Dietary Zinc Oxide and 6-Phytase Effects on Fertility Rate in Old Broiler Breeder Hens

The effects of Zinc Oxide (ZnO) and E. Coli-derived 6-phytase supplemented-diet on the reproductive performance in aged broiler breeder hens and on immune responses of their progeny chicks were studied. In a 2×4 factorial arrangement, 2 inclusion levels (0 or 300 U kg-1 diet) of E. coli-derived phytase and 4 inclusion levels (30, 60, 90, and 120 mg kg-1 diet) of ZnO were provided from 62 throughout 72 weeks of age. A total of 128 hens were randomly assigned into 8 dietary treatments with 4 replicates of 4 hens each. During 66 to 71 weeks of age, egg production and egg weights were daily recorded. Results showed that ZnO and ZnO×phytase interaction affected the egg weight and fertility rate (P