OPU (Ovum Pick Up) is the procedure in which ovarian follicles are punctured and aspirated to collect oocytes.
ICSI (Intracytoplasmic Sperm Injection) is the technique in which a single sperm cell is injected into a mature oocyte.
Although they are two separate steps, one naturally follows after the other:
OPU is always the preparation for ICSI.
These modern techniques are a valuable addition to contemporary breeding practices.
A good preparation is essential for a smooth OPU/ICSI procedure.
This checklist helps us ensure the best possible start and outcome, togheter.
Available year-round
Opu can be performed at any point in the mare’s cycle, even during winter anoestrus. This means oocytes can be collected outside the regular breeding season, offering more flexibility.
No Hormonal preparation needed
The OPU procedure does not require prior hormonal stimulation. This is ideal for sport mares, as they can stay in training without their hormonal balance being affected.
Performance mares
If your donor mare is actively competing and cannot carry a foal herself, OPU offers an excellent opportunity to still produce genetically valuable offspring, without interrupting her sport career
Use embryos at the perfect time
Embryos created through ICSI are frozen and only thawed when a suitable recipient mare is available. Unlike traditional embryo transfer, there’s no need to synchronise multiple recipients.
Option to use your own recipient mare
Since synchronization with the donormare is not required, you can use your own recipient mare. This provides more control and can help reduce costs.
Long-Term Storage of Embryos
Frozen embryos can be stored for extended periods and transferred whenever the time is right, such as early in the next breeding season.
Suitable for sub-fertile Mares
Mares that can no longer carry a pregnancy or produce embryos through flushing often still produce viable oocytes for ICSI.
Post-Mortem Oocyte Collection
If a mare dies suddenly or is euthanised, oocytes can often still be recovered from the ovaries and used for ICSI.
Efficient use of limited or valuable semen
ICSI only requires one sperm cell per oocyte. This makes it ideal for use with stallions that have limited availability, low semen quality, or highly valuable frozen semen. A single straw can often be used for multiple ICSI sessions, on average up to 10 times.
OPU can be done on any mare that is not pregnant at the time of the procedure. She should be at least 3 years old. In older mares (around 17 years and up), the number of oocytes usually starts to decrease. Mares with a foal at foot are not suitable for this procedure.
For a good chance of success, the mare should have enough follicles on her ovaries. We recommend at least 10 to 15 follicles, each between 1 and 2.5 cm in size. The procedure works best when there are several small to medium-sized follicles.
If a mare recovers well and continues to grow enough follicles, OPU can usually be repeated. We wait at least three weeks between procedures on the same mare. The mare’s health always comes first, so we never perform OPU more often than once every three weeks.
To avoid disappointment, we recommend having your mare checked by your own vet before the planned OPU. This check can also be done a few days before the appointment at Equiception. That way, we know the timing is right and everything is in place for the best possible result.
Ovum Pick-Up (OPU) can be performed all year round. However, the period from October to April is generally the most favorable. During these months, many mares are transitioning between the active breeding season (oestrus) and the resting phase (anoestrus), or the other way around. In this transition phase, mares often show what’s called a multifollicular pattern meaning they have more small follicles at the same time. This increases the chances of a worthwhile OPU.
Choosing the right stallion is an important part of preparing for an OPU/ICSI procedure. Since ICSI only requires one live sperm cell per oocyte, stallions with low fertility can still be used as long as there are living sperm cells present, even in small amounts
Both fresh-cooled and frozen semen are suitable for ICSI. Epididymal semen, collected after castration or after the stallion has passed away, can also be used successfully.
To keep everything running smoothly, please make sure the semen is delivered to Equiception no later than 24 hours before the planned OPU. If you’re not the owner of the semen, we also need written permission from the owner or stallion station, also at least 24 hours in advance.
Do you have questions about choosing a stallion or delivering semen? Feel free to contact us, we are happy to help you find the best solution.
A good starting point is key to success with OPU/ICSI. That’s why a proper check of the mare’s ovarian activity is importantWe recommend having your vet examine your mare no later than Thursday or Friday morning before the scheduled OPU the following week.During this check, the vet looks at the number of follicles measuring between 0.8 and 2.5 cm. If your mare has at least 15 follicles of the right size, the OPU can go ahead as planned. If there are fewer, you and your vet can decide together whether to proceed.
If there’s any doubt, your vet is always welcome to contact us for advice.
At Equiception, we make sure your mare is as comfortable and relaxed as possible on the day of the OPU. Preparation is just as important as the procedure itself.
Your mare will be lightly sedated and given medication (an anti-inflammatory, antibiotics, and something to relax the intestine). In some cases, an epidural is given for extra comfort, and a catheter is placed to empty the bladder.
The OPU procedure takes about 30 to 45 minutes. The vet feels the ovaries through the rectum and gently moves them into the right position. Then, an ultrasound probe is inserted vaginally. A fine needle is then used to puncture and aspirate the follicles. The fluid is collected, filtered and examined in the lab for the presence oocytes.
