Response of Beef Cows to Exogenous Progesterone and Estradiol at Various Stages Postpartum

Abstract

The response of Hereford cows to daily injections of 50 mg. progesterone and a single injection of 10 mg. estradiol-17 (β at various stages after calving was studied. Cows given estradiol alone or following progesterone treatment resumed ovarian activity earlier after calving than did untreated or progesterone treated cows. The treatment given earliest after calving caused the earliest ovulations. However, cows treated at “mid” postpartum anestrus had the shortest intervals to conception. Although estradiol was as effective when given alone as when preceded by progesterone in hastening the onset of estrus and ovulation, conception occurred earliest in cows given both hormones. Both progesterone and estradiol injections tended to decrease the variations of the intervals to estrus, ovulation and conception. Most of the treatments did not significantly affect interval to uterine involution, although some treatments tended to decrease this interval.