Advertisement: How exactly does OPU-ICSI work? We explain the four phases of modern equine reproduction in a clear and compact way, enabling you as a breeder to make well-informed decisions.
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OPU-ICSI: Understanding the process before making a decision
In breeding, every innovation is carefully scrutinised. This is not resistance to change, but rather an expression of responsibility. Horse breeding is based on long-term thinking, genetic value, and sound decisions.
OPU-ICSI is among the most significant developments in modern equine reproduction. Interest is growing steadily; however, the technique is still often perceived as complex, highly technical, or difficult to understand.
Before discussing when OPU-ICSI should be used or whether the method fits a specific breeding programme, fundamental questions must be clearly answered.
What actually happens during an OPU-ICSI procedure?
The process consists of four clearly defined phases. Each has a distinct goal and can be understood without scientific jargon.
When I first looked into OPU-ICSI, the technology honestly seemed quite abstract and technical to me. But once you break the process down step by step, it quickly becomes clear: this isn’t about a machine, but about a valuable tool that helps to achieve breeding goals responsibly and safely.
Michelle
Editor at ehorses
1) OPU – Oocyte Pick-Up
The process begins with OPU (Ovum Pick-Up), the collection of oocytes (eggs) directly from the donor mare’s ovaries.
The procedure is performed under ultrasound guidance and light sedation. It is not a surgical procedure and does not require a long recovery time. In most cases, the mare can quickly return to her normal activities, including sport.
In this phase, no embryo is created yet. The sole aim is to harvest the available oocytes. These eggs form the biological starting point of the entire process.
This step allows breeders to work with mares that are still in active sport, mares that cannot carry a pregnancy themselves, or mares whose fertility is limited using conventional methods.
2) ICSI – Targeted Fertilisation
The harvested oocytes are then transferred to the laboratory.
This is where ICSI (Intracytoplasmic Sperm Injection) is performed. A single sperm cell is carefully selected and injected directly into the oocyte.
This method allows for the very precise use of available semen. This becomes particularly relevant in situations where semen is rare, only available in limited quantities, stored in small frozen portions, or has restricted quality.
The fertilisation takes place in a controlled laboratory environment. The goal is not to replace natural biology, but to optimise the conditions under which fertilisation can occur.
This phase brings efficiency and control to the reproduction process.
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3) Embryo Development in the Lab
After fertilisation, the oocyte begins to develop. Over the following days, its progress is monitored until it reaches the embryo stage.
Not all oocytes develop into embryos—this is biologically completely normal. The embryos that reach the appropriate stage of development are selected.
A key feature of OPU-ICSI is the ability to observe and manage embryo development before the transfer. This creates a level of predictability that is not possible with purely in vivo techniques.
The embryo can then either be transferred fresh or cryopreserved (frozen) and used at a later date. This provides additional flexibility in breeding management.
4) Embryo Transfer into the Recipient Mare
In the final step, the embryo is transferred into a synchronised recipient mare.
The transfer itself is a simple and non-invasive procedure. If the implantation is successful, the pregnancy then proceeds like any other normal pregnancy.
From the foal’s perspective, there is no difference. The goal remains unchanged: the birth of a healthy foal with the desired genetics.
The technology is not abstract. It consists of a clearly structured and logical sequence of biological and technical steps. However, the quality of each phase depends decisively on experience, infrastructure, and laboratory expertise.
Avantea is one of the pioneers of OPU-ICSI technology in Europe, with decades of experience in assisted reproduction and modern reproductive biology research. The company combines:
A specialised OPU-ICSI laboratory with a high volume of cases.
An integrated scientific and biotechnological department.
An extensive and structured semen bank.
International co-operations and long-term partnerships with breeders.
This integrated structure makes a decisive difference. OPU-ICSI is not just a technical procedure; it is a complex system requiring laboratory precision, biological expertise, and consistent quality standards.
When the process is clearly understood, OPU-ICSI no longer appears as an experimental innovation, but as a structured reproductive tool in modern breeding management.
Questions & Answers
OPU-ICSI is an assisted reproduction procedure in horse breeding where oocytes are harvested directly from the mare’s ovaries and fertilised in a laboratory using targeted sperm injection to create embryos for subsequent transfer.
There is no universal number of attempts, as success depends significantly on the individual fertility of the mare, the quality of the semen, and the expertise of the laboratory.
