Journal of equine veterinary science2020; 89; 102987; doi: 10.1016/j.jevs.2020.102987

Historical Aspects of Equine Embryo Transfer.

Abstract: Early embryo transfer in equids was undertaken simultaneously in the early 1970s in Cambridge, England, and Kyoto, Japan. Both groups achieved limited success when flushing the uterine horn ipsilateral to the side of ovulation but the rates improved markedly when the whole uterus was flushed on realization of the continued movement of the embryo throughout the uterine lumen after day 6. Initial transfers of embryos to recipient mares were carried out surgically, but nonsurgical transfer via the cervix has been used subsequently with increasing success, culminating in pregnancy rates of 75%-90% today. Experimental use of embryo transfer in horses and donkeys demonstrated the unique ability of equids to carry to term a full range of interspecies hybrid conceptuses and extraspecies pregnancies created by embryo transfer. Furthermore, splitting of day 4-8 cell embryos and day 6 compact morulae allowed the creation of genetically identical twin foals. But despite these and other significant advances over the past 45 years, a persisting limitation is the relatively low embryo recovery rates from donor mares treated with exogenous gonadotropins in attempts to induce them to superovulate. This is due to the toughness of the ovarian tunica albuginea which forces ovulation through the ventrally situated ovulation fossa where multiple follicles compete with each other and luteinize before they can ovulate properly.
Publication Date: 2020-03-10 PubMed ID: 32563443DOI: 10.1016/j.jevs.2020.102987Google Scholar: Lookup
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  • Journal Article
  • Research Support
  • Non-U.S. Gov't

Summary

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The research article focuses on the historical advances in equine embryo transfer, tracking the progression from its early stages in the 1970s to the present. It also explores the challenges that have persisted over the years, particularly regarding the low embryo recovery rates from donor mares.

Initial Progress of Equine Embryo Transfers

  • The researchers discuss the history of equine embryo transfers, highlighting that early attempts were made simultaneously in Cambridge, England, and Kyoto, Japan in the 1970s. In these early stages, embryo transfers were often undertaken surgically.
  • Initially, the process involved flushing the uterine horn ipsilateral to the side of ovulation. However, this method only achieved limited success due to the continued movement of the embryo throughout the uterine lumen after day 6.
  • Upon the realization of the embryo’s continuous movement, the researchers decided to flush the whole uterus instead. This new approach led to an improvement in success rates.

Development of Non-surgical Methods and the Success of Inter-species Transfers

  • Subsequent to the surgical methods, a non-surgical technique was developed. This procedure involved transferring the embryos via the cervix and proved to be increasingly successful.
  • Using the non-surgical method, the success rates of equine embryo transfers have markedly increased over time, with current pregnancy rates between 75%-90%.
  • Further developments have included the experimental use of embryo transfers in horses and donkeys, illustrating the unique ability of equids to carry interspecies hybrid conceptuses and extraspecies pregnancies to full term.
  • This research also explored the potential of creating genetically identical twin foals by splitting day 4-8 cell embryos and day 6 compact morulae.

Persistent Challenges in Enhancing Embryo Recovery Rates

  • Despite the significant advances in the field over the past 45 years, there remain persistent issues, particularly concerning the relatively low embryo recovery rates from donor mares treated with exogenous gonadotropins to stimulate superovulation.
  • This challenge arises due to the toughness of the ovarian tunica albuginea, which forces ovulation through the ventrally situated ovulation fossa. Here, multiple follicles compete with each other and undergo luteinization before they can ovulate properly, leading to low recovery rates.

Cite This Article

APA
Allen WRT, Wilsher S. (2020). Historical Aspects of Equine Embryo Transfer. J Equine Vet Sci, 89, 102987. https://doi.org/10.1016/j.jevs.2020.102987

Publication

ISSN: 0737-0806
NlmUniqueID: 8216840
Country: United States
Language: English
Volume: 89
Pages: 102987
PII: S0737-0806(20)30078-2

Researcher Affiliations

Allen, W R Twink
  • The Paul Mellon Laboratory of Equine Reproduction, Newmarket, Suffolk, United Kingdom; Sharjah Equine Hospital Reproduction Laboratory, Sharjah, United Arab Emirates. Electronic address: twinkallen100@gmail.com.
Wilsher, Sandra
  • The Paul Mellon Laboratory of Equine Reproduction, Newmarket, Suffolk, United Kingdom; Sharjah Equine Hospital Reproduction Laboratory, Sharjah, United Arab Emirates.

MeSH Terms

  • Animals
  • Embryo Transfer / veterinary
  • England
  • Equidae
  • Female
  • Horses
  • Japan
  • Pregnancy
  • Pregnancy Rate

Citations

This article has been cited 1 times.
  1. Antczak DF, Allen WRT. Placentation in Equids.. Adv Anat Embryol Cell Biol 2021;234:91-128.
    doi: 10.1007/978-3-030-77360-1_6pubmed: 34694479google scholar: lookup