Estimate of Energy Value of Feed and Validation of Equations Proposed by NRC (2001)

Abstract

The objectives of this paper were to estimate the energy values of feeds by means of equations proposed by NRC, from feed composition present in data base of "Brazilian Tables of Feed Composition for Cattle" and of a trial that used sheep, and to validate those equations from observed values of TDN, digestible fractions of NDF (DNDF), crude protein (DCP), ether extract (DEE) and nonfiber carbohydrates (DNFC), that were obtained on Brazilian Scientific literature through in vivo experiments at maintenance level. The procedure to validate the parameters evaluated (TDN, DNDF, DCP, DEE, DNFC) was done by adjustment models of simple linear regression using predict and observed values. The observed and predict values of TDN values for forage and concentrate feeds were similar. However, when considering only the DNDF of forages estimative was verified rejection for both null hypothesis, because either intercept or coefficient of inclination were different of zero and 1, respectively. For the feed nitrogen fraction, no difference between the evaluated parameters was observed. The DEE of forages and concentrate feeds was underestimated by the equations proposed by NRC, as well as the DNFC of concentrates feed. Thus, it can be concluded that the data obtained by the equations used by NRC to estimate the energy value of feed were similar to the observed data of Brazilian feeds, however, it is suggested that these equations should be adjusted to estimate the digestible fractions of NDF of forage, DEE and DNFC of brazilian feeds.