Freezing Equine Semen Offers Advantages
by Emmy Widman, Washington State University College of Veterinary Medicine

In the past, using frozen semen was seen as a tedious process that could result in low fertility rates. Fortunately, over the years, it has become a tool that breeders can use with the help of their veterinarian to virtually ensure forever a bloodline to a valued horse, or even just to extend a breeding season.

This is a great advantage for breeds in which the registry approves artificial insemination with frozen-thawed semen.

“Some people still believe frozen horse semen does not work, but this is not the case. There has been a lot of progress, making it easier to use in recent years,” said Dr. Ahmed Tibary, WSU’s large animal theriogenologist or reproduction specialist.

“Freezing semen is really the only insurance an owner has against fertility loss in a stallion,” he said. “Many breeders know it can be very difficult to find a solution for a stallion that becomes infertile. I would encourage breeders that as soon as they purchase a potentially highly valuable young stud, that they insure its fertility by freezing an adequate quantity of semen from that horse.”

This method can be especially useful if the horse is intended for performance events such as hunting/jumping or dressage, in which stallions are often gelded for maximum performance.

“One of the biggest selling points of this technology is to be able to go back and use frozen semen from infertile stallions or high-performance geldings,” Dr. Tibary said. “It is nice to be able to retrieve the genetics if the colt turns out to be really good or very special to the owner.”

Freezing semen is also an insurance policy for colts or stallions that die prematurely or become incapacitated from an injury or illness. “Many times in an emergency situation, the owners will want to collect semen,” he said. “At that point the only way to freeze semen is to collect it chemically if the stallion is injured or from the testicles after castration if the stallion is terminally ill. Semen collected post-castration is often less fertile.”

Freezing semen can also be a valuable way for breeders to extend the breeding season for a stallion in high demand or one that spends part of the breeding season performing in competition.

Technically, frozen semen can last for thousands of years if it is stored properly in liquid nitrogen, a service that is offered at WSU if it is collected there.

As for the fertility of frozen semen, which is different for each stallion, it can be as high or slightly below fresh or cooled semen. “I recently used semen from a stallion that died a long time ago and it had very good fertility,” Dr. Tibary said.

For stallions with semen that does not freeze well, there are several techniques available at WSU that can improve the fertility of frozen sperm after it is thawed.

“The fertility rate really goes back to the both the fertility of stallion and the mare, which is highly variable,” Dr. Tibary explained. “I look at it from a convenience point of view, not just from getting the maximum fertility. There are advantages to frozen semen that are worth losing maybe ten percentage points of conception rate, and some stallions perform just as well whether their sperm is fresh or frozen.”

Stallions that come to WSU for semen collection undergo a thorough reproductive examination. Semen is collected for freeze-testing to find which freezing protocol will work best for that individual stallion. Once the freezing protocol is determined, the stallion is put on a collection schedule to freeze the desired number of doses the owner wants.

“Also, when a stallion comes here, we can test it for diseases that may be transmitted through semen, so the protocol is fairly involved,” Dr. Tibary said. “If we see a normal stallion at the peak of its reproductive ability, we can collect anywhere from nine to 12 doses of frozen sperm for each collection. That is pretty good.”

For more information about freezing semen or to make an appointment, contact the WSU Veterinary Teaching Hospital at 509-335-0711 or Dr. Tibary at This e-mail address is being protected from spam bots, you need JavaScript enabled to view it or 509-335-1963.

“Azim” and “Aran” are half brothers, both from a stallion, “Arik,” who died more than 10 years ago. The colts carry the genetics of the Akhal-Teke breed, a breed close to extinction with a global population of about 1,000 mares and 400 stallions.

“There are no stallions anywhere in the world that would be this close to the original founders of this blood line,” said owner Milena Stoszek of Akhal-Teke Ranch in Moscow, Idaho. “The successful pregnancies and subsequent deliveries of two healthy colts from Arik’s frozen semen, performed and monitored by Dr. Tibary, are a great contribution to the preservation of these genetically valuable ancient horses. It also allowed us to reach back several decades and bring to life genes that otherwise would be lost from the Akhal-Teke population. This season, thanks again to Dr. Tibary, we have one more mare pregnant to Arik, and hope for another healthy foal.”

Reprinted from the WSU College of Veterinary Medicine Equine News Fall 2006 issue. Pictures of “Azim” and “Aran” are from owner Milena Stoszek.