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Title: The influence of elevated preovulatory estradiol on apoptosis in the trophectoderm of day 16 bovine conceptuses

item NORTHROP, EMMALEE - South Dakota State University
item RICH, JERICA - South Dakota State University
item McNeel, Anthony
item SOARES, EMERSON - Universidade Federal De Santa Maria
item Cushman, Robert - Bob
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: Northrop, E.J., Rich, J.J., McNeel, A.K., Soares, E.M., Cushman, R.A., Perry, G.A. 2017. The influence of elevated preovulatory estradiol on apoptosis in the trophectoderm of day 16 bovine conceptuses [abstract]. Society for the Study of Reproduction Annual Meeting. Abstract #P60 (Scientific Program p. 302). Available:

Interpretive Summary:

Technical Abstract: Preovulatory estradiol impacts follicular growth, oocyte maturation, sperm transport, uterine environment, and embryo survival/development. It has also been reported that cows in standing estrus within 24 hours of fixed-time AI have greater pregnancy success compared to cows that do not exhibit standing estrus. Furthermore, in cattle, fertilization rate is approximately 90%, however calving rate is around 55%. This suggests around 35% embryonic mortality with most occurring between day 6 and day 18 of pregnancy. Apoptosis is critical for normal differentiation and development of the embryo; in cattle the impact of preovulatory estradiol on apoptosis in the trophectoderm around the time of maternal recognition of pregnancy is unknown. Our objective was to determine if differences in preovulatory estradiol concentrations were associated with differences in trophoblast apoptosis at day 16 of gestation. Beef cows/heifers were synchronized with the CO-Synch protocol and artificially inseminated (d 0). Cows were grouped into high and low preovulatory estradiol based on expression of estrus and circulating concentrations of estradiol (day -2 to day 0). Uteri were flushed to collect day 16 conceptuses nonsurgically (Rep 1; n =9), or following slaughter (Rep 2; n = 9). The trophectoderm was then separated from the embryo proper, and frozen into a block with OCT prior to cryosectioning. Percent apoptotic cells was determined by fluorescence BrdU staining in at least 3 different sections per conceptus. Data were analyzed using the GLIMMIX procedure of SAS with section as a random variable. There was no effect of preovulatory estradiol (P = 0.64; 29.8 ± 4.0% vs 27.6 ± 4.9% for cows with and without elevated preovulatory estradiol), replicate (P = 0.22), or estradiol by replicate interaction (P = 0.13) on apoptosis rate in the trophectoderm. In summary, there was no difference between the rate of apoptosis in the trophectoderm of day 16 conceptuses collected from cows that did or did not have an elevated preovulatory rise in estradiol. This further supports our previous research by demonstrating that conceptus survival to day 16 is not different between animals that do and do not have a preovulatory increase in estradiol prior to a fixed-time AI. Thus, differences in pregnancy success between cows that do and do not exhibit estrus likely occurs after maternal recognition of pregnancy.