The present study aims to compare the effects of removing the calf for 72 hours associated or not with Norgestomet (NOR) implant and estradiol upon estrus induction and fertility in postpartum aciclic beef cows. The temporary weaning (DT) group (n=38) was separated from their calves for 72 hours The NOR group (n= 29) received on Day 0 a 3mg Norgestomet implant subcutaneously and 5 mg of estradiol valerate, and 3mg of Norgestomet intramuscular. On Day 9 the implants were removed and the calves were separated for 72 hours. The interval from weaning to estrous was significantly shorter (P<0.05) for cows treated with progestogens (50.1 hours) compared with calf removal group (86.4 hours). The estrous induction rate was significantly higher (P<0.05) for Norgestomet and estradiol treated cows, but ovulation rate, first pregnancy rate and at the end of the breeding season were similar for both groups. The Norgestomet and estradiol treatment of aciclic beef cows improved the estrous incidence after 72 hours tempory weaning. The results demonstrate that the treatment of aciclic beef cows with Norgestomet and estradiol increases the induction of estrous after 72 hours of temporary weaning, without interfering with the pregnancy rates of first estrous and in the reproductive season.
beef cow; temporary weaning; Norgestomet
