The influence of intrinsic phytase and a microbial phytase additive on reproductive traits of sows, the composition of colostrum and milk, and on piglet rearing indices was studied. The two trials differed in the kind of grains used in the diets to give them lower (420-440 PU·kg^-1, Trial 1) or higher (1000-1150 PU·kg^-1, Trial 2) levels of intrinsic phytase. There were 3 feeding groups (34-35 animals in Trial 1 and 25 in Trial 2) in each experiment. In both trials, group 1 received the basic diet enriched with dicalcium phosphate, group 2, the basic diet without this additive (NC), and group 3, the basic diet supplemented with 500 PU·kg^-1 microbial phytase. A higher number of liveborn piglets in group 3 in comparison with group 2 in Trial 2 was noted. Also, the body weight of piglets was significantly higher in groups 1 and 3 in comparison with the NC group. The microbial phytase supplement increased the concentration of Zn and Cu in colostrum and of Zn in sow milk, regardless of native phytase activity.