[Use of microbial phytase at different phosphorus supply levels in broiler fattening. 1. Effect on fattening performance and tibia stability].

Two trials with 720 male and female Lohmann-broilers each and a fattening period of 35 days were carried out to study the effects of different phytase supplementations (0; 300; 700 units per kg feed). The basal diets with only ingredients of plant origin or of plant and animal origin contained between 0.4 and 0.5 per cent total-P. The supplementation of inorganic P was 0; 338; 675 and 1350 mg per kg feed. The feed intake increased on average by 15 and 17% resp. after adding of 300 or. 700 units phytase to diets with different phosphorus supply. The body weight of broilers increased also in dependence of feed intake. The feed conversion was not influenced by the different phytase and inorganic P-supply. The bone stability examined as bending and breaking strength of tibia was improved by supplementation of phytase and inorganic P. Based on the fattening parameters 300 units phytase can replace 0.06 per cent inorganic P in the diet.