ANN 111: Principles of Animal Nutrition and Feed Technology (2+1)

ENZYMES

• Enzymes are protein which have the property of catalysing specific biochemical reactions. They are found in all plants and animals and are responsible for growth and the maintenance of health.
• Microorganism also produce enzymes and in recent years it has been possible to produce enzymes using microorganism on an industrial scale, extract and use these enzymes in a wide range of processes for the production of feed and natural products.
• Poultry feeds are largely composed or plant and vegetables materials and there are enzymes developed to degrade, modify or extract the plant polymers found in some of the cereals and their byproducts. The enzymes can be used to improve the feeding of poultry in the following way:
  • By improving the efficiency of the utilisation of the feed
  • By upgrading cereals byproducts or feed components that are poorly digested
  • By providing additional digestive enzymes to help poultry to withstand stress conditions eg. Hot climates
• Some of the cereals are compounds of polymers either of glucose (beta glucan) or arabinose and xylose (pentosan or hemicellulose). These polymers are not well digested by poultry and this can be result in loss of energy in two ways:
  • Energy may be lost become these polymers hinder the digestion of starch by coating starch granules and preventing the action of starch digesting enzymes in the intestine.
  • Energy may be lost because the animals own enzymes are not capable of degrading the polymers and therefore they pass through the digestive system untouched.
• By adding microbial enzymes to the feed these polymers can be degraded and their energy value made available to the bird.
• The dual role of enzymes has been demonstrated in trials with barley based feed supplemented with beta-glucanase, where the apparent increase in available energy was far in excess of that available in the beta-glucan of the barley.
• In this case not only was the problem of sticky dropping completely eliminated but the chicken’s rate of growth was equivalent to that observed normally with feeds containing a higher energy density (eg. Wheat based).

Choice of enzyme

• Because feed is normally composed of a single raw material of constant quality, it is important that the correct choice of enzyme product be made.
• Even in the case of a relatively well defined problem such as that in barley, the use of multi enzyme activity products has an advantage.
• The enzymes should fulfil the following criteria for practical application:
  • The enzymes must be active at the pH of the animals digestive system and capable of surviving transit through the stomach
  • They must be in a physical form in which they can be safely and easily mixed into all forms of animal feed
  • The products should be of a high standarised activity that will remain stable both before and after incorporation into the feed or pre-mix
  • The enzymes must be capable of surviving normal pelleting conditions