The use of commercial exogenous enzymes in poultry diets is now a common practice. Broilers are predominantly fed pelleted diets; of the various unit operations in the production of pellets, grinding and conditioning are the components that can influence the efficacy of exogenous enzymes. The aim of this paper was to review the feed processing factors that influence the efficacy of exogenous enzymes in broiler diets. Recent studies have shown that the efficacy of exogenous enzymes is influenced by the degree of grinding. Available data suggest that enzyme responses on intestinal viscosity are more pronounced in feeds subjected to high conditioning temperatures. The issue of enzyme stability during conditioning and pelleting therefore becomes relevant and new enzyme technologies are being developed to overcome the high thermal processing issues. However, the effects of steam conditioning practices on enzyme stability have received less attention and need to be explored in future studies.
