Understanding How Long is a Horse Pregnant

Jessica McDaniel
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A Typical Horse Gestation Period

A horse’s gestation period is approximately 11.4 months, and this is how long it will take them to give birth to a healthy foal.

The length of the gestation period differs dependent on the breed of the horse and the individual horse.

When a mare is first pregnant, it takes approximately 3 weeks for her to be able to detect the pregnancy and become aware of the foal developing in her womb. During this time, her uterus will begin to flatten out, and the bulk of the remainder of the pregnancy will typically be recognized around the seventh month of gestation.

You can typically find very subtle changes in your horse’s behavior during this time. If you are not yet keenly aware of your horse, it may take longer for you to notice any changes that may indicate that she is pregnant.

Once the foal is fully developed, development will slow down, this is usually during the last month or so of its gestation period.

When the foal is ready to be born, the contractions of the uterus will cause the amniotic sacs to rupture, and the waters will break.

How Long is a Horse Pregnant: Gestation Stages

Horses gestation is approximately 320-340 days long, on average. Since horses don’t have an exact breeding season, foals born in the spring are typically conceived the previous fall, and vice versa. Although it is possible that a foal may be conceived in spring, born in winter and a full term.

Mares conceive at a more rapid rate than human women and will be showing confirmation of pregnancy within weeks of breeding.

Horse Breeding Season

A horse usually has her first heat between the ages of four and six. The horse will cycle at regular intervals every 21 to 31 days. However, it is still possible that she could have her first heat cycle earlier than that, with a breeding season occurring as early as two years old. A mare can have three or four heat cycles per year if she has not been bred.

A horse’s heat cycle consists of three phases. The first is pro-oestrus, which lasts for five days. This is when she will show the most interest in the stallion and will begin to display estrus behavior. During this time she will begin being aggressive toward the other mares, chasing them away, or even fighting with them. The second phase is when the mare is in heat or estrus. Her whole body will be swollen, she will dribble urine and produce large amounts of vaginal discharge. The third phase is called di-oestrus, after the pro-estrus phase is over. Horses can return to heat the following cycle, but this is uncommon. Most horses will continue to cycle once they start. However, there have been rare cases where the horse’s heat cycle became irregular after a group of mature mares were moved to a new location.

Seasonal Polyestrous: Mare in Heat

Most horse owners want to know how long is a horse pregnant, after all, pregnancy is the most important time in the life of the owner of a mare.

Of course, it’s normal for a horse owner to be concerned because the nine months a mare is pregnant pretty much defines the next year of your life, and costs you a lot of money. However, the good news is that you can reduce the risk of unwanted pregnancy and money costs by knowing how long is a horse pregnant.

Vaginal Temperature can help you find out when your mare is in heat and may be pregnant. From the main, mare’s external (vocal) symptoms of being in heat are visible, and you can monitor it with regular daily interaction with your horse, unless you live in a multi-horse household.

However, there are many other factors that can delay the breeding process or prevent it a mare from getting pregnant.

If you are trying to determine when your mare is in heat, you’ll want to record the earliest and latest times that the mare goes in heat. These times will be used in the calculation of how long is a horse pregnant. Monitoring the cycle of your mare, using a temperature chart can help you determine the day that your mare is most likely to get pregnant.

How Long is a Horse Pregnant: Twins

Vs. Singleton

The horse’s gestation (the time from conception to birth) is 11 months. Commonly, it is said that a horse can have one or two foals (also called lambs, colts, fillies or foals). That’s because only one placenta is developed, but up to two different embryos can attach to that one placenta. These embryos have the potential to be totally different sexes (female foals or colts and male colts or fillies).

It’s when they have two embryos on one placenta, that’s when they can split and each baby can create a separate placenta, and eventually, they are known as twins. Twins are very rare compared to the number of foals conceived each year.

Keep in mind that twins can only occur on the same ovulation (ovulation is when the mare releases one egg per cycle). So basically, it’s twins or nothing in your mare! If she ovulates twice in a three week period or has a multiple ovulation, then she produces two different embryos that attach to the only placenta present.

How Long is a Horse Pregnant: The Most Exciting Part

The gestation period is usually a length of time that is between 11 months and 13 months from conception to birth. This time period can vary depending on the size and age of the mare. The gestation period in horses is around 11 months unlike most mammals which are pregnant for roughly 10 months.

The gestation period in horses can also get longer than the normal time frame if the foal is particularly large or if the mare has multiple fetuses. After the gestation period is done, the horse will have her foal.

During the gestation period, the fetus will attain all of its required human characteristics. The fetus will have all of the bones in place and will be almost three-quarters of its adult size by the time it is born.

The horse won’t yet have the muscles in place or be filled out, which will happen after it is born.

The mare will generally have a mild yoga pregnancy but she may eat more than usual because she is nurturing the egg inside of her.

She will also have lower back pain for a majority of the pregnancy because of the weight of the egg.

Most mares will need some help getting up and down during the gestation period because they are uncomfortable.

Signs a Mare is About to Give Birth

You can expect your mare to give birth within the next 21 days if she has not already given birth. Signs that pregnancy is in the final trimester include swollen nipples, milk dribbling out of them, a dull coat and a dull stare, foaming at the mouth, lathered up extremities, and the horse’s belly is pulling in (it will no longer be relaxed down to her knees). You may also notice the mare snorting as its gestation comes to an end.

Most horse pregnancies last from 305-330 days. The day a horse gives birth is officially considered day 1 of the next pregnancy, so the average between pregnancies is between 12-18 months.

A Beautiful New Life

Horses are pregnant anywhere from 345 to 545 days, depending on what source you consult. A foal develops in utero for approximately 11 months if born in the spring, or 12 months if born in the fall.

The majority of mares will foal (give birth) in the spring, generally taking place anywhere from late January to mid-April. The gestation period lasts approximately eleven months.

When a mare foals, she has to draw upon a number of internal and external resources to nurture her foal. The horse has to come into contact with oxygen, food, and water. She has to maintain vital body temperature to keep her and her baby healthy. She faces possible predators and other natural hazards.

There are potential fatal problems that can occur for a horse throughout her pregnancy. These include colic, laminitis, mal-presentation, and predators such as coyotes. Horses also rely on certain support both from their owners and their environment to give birth successfully.

Worth the Wait

Any pregnancy is a long haul, but waiting for a horse gives you a better idea of the time period because horses gestate for a rather long time. In fact, a horse pregnancy can last up to 11 months. That’s a long time compared to other animals. So if you’re expecting a horse, you will probably notice at the end of the pregnancy that it’s been longer than you had thought.

For example, human pregnancy lasts for nine months (38 weeks). A cat pregnancy lasts for 60 to 63 days. Dogs can breed up to twice a year and have an average gestation period of 58 to 62 days.

Depending on whether the mare becomes pregnant right away, the time frame can vary, but don’t forget about winter. In northern climates, the gestation period for horses can be more than 11 months. However, the USDA has confirmed that the average length of a horse pregnancy is about 11 months.