Dose-response effects of phytase superdosing on performance and mineral metabolism in late-phase laying hens

This study evaluated the effects of graded levels of phytase on performance, egg quality, intestinal morphometry, and bone characteristics of Hy-Line W80 laying hens from 40 to 80 weeks of age. A total of 480 hens were assigned to six treatments: a positive control (PC), a negative control with reduced calcium and available phosphorus (NC), and the NC supplemented with 600, 1200, 1800, or 2400 FYT/kg of phytase. Phytase inclusion improved productive performance (P < 0.05), reducing feed intake and enhancing egg mass and feed conversion, with predominantly quadratic responses. Egg components (yolk, albumen, and shell weight) increased with phytase supplementation, indicating improved nutrient utilization. Intestinal morphology responded positively to increasing phytase levels, with significant improvements in villus height and villus: crypt ratio in the duodenum and jejunum, demonstrating enhanced absorptive capacity. Bone parameters showed variable responses, with moderate phytase levels optimizing some structural characteristics. Overall, phytase supplementation enhanced nutrient efficiency, performance, and intestinal development in late-phase laying hens. Considering the evaluated responses and the tested treatments, phytase inclusion at 1800 FYT/kg is recommended as a practical level to optimize productive performance and gut health under the conditions of this study.