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< 0.01). adding zno and phytase to diet increased the relative weight of bursa of fabricius and liver in the hatchlings. also, the interactive effect of zno and phytase on the relative weight of heart was significantly affected by the hatchlings (p< 0.01). in conclusion, dietary supplementation of zno and e. coli-derived 6-phytase profoundly improved the fertility rate in aged broilers breeder hens, although the effects on immunity of their progeny were negligible.