The set of sample was classified by the phenophases: before the heading, the beginning of heading and full heading. Each group contained 12 samples. The parameters of nutritional value were evaluated. The chemical compositions (CP, PDIN a DOM) were highly significantly affected (P < 0.01) by the phenophases. The best results have been reported in grass silage harvested in the phenophase before the heading. The chemical compositions CF and NEL were better (P < 0.01) in the grass silages harvested in the phenophase before the heading and in the phenophase the beginning of heading against grass silage harvested in the phenophase full heading.