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ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Publications at this Location » Publication #310862
Title: Effects of preovulatory estradiol on embryo survival and pregnancy establishment in beef cows

Author
item MADSEN, CRYSTAL - South Dakota State University
item PERRY, GEORGE - South Dakota State University
item DALY, RUSSELL - South Dakota State University
item Macneil, Michael
item Geary, Thomas

Submitted to: Biology of Reproduction
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/7/2015
Publication Date: 7/1/2015
Citation: Madsen, C.A., Perry, G.A., Daly, R.F., MacNeil, M.D., Geary, T.W. 2015. Effects of preovulatory estradiol on embryo survival and pregnancy establishment in beef cows. Biology of Reproduction. 158:96-103. http://dx.doi.org/10.1016/j.anireprosci.2015.05.006.

Interpretive Summary: An increase in estrogen around the time of estrus is thought to be important for pregnancy success in cows. To study the importance of estrogen during this time, spayed cows were given estradiol cypionate (ECP), estradiol benzoate (EB) or no treatment (CON). All cows received a device that releases progesterone (CIDR) for 7 days before treatment. Prostaglandin was given at CIDR removal (day -2) to all cows. An injection of gonadotropin releasing hormone (GnRH, day 0) was given 2 days later to mimic the follicular phase. Cows received either ECP 36 hours before GnRH injection, EB 12 hours before GnRH injection, or no treatment (CON). Early pregnancy was mimicked with progesterone injections from day 3 to 6 and use of CIDRs from day 7 to 29. On day 7 after GnRH injection, each cow received one embryo and a CIDR. Another CIDR was added 24 hours following embryo transfer. Every 6 days, the older of the two CIDRs was replaced with a new CIDR. Blood was collected every 4 hours between day -2 and day 0 to measure estrogen. Blood was collected on day -2, -1, 0, 3 to 7, 13, and 17 to 29 to measure progesterone. Blood estrogen profiles were different (P < 0. 001) between treatments. Blood progesterone levels were decreased for EB and ECP treated cows compared to CON cows. Pregnancy diagnosis on day 29 indicated that 4% of CON, 29% of EB, and 21% of ECP cows were pregnant. Expression of pregnancy specific genes ISG15, Mx2, and Oas1 on day 19 indicated that 68.7% of cows were pregnant. Thus, 62, 39.7, and 50% of pregnancies in CON, EB, and ECP cows were lost from day 19 to 29. Overall, embryo survival was greater in cows exposed to estrogen. In general, embryos were unable to implant in the uterus of cows that did not receive estrogen.

Technical Abstract: The role of preovulatory estradiol on embryo survival and pregnancy establishment has not been well characterized in beef cows. We hypothesized that preovulatory estradiol is important for embryo survival and pregnancy establishment in beef cows. Twenty-four ovariectomized multiparous cows were used in a 3 x 3 Latin Square design. Cows received either 1) estradiol cypionate (ECP) 36 h, 2) estradiol benzoate (EB) 12 h , or 3) no estradiol (CON) before a gonadotropin-releasing hormone (d 0) induced LH surge. Luteal phase progesterone was mimicked with twice daily progesterone injections from d 3 to 6. On d 7 each cow received one embryo and progesterone was supplemented with progesterone-releasing devices (CIDR). Expression of interferon stimulated genes, ISG15, MX2, and OAS1, in leukocytes was determined on d 17, 19, 21, and 28 to determine the capability of embryonic signaling. Pregnancy specific protein B concentrations were measured in serum samples from d 17 through 29 to determine embryonic attachment. Transrectal ultrasonography was performed on d 29 and 32 to determine pregnancy viability (heartbeat). Serum estradiol profiles during simulated proestrus/estrus were different (P < 0. 001) between treatments. Mean serum progesterone concentrations from d 17 to 24 were decreased (P = 0.05) in EB and ECP treated cows compared to CON. Transrectal ultrasonography indicated that fewer CON (4%) cows had a viable embryo present compared to estradiol treated cows (25%). Embryonic loss in cows that did not receive estradiol during the simulated preovulatory period occurred following maternal recognition of pregnancy, indicating that its impact was likely on uterine receptivity and embryonic attachment.