A 21-day experiment was conducted with day-old male broilers to evaluate the effectiveness of supplement phytase for improving the effectiveness of phytateß phosphorus when varying levels of phosphorus was fed. The semi-purified basal diet containing soybean meal as the only protein source was supplemented with seven levels of phytase. A 2:1 calcium-to-total-phosphorus ratio was maintained in all diets. Body weight and feed intake were improved (P>.001) by phytase at all nonphytate phosphorus levels, but the response was greatest at low nonphytate phosphorus levels. Gain/feed was unaffected by phytase level. Ash percentage of toes and tibia and shear force and stress of fibia increased with added phytase. These responses clearly show that the phytate-bound phosphorus in SBM was made more available to broilers by microbial phytase, and the total response was related to the phytase and nonphytate phosphorus levels. Body weight gain, feed intake, and toe ash percentage were the most sensitive indicators assessing phosphorus availability, followed by tibia force and ash percentage.
Denbow, D.M., V. Ravindran, E.T. Kornegay, Z. Yi and R.M. Hulet. 1995. Poultry Sci. 74(11): 1831-1842.
