Phytic phosphorus and phytases in poultry nutrition

Abstract

Phytic acid and its salts are the most common phosphoric carbohydrate compounds present in seeds. Their digestibility depends on both their water solubility and activity of phytase enzymes contained in the grain itself. This activity is high in wheat, rye and barley, which explains why phosphorus availability for chicken hone mineraliziltion is above 50 % in these three grains, white it is less than 20 % in corn or soyameal. When these true availability coefficients are used (instead of the former average 30 % figure), inorganic phosphate addition to poultry diets can be greatly decreased or even eliminated (from laying hen diets). However it remains possible that phytic phosphorus is slightly less available for bone accretion than for body weight gain. Exogenous phytase (mainly from fungus) added to chicken diets, allow inlestinal phytate hydrolysis. Grein fermentation also increases phytic phosphorus availability while the exact effect of steam pelleting is not still clearly demonstrated.