Home Health and vet Clinical equine in vitro embryo production success rate

Clinical equine in vitro embryo production success rate

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By A. Claews, T.A.E. Stout

In vitro embryo production (IVEP) via Ovum Pick-Up (OPU) and Intracytoplasmic Sperm Injection (ICSI) has become a popular breeding technique in Warmblood mares because of the high success rate and several practical advantages.

IVEP offers a solution for a variety of reproductive issues including, but not limited to, sub-fertility in stallions or mares, poor quality or scarce frozen semen, difficulty in synchronizing donor and recipient mares, and inefficient use of recipient mares. In 515 OPU-ICSI sessions performed in our facility in 2021, a mean of 25.9 antral follicles were aspirated yielding an average 13.8 immature oocytes, which were shipped overnight to a specialized ICSI laboratory (Avantea). One or more blastocysts (range: 0–13 blastocysts) were produced from 78% of procedures with a mean of 2.12 blastocysts per session; the likelihood of pregnancy after transfer of a cryopreserved thawed IVP blastocysts in 2021 (n = 781) was 77.7%.
Several donor mare, recipient mare, stallion and embryonic factors influence the likelihood of producing an in vitro blastocyst or achieving pregnancy. Approximately 60% of the transferred IVP blastocysts yield a foal; moreover, neither gestation length nor the health of foals is noticeably influenced by IVEP. On the other hand, a skewed sex ratio towards colts is apparent among IVEP foals resulting from day seven but not day eight embryos, suggesting that male embryos develop more rapidly in vitro. Although serious complications after OPU are uncommon, owners should be aware of their existence, because some complications can be life-threating.

1. Introduction

In vitro embryo production (IVEP) via Ovum Pick-Up (OPU) and Intracytoplasmic Sperm Injection (ICSI) is an advanced breeding technique that has seen an enormous increase in popularity in sport horse breeding over the last five years, largely because of improvements in oocyte recovery and blastocyst production rates[1,2]. IVEP is popular among breeders of Warmblood mares because of the high success rate and a number of advantages over other breeding techniques. In particular, OPU-ICSI allows breeders to produce foals from stallions and mares with various fertility problems that other breeding techniques cannot remedy[3]. Furthermore, IVEP can be performed at any stage of the estrous cycle or season[4], and it is the only breeding technique that can be applied in the case of a mare that dies suddenly or needs to be euthanized due to a fracture, colic, etc.[5]
Another important advantage is that hundreds of IVP blastocysts can be produced from a single straw of frozen semen, because ICSI allows semen to be used very efficiently. Finally, IVP horse embryos tolerate cryopreservation better than large in vivo, flushed embryos probably as a result of their physical characteristics, including their small size and minimal blastocoele fluid content, and the absence of a confluent embryonic capsule[6]. The ability to cryopreserve IVP embryos with negligible loss of viability has allowed the development of an international trade in embryos and enables much more efficient use of recipient mares. In particular, recipient mares can be used early in the season and their cycle does not need to be synchronized with that of the donor mare. Last but not least, the overall success of IVEP appears to be similar or to exceed that of traditional embryo transfer and allows the possibility of producing one or more embryos from different stallions in a single treatment session[1]... To read the complete article you need to be a subscriber
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