What happens if a beloved mare dies, but you still want the chance to produce a foal from her?
Advances in equine reproductive technology mean that, in some circumstances, it is possible to recover oocytes from a mare after her death and use them to produce embryos through ICSI.
I spoke with Kindra Rader, founder of Vita Nova Reproduction Center and formerly the program coordinator of the equine reproductive laboratory at Texas A&M University, to find out how the process works, how quickly everything needs to happen, what it costs, and what mare owners need to think about before they are faced with losing a valuable mare.
How did you get into equine reproduction?
Kindra: I started at Texas A&M University and spent about seven years working in the equine reproductive laboratory under Dr. Katrin Hinrichs. I started as a technician and worked my way up to program coordinator.
We did a lot of ICSI — intracytoplasmic sperm injection — and in vitro embryo production. I was involved in the laboratory work, client communication, billing, data and record keeping, research projects and embryo vitrification.
I started Vita Nova Reproduction Center in 2022.
What exactly happens when you harvest a mare's ovaries after death?
The first thing to understand is that time matters.
Ideally, the ovaries should be removed as soon as possible after the mare dies. Kindra recommends aiming for within six hours.
The ovaries are then transported to the laboratory, where the oocytes — the mare's unfertilized eggs — are recovered from the ovarian tissue.
Those oocytes are then placed into a maturation culture. The purpose of this is to recreate, in the laboratory, some of the process that would normally happen inside the mare as an oocyte matures toward the stage at which it can be fertilized.
Why does it matter how quickly the ovaries reach the laboratory?
Kindra explains that once the mare has died, the ovarian tissue is no longer receiving oxygen and nutrients through the mare's blood supply. The tissue begins to deteriorate.
The oocytes are surrounded by ovarian tissue and follicular fluid, and as that tissue degrades, it can negatively affect the environment around the oocyte.
That's why getting the ovaries to the laboratory quickly is so important.
Interestingly, once the oocytes have been removed from the ovary and placed into an appropriate holding medium, you have considerably more time. The real race against the clock is getting the ovaries processed.
Can the ovaries be put on ice?
No.
This is one of the important differences between ovarian tissue and some other reproductive tissues, Kindra explains.
Oocytes do not tolerate being cooled in the same way sperm do. They contain a relatively high amount of lipid, and simply putting the ovaries on ice can damage the oocytes.
Kindra generally receives ovaries at room temperature. If longer transport times are unavoidable, they can be slightly cooled, but they should not be placed directly on ice.
The ovaries can be placed in a sealed bag or palpation sleeve with a small amount of saline to prevent the tissue from drying out.
What if the mare has already been euthanized?
Ideally, the ovaries are removed before euthanasia, because there is some concern that the euthanasia drugs could potentially affect the oocytes.
However, Kindra has successfully worked with ovaries from mares that had already been euthanized, including ovaries that arrived more than 12 hours later.
That doesn't mean that waiting is advisable. The chances of success are generally better when the process is planned in advance and carried out quickly.
And that leads to one of the biggest messages from our conversation: if you have a mare whose genetics you desperately want to preserve, don't wait until she is dying to work out what you're going to do.
What happens to the oocytes once they reach the laboratory?
The oocytes are recovered from the ovaries and placed into a maturation culture.
In Kindra's laboratory, approximately 50–60% of recovered oocytes typically mature sufficiently to be fertilized. The exact results vary depending on factors including the mare, her age and her reproductive history.
Once mature, the oocytes are fertilized using ICSI.
The resulting zygotes are then placed into culture for approximately seven to ten days.
How do you know whether the embryos are developing?
The embryos are monitored during their development.
Around day five after fertilization, the laboratory can assess whether the embryos have undergone cleavage — essentially, whether the cells have begun dividing as expected.
But cleavage doesn't mean you have an embryo ready to transfer yet.
You have to wait.
By approximately day seven to ten after fertilization, embryos may have developed sufficiently to be considered transferable.
What are the chances of actually getting an embryo?
Kindra reports an average embryo production rate of approximately 32–36% from the oocytes that are fertilized.
But this is one of those areas where individual results can vary enormously.
