Evaluation of the Tabular Feed Energy and Protein Undegradability Values of the National Research Council Nutrient Requirements of Beef Cattle

Abstract Evaluations with animal performance data indicated the tabular feed energy and undegraded intake protein ( UIP ) values used by the National Research Council's ( NRC ) Nutrient Requirements of Beef Cattle (2000) model Level 1 were less accurate than those predicted by their model Level 2 (the Cornell Net Carbohydrate and Protein System model; CNCPS ; Fox et al., 2004 ) or by an alternative mechanistic equation developed by Weiss et al, (1992) ( WEISS ). The r 2 of observed vs predicted ADG using tabular, WEISS, and CNCPS total digestible nutrients ( TDN ) were 0.61, 0.73, and 0.80 for ME-allowable ADG and were 0.80, 0.79, and 0.92 for metabolizable protein ( MP )-allowable ADG, respectively. The tabular system overpredicted ME- and MP-allowable ADG by 11 and 4%, respectively, whereas WEISS and CNCPS biases were http://www.cncps.cornell.edu .