A rationale for the development of feed enzyme products for ruminants

Abstract

The use of exogenous cell wall degrading enzymes is an emerging technology that shows potential in terms of improving feed utilization by ruminants. This review discusses current information related to enzyme product formulation for ruminants, and addresses the conditions necessary to ensure effective and consistent in vivo results of providing feed enzymes to ruminants. Research has demonstrated that, in some cases, adding fibrolytic enzymes to dairy cow and feedlot cattle diets improves cell wall digestion and, consequently, weight gain or milk production are enhanced. However, considerable research is required to develop more effective enzyme products and to ensure consistency of responses in vivo. There is a need to identify the key enzyme activities involved in the positive responses observed in vivo and these enzyme activities should be assessed using a temperature and pH representative of the conditions in the rumen. However, to date, it has not been possible to accurately evaluate exogenous enzymes based only on their biochemical characterization because the model substrates used do not represent the complexity of plant cell wall material. In vitro techniques using feed substrates, buffer and ruminal fluid can be used more reliably as a bioassay to predict in vivo response to exogenous enzymes, however, other factors, including under or over-supplementation of enzyme activity, method of providing the enzyme product to the animal, composition of the diet, and the target animals must also be considered. Key words: Cattle, digestion, fibre digestion, enzymes, cellulases, hemicellulases