PREDICTION OF THE ENERGY VALUES OF COMPOUND FEEDS FOR RUMINANTS

Estimation of the net energy value of compound feeds for ruminants is important for both the feed compounder and the farmer. It is thus necessary to predict these values with good accuracy and at a low cost. This study concerned 83 compound feeds which are as representative as possible of the variety generally in use. The range of their organic matter digestibility was 65-90%. Samples of the feeds were studied in vivo in France by INRA Theix (17) and Paris (18), in The Netherlands by IVVO at Lelystad (24) and in the UK by the Rowett Research Institute at Aberdeen (24). All laboratories measured organic matter (OM) and energy digestibility. In addition, urinary energy losses and methane losses were measured at Theix and the Rowett Institute. Cell wall (crude fibre and neutral detergent fibre), lignocellulose (acid detergent fibre). acid detergent lignin (ADL) and Christian lignin contents were determined as well as enzymatic degradability. The 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. This approach led to the formulation of equations predicting the net energy content expressed in net energy value for milk (NE1) or for meat production (NE(mf)) with respective residual standard deviations varying from 0.350-0.446 MJ NE1 kg-1 OM and from 0.455-0.547 MJ NE(mf) kg-1 OM according to the analytical criteria considered. The major interest of this study lies in the fact that numerous in vivo measurements were performed, that a large number of laboratory methods were used and that the compound feeds were representative of the variability generally in use at the present time.