The methodic is intended to extend information about the quality of grass silages, which is one of the most important roughage feed for ruminants. Presented prediction equations allow to easily and quickly determine the degradability parameters and effective degradability of dry matter on the basis of chemical composition commonly determinable in agricultural laboratories. It provides comprehensive information on practices relating to the quality of grass silages, without the necessity of time consuming, labour and expensive in vivo, in situ and in vitro methods predominately used in research institutes. Methodic deals with the prediction of rumen degradability of grass silages, thereby extending knowledge of the grass degradability. For determination of the digestibility and rumen degradability is important to use the equations reflecting the technological process of treatment of forage, which can significantly affect the qualitative parameters of the original grass material.