Mares & Embryo Transfers
Embryo Transfer (ET)
Embryo transfer is an advanced reproductive option that allows a mare to produce a foal without carrying the pregnancy herself. This technique makes it possible for performance mares, older mares, or mares with physical limitations to continue their careers while still passing on their genetics.
Why Choose Embryo Transfer?
Embryo transfer is ideal for:
• Performance mares who are actively competing
• Mares that cannot safely carry a pregnancy
• Older mares with valuable bloodlines
• Owners wishing to produce multiple foals from one mare in a season
With ET, your mare becomes the genetic mother, while a carefully selected recipient mare carries and delivers the foal.
How the Process Works
1. Breeding the Donor Mare
Your mare (the donor) is bred through artificial insemination or live cover, just like a traditional breeding.
2. Embryo Collection
About 7–8 days after ovulation, a specialist or veterinarian flushes the embryo from the donor mare’s uterus. This process is safe, minimally invasive, and does not harm the mare.
3. Transfer to a Recipient Mare
The collected embryo is immediately transferred into a healthy recipient mare whose cycle has been synchronized with the donor.
4. Pregnancy & Foaling
The recipient mare carries the foal to term and delivers it. The foal is genetically 100% from the donor mare and stallion.
Benefits of Embryo Transfer
• Allows mares to stay in training or competition
• Preserves valuable genetics
• Reduces physical stress on the donor mare
• Can increase the number of foals produced in one breeding season
What to Expect
Embryo transfer requires careful timing, expertise, and healthy recipient mares. Success rates can vary depending on the donor mare’s health, age, and reproductive history, as well as stallion semen quality.
At Last Resort Stallion Station, we work closely with clients to explain each step, coordinate scheduling, and ensure the best possible outcomes.
Is Embryo Transfer Right for You?
Embryo transfer is a great option for many breeding programs, but it isn’t necessary for every mare. On average, equine embryo transfer success rates range from 50-75% per cycle when managed by experienced professionals using healthy donor and recipient mares.
If you’re unsure whether ET is the right choice, we’re happy to talk through your goals and help you decide what makes the most sense for your mare and your program.
What Affects Success Rates?
Several factors influence embryo transfer outcomes, including:
• Donor mare age and reproductive history
• Overall health and body condition of the mare
• Quality of semen used
• Timing of ovulation and embryo collection
• Recipient mare health and cycle synchronization
• Stress levels and management practices
Younger, healthy mares with good reproductive histories generally have the highest success rates.
Donor & Recipient Mare Options
Last Resort Stallion Station offers flexibility when it comes to embryo transfer services. We have a limited number of quality donor and recipient mares available for clients who do not have a mare of their own or who prefer a fully managed option.
Clients are also welcome to bring their own donor mare and/or recipient mare. All outside mares must meet basic health and veterinary requirements to ensure the safety and success of the embryo transfer process.
We are happy to discuss available mares and help determine the best option for your breeding goals.
Important Things to Know
• Embryo transfer is not guaranteed, even under ideal conditions
• Multiple attempts may be recommended to achieve a pregnancy
• Some mares are excellent embryo producers, while others may require adjustments
A transparent, well-managed program focuses on maximizing chances while setting realistic expectations.
Contact us to learn more about embryo transfer services or to discuss your breeding plans.
Mare Management
Care For Sub-Fertile & Problem Mares
Mares that have experienced difficulty conceiving or maintaining a pregnancy—often referred to as sub-fertile or problem mares—benefit from additional evaluation and planning prior to the breeding season.
An initial reproductive evaluation may include ultrasound examination, uterine culture or biopsy, and assessment of the mare’s external reproductive anatomy. A mare’s previous breeding history is also an important part of the process and helps guide decisions moving forward.
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Breeding & Post-Breeding Management
Mares with reduced fertility often require additional care during and immediately following breeding. One of the most common challenges is post-breeding uterine inflammation, which can result in fluid accumulation. In some cases, this inflammation may progress to post-breeding endometritis.
For mares that are known to be at higher risk, post-breeding treatments may begin shortly after insemination. Management strategies may include uterine therapies, supportive medications, and other veterinary-guided interventions aimed at improving the uterine environment and supporting early pregnancy.
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Individualized Treatment Plans
There is no single approach that works for every mare. Treatment protocols are developed on an individual basis, taking into account the mare’s age, reproductive history, and specific challenges.
Ongoing advancements in reproductive medicine continue to improve outcomes for mares with fertility concerns. New treatment options and strategies can be discussed in advance to help optimize the chances of a successful and healthy pregnancy.
ArtificiaL Insemination with Fresh Semen
AI Services
Stallions may be collected on site or at approved local facilities. Semen is evaluated immediately for motility and concentration, then diluted using an appropriate extender. These extenders are designed to support semen quality, extend viability, and improve the likelihood of conception.
For stallions with lower semen quality, or in cases involving sub-fertile mares, daily insemination with fresh semen may be recommended to optimize breeding success.
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Insemination with Cooled Semen
When using cooled semen, coordination and timing are essential. The facility managing the stallion is notified that the mare is being monitored at Last Resort Stallion Station. A current negative EVA test is required for all stallions prior to shipment.
Information regarding collection schedules and semen quality is gathered in advance to allow proper synchronization with the mare’s cycle. Semen is typically ordered when the mare has a mature follicle along with uterine edema and cervical relaxation, as confirmed through ultrasound evaluation.
Not all mares display obvious behavioral signs of heat, making reproductive monitoring and ultrasound expertise critical during this stage. Follicle size at ovulation can vary depending on the individual mare and breed.
Whenever possible, semen is shipped overnight via FedEx or UPS. In cases where semen quality or timing does not allow for next-day delivery, same-day shipment or airport pickup may be arranged. Upon arrival, semen is immediately evaluated for motility and concentration.
Pregnancy rates are optimized when insemination occurs within 24 hours prior to ovulation or within 6 hours following ovulation.
