Para evaluar la tasa de prenez de dos periodos post-parto diferentes utilizando gonadotrofina corionica equina eCG, se conto con 36 vacas Bos indicus divididas en dos grupos de 18 vacas con diferente periodo post-parto; el primero de 40 a 60 dias y el segundo entre 150 y 180 dias. Cada grupo de 18 vacas fue subdividido en tratamiento uno T1 (sin eCG) conformado por nueve vacas y tratamiento dos T2 (con eCG) con igual numero de animales. El tratamiento uno consistio en lo siguiente: el dia cero se coloco un dispositivo intravaginal bovino de 0,5 g de progesterona mas 2 mg de benzoato de estradiol; el dia ocho se retiro el dispositivo y se aplico 0,15 mg de prostaglandina; en el dia nueve se aplico 1 mg de benzoato de estradiol y se realizo la inseminacion artificial 54-56 horas mas tarde del retiro del dispositivo, frente al tratamiento dos, el cual, el dia ocho presento la adicion de 300 UI de la hormona gonadotrofina corionica equina (eCG). Durante los tratamientos uno y dos, a los animales de cada grupo se realizo destete temporario. Una vez realizada la inseminacion, a cada grupo se les asigno dos toros para realizar repaso; despues de 60 dias de efectuada la inseminacion artificial se determino la prenez mediante ultrasonografia. Los datos se analizaron mediante la prueba de chi-cuadrado (χ 2 ), obteniendo como resultado, en el periodo postparto temprano de 40-60 dias, una tasa de prenez del 11,1% en el T1, mientras que en el T2 se obtuvo una tasa de prenez del 55,6%, encontrandose una relacion estadisticamente significativa, lo que indica que la adicion de la hormona eCG en el postparto temprano aumenta la tasa de prenez. En el periodo postparto tardio, de 150-180 dias, no se encontro relacion estadisticamente significativa en la utilizacion de la hormona eCG. Palabras clave: inseminacion artificial, destete, periodo postparto, diagnostico de gestacion EVALUATION OF PREGNANCY RATE IN TWO DIFFERENT POSTPARTUM PERIODS BY USING EQUINE CHORIONIC GONADOTROPIN (eCG) IN MERCADERES, CAUCA, COLOMBIA ABSTRACT To evaluate the pregnancy rate of two different postpartum periods by using equine chorionic gonadotropin eCG, 36 Bos indicus cows, divided into two groups of 18 cows with different postpartum period, were taken. The first group from 40 to 60 days, and the second one between 150 and 180 days; each group of 18 cows was subdivided into treatment one T1 (without eCG) with nine cows, and treatment two T2 (with eCG) with an equal number of animals. The T1 is summarized as follows: on day zero, a bovine intravaginal device of progesterone 0.5 g was placed, plus 2 mg of estradiol benzoate. On day eight, the device was removed and 0.15 mg of prostaglandin was applied. On day nine, 1 mg of estradiol benzoate was used, and the artificial insemination was performed 54-56 hours after removing the device, contrary to the treatment two, which, on day eight, presented the addition of 300 UI of the equine chorionic gonadotropin hormone (eCG). During the treatments, all the animals of the investigation were weaned temporarily. Once the insemination was carried out to every group, two bulls were assigned to carry out rectification, and 60 days after the artificial insemination, pregnancy was determined through ultrasonography. The data was analyzed by means of the Chi-square test (χ 2 ), and the results showed a pregnancy rate of 11.1% in T1 in the early postpartum period of 40-60 days; meanwhile, the pregnancy rate in T2 was 55.6%. Those findings showed a statistically significant relationship, indicating that the addition of the eCG hormone in early postpartum increases the rate of pregnancy. In the late postpartum period of 150-180 days, the utilization or not of the eCG hormone did not show statistically significant relationship.