As we enter another breeding season, all breeders ‒ whether first-timers, backyard breeders or seasoned pros ‒ have to decide on what type of semen to use with their broodmares: fresh, frozen, or fresh-cooled. While fresh isn’t always available locally, and frozen has lower success rates, fresh-cooled has become a solid option for many breeding programs.

But what is it exactly, and what are its advantages? We’ve compiled a guide on everything you needed to know about fresh-cooled semen, but were afraid to ask.

What is Fresh-Cooled Semen?

A bit of history: the use of cooled semen has been around since the early 1930s when it was first developed for use in cattle and sheep before becoming popular in the equine industry.

Technically, fresh-cooled semen is semen that has undergone a process of evaluation, dilution (with extenders) and storage at refrigeration temperatures of 4-5° Celsius. More plainly, “[It’s] as simple as semen that we refrigerate in order to extend the life of the spermatozoids,” explains Dr. Rafael Gomez, DVM, an Ontario-based vet at McKee-Pownall. “When we dilute the semen, we are maximizing the use of each ejaculate by dividing it into several insemination doses, which is 500 million-1 billion progressively motile spermatozoids (PMS) and we are adding protection and nutrition to the sperm cells in order to extend their life.”

Advantages of Fresh-Cooled Semen

Dr. Gomez, who has a special interest in equine reproduction, provided a list of advantages of using fresh-cooled semen for breeding.

  • Cheaper to transport the semen rather than the mare;
  • Ability to transport the semen longer distances;
  • Opportunity to evaluate the stallion’s semen prior to insemination, ensuring that live motile spermatozoa are placed in the uterus;
  • Reduced likelihood of transmission of diseases;
  • Less stress and risk on the mare to be inseminated than live cover;
  • Allows an improvement of genetics by making superior stallions available for mares in other locations around the world.
  • Increases the number of mares bred by a single stallion.

How does it compare to the frozen stuff? “Frozen semen is harder to ship because it needs special shipping containers to keep it frozen, it also needs to be stored in a liquid nitrogen tank if it can’t be used right away,” says Nadia Walch, the office administrator at W. Charlot Farms, a sport horse breeder who has been awarded USEF leading breeder 2004-2013, 2016-2020, and was Equine Canada Breeder of Year in 2015. “There are also more vet costs associated with frozen semen but if it’s on hand then sometimes it can be easier to inseminate a mare instead of trying to time it just right with the fresh cooled.”

An Equitainer storage container.

An Equitainer storage container.

Use and Storage

The viability of cooled semen depends on different factors, including the reaction of a particular stallion’s semen to the cooling process, type of extender, cooling rate and the transportation container. Overall, the optimal time for cooled semen viability is 48 hours post-collection.

There are several commercially-available containers available for transportation that are designed for cooled semen. The most well-known one is the Equitainer®, but there are a variety of other shipping containers available in the market. The main difference between containers is the protection against environmental temperatures and their ability to maintain 4-6°C for a longer period of time.

“The technique for artificial insemination with cooled semen is the same that we use for fresh semen and is relatively easy to perform,” says Dr. Gomez. He also adds that this technique is referred to as transcervical insemination, which means that the vet will deposit the semen directly into the uterus body.

Pregnancy Rates

According to Dr. Gomez, the pregnancy rates with cooled semen, as with any other method, will depend on many different factors. The most important ones are the semen and its ability to be cooled, a factor that varies with each stallion; the extender used; the cooling method and shipping container; the insemination process; and the mare to be inseminated.

“When all the conditions are optimal and the semen is of excellent quality, the pregnancy rate can be as high as 87 per cent, similar to fresh semen rates,” Dr. Gomez says. That’s a high rate of success when compared to frozen semen which averages only 30-60%. The reason for the discrepancy is that when semen is frozen and thawed there is a greater stress to the spermatozoid, which affects its viability.

Thing to Consider

For a cooled semen breeding program, Dr. Gomez recommends following the estrous cycle of the mares closely in order to inseminate them at the best time. You should also have a good working relationship with your veterinarian so you can plan the program together and get a better outcome.

It is also essential that the mare owner is familiar with the stallion collection dates and semen shipment instructions. “Most stallions have a fixed collection schedule for the season,” says Dr. Gomez. “There is typically a deadline to register the mares that will be receiving a dose per collection. It is relevant to know the length of time it takes the semen to get from the stallion to your location. The management of the mares will be different depending on if semen can get there before or after twenty-four hours. Other factors could be quarantine and import/export regulations should the semen be crossing country borders.”

Importing Fresh-Cooled Semen

W. Charlot Farms, which is based in Stratford, Ontario, do not import semen, but do ship their stallions’ fresh-cooled semen within all of Canada and into the US. There is no special paperwork required for shipping within Canada. “We collect the fresh-cooled semen on Monday, Wednesday and Fridays,” Walch explains. “It is shipped in special cooling boxes that stay cool for at least 24 to 36 hours. It is best if the mare is inseminated within this time frame. The semen can often still be used after 48 hours, but typically is best if used before then.”

If you do plan to import semen from outside Canada, then your first step is to check the Automated Import Reference System (AIRS) for import requirements. It is a reference tool that shows the import requirements for Canadian Food Inspection Agency (CFIA) regulated commodities. It includes the requirements for an import permit, zoosanitary certificate, or other documentation.

If an import permit is required, the importer must complete an application for a permit to import through the MyCFIA portal. For importing fresh semen from the EU, importers must check the requirements from each member state from which they want to import the fresh semen. Similarly, requirements to import semen from the US or any other country can be assessed through AIRS.

If the importation is prohibited in AIRS, a risk analysis and possibly an on-site evaluation could be conducted by the CFIA before it can allow or deny the import of a commodity.

Additional information about the import policy and how to apply to import semen, embryos, live animals, or animal products and by-products, is available on the CFIA’s website here:

Request to Import a New Commodity or Import from a New Country of Origin

Applying to import live animals, semen, embryos, animal products and by-products

Ultimately, the choice of which type of semen to use in your breeding program “very much depends on customer preference if they use fresh cooled or frozen,” says Walch, adding that, “Most stallion owners only offer a live foal guarantee for fresh cooled semen and not for frozen.”