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Artificial Insemination (Fresh Chilled or Frozen Semen)

We are pleased to offer AI services with both fresh chilled and frozen semen to our clients at the KVC. Artificial insemination offers many advantages to natural breeding:
- no need to transport the mare to the stallion or vice versa
- ability to choose stallion from any location (including outside North America)
- minimizes the spread of venereal diseases
- fewer injuries to mares/stallions compared to natural breeding
- allows evaluation of semen after collection and at the time of insemination
- allows the use of older or injured stallions

Our goals for AI center around a happy healthy pregnancy – but there is a lot of time, effort and expertise invested before we get there. As a mare owner, you need to choose a stallion and determine if the semen purchased will be of the fresh chilled or frozen variety, as this will have an impact on the amount of money you spend, and the likelihood of a viable pregnancy.

Our protocol for AI with fresh chilled semen generally involves an initial ultrasound examination to determine where your mare is in her reproductive cycle. Mares naturally cycle in this climate from April to October, and this is also when they tend to be the most fertile. If your mare is in heat, we will measure they size of the largest follicle on her ovary, and follow it until it reaches a minimum size of 36mm. Once the follicle reaches this size, semen is ordered. Depending on the days the stallion is collected, we may or may not give the mare an ovulatory agent to ensure she ovulates within a given time period from the insemination. When the semen arrives, it is placed sterilly into the mare’s uterus. The mare is then re-ultrasounded 48 hours post-insemination, and if she has not ovulated a second dose of semen may be required.

Breeding a mare with frozen semen requires further consideration. Often breeding with frozen semen seems advantageous at first glance, as it can generally be obtained from any stallion you desire – sometimes even from stallions that are no longer living! Frozen semen can be kept “forever” as long as it is collected and stored properly, which means there is no worrying about what days of the week the stallion can be collected, or how many doses you might need.

There are also some disadvantages to frozen semen. Conception rates are generally lower with frozen semen than with fresh chilled or fresh semen. Conception rates are highest when insemination is timed as close as possible to ovulation – which means much more intensive management, including as many as 4 ultrasounds per day while the mare is in heat. The expertise required in handling frozen semen is greater than with fresh chilled, as any error in freezing or thawing can result in destruction of the semen. Also, a liquid nitrogen tank is required to store frozen semen when it is not needed.

There are two methods of breeding with frozen semen. The first involves ‘timed breeding” where 1-2 doses of frozen semen are used. Once the mare has a follicle greater than 36mm in size, she is given a dose of an ovulatory agent, and rechecked for ovulation at 24 hours. If she has ovulated at this time, she is bred with a dose of frozen semen. If she has not ovulated, she will be checked again 8 hours later. If she has not ovulated by the 40 hour mark, the second dose of semen will generally be used. We aim to breed in the window of 6 hours pre or post ovulation.

The second method involves ‘breeding to ovulation’ where only one dose of semen is required. The mare is checked until she reaches a 36mm follicle, and then given an ovulatory agent. She is then checked for ovulation at 24 hours, and every 6 hours after that until ovulation occurs, at which point she is inseminated. This method is usually much more labour intensive, and thus, costly. Timed breeding is usually the method of choice unless we know the semen quality to be very low – then the closer the insemination is to ovulation, the better the chance of conception will be.

If you are thinking of breeding your mare and have any lingering questions for us, please let us know! Better planning leads to greater success and happy foals!