The objectives of this study were to compare the ruminal degradability of neutral detergent fibre (NDF) and indigestible NDF (INDF) between silages (n = 24) originated from three different grass species, Dactylis glomerata L.; Festuca arundinacea L. and hybrid Felina – Lolium multiflorum L. × Festuca arundinacea S., and to create prediction equations for effective degradability of NDF (EDNDF), assuming ruminal solid outflow rates of 0.02 (low), 0.05 (medium) and 0.08/h (high), and INDF. The highest values for the potentially degradable fraction of NDF (b), EDNDF2, EDNDF5 and EDNDF8 (874, 560, 366 and 272 g/kg NDF, respectively) and the lowest for INDF (73.1 g/kg DM) were found for F. arundinacea. These parameters were significantly different from the hybrid, Felina, which presented the lowest rate of NDF degradation (c), EDNDF5 and EDNDF8 (0.033/h, 341 and 250 g/kg NDF, respectively).