The samples of grass silages, made from the five most widely used grass species in ruminant nutrition (Dactylis glomerata L., Phleum pratense L., Lolium perenne L., Festuca arundinacea L. and hybrid Felina) were tested in the present study. These grass species conserved by an ensiling process were compared among each other according to dry matter (DM) rumen degradability parameters. Based on the chemical composition of grass silages the regression equations for prediction of effective degradability of DM (EDDM) were evaluated. The influence of the ensiling process on dry matter degradability parameters was also assessed. The best values of EDDM were determined for Lolium perenne. The best predictor was neutral detergent fibre (NDF). Using two predictors the accuracy level increased. The regression equations based on the most important grass species harvested in different vegetation periods seem to be a useful tool for practical use.