Session: Physiology and Endocrinology I

239 - Increased Preovulatory Estradiol Improves Pregnancy Success of Embryo Transfer in Beef Cows

Friday, July 16, 2021

9:00 AM – 9:15 AM EST

Location: Kentucky International Convention Center (KICC), M109 & 110

Presenting Author(s)

Jaclyn N. Ketchum, n/a

PhD Student
Texas A&M University, Department of Animal Science
Overton, Texas

PDF Slides and Audio

Author(s)

GP

George A. Perry

Texas A&M AgriLife Research, Overton
Overton, Texas
Kaitlin M. Epperson, MS

Graduate Student
Texas A&M University
College Station, Texas
Lacey Quail, M.S.

Graduate Student
Texas A&M University
College Station, Texas
Mo

Makayla ogg

South Dakota State University
Brookings, South Dakota
AZ

Abigail L. Zezeski

USDA-ARS Fort Keogh
Miles City, Montana
Jerica J J Rich, Ph.D.

Assistant Professor of Animal Science
Arkansas State University - College of Agriculture
Jonesboro, Arkansas
Saulo Menegatti Zoca, PhD Candidate

Graduate Student
South Dakota State University
Brookings, South Dakota
Adalaide C. Kline

Graduate Student
South Dakota State University
Mission Hills, Kansas
Taylor Andrews

Graduate Student
South Dakota State University
Brookings, South Dakota
MO

M. Sophia Ortega

University of Missouri
Columbia, Missouri
MS

Michael F. Smith, Ph.D.

Professor of Animal Science
University of Missouri-Columbia
Columbia, Missouri
TG

Tom W. Geary, n/a

USDA-ARS Fort Keogh
Miles City, Montana

Preovulatory estradiol concentrations and expression of estrus have been associated with greater pregnancy rates in beef cattle following AI, thus an experiment was designed to determine if supplemental estradiol (E2) at GnRH-induced ovulation would improve pregnancy retention in postpartum beef cows after embryo transfer. Cows were synchronized with the 7-d CO-Synch + CIDR^® protocol. On d0 (48h post-prostaglandin) cows were grouped by estrual status (Estrual; n=198, nonestrual; n=406). Nonestrual cows were administered GnRH and randomly assigned to either no treatment (Control; n=204) or administration of 0.1 mg (IM) estradiol 17-𝛽 (Estradiol; n=202). In a preliminary study, 0.1 mg (IM) estradiol 17-𝛽 increased plasma estradiol (17.11±3.4 pg/mL; P < 0.01) and remained elevated above baseline for approximately 8h compared to control (1.70±0.58 pg/mL). All cows received an in vivo produced embryo on d7. Embryos were matched by grade, stage, and flush across treatments. Pregnancy was classified on d30 by either plasma pregnancy-associated glycoproteins analysis (Year 1) or ultrasonography (Year 2). Plasma estradiol concentrations (d-2, d0h0, d0h2) were analyzed by PROC MIXED as repeated measures in SAS(9.4), while GLIMMIX procedures were used to analyze differences in pregnancy rates with treatment, group, year, and their interactions as fixed effects. There was a treatment by time interaction (P < 0.001) in E2 concentration. There was no difference in plasma E2 concentrations on d0h0 (P >0.30) between treatments. At d0h2, Estradiol cows (15.7±0.25 pg/mL) had greater plasma E2 compared to Estrual (4.0±0.13 pg/mL) or Control (3.4±0.25 pg/mL) cows (P < 0.001), and Estrual cows had greater plasma E2 than Control cows (P = 0.02). Control cows had decreased (26%) pregnancy rates compared to both Estradiol (37%; P = 0.03) and Estrual (40%; P = 0.01) cows. Pregnancy rates did not differ (P = 0.51) between the Estrual and Estradiol cows. In conclusion, elevated preovulatory concentrations of estradiol are critical for improved pregnancy retention following embryo transfer.