Phytase applications in poultry feeding: Selected issues

摘要

The paper critically reviews the literature concerning phytase applications in poultry feeding with an emphasis on st strategy that partly overcomes limitations of the enzyme efficacy in broiler and turkey diets. Microbial sources of phytase, commercial forms of the enzyme, its desirable features and mode of action are discussed as well as properties of the substrate in plant tissues and the enzyme-substrate interactions in the intestinal tract of poultry. Phytase interactions with supplemental inorganic phosphorus and partial rather than complete dephosphorylation of feed phytates were identified as the key factors that limit phytase efficacy in the diets of poultry. Research on enzymic cocktails that comprised phytase A, phytase B, pectinase and citric acid are reviewed. Enzymic cocktails in either soluble or intracellular form (fungal mycelium) enhanced the yield of dephosphorylation and influenced phytate conversion rate. Examples of enzymic cocktails which improved performance and bone mineralization of broilers fed wheat-based, low phosphorus diets, close to or even above values found in birds receiving a diet high in inorganic phosphate, are given. The enzymic cocktail strategy when applied to poultry diets resulted also in the highest values of phosphorus retention (72-75% in broilers, 77-80% in turkeys) known in the literature.