FEED ENZYMES

An increasing proportion of barley is being incorporated into diets for broilers as a result of the price advantage of barley over wheat and the availability of enzymes able to minimise the undesirable consequences of high barley inclusion. The successful use of enzymes in this branch of the poultry industry has stimulated interest in the application of enzymes to barley-based diets for turkey poults and for layers. The mechanism of enzyme action in cereal-based diets for poultry is not fully understood. Destruction of gel-forming polysaccharides leached from grains does not fully account for the production response. Increased availability of dietary components (starch and protein) released by enzymes from intact cells is probably of equal importance and argues for the use of multi-enzyme preparations. The value of supplementary enzymes to the pig industry is inconclusive. Although there are physiological reasons for augmenting the digestive capacity of pigs with supplementary enzymes at the time of weaning, feeding trials have failed to produce definitive results in terms of improved performance or reduced neonatal mortality. A similar variable response to enzyme addition to grower and finisher diets has been found. The limited nutritive value of some released carbohydrate and variable survival of enzymes during processing and within the digestive tract may account, in part, for variations in response. Phytase, an enzyme newly available in commercial amounts, may prove of value in reducing the phosphorus content of effluent from intensive rearing facilities.