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Home > Horses > How Often Do Horses Go Into Heat? (Understanding a Mare’s Cycle)

How Often Do Horses Go Into Heat? (Understanding a Mare’s Cycle)

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Healthy female horses, or mares, go into heat periodically throughout their life. Heat means that the body is ready to be bred. It is important to know when your horse is expected to go into heat for a number of reasons. Mares in heat are hard to deal with and can be dangerous. Heat is also when your mare can become pregnant, so you need to manage that to facilitate pregnancy or prevent it. Mares typically go into heat every 3 weeks during the breeding season but they don’t go into heat year-round. They also don’t go into heat as they age. Every horse is a little different so you should track your horse’s behavior to get exact numbers.

Here is everything you need to know about how often horses go into heat, how long heat lasts, and what parts of the year they go into heat.

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Time between cycles: 3 weeks
Breeding Season: Long Daylight Days (Summer)
Days in heat: 2–8 per cycle
Total days in heat per year: Average: ~30 | Low: 10 | High: 50+
Starting age: 2 years
Reproductive Decline ~15-20 years
Horse Mare
Image By: Freddy, Pixabay

Heat Every 3 Weeks

During the breeding season, horses will go into heat every 3 weeks. Typically, that means three full weeks from the end of the previous heat cycle. This is called the estrus cycle. It is important to track when your mare is in heat or going into heat because mare’s can become extremely unruly during these times. The presence of nearby stallions can make mares in heat very hard to handle.

It is also important to know the heat cycles for your mare if you are planning on breeding your horses. A mare can only get pregnant when they are in heat and are paired with a fertile stallion. You need to know when to put your horses together for the best results.

This means that a healthy mare will go into heat roughly once per month and will have an estimated 5 days in heat per month.

How Long Do Heat Sessions Last?

Heat cycles can vary in length. The shortest heat sessions can last just a day or two. The longest heat sessions can last up to 10 days. The exact number of days that your mare is in heat is going to depend on your mare. Every horse is different. It can also be influenced by your horse’s age, health, diet, and whether there are any stallions nearby.

Image By: Vera Zinkova, Shutterstock

Long Day Breeders

It is important to remember that horses are long-day breeders. That means that they do not go into heat during the winter months. In the Northern Hemisphere, horses will start going into heat around April after the spring equinox when the days start getting longer. They will have heat cycles through summer until the autumn equinox when the days start getting shorter again. That means the horse breeding season runs roughly between April and September. Horses always breed when the days are longer than the nights.

The exact season can vary based on your particular location. If you live in far northern or far southern regions the days will get shorter or longer faster which can lead to shorter or longer breeding seasons. Equatorial breeding seasons will be longer than northern ones. That is one of the reasons that Florida and California are big areas for horse breeding; they have longer seasons.

Signs a Mare Is in Heat

There are some obvious signs that tell you that a mare is in heat. They will stand with their legs spread more broadly. They will urinate frequently. Mares will also become more vocal, especially if there are stallions around. This vocalization can manifest as a high-pitched squealing. Mares will also lift their tail more and turn to show their backside to other horses in the area.

Mares in heat can be hard to ride. They might not want to stand or tie. They can kick, rear, and run off, even if they don’t normally exhibit this kind of behavior. Mares can be sketchy to ride if they are in heat, especially for inexperienced riders. It can also be dangerous to handle or ride a mare in heat when there is a stallion in the area.

Look for these signs and plan on dealing with your mare differently if you suspect that they are in heat.

chestnut brown mare running on a cloudy foggy meadow
Image By: el-ka, Shutterstock

When Do Horses Start Having Heat Cycles?

Horses typically start going into heat when they turn 2 years old. They will have heat cycles every summer until they are about 20 years old. Like people, these numbers can vary from horse to horse. Some horses might have heat cycles past 20 and others might start a little later in life. But typically, 2 to 20 is the age range for horses in heat.

My Horse Stopped Going Into Heat

If your mare has stopped going into heat after having regular cycles, then the mare is likely pregnant. If your mare skipped a few heat cycles and then appears to be going into heat again, it could have gotten pregnant and then lost the pregnancy early. Roughly 10% of mares will continue to show signs of an estrus cycle while they are pregnant, so that is something to keep an eye on as well.

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Horses go into heat every 3 weeks during the longest days of the year. Horses are long day breeders and will have 6 months of the year in which going into heat is common. A healthy mare can be in heat for 30 to 60 days per year, giving you ample opportunity to breed if that is your desire. As horses age, they will stop having heat cycles, usually around 20 years old.

Featured Image Credit: Sarah Olive, Unsplash

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