Respuesta estral y porcentaje de concepción en vacas Bos taurus-Bos indicus posparto, tratadas con la hormona bovina del crecimiento en un programa de inducción de la ovulación con progestágenos y eCG

bovine somatotropin (bst) injection was administered at the beginning of the ovulation induction with progesterone and ecg, and a second one during insemination to prove if it increased estrous response and conception rate (cr) in postpartum beef cows. a hundred and seventy four cows (bos taurus-bos indicus) of 60 to 100 days postpartum, with offspring and body condition of 2 to 2.5 were used. a progesterone-releasing intravaginal device (cidr) was inserted to all females for 9 days and, while removing it, pgf2a was injected. cows were randomly assigned to the following treatments: ecg (n = 44), received 400 iu of ecg at the moment cidr was removed; bst (n = 44), received 500 mg of bst when cidr was inserted and 500 mg of bst during insemination; bst-ecg (n = 44), received 500 mg of bst when cidr was inserted and 400 iu of ecg while removing it; and 500 mg of bst during insemination; control (n = 42), only received the cidr. progesterone concentrations were assessed before the insertion of cidr. igf-i serum concentrations were determined in seven cows of each group. at the beginning of the experiment, 93% of the cows were in anoestrus. the rate of cows that showed estrus was similar (p > 0.05) between treatments [ecg (36.4%; bst (45.4%); ecg-bst (52.2%); control (40.4%)]. the cr was not different (p > 0.05) between treatments [ecg (31.2%); bst (15%); ecg-bst (34.7%); control (40%)]. cows treated with bst had higher igf-i concentrations than control cows. it is concluded that the injection of bst at the beginning of the ovulation induction with progesterone and ecg, and a second one during insemination does not improve estrous response or fertility in postpartum beef cows.