On average, we recover around 65% of the oocytes. These are assessed and prepared for transport to the ICSI lab.
You’re welcome to bring your mare a day or two before the procedure to avoid travel stress on the day itself.
Prefer to wait? The full visit takes about 1.5 to 2.5 hours, including prep and aftercare. While you wait, we’ll make sure there’s coffee or tea. If all goes well, your mare can go home the same day.
Good aftercare is just as important as the procedure itself. After the OPU, you’ll receive medication from us for post-treatment care.
Your mare might appear a bit low in energy, eat less, or have a slightly elevated temperature the evening and day after the procedure. This is temporary. In rare cases, a mare might feel unwell for a few days.
Please keep a close eye on your mare during the first few days—pay attention to her general condition, appetite, and temperature. If you’re unsure about anything, don’t hesitate to contact us or your own vet.
Rest is important. We recommend giving your mare at least one week off from intensive training. Light groundwork, time on the walker, or turnout in the field is perfectly fine, but avoid heavy exercise.
If you have any questions or concerns about your mare’s well-being after the procedure, please don’t hesitate to contact us.
Each step in the OPU-ICSI process comes with natural losses. The final outcome depends on several factors, including the mare’s age, health, and breed. Egg quality declines with age, so younger mares generally give better results than older mares (17 years and up).
At Equiception, we recover oocytes from about 65% of the follicles we aspirate. This can vary from mare to mare. Some produce only 30%, while others may reach nearly 100%. Of the collected oocytes, around 60% are successfully fertilised through ICSI after maturation and evaluation.
In the end, the chance of getting one or more frozen embryos per attempt is about 60%. A successful procedure results in an average of 2 embryos. When an ICSI embryo is thawed and transferred into a recipient mare, the chance of pregnancy is » 80%. The risk of early embryonic loss is slightly higher than with natural pregnancies: 8 to 15%.
In summary: On average, 4 out of 10 OPU-ICSI attempts may not produce any embryos. The remaining 6 attempts usually result in 11 to 12 embryos in total.
The results are available on Monday in the second week after the OPU has been performed. On that day, you’ll receive an email from us with the outcome, including how many embryos successfully developed and were vitrified (frozen).
Like any veterinary procedure, OPU does carry some risks, though complications are rare. During the procedure, a needle is guided through the vaginal wall to the ovary under ultrasound guidance. Because the needle passes through the vagina, there is a small risk of infection.
Possible complications may include bleeding (vaginal, rectal, or from the ovary), rectal tears, abscesses, or in very rare cases, peritonitis (inflammation of the abdominal lining). In extreme cases, this could be life-threatening but such complications are extremely uncommon.
At Equiception, your mare is in the hands of experienced professionals, and we monitor her closely throughout the procedure. The process takes no longer than 45 minutes and can be stopped if needed.
Most mares recover quickly, and are fit to go home the same afternoon. Some mares may be a bit quiet or have a mild fever during the first 24 hours. Serious after-effects are very rare.
Do you have concerns about the risks or whether your mare is a good candidate for OPU?
Feel free to contact us, we are happy to help.
The cost of an OPU/ICSI treatment can vary, depending on several factors, such as whether you use your own recipient mare or rent one, and how many sessions are needed to achieve a pregnancy.
While the initial cost per session is typically higher than with traditional embryo transfer, OPU/ICSI is often more efficient. Because more embryos are usually produced per session, the average cost per embryo can be lower in the end.
You can find a full overview of our current rates in our pricelist.
No, your mare does not need to be tested for CEM (Contagious Equine Metritis) or EIA (Equine Infectious Anemia) before undergoing OPU/ICSI at Equiception.
However, if you would like the ICSI to be performed at Avantea in Italy, these health tests are required. This is necessary to comply with strict EU regulations for exporting oocytes to Avantea and possibly re-importing embryos.
In that case, your mare must be tested for both CEM and EIA, and the results must be fully negative in order for us to send the oocytes. Please make sure we receive the test results at least three working days before the scheduled OPU. The results are valid for 90 days from the sample date.
No, OPU does not negatively affect your mare’s future fertility. The procedure only has a short-term effect on the ovaries. Within about three days, the tissue has largely recovered, and the mare can resume her cycle normally with new follicle development and ovulation. Only the follicles on the ovary are punctured during the procedure; the uterus and oviducts remain untouched. Even after repeated OPU procedures, no significant changes are seen in the structure or function of the ovaries.
A mare is born with a fixed supply of oocytes which become active in small groups over time. In each cycle, several follicles begin to develop, but usually only one ovulates the rest naturally degenerate. With OPU, we collect oocytes from the larger follicles that would otherwise be lost. The small, resting follicles needed for future cycles are left untouched. So in effect, we make use of the mare’s natural cycle without compromising her long-term fertility.
