Evaluation of Using Phytase Nutrient Equivalency Values for Layer Hens and Broiler Chickens

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 ex-periment, ۶۴۰ commercial broiler chicks were used from ۱۱ to ۴۹ days of age. The ex-perimental units were allocated at random to ۴ dietary treatments two sexes with ۴ rep-licates per treatment. The first dietary treatment was formulated with no addition of phy-tase (C), the second diet contained ۵۰۰ FTU kg-۱ phytase over the top (C+P), and the third diet contained ۵۰۰ FTU kg-۱ phytase which was calculated as half of the nutrient equiva-lency values for phyatse (۵۰E). The fourth dietary treatment contained ۵۰۰ FTU kg-۱ phyatse which was calculated as the total nutrient equivalency values for phytase (۱۰۰E). In the second experiment ۲۸۸ Hy-line W-۳۶ hens were used from ۶۰ to ۷۲ weeks of age. The treatments consisted of a control diet (C) with no addition of phytase, a control diet supplemented with ۳۰۰ FTU kg-۱ phytase over the top (C+P), and a third diet containing ۳۰۰ FTU kg-۱ phytase which was calculated as the total nutrient equivalency values for phyatse (۱۰۰E). No significant difference was observed among the four dietary treatments for broiler final body weight, feed conversion ratio (FCR) and carcass characteristics (P> ۰.۰۵). The toe ash, and toe ash Ca and P percentage of broiler chickens increased with the addition of phytase (P< ۰.۰۵). Hen day egg production for the C, C+P and ۱۰۰E group were ۷۵.۲۵, ۷۷.۲۵ and ۶۶.۰%, respectively; as egg production declined, FCR increased significantly (P< ۰.۰۵). 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 equiva-lency 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.

Keywords:

Broiler , Layer hens , Nutrient Equivalency , Performance , Phytase