Improving Forage Quality and Animal Performance with Fibrolytic Enzymes

Enzymes have been used for decades to improve the utilization of swine and poultry diets. For instance phytase, amylase, ß-glucanase and xylanase are added to the cereal-based diets of such monogastrics to increase the utilization of dietary phosphorous, starch, ß-glucans and arabinoxylans respectively. For many years, researchers were discouraged from using enzymes to enhance the utilization of ruminant diets because of perceptions that the hydrolytic capacity of the rumen could not be enhanced by supplemental enzymes, and concerns that such enzymes would be ineffective due to ruminal proteolysis. These concerns have been disproved by several recent studies that have demonstrated that fibrolytic enzyme supplementation enhances the productivity of livestock, and several fibrolytic enzyme products are currently commercially available. However in vitro and animal-based studies on the effects of fibrolytic enzyme application to feeds have not been unanimously supportive of their benefits. The interplay of several enzyme, host, feed and management – related factors determine the effectiveness of enzymes in hydrolyzing feed components. Several excellent reviews have been published on this subject (Kung 2001a, b; McAllister et al., 2001; Beauchemin et al., 2003; Beauchemin et al., 2004). However, these have either only focused on direct fed enzyme application with the exclusion of enzyme application at ensiling, and have not considered the potential of using enzymes to improve the quality of tropical forages. The intention in this paper is to review the literature on the effects of enzyme application to feeds at ensiling or feeding, and the determinants of such effects, and to present the results of certain preliminary studies aimed at improving the utilization of tropical forages with fibrolytic enzymes.