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ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Nutrition and Environmental Management Research » Research » Publications at this Location » Publication #338950

Research Project: STRATEGIES TO IMPROVE HEIFER SELECTION AND HEIFER DEVELOPMENT

Location: Nutrition and Environmental Management Research

Title: Estrous cycle regulatory mechanisms of the uterus are altered in cows that do not demonstrate behavioral estrus during an ovulation induction protocol

Author
item Cushman, Robert - Bob
item NORTHROP, EMMALEE - South Dakota State University
item RICH, JERICA - South Dakota State University
item Chase, Chadwick - Chad
item PERRY, GEORGE - South Dakota State University

Submitted to: Society for the Study of Reproduction Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 4/11/2017
Publication Date: 7/10/2017
Citation: Cushman, R.A., Northrop, E.J., Rich, J.J., Chase, C.C., Perry, G.A. 2017. Estrous cycle regulatory mechanisms of the uterus are altered in cows that do not demonstrate behavioral estrus during an ovulation induction protocol [abstract]. Society for the Study of Reproduction Annual Meeting. Abstract #P230 (Scientific Program p. 227). Available: http://www.ssr.org/sites/ssr.org/files/uploads/attachments/node/482/ssr2017abstracts.pdf

Interpretive Summary:

Technical Abstract: Estrus is the start of an estrous cycle in cows, and triggers several precisely timed events including receptivity to the bull, ovulation, conception, formation of the corpus luteum, and recognition of pregnancy. In the absence of a pregnancy signal, the corpus luteum (CL) must regress in response to uterine prostaglandin F2a to initiate a new follicular phase and a new opportunity to become pregnant. When using ovulation induction protocols with timed artificial insemination, cows that demonstrate behavioral estrus between the prostaglandin injection and the time of insemination have greater fertility than those that do not, due to improper uterine function. Given the role of the uterus in initiating luteolysis and controlling the estrous cycle, questions remain about uterine function in the subsequent estrous cycle in cows that do not demonstrate estrus and do not conceive. Therefore, we hypothesized that disruption in uterine synchrony among cows that are induced to ovulate and do not exhibit estrus carries over to the subsequent estrous cycle. Cows (n = 20) with a palpable CL were injected with GnRH (100 ug, i.m.) and monitored for estrus. Seven days later, cows were injected with prostaglandin F2a (25 mg, i.m.) and estrus activity was monitored. Three days later, five cows that had exhibited estrus and five cows that had not were injected with GnRH (100 ug, i.m.). Cows were harvested on day 5 after GnRH. Endometrial explants (50 mg) were cultured for 24 h without (0 uM) or with 0.1 uM estradiol to simulate an artificial follicular phase, low P4 and increased E2. At the end of the culture, total cellular RNA was extracted, and relative abundance of oxytocin receptor (OTR), progesterone receptor (PGR), Period 1, and glyceraldehydes-3-phosphate dehydrogenase were determined by real-time RT-PCR. Relative transcript abundance was analyzed using the MIXED procedure of SAS with estrus (yes or no), estradiol dose (0 or 0.1 uM), and the interaction as the class effects in a repeated measures model. Uterine weights were greater at harvest for cows that demonstrated behavioral estrus than those that did not (P < 0.01). There was an interaction of estrus and estradiol dose such that estradiol increased OTR transcript abundance in cows that demonstrated estrus but not in those that did not (P < 0.05). An opposite effect was observed for PGR, transcript abundance was increased by estradiol in cows that did not exhibit estrus but not in cows that exhibited estrus (P < 0.05). Transcript abundance of the clock gene, Period 1, did not differ due to estradiol treatment but was decreased among cows that exhibited estrus compared to those that did not (P < 0.05). These results demonstrate that transcriptional mechanisms controlling uterine synchrony are different in cows that do not exhibit behavioral estrus before induction of ovulation. This could lead to an alteration in uterine synchrony negatively impacting fertility in the next follicular phase for cows that do not exhibit estrus and that do not conceive to timed artificial insemination.