Artificial insemination (AI) is a process by which semen is collected from a stallion, processed and tested, frozen for preservation, then thawed and deposited within the mare's reproductive tract, the uterine body, when she is in season and is most fertile. Each step in the process has to be done carefully and accurately to ensure that the semen is preserved properly and that the mare is also at the right part of her reproductive cycle to be able to conceive. Although historically AI has been performed in less than clinical settings, most breeders and owners that practice AI complete certification as AI technicians or hire a professional AI service to handle the semen collection and insemination process.
The semen is collected from the stallion by the use of a temperature controlled tube or sleeve known as an artificial vagina. The stallion is haltered and is brought around a mare in season, known as a teaser mare. The hormones produced by the mare arouse the stallion and he will then attempt to mount the mare.
When the stallion mounts the mare the handlers insert the stallion's penis into the artificial vagina that has been warmed to a temperature of approximately 44 degrees Celsius. The stallion then ejaculates into the artificial vagina and the semen is taken into the lab or work area. It is very important to carefully protect the temperature of the collected semen as temperatures that are either too hot or too cold will affect the viability of the sperm or may even completely kill the sperm, resulting in the disposal of the collected material.
Once in the lab the actual sperm is removed from the gel or liquid carrier component of the collected material. An extender or substitute carrier is added to the sperm to keep it viable and at a temperature of no less than 37 degrees Celsius. The sperm is examined under a microscope for motility or movement, as well as to examine the condition of the sperm and the number of sperm in the test measurement. From this information the technician is able to calculate how much sperm and extender must be added to each vial to ensure that the mare will become pregnant after the insemination.
Through natural breeding a stallion will produce many times the amount of semen needed to actually impregnate a mare. This is nature's way of ensuring that fertilization will occur. With the use of machines and instruments that evaluate the motility and sperm volume, the semen that would normally be produced in breeding one mare can be dividing and will breed several mares, depending on the individual stallion's production and sperm motility.
Semen is frozen in small vial, actually about the size of straws, and is kept in liquid nitrogen to maintain the ideal temperature. These tanks are very small and can be kept easily in a barn or virtually anywhere.
Thawing and Insemination
The frozen straws of semen are taken directly from the liquid nitrogen storage tank and placed for a very short period of time, less than 10 seconds, into hot water baths of very specific temperatures. This allows the semen to thaw without damaging the motility of the viability of the sperm. Immediately after thawing, the semen is inserted into the mare through the use of a pipette that is inserted into the uterine body, just past the cervix. This is a relatively easy process that most breeders do themselves.