Digestibility of whole grain crop silages was estimated by an in vivo method and by three different in vitro techniques: in situ nylon bag, in vitro true digestibility (IVTD) and in vitro gas production (GP). The silages were made of oat (Avena sativa, var. Senator) and triticale (var. Bogo), cut at three stages of maturity: heading (H), milk (M) and milk-dough (MD). Starch contents (g kg^-1 DM) in oat silages were 13, 110 and 130 and in triticale 7, 78 and 147, for H, M and MD stages of maturity, respectively. For the same silages and stages of maturity, NDF contents (g kg^-1 DM) were 471, 506, 483 and 517, 551, 499, respectively. The silages made at heading stage had the highest in vivo DM digestibility and in situ DM effective rumen degradability (ERD). In vivo DM digestibility was significantly correlated with the starch content in the silages. There was no significant correlation between ERD and starch and NDF contents but significant correlations between starch content and A, B and C parameters of DM degradability were found (r>0.90; P<0.05). Regardless of the species, silages made at M and MD stages had a lower IVTD than H silages. There was no significant correlation between IVTD and starch and NDF contents. Total gas production (TGP) as well as GP rate constant pointed at MD silages, especially oat, as the most digestible. There was no significant correlation between TGP and starch and NDF contents. However, a significant correlation (P<0.05) was found between GP rate constant and starch content. Among the methods compared, the highest correlation with in vivo DM digestibility was found for fractions A and B (in situ method), IVTD 48 and GP rate constant (gas production technique).