The experiment was aimed at confirming that silages made of two very similar hybrids could have different in vivo digestibility, primarily amylase-treated neutral detergent fibre digestibility (aNDFD), which could strongly influence the result of the calculation of energy value of fodder. Both the stay-green whole-plant types were grown at the same locality during two years and harvested at the same days at two-thirds milk line maturity. In the two subsequent years, silages without preservatives were made of both hybrids tested. All silages were fermented for 90 days. The in vivo digestibility of silages was measured in digestion trials with six sheep. All silages had good fermentation quality, and no differences in that regard were found between hybrids or years (P > 0.05). Hybrid had stronger effect than year on all indicators of chemical composition and digestibility of nutrients other than dry matter (DM). Hybrid significantly affected all indicators measuring chemical composition and digestibility of nutrients other than DM (P = 0.18). The aNDFD was closely correlated with all other measures of nutrients digestibility (P < 0.01). The results confirm the importance of breeding hybrids and analyzing silages for aNDFD.