Breeding Basics

A few things to know before breeding your mare...
  • gestation for mares is usually eleven months
  • mares go into heat once per month for less than a week, and are usually only willing to breed during this time
  • mares can get pregnant only during a brief 24 hour period at the end of their heat cycle each month
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TIMING 
The timing involved in getting a mare pregnant isn't always easy or completely under human control, but you can make a good start of it by considering a few things when choosing your breeding time.
  1. When do you want the foal born?
  2. When can you do without your mare?
  3. When is your mare going to come into heat?
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1. When do you want the foal born?

A mare's gestation last for about eleven months. Thus, if you want the foal to be born in April, you try to get your mare pregnant in May. However, you must also take into consideration the uncertainty inherent in getting a successful breeding. Some mares don't get pregnant on the first try and need to breed through multiple cycles, so be prepared to be flexible.

Some things to consider when deciding when you want your foal born include: weather in your area at the time of birth, and when you will want to be able to ride your mare.

The Rocky Mountain Horse breed is extremely hardy and I have had foals born on nights when the temperatures got down to -30 degrees Fahrenheit and still thrive. To be sure, we brought the horse into a barn and ran heaters to keep her stall as warm as we could get it (mostly stayed just bellow freezing) for two days, but within 24 hours the foal was running around outside in the full cold like nothing was amiss. However, most breeds are not as hardy as the Rocky Mountain Horse breed, and in any case, I certainly don't recommend doing this on purpose.

Most people aim for April or May so the foal is born in the spring when there are not likely to be such extreme cold temperatures, but in Montana, April and May are still quite cold and often filled with snow. Thus, many Montana horse breeders like to aim for June, but it happens that June, in our immediate area is usually very wet and our best birthing barn and foal pasture is prone to being knee deep in mud this time of year, so at Wild Mountain Farms we often wait until July. Certainly, there is no reason you can't wait until later in the summer or even fall. The only down side to that is that a more delicate breed of horse may have more difficulty thriving if it has not had time to grow big enough to handle the winters by the the time the cold weather hits. 
2. When can you do without your mare?

Another reason people often want their mares to foal as early as possible, however, is so that they can spend time during the summers riding them. Because most of the foal's growth happens during the last three moths of gestation, a mare will spend about 3 months prior to the foal's birth getting visibly big in the belly, finding strenuous work more difficult and uncomfortable, and probably not fitting any of her normal saddles well. Many people don't want to ride the mare during this time. Then, after the birth, most mares needs at least one month to recover and focus just on their foal before beginning to be ridden again. After a month, the mare can begin to be ridden either with the foal or away from the foal for short periods of time (assuming that you do appropriate training to allow her and her foal to handle this change safely). 
3. When does your mare come into heat?

It will help a great deal in timing your breeding if you can tell when your mare comes into heat. Many mares make this obvious, as their behavior changes during this time, but some mares show no outward signs of this at all. In that case you must either choose a date without knowing your mare's cycle or have the vet ultrasound her (often multiple times throughout a month) to discover her timing for you. 

Many mares make their heat cycles obvious. A mare in heat will typically be more reactive to other horses with which she comes into close proximity. (This is a more polite way of putting this than many mare owners use - it is common to say that mares in heat are much more bitchy towards other horses.) To another mares walking near her, she is more likely to squeal, strike out a front hoof or kick. To a gelding or stallion, she may do these things as well, but is also likely to show interest in being near the male horse and be difficult to separate from him.

Mares show interest in strange ways, by human standards - typically, they back up to the other horse, present their buts, lift their tails and pee in front of the male horse. (During their heat cycle, their pee smells different and a stallion will immediately react to this smell with the desire to breed.) A mare in heat will often "squat" - stop in front of a male horse and bend her legs a little - flag her tail and "wink" her vulva a number of times, then squirt out pee. She may do this repeatably in a short period of time. 

Your mare will most likely begin to come into heat in early spring, possibly with a very short or a very long cycle, then even out and quickly cycle on a generally regular schedule for the rest of the summer and into the fall. The heat will usually last 3-5 days, then there will be 20-25 days before the next heat. Start looking for these signs in February or March of the year you plan to breed your mare and try to come up with a good predictor of her heat cycles as soon as possible.
Once you know when your ideal breeding time will to be and have an idea of what schedule her cycle is on, you can arrange the rest with the breeder. At this point, timing differs depending on if you are going to breed her in person (live cover) or by Artificial Insemination.
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Timing for Artificial Insemination:
If you are going to breed you mare by Artificial Insemination, your vet will check the follicle size with an ultrasound multiple times starting at the beginning of her heat cycle the month you want her to get pregnant. He or she will try to guess when ovulation will be. When the vet thinks your mare is within two days of ovulating, you will contact the breeder and they will have their vet collect their stallion. They will ship the semen in a special container directly to your vet with one-day-shipping. Your vet will implant this into your mare on the day he or she thinks is most likely within 24 hours of the end of her heat cycle.
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Timing for Live Cover Breeding:
If you are going to have your mare physically breed with the stallion, the timing you need to be concerned with is not when she is ready to breed, but when you should get her to the stallion. At Wild Mountain Farms, we find it usually helps if the mare is comfortable in her surroundings prior to being ready to breed, and we recommend that you bring her at least a week before you expect her to go into heat. We keep her near the stallion and judge her heat cycle by the way in which she and the stallion react to each other. Once she is receptive to breeding, we bring the two of them together and breed them, then take them each back to their respective stalls. We repeat this once every day (or every other day in some cases) until she is no longer receptive to breeding. 
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This is the end of your part of the timing game, but not the end of the breeder's. Click bellow if you want to understand more about how the breeder determines when to breed your mare.