BACKGROUND: There are different kinds of phytase from different sources used in poultry nutrition.OBJECTIVES: The present study aimed to evaluate the effects of addition of 2 sources of 6- phytase to the diet of male broilers in terms of growth performance, Tibia biometric, breacking straight, mineralization, blood biochemical parameters, and carcase yield.METHODS: Herein, we recruited 216 1-d-old male Ross broilers and divided them to three experimental groups and six replications for 42 D. The treatment (T) diets included: T1 (without phytase (control)), T2 (supplemented with 500 FTU/kg diet of Aspergillus niger phytase (fungi phytase)), T3 (supplemented with 500 FTU/kg diet of phytase produced by a genetically modified strain of Aspergillus oryzae by doner Citrobacter braakii gene (genetically modified phytase)).RESULTS: Serum P in the birds supplemented by genetically modified phytase was higher compared with that in the control birds (P<0.05). Additionally, Tibia P in this group was higher than that of birds supplemented by fungi phytase (P<0.05). However, Tibia breaking straight in birds supplemented by genetically modified phytase did not differ significantly with those fed with a diet with fungi phytase. Meanwhile, Tibia breaking straight in birds supplemented by genetically modified phytase was higher than control (P<0.05). Growth performance, Tibia length, diameter, ash, Ca, dry weight, average serum HDL, Triglyserid, Cholesterol, Ca, Alkalin phosphatase, Glucose, Total Protein, and Carcase yeild were not significantly different among any of the treatments.CONCLUSIONS: Supplementation of male broilers diet with genetically modified phytase (500 FTU/kg), without any differences in terms of performance, could increase P of serum, P of Tibia and breacking straight of Tibia compared to supplementation diet with Aspergillus niger phytase.