The influence of phytase enzyme supplementation on performance and calcium and phosphorus metabolism of broiler chicks

Two experiments were conducted to study the effect of phytase supplementation to lowphosphorus starter and finisher broiler diets on mineral utilization and growth performance. All diets in this study were isonitrogenous, isocaloric and corn-soybean diets. In Experiment 1, four replicate groups of 15 commercial broiler chicks, one-day old, were randomly assigned to each of two dietary treatments. Control diet contained 0.9% Ca and 0.45% available P. Enzyme diet contained 0.9% Ca and 0.27% available P with 600 ppm commercial phytase (RONOZYME-P) units added. The finisher diets were a control finisher diet (CFD) containing 0.9% Ca and 0.35% available P, and the enzyme finisher diet (EFD) containing 0.9% Ca and 0.17% available P (very low-P enzyme diet). The trial ran for 5 weeks. Birds fed the control diet had significantly (P<0.05) higher weight than the enzyme treated birds during the starting and finishing periods. A similar trend was observed regarding feed conversion ratio (FCR); birds fed the very low-P diet plus phytase had higher FCR than the control-fed birds during both periods. Tibia and toe ash contents decreased in birds fed the very low-phosphorus diet plus phytase compared to the control. In Experiment 2, the effect of enzyme supplementation was only carried out during the finishing period on broiler chicks grown under a normal management condition and all birds were fed a balanced starter broiler diet until age 21 days. Four replicate groups of 52 commercial, 21-day old chicks were randomly assigned to each of the three dietary treatments. Diet 1 was the same as the previously mentioned CFD; Diet 2 was a finisher diet containing 0.9% Ca and 0.26% available P with 300 ppm phytase units (low-P enzyme diet); Diet 3 was similar to EFD containing 0.9% Ca and 0.17% available P with 600 ppm phytase units. The experiment was run until chicks attained the regional market weight (5 weeks of age). Body weight gain, feed intake and FCR were similar in all treatments. Also, toe ash content and plasma total Ca, P, Zn and Fe levels were not significantly affected by dietary treatments. The data showed that the supplementation of phytase enzyme to the broiler diets significantly improved growth performance and bone mineralization of birds fed a balanced starter diet and low-phosphorus finisher diets supplemented with phytase enzyme. __________________________________________________________________________________