IntroductionGrass silage is a forage biomass that is mainly used as a winterfodder for dairy cows and is the most important form of conservedforage for ruminants in many regions of Europe [1]. Protein in grasssilage is more degradable in the rumen than protein in grass hayand fresh grass due to the fermentation processes in the silos [2].Ruminal degradation of different components of grass silages isinfluenced by many factors such as stage of maturity, preservationmethod, forage species and cultivars [3–5].To optimize diet formulation in terms of performance, nutrientlosses, animal well-being and economical profitability, informationis required on the nutrient requirements of animals and nutri-ent availability of various feedstuffs. In ruminants, the nutrient