Small day 8 equine embryos cannot be rescued by a less advanced recipient mare uterus.
Abstract: Equine embryos tolerate an unusually large degree of negative uterine asynchrony (recipient mare up to 5 days behind the donor mare). By contrast, positive asynchrony of more than 2 days results in a high incidence of early embryonic loss (EEL). Day 8 embryos range in diameter from approximately 130-1300 μm, with embryos smaller than 300 μm reported to suffer an increased incidence of EEL. However, it is not known whether this reduced viability is due to intrinsically poor embryo quality, or to inadvertent recipient uterine stage-embryo (positive) asynchrony. To examine whether small embryos survive better in Day 4-5 recipients than in recipients with a more advanced uterine stage, the likelihood of pregnancy (PR) and EEL for 62 small (<300 μm) and 215 larger Day 8 horse embryos were compared after transfer to recipients at different uterine stages (Days 4-5, 6-7 and 8-9) using logistic regression. Overall, EEL was higher (21.2%; P < 0.05) for small than larger embryos (7.1%). However, neither PR nor EEL were influenced by the recipient's uterine stage at the time of transfer (P > 0.1). The EEL for small embryos transferred into Day 4-5, 6-7 and 8-9 recipients was 20.8, 18.7 and 25.0%, respectively. We conclude that embryos recovered on Day 8 with a diameter <300 μm are at increased risk of EEL due to reasons other than inadvertent positive asynchrony with the recipient mare's uterus.
Copyright © 2018 Elsevier Inc. All rights reserved.
Publication Date: 2018-11-26 PubMed ID: 30513402DOI: 10.1016/j.theriogenology.2018.11.026Google Scholar: Lookup
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- Journal Article
Summary
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This research focused on whether smaller equine embryos can be successfully developed in the uterus of a less advanced recipient mare, with the results indicating that this is not a viable solution for reducing early embryonic loss (EEL). The study found that neither successful pregnancy rates nor EEL rates were influenced by the stage of the recipient mare’s uterus at the time of embryo transfer.
Research Method and Variables
- The study examined whether smaller equine embryos, which suffer increased EEL, could survive better if transferred into recipient mares with a less advanced uterine stage.
- The variable being tested was the stage of the recipient mare’s uterus (Days 4-5, 6-7, and 8-9) at the time of the embryo transfer.
- The researchers compared the chances of successful pregnancy and EEL for two sets of Day 8 horse embryos of varying sizes – 62 small embryos (<300 μm in diameter) and 215 larger ones – using logistic regression.
- The viability of smaller embryos (those smaller than 300 μm in diameter) is often less, but it was uncertain whether this was due to embryo quality or inadvertent positive asynchrony (when the recipient’s uterus is more advanced than the embryo).
Results and Findings
- The research found that the EEL was higher (21.2%; P < 0.05) for small embryos than for larger embryos (7.1%).
- However, the data indicated that neither pregnancy rate nor EEL rate was affected by the recipient mare’s uterine stage at the time of transfer (P > 0.1).
- The EEL for small embryos transferred into Day 4-5, 6-7, and 8-9 recipients showed rates of 20.8%, 18.7%, and 25.0% respectively.
Conclusion of the Research
- The research concluded that smaller Day 8 embryos (those with a diameter of less than 300 μm) are at an increased risk of EEL, but the reason does not relate to inadvertent positive asynchrony with the recipient mare’s uterus.
- Overall, the viability of smaller equine embryos cannot be improved by transferring them into the uterus of a less advanced recipient mare.
Cite This Article
APA
Cuervo-Arango J, Claes AN, Stout TAE.
(2018).
Small day 8 equine embryos cannot be rescued by a less advanced recipient mare uterus.
Theriogenology, 126, 36-40.
https://doi.org/10.1016/j.theriogenology.2018.11.026 Publication
Researcher Affiliations
- Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, the Netherlands. Electronic address: j.cuervo-arangolecina@uu.nl.
- Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, the Netherlands.
- Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, the Netherlands.
MeSH Terms
- Animals
- Cell Size
- Embryo, Mammalian / cytology
- Embryo, Mammalian / physiology
- Embryonic Development
- Estrus Synchronization
- Female
- Horses / embryology
- Logistic Models
- Reproductive Techniques, Assisted / veterinary
- Uterus / physiology
Citations
This article has been cited 2 times.- De Coster T, Zhao Y, Tšuiko O, Demyda-Peyrás S, Van Soom A, Vermeesch JR, Smits K. Genome-wide equine preimplantation genetic testing enabled by simultaneous haplotyping and copy number detection. Sci Rep 2024 Jan 23;14(1):2003.
- Donato GG, Necchi D, Vandaele H, Vita ME, Bertero A, Vincenti L, Nervo T. Influence of Intrauterine Fluid Detection, Number of Transfers and Age of the Recipient on Pregnancy Rate and Early Embryonic Loss in a Commercial Embryo Transfer Program. Animals (Basel) 2023 May 29;13(11).
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