A broiler chicken study was conducted for 42 D to evaluate their responses to 3 commercially available microbial phytases. Growth performance, nutrient digestibility, and bone mineralization at days 21 and 42 posthatching were used as parameters of evaluation. The study was a randomized complete block design with 12 treatments, 8 replicate pens, and 25 birds per pen. Treatments included a positive control (
PC
), a negative control (
NC
) with crude protein (
CP
), nonphytate phosphorus (
P
), and calcium (
Ca
) reduced by 18, 1.5, and 1.8 g/kg, respectively; the NC + 4 levels of phytase A (250, 500, 750, 1,000 FTU/kg), 3 levels of phytase B (250, 500, 750 FTU/kg), and 3 levels of phytase C (500, 750, 1,000 FTU/kg). Broilers fed the NC diet had reduced (
P
< 0.05) performance and digestibility measures at days 21 and 42 relative to the PC. All phytase enzymes improved (
P
< 0.05) BW, gain, feed efficiency, and tibia ash weight and percent. Inclusion of phytase at the highest levels improved (
P
< 0.05) tibia ash weight by an average of 18.5 and 22% at days 21 and 42, respectively, over the NC. Phytase A linearly improved (
P
< 0.05) the apparent ileal digestibility (
AID
) of DM, Ca, P, copper, and sodium at day 21, and the AID of energy, nitrogen, and all amino acid (
AA
) digestibility at day 42 posthatching. Phytase B linearly (
P
< 0.05) improved BW gain and feed efficiency of birds at day 21 and quadratically improved (
P
< 0.05) the AID of nitrogen and all AA in birds at day 42. Supplementation of birds fed the NC with phytase C linearly improved (
P
< 0.05) the BW gain, feed intake, feed efficiency, and AID of DM, energy, nitrogen, all AA, and all minerals except manganese at day 42. In conclusion, all 3 phytase products improved the growth performance, nutrient and mineral digestibility, and bone mineralization of birds fed diets deficient in nitrogen, Ca, and P similar to or more than birds fed diet adequate in P and CP.
