OPU / ICSI Frequently Asked Questions (FAQs)

OPU / ICSI Frequently Asked Questions (FAQs)

OPU / ICSI Frequently Asked Questions (FAQs)


Are all mares suitable for OPU?

In principle all mares are eligible for OPU. However, mares which had a foal have an advantage as there is a lot more manoeuvrability of their ovaries, aiding comfort of the mare during and after the procedure and efficiency of the OPU session. The ovarian ligaments are relatively tight in young mares. Manipulating and puncturing the ovaries can therefore cause discomfort regardless of all taken precautions.

Mares which have a history of reproductive problems, such as uterine pathology, persistent fluid or uterine infections, endometrial cysts, damaged reproductive tract due to dystocia (bad foaling) are ideal candidates.  Mares that do not become pregnant or do not give embryos via embryo transfer are candidates for OPU.

Older and aged mares still produce quality oocytes but tend to have less follicles on their ovaries. This could mean that multiple OPU sessions are necessary before viable embryos can be produced.



How long does the OPU procedure take?

The duration of the OPU procedure takes between 30 minutes up to one hour. This includes preparation of the mare and the OPU session itself.  Afterwards the mare goes back to their stable or paddock.   We routinely monitor the mare for three days, keeping check on her appetite, general well-being, and rectal temperature.  After 3-4 days mares can start in light work.



Are there any risks involved with OPU?

There is risk associated with both rectal examination and transvaginal aspiration of follicles of the ovaries of the mare.  Our team makes the mares well-being and safety the highest priority.

Strict hygiene, prophylactic antibiotics, anti-inflammatories, epidural anaesthesia, and sedation are routinely administered.  Our highly experienced team performs the procedure in a quiet and relaxed atmosphere ensuring the mare is relaxed.  If at any time of the procedure the conditions change, the risks and mare’s situation is assessed, the procedure will be stopped and possibly rescheduled for a later date. 

Mare owners must be aware that complications may occur with OPU.  Possible complications include rectal tears, rectal, vaginal, and ovarian bleeding, rectal and ovarian abscesses, and peritonitis, which in rare cases can all lead to death of the mare.  A small number of mares can experience slight discomfort, fever, or loss of appetite for a few days after OPU.

Ocyte Pick Up (OPU) is performed at the owners risk and Willinga Park Vet Hospital takes no liability for loss of the mare.  Mare owners are responsible for insurance of the mare.



Does OPU affect the future fertility of my mare?

OPU has no negative impact on the fertility of the mare. OPU sessions can be repeated with intervals as short as three weeks. We prefer to wait at least six weeks between OPU procedures allowing ample time for the mare to recover. 

Repeated OPU procedures do not change or affect the integrity, structure, or function of the ovary.

Mares can be inseminated and flushed for an embryo in between OPU procedures. Mares can undergo an OPU session and have an in vitro produced embryo transferred into herself (auto transfer) successfully carrying the foal. Mare can be bred after OPU and successfully carry their foal.



What about the semen in OPU-ICSI?

OPU-ICSI is ideal when semen of a desired stallion is only available in small quantities. Only one sperm is needed to fertilize a mature oocyte. Multiple embryos can be produced from a small sperm sample. This makes ICSI a perfect choice for exclusive and high-priced frozen semen.

Frozen semen straws can be cut and the small amount of prepared semen can be used on oocytes recovered and matured from different mares. A single straw of frozen semen can therefore be used for multiple ICSI sessions.

Semen of stallions which have compromised fertility can be successfully prepared and viable sperm selected for fertilization to produce embryos.  


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Drive straight through the main gate, stay on this road for approximately 1km.  At the intersection at the top of the hill turn right at the 'Tree of Paradise' sculpture (red tree sculpture) and follow the road past the arenas and down the hill to the Vet Hospital.


Willinga Park Vet Hospital
02 4405 5658