Plasma Estradiol and Endometrial Edema Profile in Acyclic Mares After Single Administration of 17-β Estradiol, Estradiol Benzoate and Estradiol Cypionate.
Abstract: A longer endometrial exposure to estradiol before progesterone has been shown to be beneficial in cyclic and acyclic recipient mares. Therefore, the selection of an estradiol ester that promotes longer endometrial exposure to estradiol using a single administration would be advantageous when preparing acyclic mares as embryo recipients. This study investigated plasma estradiol profiles in acyclic mares after a single administration of 17-β estradiol (17-β), estradiol benzoate (EB) and estradiol cypionate (EC), and the correlation between plasma concentrations and endometrial edema. Fifteen non-cyclic mares were divided into groups 17-β (n = 5), EB (n = 5) or EC (n = 5), receiving a single dose of 10 mg of the respective hormone. Blood sample collections and transrectal ultrasonography were performed every 6 h from hour 0 to 12, every 12 h from 12 to 48 h, and every 24 h from 48 to 120 h after hormone administration. Five of the acyclic mares were used during the breeding season as a cyclic control. Greater median concentrations were detected using EB (38.6 pg/mL; p < 0.05). For 17-β, peak concentration was observed at 6 h (29.7 pg/mL) and decreased 24 h after administration (5.9 pg/mL; p < 0.05). In the EC group, there was a modest peak starting from 12 h (11.7 pg/mL; p < 0.05), remaining relatively constant until 120 h. A more rapid increase of edema to moderate and high scores was found when using 17β estradiol, although edema scores and persistence until Day 5 were similar among the oestrogens used. A correlation between estradiol concentration and endometrial edema was only seen when using EC, and this hormone also produced the most similar concentration values to those found in natural cycling mares. Therefore, it is likely that EC would be a suitable hormone for preparing acyclic mares as embryo recipients.
© 2025 The Author(s). Reproduction in Domestic Animals published by Wiley‐VCH GmbH.
Publication Date: 2025-08-05 PubMed ID: 40760876PubMed Central: PMC12322513DOI: 10.1111/rda.70108Google Scholar: Lookup
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Summary
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This study investigated the impact of single doses of three different forms of the hormone estradiol on endometrial exposure and edema in mares that are not in a cycle of reproductive activity. The results suggest that Estradiol Cypionate may be the most suitable of the three for preparing these mares to receive embryo transfers.
Study Approach
- The purpose of this study was to identify the most effective type of estradiol for lengthening the amount of time the endometrium is exposed to this hormone in mares that are not currently in a reproductive cycle.
- A longer exposure to estradiol before the release of progesterone can be beneficial for these non-cycling mares, especially when preparing them for embryo transfers.
- The three different types of estradiol tested in this study were 17-β estradiol, estradiol benzoate, and estradiol cypionate.
- The non-cycling mares involved in the study were divided into three groups, each of which was administered a single dose of one form of estradiol.
- Over the course of five days, blood samples were collected and ultrasonography was carried out to monitor the concentration levels of estradiol in the plasma and measure endometrial edema.
Findings
- The highest median concentrations were detected in mares who received estradiol benzoate.
- In contrast, the concentration of 17-β estradiol peaked at 6 hours and then significantly decreased by 24 hours.
- Mares given estradiol cypionate had a modest peak starting from 12 hours, but it remained relatively stable until 120 hours.
- While there was a rapid increase of edema observed in the mares given 17-β estradiol, the overall edema scores and persistence were remarkably similar for all three types of the hormone.
- Only estradiol cypionate demonstrated a correlation between estradiol concentration and endometrial edema.
Conclusion
- The study concluded that estradiol cypionate is likely the most suitable type of this hormone to use in preparing non-cycling mares for embryo transfers.
- This is due to its stable concentration levels over the five-day period, its correlation with endometrial edema, and its similarity to the estradiol values found in naturally cycling mares.
Cite This Article
APA
Barbosa LA, Maran AP, de Almeida MER, Guimarães EC, Bringel B, Douglas RH, Lima TFG, da Silva ESM.
(2025).
Plasma Estradiol and Endometrial Edema Profile in Acyclic Mares After Single Administration of 17-β Estradiol, Estradiol Benzoate and Estradiol Cypionate.
Reprod Domest Anim, 60(8), e70108.
https://doi.org/10.1111/rda.70108 Publication
Researcher Affiliations
- School of Veterinary Medicine and Animal Science, Universidade Federal de Uberlândia, Uberlândia, MG, Brazil.
- School of Veterinary Medicine and Animal Science, Universidade Federal de Uberlândia, Uberlândia, MG, Brazil.
- School of Veterinary Medicine and Animal Science, Universidade Federal de Uberlândia, Uberlândia, MG, Brazil.
- School of Mathematics, Universidade Federal de Uberlândia, Uberlândia, MG, Brazil.
- B.E.T. Laboratories, Rio de Janeiro, RJ, Brazil.
- B.E.T. Laboratories, Lexington, Kentucky, USA.
- B.E.T. Laboratories, Rio de Janeiro, RJ, Brazil.
- School of Veterinary Medicine and Animal Science, Universidade Federal de Uberlândia, Uberlândia, MG, Brazil.
MeSH Terms
- Animals
- Female
- Horses
- Estradiol / analogs & derivatives
- Estradiol / blood
- Estradiol / administration & dosage
- Estradiol / pharmacology
- Endometrium / drug effects
- Endometrium / pathology
- Endometrium / diagnostic imaging
- Edema / veterinary
- Edema / chemically induced
- Horse Diseases / chemically induced
- Estrous Cycle
Conflict of Interest Statement
The authors declare no conflicts of interest.
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