[Prediction of the Voluntary Intake of Grass Silages By Growing Sheep]

A mathematical model (non linear multiple regression) was developed for prediction of the voluntary intake (VI, g DM/kg BW.75/d) of grass silage by growing Texel sheep (32 to 83 kg BW). Four main parameters describing the silage quality and or its physical structure are used in the model: the level ammonia nitrogen (in % of total N) and the pH of the silage, the level of corrected dry-matter of the forage (%) and the mean chop length of partiels (in cm). Relations between VI and each parameter are found to be curvilinear and cover a large range of data (VI between 35 and 73 g DM/kg BW.75/d). The validity of the model was tested on a set of 10 independent grass silages and a significant linear relationship (R2 = 0.902) was obtained between predicted and actual VI values. The main prediction bias was low (-1.7 g DM/kg BW.75/d) and the calculated mean prediction error was of 8%