The ICSI procedure explained

IVF/ICSI is an extension of the embryo transplantation treatment. A large part of the treatment is similar to this technique (see In embryo transplantation, the embryo develops in the donor mare after insemination. It is flushed from the uterus at 7-8 days after ovulation and is transferred to a recipient mare. In the case that it is not possible to obtain an embryo for whatever reason, an IVF/ICSI treatment can be performed.

In IVF/ICSI, oocytes are recovered from the ovaries of the donor mare by a transvaginal aspiration of the follicles during a so-called Ovum Pickup procedure (OPU). During an OPU, oocytes are recovered from large, preovulatory follicles as well as from small, immature, subordinate follicles. These oocytes will have to undergo a maturation phase in vitro in the laboratory. After this, the oocytes are fertilized using the ICSI technique: the injection of a single sperm into each oocyte. After ICSI, further development of the fertilized oocytes is monitored during several days. After approximately one week the embryo develops to the blastocyst stage at which stage it is transferred to a recipient mare.


The success of the IVF/ICSI procedure is strongly affected by many factors. Although the recovery of oocytes during an OPU treatment is in most cases successful, not all of these oocytes will be viable. The chance that a fertilized embryo develops into an embryo that can be transferred to a recipient mare varies between 20% and 30%. The chance of success strongly varies between donor mares and is dependent on the age and breed of the mare. Furthermore, the semen quality of the stallion is an important factor determining the success rate. This means that in some cases the first IVF/ICSI procedure can lead to a successful pregnancy while in other cases more than one IVF/ICSI procedure will be necessary.

  • Equine Fertility Centre
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