IntroductionLegume species provide high quality forages for animals with a positive effect on the environment due to reduction in theuse of inorganic-N fertilizer thanks to their N2-fixation ability (Lüscher et al., 2014). However, the protein level in legumes israther high and the natural digestion process of proteins in ruminant is quite inefficient. To cope with this problem, the use ofgrass–legume mixtures is interesting as they balance the energy: protein ratio, increase biomass production by transferringthe symbiotically fixed N from legumes to grasses and can stimulate voluntary intake (Niderkorn et al., 2014). In addition,some legume species contain bioactive compounds that are potentially active on rumen fermentation processes including NAbbreviations