Clinical Application of Ovum Pick Up, Intracytoplasmatic Sperm Injection and Embryo Culture in Equine Reproduction

For many years artificial insemination has been the most widely used assisted reproductive technique (ART) in the horse breeding industry (Squires 2005), while other procedures based on the in vivo and in vitro production of equine embryos have emerged only in recent years.

Reasons for the delayed development of in vivo and in vitro production of equine embryos, compared to other domestic species, namely ruminants and pigs, include the scarce availability of abattoir ovaries and the lack of interest from horse breeders and registries. Moreover, in spite of the early success of equine oocyte in vitro maturation (Zhang et al. 1989), no further relevant research on the issue was reported in the horse for some time. Many efforts instead concentrated on conventional in vitro fertilization (IVF) but, unfortunately, the successes with IVF in other species never occurred with horses and only two foals were reported as born from IVF and both were derived from in vivo matured oocytes collected by ovum pick-up (OPU) from gonadotrophin- stimulated mares (Palmer et al. 1991; Bezard 1992).

The application of intracytoplasmatic sperm injection (ICSI) to the horse has overcome the barrier of inefficient IVF, resulting in the first pregnancy derived from an in vitro matured oocyte (Squires et al. 1996) which was successfully carried to term. In the following years, a few other scientific reports showed that it is possible to obtain pregnancies and live foals after collection of immature oocytes by Ovum Pick Up (OPU) followed by in vitro maturation, ICSI and immediate transfer (Cochran et al. 1998, McKinnon et al. 2000)), or in vitro embryo culture (IVC) and non-surgical transfer of blastocyst stage embryos (Galli et al. 2002).

Today the most practical use of OPU or trans-abdominal follicle aspiration is to recover in vivo matured oocytes (Carnevale 2004) for oocyte transfer. It has been shown that the use of this procedure results in satisfactory pregnancy rates except for intrinsically compromised oocytes collected from geriatric mares (Carnevale and Ginther 1995, Carnevale et al. 2005). [...]