Mare age, mare fertility and stallion fertility can all influence the outcome. Some mares produce several embryos; others require multiple attempts before an embryo is produced.
And sometimes an oocyte that doesn't initially look promising can still surprise you.
Kindra's philosophy with postmortem cases is essentially: no oocyte left behind. These may be the last oocytes that mare will ever produce.
What happens if you don't have a recipient mare ready?
This is one reason embryos from postmortem cases are often vitrified and stored.
A mare dying unexpectedly isn't exactly something you can schedule around the recipient mare's reproductive cycle.
If a transferable embryo is produced in October, for example, there may not be a suitable recipient mare ready to receive it.
Vitrifying the embryo allows the mare owner to find an appropriate recipient later and transfer the embryo when the timing is right.
Is a fresh embryo better than a frozen embryo?
Historically, fresh transfer was considered preferable.
However, according to Kindra, improvements in embryo vitrification and warming techniques mean that the difference is now much smaller.
Her laboratory has seen frozen embryo pregnancy and foaling results that are very close to those achieved with fresh transfers. The ability to carefully select and prepare the recipient mare can also help.
What exactly is vitrification?
Vitrification is essentially a very rapid cryopreservation process designed to minimize the formation of damaging ice crystals.
The embryo is exposed to cryoprotectants and then rapidly frozen, ultimately being stored in liquid nitrogen.
It is a highly controlled process, and the exact protocols continue to evolve as research develops.
What happens to the embryo after it is frozen?
The embryo can remain stored at the laboratory until the mare owner is ready to use it.
When the time comes, it can be shipped to a reproductive veterinarian who is experienced in warming and transferring vitrified embryos.
Kindra even sometimes sends a research embryo to veterinarians who haven't previously warmed one of her frozen embryos so they can practice the procedure before handling a valuable embryo.
That's a pretty good illustration of how much attention to detail goes into this process.
What does all of this cost?
This varies considerably depending on the veterinarian, laboratory, location, transportation and stallion being used.
Kindra estimates that a postmortem case involving ovary processing, maturation, ICSI and producing and freezing one embryo can easily involve several thousand dollars once all costs are included.
There may be costs for:
- Veterinary services
- Euthanasia
- Ovary removal
- Transportation
- Ovary processing
- ICSI
- Embryo production
- Embryo vitrification
- Stallion semen
- Recipient mare services
And importantly, the stallion contract matters. Some stallion owners charge a stud fee per embryo. Others may have different arrangements for ICSI or deceased-mare cases.
You need to understand those terms before you are sitting at the laboratory with potentially multiple embryos and a very large unexpected bill.
What should a mare owner do now if they want to preserve a mare's genetics?
Make a plan before you need it.
You may never need the plan.
But if your mare dies unexpectedly, you don't want to be trying to research ICSI laboratories, find a veterinarian who can remove her ovaries, contact a stallion owner and organize transportation while you are grieving.
As Kindra put it, having a plan means that when something happens, you can simply put the plan into motion.
Why is this technology particularly important for older or rare-breed mares?
For some mares, this may be the last opportunity to preserve their genetics.
That is particularly meaningful for owners of older mares, once-in-a-lifetime horses and mares from rare or endangered breeds.
Kindra herself has a particular interest in making the technology accessible to breeders who might otherwise assume that ICSI is completely out of reach. She also offers discounted services for rare breeds recognized by the Livestock Conservancy.
One last thing: this technology is changing quickly
Perhaps the most interesting thing we took away from the conversation was how rapidly this area of reproductive technology is developing.
Vitrification protocols are evolving. ICSI continues to become more accessible. Embryo biopsy and genetic testing are developing. Laboratories are learning more all of the time. It is a very "watch this space" industry, and one we intend to watch and keep you informed about.
Huge thank you to Kindra Rader and Vita Nova Reproduction Center for giving us such insight into the day-to-day operations at Vita Nova Lab.
Links and further reading
- Vita Nova Reproduction Center — website
- Vita Nova Reproduction Center — Facebook
- Equine Reproductive Procedures (Blackwell) — on Google Books
- The Livestock Conservancy genetic preservation manual — on Instagram