An integrated tool to predict feed value for ruminants : PrévAlim for INRAtion

Abstract

This paper presents the bases of an integrated tool developed to estimate the feed value of forages and concentrates from their laboratory analysis. The computer program PrévAlim, available with the new version of INRAtion software, calculates the nutritive value of feed (feed unit UF and protein value PDI) and the fill unit (UE) of forages from the measurement of some characteristics of each feed. To calculate the nutritive value, a sequential approach is used, based on estimates of organic matter digestibility (dMO) and rumen degradability of feed protein (DT). UF and PDI values are then calculated using stepwise equations of the INRA (1988) systems. Estimates of the dMO are preferentially achieved from the enzymatic degradability method using pepsin-cellulase (dCs or dCo), or determined using the chemical composition of feed or the age of the plant. Estimates of the DT and the PDI values of concentrate feeds are achieved from the enzymatic degradability method using a protease (DE1). Fill values of forages are calculated from the estimates of their voluntary intakes based on their chemical composition or dMO. Equations for different types of forages are calculated from the INRA (1988) feed tables. PrévAlim integrates, co-ordinates and updates different tools already available (prediction of nutritive value) and a new one that estimates fill values of forages. The computer program ensures that the calculated values (UF, PDI and UE) are coherent with themselves and with the feed tables. The hierarchical approach we used allows 1- to estimate feed value even in case of some missing information 2- to choose the most relevant estimates in case of redundant information.