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So, You Want to Breed That Mare

The days are getting longer and the horses are starting to shed out. It must be spring! With coming of spring, we start to see the new arrivals around the countryside; newborn calves, lambs and a few foals. One might have the idea, how nice would it be to have your own mare with a foal following her in the pasture or paddock next year. So, what does it take to get that mare in foal and how much is it going to cost?

First, I will review the basics of horse breeding and reproduction. Then I will talk about the two methods of breeding horses and the expected cost difference between the two methods.

Horses, as a species, are seasonal breeders. In other words, they cycle differently at different times of the year. The horse is most reproductively active as the daylight increases from spring into summer and then cycling less into fall. Starting in the late winter, early spring months, (January through mid March) mares will go through a transitional phase where their hormones and cycles are unreliable and many times infertile. This is a very difficult time to try to breed the mare and have her conceive. The mare's cycle is about 21 days in length, with 3-5 of those days in a standing estrus. This is the time when she would be most receptive to breeding by a stallion (with some mares being more receptive than others). Towards the end of the estrus period, the mare will usually ovulate one ovum or egg, from one of the ovaries. During the next 16-18 days, the mare will produce progesterone in anticipation of an embryo and a subsequent pregnancy. If no semen is present or if there is no conception, then the mare will start to come back into heat and repeat the cycle again. If the mare becomes pregnant, she will normally carry the foal about 11 months before she gives birth. Taking this into consideration, if we breed a mare on April 10 and achieve a successful conception, we would expect the mare to give birth sometime around March 10 of the next year.

There are two basic methods of breeding horses, natural cover or artificial insemination (AI). Natural cover is basically how the general horse population has reproduced for the past several thousands of years. This can be as easy as turning a stallion out with a herd of mares and letting nature take its course, or by hand breeding, where handlers are in "control" of both animals. This method of breeding is required for racing thoroughbreds to be registered with the Jockey Club. This can be a fairly inexpensive method of breeding. Expected expenses would include stud fee, transportation to and boarding of the mare at the stud farm, palpation and/or ultrasounds to estimate ovulation or to detect pregnancy and trip charges for the veterinarian. Other veterinarian related expenses depend on the mare and her reproductive health at the time.

Artificial insemination entails collecting semen from a stallion, processing the semen, shipping it to the mare and placing it into the mare. Sounds easy enough, but this type of procedure has some definite pros and cons. The first advantage for the procedure is that it is safer for both the mare and stallion. The stallion semen is collected with an artificial vagina off a breeding "dummy" (a large piece of equipment made for a stallion to mount) or with a jump mare that is given hormone injections to always be in heat. The next advantage is that the stallion can effectively breed more mares per season. Also, when inseminating artificially, less motile spermatozoa are needed, therefore, the semen can be "extended out" and the same ejaculate that was used to breed one mare can now breed several mares. Another benefit of AI is if one wants to breed to a stud that is several hundreds, or even thousands of miles away, you do not have to haul the mare there to get her bred.

There are two large disadvantages to AI and they are the increased cost and the intensive time management involving the mare's cycling. With AI, timing becomes even more critical compared to natural cover. First, insemination needs to be relatively close to ovulation. Horse semen is short-lived after it is manually collected, extended, and cooled for shipment. We can expect sperm to live inside a mare's uterus when delivered by live cover up to 72 hours. Contrast that with AI; we can expect sperm to live only about 24 hours in the mare. Studies have found that the best conception rates using AI were achieved when the semen was deposited in the mare within 12 hours or less before ovulation.

To do this, one has to follow the mare's cycle closely with ultrasound exams to predict ovulation and then time the insemination fairly precisely. We can also attempt to manipulate the mare's cycle using different drugs to help insure a more predictable ovulation. This also means that one needs to be able to predict when the best time to order the semen is so it can be delivered at the most optimal time for insemination. With this intense management, frequent exams, ultrasounds, and drugs, the costs are higher for this method of breeding. Expected expenses would be the stud fees, more frequent palpation and ultrasounds to estimate ovulation or to detect pregnancy, drug costs, trip charges for the veterinarian, insemination fees, collection fees (cost of collecting and extending semen), and shipping fees (i.e. Federal Express overnight shipping of the container from the stallion owner and back again). Other veterinarian related expenses depend on the mare, and her reproductive health at the time. A comparison of the veterinary costs using AI verses natural cover is helpful in determining the method that works best for the horse owner. Veterinary costs for AI are roughly $300-500 per cycle. The veterinary costs for natural cover can be substantially lower, however, the costs can range from $100 per cycle to $300-400 per cycle.

Looking at the reality of breeding mares, cost of breeding is certainly a component of the decision making process. However, with solid information, a trusting relationship with your veterinarian, and knowing how to take good care of your mare, breeding your mare and the birth of her foal can be a magical experience with many years of reward.