The objective of this approach was to characterise variations that one can observe in the course of a pasture season using near infrared spectrometry (NIRS) applied to the analysis of the grass and faeces collected during the season. Available grass and faeces of Belgian Blue White young bulls have been collected 3 times a week since the beginning of May until mid-October. The samples have been predicted in NIRS technique according to a calibration previously developed on the faeces of sheep fed ad libitum in cage with green grass. The NIRS provides a useful tool to provide a relative description and a monitoring of the evolution of the quality and of the daily intake of grass, that could provide useful information to adapt the supplementation according to the changing quality of the grass
