Exogenous enzymes in monogastric nutrition - their current value and future benefits

Exogenous enzymes which, for the purpose of this paper, include carbohydras es and phytase, are now extensively used throughout the world as additives in non-ruminant diets. The chemical effects of these enzymes are well under stood, but the manner in which their benefits to the animal are brought abo ut is still under debate. Regardless, the overall effect of carbohydrase en zyme use is to reduce the variation between good and bad samples of a targe t ingredient substantially. The net benefit is that the nutrient requiremen ts of the animal are met more frequently, and with diets of lower nutrient concentration. Variation in animal performance from flock to flock is also reduced. Phytase, on the other hand, was originally used for one express pu rpose - to increase the availability of plant phytate phosphorus, which red uces phosphorus pollution and allows reductions in the amount of inorganic phosphate used. Further benefits of phytase utilisation on energy and amino acid availability have recently been identified which will, with appropria te dietary modifications, allow for further improvements in resource utilis ation. Current issues of concern for all enzymes include variability in res ponse. Substrate variability and interactive factors significantly influenc e the response to exogenous enzymes. Currently, there are methods which tak e such factors into account and allow for prediction of optimum dose of car bohydrase enzymes in wheat and barley based diets and efforts are underway for maize based diets or for optimisation of the use of phytase. Future res earch in these areas will allow for more efficient use of the current enzym es and development of more efficient future products. Development of more t hermotolerant enzymes will also allow their use in diets where they current ly cannot be applied. (C) 2000 Elsevier Science B.V. All rights reserved.