = .0001). The new equations gave numerically lower energy allowable ADG by steers compared to the linear equation currently used by the CNCPS model. The estimates were lower due to a higher predicted indigestible NDF, which resulted in a lower estimated forage energy value.
我们利用温带和热带草料的化学成分及体外消化率数据，来建立木质化指数与草料不可消化中性洗涤纤维（NDF）之间的关系。随着NDF中木质素浓度的增加，中性洗涤纤维的不可消化性呈非线性增加。使用针对特定草料类别（C3和C4禾本科植物及豆科植物）建立的方程估算不可消化NDF时，与使用通用方程估算的结果相比，差异较小，可能在生物学上并不显著。将选定的方程与康奈尔净碳水化合物和蛋白质系统（CNCPS）进行比较，以预测平均日增重（ADG）。CNCPS和牛肉营养需求委员会（Beef NRC）使用的线性方程（NDF木质素含量的2.4倍）由于平均偏差而存在一些最大误差。当使用高锰酸盐木质素时，对数-对数模型[4.37×(木质素/NDF)(.84)]在总预测误差低、平均偏差低以及回归偏差导致的误差最小方面提供了最佳组合。基于硫酸木质素的类似方程[6.17×(木质素/NDF)(.77)]也符合上述标准。然后，使用这些方程与CNCPS模型一起，根据不同草料质量日粮的动物生长数据进行评估。无论使用哪个方程来预测不可利用纤维，CNCPS都低估了日增重，平均偏差范围为-0.10至-0.22千克/天。回归偏差范围为0.13至0.14千克/天，系数与1不同（P = 0.0001）。与CNCPS模型目前使用的线性方程相比，新方程得出的育肥牛能量允许的ADG在数值上更低。这些估计值较低是因为预测的不可消化NDF较高，这导致估计的草料能量值较低。
