Two experiments were conducted to determine the effect of phytase supplementation on layer hens and broiler chickens performance and compare the use of phytase nutrient equivalency values in feed formulation with those fed conventional diet. In the first experiment, 640 commercial broiler chicks were used from 11 to 49 days of age. The experimental units were allocated at random to 4 dietary treatments x two sexes with 4 replicates per treatment. The first dietary treatment was formulated with no addition of phytase (C), the second diet contained 500 FTU kg(-1) phytase over the top (C+P), and the third diet contained 500 FTU kg(-1) phytase which was calculated as half of the nutrient equivalency values for phyatse (50E). The fourth dietary treatment contained 500 FTU kg(-1) phyatse which was calculated as the total nutrient equivalency values for phytase (100E). In the second experiment 288 Hy-line W-36 hens were used from 60 to 72 weeks of age. The treatments consisted of a control diet (C) with no addition of phytase, a control diet supplemented with 300 FTU kg(-1) phytase over the top (C+P), and a third diet containing 300 FTU kg(-1) phytase which was calculated as the total nutrient equivalency values for phyatse (100E). No significant difference was observed among the four dietary treatments for broiler final body weight, feed conversion ratio (FCR) and carcass characteristics (P>0.05). The toe ash, and toe ash Ca and P percentage of broiler chickens increased with the addition of phytase (P<0.05). Hen day egg production for the C, C+P and 100E group were 75.25, 77.25 and 66.0%, respectively; as egg production declined, FCR increased significantly (P<0.05). There were no significant differences in egg specific gravity, egg shell thickness, shell breaking strength and egg and toe mineralization among the dietary treatments. The results of the present study indicated that using phytase nutrient equivalency in feed formulation has a beneficial effect on broiler performance, but did not have any beneficial effect on the performance of old layer hens. In conclusion, using the same AME and protein equivalency values of phytase for broiler and old layers is not a valid approach.
