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ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Nutrition, Growth and Physiology » Research » Publications at this Location » Publication #303261
Title: Association of circulating concentrations of estradiol during the preovulatory period and expression of steroidogenic enzymes in beef cows

Author
item LARIMORE, ERIN - South Dakota State University
item AMUNDSON, OLIVIA - South Dakota State University
item BRIDGES, GLEN - University Of Minnesota
item McNeel, Anthony
item Cushman, Robert - Bob
item PERRY, GEORGE - South Dakota State University

Submitted to: International Symposium on Reproduction in Domestic Ruminants
Publication Type: Abstract Only
Publication Acceptance Date: 4/16/2014
Publication Date: 8/1/2014
Citation: Larimore, E.L., Amundson, O.L., Bridges, G.A., McNeel, A.K., Cushman, R.A., Perry, G.A. 2014. Association of circulating concentrations of estradiol during the preovulatory period and expression of steroidogenic enzymes in beef cows. In: Juengel, J. L., Miyamoto, A., Price, C., Reynolds, L. P., Smith, M. F., and Webb, R., editors. Reproduction in Domestic Ruminants VIII. Leicestershire, England: Context Products Ltd. p. 610.

Interpretive Summary:

Technical Abstract: Cows with greater circulating concentrations of estradiol during the preovulatory period (HighE2) have increased pregnancy success following a fixed-time AI protocol. Furthermore, these animals have an enhanced ability to produce estradiol as indicated by increased expression of CYP19A1 and LHR within granulosa cells and increased concentrations of androstenedione within the follicular fluid of the dominant follicle. This study was conducted to determine if there were changes within the steroidogenic pathway, prior to androstenedione production, associated with increased circulating concentrations of estradiol. Beef cows (Rep1; n=32, Rep2; n=20) were synchronized by an injection of GnRH (100µg; i.m.) on d -7 and an injection of PGF2a (25mg; i.m.) on d 0. In Rep1, estrus was monitored and blood samples were collected every 3 h from PGF2a on d 0 to h 33 after PGF2a and at slaughter (h 36 to 42; n=10). At slaughter, follicular fluid (FF) and granulosa cells were collected from the dominant follicle. In Rep2 the dominant follicle was aspirated via ultrasound-guided follicular aspiration (ASP) to collect FF and granulosa cells (h 38 to 46). In Rep2, estrus was monitored and blood samples were collected every 8 h from PGF2a until ASP. Circulating concentrations of estradiol and FF concentrations of progesterone were determined by RIA and cows were classified as either HighE2 (peak >/=6.0 pg/mL; n=4, and >/=7.3 pg/mL; n=6) or LowE2 (peak =4.5 pg/mL; n=5, and