EN
The objective of the examinations performed on 230 cows and 36 embryo recipients was to establish if 1—3 doses of progesterone applied between the 17th and 19th day after insemination or on the 10th day after embryo transfer help the stabilization of pregnancy. After one dose of P4 (250 mg) 51,1% of conceptions were noted, after 2 doses 63,8% and after 3 doses 76,6% of conceptions were observed. In a control group 30,3% of the cows became pregnant. In embryo recipients after one anpplication of an exogenous progesterone at a dose of 125 mg the pregnancy rate was 44,4% as compared to a control group in which the rate was 27,8%. In pregnant cows initial levels of progesterone varied from 1,96 to 8,1 ng/ml. In the group of cows receiving 1 dose of P4 an average increase of the level of progesterone was by 1,1 ng/ml, in the group receiving two injections by 3,36 ng/ml, and in the group receiving three injections of P4 by 4,9 ng/ml. In the control group on the 19th day after insemination in 37,2% of pregnant cows the level of progesterone in blood plasma decreased by an average of 1,65 ng/ml. It can be assumed that the application of exogenous progesterone in inseminated cows with subclinical disturbances of endometrial functions and in embryo recipients positively affects the stanilization of pregnancy.