The Art of Breeding Horses: A Summary of the Methods of Breeding Horses

By Debra Ottier

Iron Horse Equine

So, you wish to breed your mare but are confused about all this talk about live cover, AI, shipped semen and frozen semen. Which method of breeding gives the best results?  Which is safer for my mare?  What about costs?  These are all questions often asked by the mare owner when looking to breed.

Here is some information about each of the breeding methods currently used today in the horse industry to aid you in making an informed decision.

Natural or Live Cover

The mare is brought to the stallion, and they breed naturally when the mare will accept the stallion. This method is the easiest in terms of labor, but it is not necessarily the safest method for either the horses or handlers. There are inherent risks of being kicked or bitten during the breeding process, and risks of injury to the mare during transport. While these risks are the obvious ones, one often forgets about the transmission of bacteria and disease through natural cover, either from horse to horse or even farm to farm in the case of airborne viruses.

The breeders’ skill level required is minimal with knowledge of mares’ heat cycles being the major concern.

Live cover costs include the stallions’ fee, daily board for the mare, and foal if present, transport of the mare (and foal), coggins test, if required, and definitely a uterine swab and culture.

The success of natural or live cover varies with the stallion and the mare, but an overall success rate of 65 – 75% across North America has been demonstrated. The Canadian Horse has had relatively excellent success with live cover, with 80% foaling rate seen overall.

On Farm Artificial Insemination

This involves transporting the mare to the stallions’ farm, having the stallion collected and the semen deposited into the mare artificially. Most on farm inseminations will follow the natural cover method of inseminating the mare on days 3 and 5 of their heat cycle. The risks of injury during breeding are removed here, as the stallion does not come in contact with the mare.   The risk of direct disease transmission is reduced with AI, although the mare can still transmit airborne viruses to the stallions’ farm, or bring it home. If the stallions’ semen contains a virus, there is nothing to prevent this transmission from occurring.

There is some degree of skill required here, as the inseminator needs to know how to collect and handle the semen and how to inseminate the mare.

The costs for on farm AI may include, in addition to the live cover costs, a collection fee in addition to the stallions’ fee.

The success rate of on farm AI has not been well documented as most breed associations group all AI breedings together in one category. The overall success of AI has been estimated at 65 – 70%.

Artificial Insemination with Cooled, Transported Semen (Shipped Semen)

A method that has been widely adopted by almost all breeds associations, this method involves collecting the stallions semen, mixing it with a suitable extender, then cooling and transporting it to the location of the mare, where she is inseminated at the appropriate time in her cycle (usually within 12 hours of ovulation). With transported semen, an increased level of communication is required between mare and stallion owner, as it takes time to collect and ship the semen to the mares’ location. Transported semen lasts approximately 12 – 72 hours, depending upon the stallion.

The level of skill required is quite high, as the collector needs to know how to collect and handle the semen properly, and the mare owner or her vet, needs to know how to handle the semen upon arrival. A veterinarian via diagnostic ultrasound determines the timing of insemination. It is imperative that all involved are well experienced with handling cooled semen.

The costs for AI with cooled, transported semen include the stallions’ fee, uterine swab and culture, a collection charge (if not included in fee), transport of the semen, ultrasound and vet expenses. These costs are essentially the same in value to live cover, as the cost of boarding and shipping the mare is offset by collection, transport and vet charges. In some cases, AI is cheaper when a long distance is involved for transporting the mare.

The success rate of AI with cooled transported semen also has not been isolated, but overall, AI has a success rate of 65 – 70%

The Canadian Horse and the use of AI has been somewhat limited, with only a small percentage of the stallions standing offering AI. Based upon the stallions that Iron Horse Equine has worked with, the overall first cycle pregnancy rate is 85% with shipped semen.

Artificial Insemination with Frozen Semen

This method offers more flexibility in the transport of a stallions’ semen. Semen can be collected and frozen at anytime from the stallion and stored. It can also be shipped at anytime, and stored at the mares’ location until the mare is ready to breed. This allows a stallion to continue a show career without the interference of breeding and acts as insurance should the stallion become ill and unable to breed, or even die. Frozen semen lasts indefinitely as long as it is stored properly.

The level of skill required for frozen semen is much higher than the other methods. Mishandling of frozen semen can lower the success rate of AI with frozen semen. The thawing of frozen semen is done prior to insemination, and this procedure is critical to success. Improper timing of insemination can also lower the success rate of AI with frozen semen.

With frozen semen, the mare must be bred within 8 hours of ovulation. This requires a veterinarian to ultrasound every 8 – 12 hours to accurately determine ovulation. Only skilled persons well versed in the area of frozen semen should consider applying this technology. There are facilities/people that work extensively with frozen semen to help mare owners in this field.

The costs for AI with frozen semen include the stallions’ fee, shipment of the semen, uterine swab and culture, ultrasound costs and vet expenses or inseminator fees. Again, this route can be a cheaper route in the long run, if all persons are knowledgeable of frozen semen.

The success rate of AI with frozen semen is usually approximately 10% lower than with AI in general. This is excellent considering the degree of skill required. It is also recommended that mares with proven poor reproductive performance not be inseminated with frozen semen, as this will lower success.

There is limited data available for success, with the stallions that Iron Horse Equine has worked with having a first cycle pregnancy rate of 70%. Selection of mares is crucial for this technology, as mares that have had problems conceiving previously should not use frozen as a last resort. They have other reproductive issues that frozen semen cannot solve, and thus, need special attention in order to achieve success, but that is another article in itself!


Finally, there are many facilities that carry out shipping of semen. An accreditation program has not been implemented in the horse industry, and it is, therefore, wise to check out the facility you are dealing with. Ask questions about success rates, per cycle pregnancies and number of shipments they have carried out. Mare owners also need to ask their veterinarians if they are skilled in the various areas of reproduction, as this is not generally taught in the veterinary curriculum.


Deb Ottier of Iron Horse Equine is a highly qualified individual.  She has worked as Reproduction Researcher and Distance Learning Coordinator at the former Equine Research Centre in Guelph, Ontario, and has recently completed a Masters Degree in Reproductive Physiology. She travels across Canada in her Mobile Reproduction Lab providing on farm semen evaluation, freezing services and AI training courses and seminars.