Prolonged increased concentrations of 17beta-estradiol associated with development of persistent ovarian follicles do not influence conception rates in beef cattle

Journal of Animal Science
K E FikeJ E Kinder

Abstract

Objectives were to evaluate conception rates and time to estrus following cessation of treatments designed to either cause prolonged elevated concentrations of 17beta-estradiol associated with development of persistent ovarian follicles or to inhibit elevated concentrations of 17beta-estradiol and development of persistent ovarian follicles. Beef heifers (n = 80) and 2-yr-old nonlactating cows (n = 39) were stratified by age, blocked by estrual status (previously exhibited estrus or anestrus) and assigned to receive either 1) four norgestomet implants (4 Norg; n = 59) for 9 d (d 0 = treatment initiation) or 2) one norgestomet implant from d 0 to 7 and three additional norgestomet implants from d 7 to 9 (1 + 3 Norg; n = 60). All animals received PGF2alpha on d 0 to lyse corpora lutea. All implants were removed on d 9 followed by estrus detection every 6 h for 7 d following implant removal. Females exhibiting estrus were artificially inseminated 6 to 12 h after detection of estrus. A treatment x day interaction (P < .01) for concentrations of 17beta-estradiol from d 0 to 9 of the experiment with elevated 17beta-estradiol occurring in females treated with 1 + 3 Norg implants. The interval from treatment withdrawal to estrus was lo...Continue Reading

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