The objective of this research is to evaluate the nutritive value of forages using different laboratory methods (chemical, enzymatical and biological methods: in vivo, in sacco and in vitro). This study includes presently measurements of the nutritive value of four temperate grasses (foxtail, tall meadow oat, red fescue, rye-grass), who are recommended within the framework of the program set up for nature conservation in Belgium, as well as three tropical grasses (Eragrostis olivacea, Setaria sp, Tripsacum laxum) usually fed to ruminants in Burundi.