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

Exogenous enzymes which, for the purpose of this paper, include carbohydrases and phytase, are now extensively used throughout the world as additives in non-ruminant diets. The chemical effects of these enzymes are well understood, but the manner in which their benefits to the animal are brought about is still under debate. Regardless, the overall effect of carbohydrase enzyme use is to reduce the variation between good and bad samples of a target ingredient substantially. The net benefit is that the nutrient requirements 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 purpose - to increase the availability of plant phytate phosphorus, which reduces 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 appropriate dietary modifications, allow for further improvements in resource utilisation. Current issues of concern for all enzymes include variability in response. Substrate variability and interactive factors significantly influence the response to exogenous enzymes. Currently, there are methods which take such factors into account and allow for prediction of optimum dose of carbohydrase enzymes in wheat and barley based diets and efforts are underway for maize based diets or for optimisation of the use of phytase. Future research in these areas will allow for more efficient use of the current enzymes and development of more efficient future products. Development of more thermotolerant enzymes will also allow their use in diets where they currently cannot be applied. (C) 2000 Elsevier Science B.V. All rights reserved.