Assisted reproduction techniques in the horse.

The research article reviews various assisted reproduction techniques used for horses, discussing challenges, efficiency and developments in the field. Some techniques covered include embryo transfer, in vitro maturation of immature oocytes, and intracytoplasmic sperm injection.

Embryo Transfer and Superovulation

• Embryo transfer is the most widely-used equine assisted reproduction technique (ART). However, its usage is curbed by the inability to superovulate mares effectively. Superovulation involves stimulating an organism’s ovary to produce more than one ovum during a cycle. This process is more challenging in horses compared to other species due to the anatomy and physiology of mares.

Oocyte Recovery and In Vitro Maturation

• The study presents two techniques for recovering immature oocytes. These can be recovered from immature follicles using transvaginal ultrasound-guided aspiration or from ovaries postmortem.
• The immature oocytes can then be matured in a lab setting, through a process known as in vitro maturation. In contrast, in vivo-matured oocytes can be easily recovered from the stimulated preovulatory follicle.

In Vitro Fertilization and Intracytoplasmic Sperm Injection

• Despite advancements, standard in vitro fertilization (IVF) remains inconsistent in horses. However, embryos and foals can still be produced either by surgical transfer of mature oocytes to inseminated recipient mares’ oviducts or by intracytoplasmic sperm injection (ICSI).
• ICSI and in vitro embryo culture techniques are performed routinely, but only by a handful of laboratories. However, the reported blastocyst development rates show promising results, approaching those found in bovine IVF, between 25% and 35%.

Nuclear Transfer and Embryo Biopsy

• Nuclear transfer in equine reproduction has shown relative efficiency with up to 26% live foal rates per transferred embryo.
• Also, equine blastocysts can be biopsied using micromanipulation, yielding normal pregnancy rates after biopsy and accurate genetic analysis.

Vitrification of Equine Blastocysts

• Finally, the research discusses the vitrification of equine expanded blastocysts. These can be vitrified after they are collapsed through micromanipulation, with normal pregnancy rates after warming and transfer.
• These methods, along with the others reviewed in the research, are now in clinical use and demonstrate the rapid advancements in the field of equine assisted reproduction.