Near infrared spectroscopy is increasingly use as an alternative to classical analytical method to evaluate quality and functional properties animal feeds and human food. This method provides a rapid, clean and green, and accurate measure of chemical composition of diet. At the same time, attempts to evaluate these parameters in grazing systems are laborious, time consuming, costly and introduce bias in parameter estimation. The aim of this study is to evaluate the potential of faecal and forage NIRS to assess functional properties of diet ingested by Creole sheep. Derived standard errors of cross validation (SECV) and coefficient of determination using faecal spectra were 2.18% and 0.70 for organic matter digestibility, 9.27g/kgP0.75 and 0.28 for organic matter intake and 6.76 g/kgP0.75 and 0.27 for digestible organic matter intake. Association of faecal and herbage spectra lead to increase of prediction accuracy of 17.4, 7.4 and 7.2 % for organic matter digestibility, organic matter intake and digestible organic matter intake respectively. These results clearly indicate that near infrared reflectance spectroscopy represent a new tool to study and monitor breeding systems.