Influence of preovulatory estradiol treatment on the maintenance of pregnancy in beef cattle receiving in vivo produced embryos

Authors: KETCHUM, JACLYN - Texas A&M University; PERRY, GEORGE - Texas A&M Agrilife; QUAIL, LACEY - Texas A&M University; EPPERSON, KAITLIN - Texas A&M University; OGG, MAKAYLA - Montana State University; Zezeski, Abby; RICH, JERICA - Arkansas State University; ZOCA, SAULO - University Of Tennessee; KLINE, ADALAIDE - Kansas State University; ANDREWS, TAYLOR - New Mexico State University; ORTEGA, M. SOFIA - University Of Wisconsin; SMITH, MICHAEL - University Of Missouri; Geary, Thomas

Submitted to: Animal Reproduction Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/2/2023
Publication Date: 6/7/2023
Citation: Ketchum, J.N., Perry, G.A., Quail, L.K., Epperson, K.M., Ogg, M.A., Zezeski, A.L., Rich, J.J., Zoca, S.M., Kline, A.C., Andrews, T.N., Ortega, M., Smith, M.F., Geary, T.W. 2023. Influence of preovulatory estradiol treatment on the maintenance of pregnancy in beef cattle receiving in vivo produced embryos. Animal Reproduction Science. 255. Article 107274. https://doi.org/10.1016/j.anireprosci.2023.107274.
DOI: https://doi.org/10.1016/j.anireprosci.2023.107274

Interpretive Summary: Many factors are involved with pregnancy success in cattle, and it is especially true when assisted reproductive techniques like embryo transfer (ET) are used. One of these factors appears to be whether a cow expresses estrus (heat) or has elevated estrogen (E2) 7 days before ET. We compared cows that were in heat with cows that received hormone induced ovulation with or without E2. Pregnancy was evaluated on day 19, 24, 30, and 56 in this study. On day 19 pregnancy rates did not differ between treatments. On day 24, cows in heat had greater pregnancy rates than cows that did not receive E2. On day 30, pregnancy rates were lower for cows that did not receive E2 compared to other groups. Thus, pregnancy loss is greater when cows do not experience high E2 levels 7 days before ET. Future studies will evaluate how E2 improves embryo survival and pregnancy success.

Technical Abstract: This experiment was designed to determine the role of preovulatory estradiol in pregnancy retention after embryo transfer (ET). Cows were synchronized with the 7-d CO-Synch + CIDR® protocol. On d0, cows were grouped by estrual status (estrual [Positive Control] and nonestrual), and nonestrual cows were administered Gonadotropin Releasing Hormone (GnRH) and randomly assigned to either no treatment (Negative Control) or Estradiol (0.1 mg estradiol 17-'' IM). All cows received an embryo on d7. Pregnancy status was retrospectively classified on d55/56/58, 30, 24, and 19 by either ultrasonography, plasma pregnancy-associated glycoproteins analysis (PAGs), expression of interferon-stimulated genes, plasma progesterone (P4) concentrations, or a combination of the factors. There was no difference in estradiol concentrations on d0h0 (P > 0.16). At d0h2, Estradiol cows (15.7 ± 0.25 pg/mL) had elevated (P < 0.001) estradiol compared to Positive Controls (3.4 ± 0.26 pg/mL) or Negative Controls (4.3 ± 0.25 pg/mL). On d19, pregnancy rates did not differ (P = 0.14) among treatments. On d24, Positive Controls (47%) had greater (P < 0.01) pregnancy rates than Negative Controls (32%); Estradiol cows were intermediate (40%). There was no difference (P = 0.38) in pregnancy rates between Positive Control (41%) and Estradiol (36%) cows on d30, but Negative Control (27%) cows had (P = 0.01) or tended (P = 0.08) to have decreased pregnancy rates, respectively. Thus, preovulatory estradiol may elicit an effect on early uterine attachment or alter histotroph components, consequently improving pregnancy maintenance through d30