Use of grass/forage tree silages have prove to be a viable alternative for animal production in the tropics (Sol et al., 2002a,b). It is also an adequate strategy to cope with seasonal fluctuation of biomass availability (both grass and forage tree). However, limited data is available on the nutritive value (e.g. digestibility, energy content) of this mixtures. Therefore, the objective of the present work was to evaluation the in vitro gas production, apparent digestibility and energy content of silages containing grass and forage trees.