Estimation of ruminal protein degradation in vitro – limitations and perspectives of methods based on isolated enzymes

Following the aim of reducing animal-based methods, it is crucial to develop, validate and standardize enzyme-based in vitro methods for feed evaluation. In the context of protein evaluation of ruminant feeds, proteases are used to estimate ruminal protein degradation. This review summarizes the current development of these methods and identifies main limitations, which can be attributed to the properties of the feed matrix in particular. The article shows where such methods can be used effectively and where further research is needed.