Prediction of net energy value of compound feeds for ruminants

Abstract

Until now net energy (NE) value of compound feeds for ruminants had been calculated from a data bank of single concentrate feed. This study concerned 83 compound feeds, as representative as possible of the variety generally in use : for example, their cereal content varied from 0 to 90 %. In vivo organic matter (OM) or energy digestibility was measured in France by INRA (Theix and INA-PG, Paris,) in UK by the Rowett Research Institute, and in the Netherlands by IVVO, Lelystad. In addition, urinary energy losses and methane losses were measured by Theix and the Rowett Institute. Contents were determined for example, for the cell wall, lignocellulose, lignin (methods of Van Soest and Christian), as well as enzymatic degradabilities. Net energy value of compound feeds was calculated by a step-wise analytical procedure. At each step, the maximum amount of in vivo data was used, after their reliability had been checked. The validity of the estimation criteria necessary at each step was discussed with respect to both to their precision and reliability. This approach led to the formulation of equations predicting the content in NE expressed in feed units (UFL and UFV) with residual standard deviations respectively varying from 0.05 to 0.06 UFL/kg OM and from 0.06 to 0.08 UFV/kg OM according to the analytical criteria considered. The association « direct lignin, crude protein, ether extract », which, at first sight seems to be the easiest one to obtain reliably, gave a residual standard deviation of 0.056 UFL and of 0.068 UFV/kg OM. In conclusion, the interest of this study lies in the fact that numerous in vivo measurements were performed, that the compound feeds were representative of those generally in use, and that a large number of laboratory methods were used.