INFLUENCE OF SUPPLEMENTAL PHYTASE ON CALCIUM AND PHOSPHORUS UTILIZATION IN LAYING HENS

A 6-wk study was conducted to determine the influence of supplemental phytase on Ca and P utilization in commercial laying hens. Diets were arranged factorially with three levels of dietary Ca (2.5, 2.8, and 3. 1%), fed at two levels of nonphytate P (0.1 and 0.3% NPP) with and wit hout supplemental phytase. Each diet was replicated eight times, with 16 hens per replicate. Criteria evaluated included egg specific gravit y, feed consumption, egg production, egg weight, eggshell weight, bone quality, and body weight. Increasing dietary Ca significantly improve d shell quality within 1 wk. A significant improvement in shell qualit y due to phytase supplementation was also observed during the 1st wk. Increasing NPP from 0.1 to 0.3% had not effect on egg specific gravity until Week 3, suggesting that the phytase benefit during Weeks 1 and 2 was related to improved Ca utilization. From Weeks 3 to 6, a signifi cant P by phytase interaction was observed in which the magnitude of s hell quality improvement was greatest when the 0.1% NPP diet was suppl emented with phytase. This interaction was also observed from Weeks 3 to 6 for feed consumption and egg production and during Weeks 4 and 6 for egg weights. Phytase supplementation completely overcame the adver se effects associated with low dietary P and significantly reduced the impact of low dietary Ca on hen performance.