Abstract First a suitable protease for enzymatic determination of in vitro rumen protein degradation was selected. The actions of Pronase E, papain and bromelain were compared. The highest correlation coefficient for protein degradation estimated by the in sacco method compared with the enzymatic method was obtained with bromelain in a set of 13 feeds. This enzyme was subsequently used for analysis of more than 200 ruminant feed components. Feeds were separated on the basis of their chemical properties into the following five groups: cereals, forages, hays, protein concentrates, silages. In these groups, correlation coefficients of linear regression equations for rumen protein degradability estimated by the in sacco method and bromelain were 0.839 for concentrates, 0.730 for fresh forage, 0.741 for hays and 0.876 for silages. Feeds with high starch content had to be treated with α-amylase to obtain the correlation coefficient r=0.809. The method is going to be used for preliminary testing of ruminant feeds.