Phytate utilization and phosphorus excretion by broiler chickens fed diets containing cereal grains varying in phytate and phytase content

Eighty, 12-day-old, male broiler chicks, were fed one of four diets to determine the effects of feeding grains varying in phytate phosphorus (P) and intrinsic phytase activity on ileal and excreta P digestibility and composition. The diets contained approximately 970.7 g grain kg−1 (maize, high fat–low lignin oat, normal barley or low-phytate barley) with the cereal supplying the sole source of dietary P. The diets were fed for a 7-day acclimation period followed by a 2 day excreta collection while ileal digesta was collected at slaughter on day 21. The coefficients of ileal apparent digestibility (CIAD) for P and phytate P ranged from 0.79 (normal barley) to 0.86 (maize and low-phytate barley) and 0.76 (low-phytate barley) to 0.89 (maize), respectively. The CIAD for phytate P was significantly greater in the maize and high fat–low lignin oat diets, while the low-phytate barley diet had the lowest coefficient (P>0.002). The coefficients of total tract apparent digestibility (CTTAD) for P and phytate P ranged from 0.25 (maize) to 0.35 (low-phytate barley) and 0.90 (maize and low-phytate barley) to 0.96 (high fat–low lignin oat), respectively, with no significant differences between diets. There was very little phytate P in excreta regardless of the type of grain fed (<0.13 of total P) with no significant differences between diets. Phytate P degradation was not related to the level of intrinsic phytase in the diet. In summary, current results indicate that, regardless of the type of grain fed, dietary phytate P is highly digestible when large amounts of calcium and P are not added into poultry diets and little phytate P is excreted.