Feed enzymes for ruminants have received considerable attention recently, because of their potential to improve animal performance. However, the commercial preparations available are generally mixtures and are poorly characterised. Furthermore, their role in improving the nutritive value of ruminant feeds is not well understood. Previous work with a commercial enzyme applied at ensiling of maize stover showed a significant decrease in cell wall contents (Altaf et al., 1997). The present study evaluated the enzyme used by Altaf et al. (1997) in terms of a) main enzyme activities; b) ability to hydrolyse feeds at three different pHs and c) HPLC analysis of the products released.