ICSI – an acronym you should know

by Alan Leavitt

ICSI (pronounced ick-see) is an acronym for Intracytoplasmic Sperm Injection, and it represents a major breakthrough in equine reproduction. It can be the salvation of top mares who, for any reason or another, are unable to produce a foal by normal reproductive methods.

Basically, ICSI is a specialized form of invitro fertilization. It involves the injection of a single sperm into a mature egg.

We, here at Walnut Hall, have been doing ICSIs for two years, and I can best explain the process by describing what I, a total layman, have observed and learned.

We are blessed to have the services of Dr. Karen Wolfsdorf, recognized as one of the world’s leading equine reproductive vets. She’s backed up by a full staff of other world class equine specialists at her clinic, Hagyard Equine Medical Institute.

Dr. Wolfsdorf recommends doing an ICSI on a mare that is well-nigh impossible to get in foal, or one who has a history of getting foal but never carrying to term. Although it gets trickier the older a mare is, by doing an ICSI we have successfully gotten a foal from Canland Hall, at age 24, when she could not reproduce in any other way.

The process starts with a vet, in our case, Dr. Wolfsdorf, scanning the uterus of the mare in question. This can be done at any time for these purposes, although it is best done when the mare is not in season. On her ultrasound screen, her trained eye can pick out and count the number of eggs, or oocytes, on each horn of the uterus. You like to have 12 or more, but you can still go forward with as few as seven or eight.

The mare then goes to the Hagyard Clinic, where another specialist removes all the eggs, technically oocytes. This is a simple procedure, for someone who is highly trained and skillful, and there’s no discomfort to the mare. Let me emphasize, it is not a painful procedure. The technical term for removing the oocytes is aspiration.

Once the oocytes are retrieved, they get shipped off, in our case, to the Equine Medical Services Clinic, in Columbia, MO. Dr. Foss is the major magician there, and it is his clinic.

The day after the oocytes arrive at Dr. Foss’ clinic, a full dose of shipped semen from the stallion of choice must also be delivered there. That is fresh, chilled semen, exactly what is shipped every day of the breeding season in our business.

Once Dr. Foss has both the oocytes and the semen, he isolates single sperm cells and injects one sperm into each egg. Then there’s a wait of about five days, and if the process has succeeded, at least one of the injected oocytes will develop into an embryo. Then it’s a simple matter for Dr. Foss to transfer the embryo into a recipient mare, wait till it’s been at least 12 days, and then check to see if the embryo took. If the ultrasound exam shows a pregnancy, voila!, you’re on your way to the foaling barn in 11 months.

If the ICSI process should produce more than one embryo, the additional one can be frozen and used the following breeding season.

I’m sure this whole deal sounds complicated, and it is, but it does work, at least most of the time. And if it doesn’t, you can just start over and try again. And the complications can be well worth it if the end result is a good looking colt or filly from a great mare, who otherwise would be condemned to being barren for the rest of her life.


The whole process will cost a good $7,500, and that will probably go up every year. On top of that, you also have the cost of the recipient mare, both the shipping from Missouri and then her expenses after she arrives. With Dr. Foss, you can return the mare, so you pay a $1,000 “rental fee.”

As I said earlier, I think of ICSI in terms of old or problem mares, but there is also a totally different and important aspect. Because the mare can be anywhere when the oocytes are aspirated, this process can be used to great advantage while the mare is still in full training and racing every week. If I were lucky enough to own Manchego, I’d be doing an ICSI on her every year, and still not miss a beat on the racetrack.

As to who to breed her, that’s beyond this kid’s remit, but it sure would be a nice problem to have. And there’s still time, if one moves fast, to do an ICSI on her this season.