Equine Artificial Insemination

Horse Breeding through Artificial Insemination

Artificial insemination of mares is an option available for several situations. However, this is not something that is not without risk and a list of pros and cons! In natural mating of Thoroughbreds roughly 50-60% of the mares will get pregnant with one cover, and at the end of the season roughly 89% of mares are pregnant but 10% of those lose the foal before full term. Using fresh or chilled semen can increase the chances of first covers by 5-10% if attention to detail is practiced. Using frozen semen can result in 70% of mares bred however using artificial insemination – AI – takes exacting timeframes as well as careful handling of the semen. However, unlike other species horse sperm doesn’t tend to survive the thaw well, making “cooled” semen the only option.

Early references to artificial insemination appear in Arabic texts in the 1300s but it was an Italian in the 1700s who documented the use including of cooled semen. Mares have regular fertile cycles in the breeding season from spring to fall. In the winter months ovulations stop during the short days but this can be altered by putting open mares under lights.

Generally the cycle is 21 days during which they are receptive to the stallion for 4-6 days and a follicle is shed from the ovary and within a day or so the mare goes out of heat. It is after ovulation that the mare should be inseminated for maximum fertility. If she doesn’t get pregnant she will cycle again.

This is where timing is so very critical. An example is you find your mare is in season, the stallion is collected, semen cooled, packed and shipped. Remember that in most cases semen has a 48 hour life. This means a very narrow window of time from collection to handling to packing to shipping cross country to insemination of the mare! A late flight, rough weather, improper handling of semen and the entire expense and effort is for nothing! Add to this that some farms collect semen on a Monday, Wednesday and Friday schedule. If the semen is collected on Friday morning and shipped will your veterinarian be available on the weekend to inseminate her? If you find that on Saturday she’s ovulated by the time Tuesday comes around for semen delivery she may no longer have a viable breeding.