Horse Reproductive Cycle: How Long Are Horses Pregnant For?

Horses are mammals, and like all other mammals they have a reproductive cycle. But what happens during this cycle? What triggers it? And how long are horses pregnant for? They are larger than humans, so it makes sense that their gestation is longer than ours – but it is a surprisingly small amount of extra time, especially given that their babies are so much bigger than ours when they enter the world!

Reproductive Cycle Of The Horse

horse reproductive cycle

Horses, along with all other mammals, carry their young inside them, then nurse them for a period when they are born before the young weans itself off onto solids – in the case of the horse this is grass, hay and other forage.

Horses, unlike humans, generally don’t have babies at any time of the year, due to their wild origins and the fact that, despite the fact that they are domesticated, they are still governed by their natural habits.

It is far better to have a baby when the weather is temperate and there is plenty of food, than to have one in the freezing winter months when finding food might be difficult!

Mare’s Estrus Cycle

A mare’s estrus cycle, when she is sexually receptive to a stallion, is controlled by the length of the day, and is first triggered when the days begin to get longer.

The estrus cycle lasts on average 21 days, and as the days shorten the mare returns to anestrus, meaning she is not sexually receptive.

If a mare has been covered by a stallion during her fertile period, she will usually carry a foal to term with no trouble whatsoever, as horses are natural reproducers.

The Best Breeding Time For Horses

how long are horses pregnant
  1. In the wild, horses generally time their breeding so that the foal will arrive in mid to late spring, when there is the best chance of survival – the weather is good, and there should be plenty of food for the mother. The mother mare needs to up her calorie intake to make milk for her baby, and the baby then needs to be able to find food easily when it is ready to wean, so spring and summer are by far the best times for horse reproduction. Even though the foal will continue to nurse usually until its mother is pregnant with another foal, it is important for it to find its own forage too.
  2. With domesticated horses, it is possible to breed at other times of the year apart from spring, by artificially bringing the mare into estrus. This can be achieved with artificial lighting in her barn, to trick her body into thinking spring is coming – but it is generally best to leave nature’s methods alone, as they are tried and tested and work the best. Some breeders, especially in the racing world, have to try to time their foals to be born as close to January 1st in the Northern hemisphere, and August 1st in the Southern hemisphere, so they will have an advantage of size and maturity when competing against their age group.

How Long Are Horses Pregnant For?

After a mare is covered by a stallion, she will carry her baby for a gestation period of eleven months, or more specifically 340 days.

This can vary from individual to individual, although the normal average timespan is 320-370 days.

How Many Foals Can A Mare Have?

Each mare can only produce one foal a year – unless she gives birth to twins, which is much less common in horses but does still happen.

A twin birth will not increase or decrease the gestation period, and twin foals are generally much smaller than their single counterparts, and care must be taken to ensure both survive.

How Many Mares Can A Stallion Breed In One Year?

A stallion, of course, can produce many more offspring – around 200 a year! Mares can carry foals until they are in their late twenties, and the age will not affect the gestation period – though they will find it harder to bounce back after birth, and should be well looked after and fed.

When Can Horses Get Pregnant?

Mares can, in theory, start to bear young at about 18 months of age, but it is far better for her body and her capabilities of looking after a youngster if reproduction begins around the age of four.

Stallions obviously, can start much younger, but again it is better for all concerned if he waits until his body is mature – in the wild a colt wouldn’t have a chance to reproduce as the dominant stallion would not allow it; in domesticated horses young male horses can breed more easily.

Frequently Asked Questions

how long are horses pregnant Frequently Asked Questions
1. Do old mares go through menopause?

Mares may become less fertile as they age, and a very senior mare (e.g. age 20) may simply choose not to participate in breeding and reproducing; however, there is no set age of menopause for mares. Surprise foals from senior mares are fairly common.

2. Are foals from older mares more likely to have problems?

If the mare and stallion both have good DNA, and the mare is reproductively sound, well fed and well cared for, her foal should have just as good a chance as any other of being born free of congenital or hereditary defects.

3. How long is a mare’s estrus cycle?

A healthy mare should have a 21 day estrus cycle. Just as with people, there can be some variation from one mare to the next.

4. Why do wild horses have a better pregnancy rate than domestic horses?

It’s a matter of natural selection. In the wild, mares that are not reproductively sound are not able to maintain status in the herd and are picked off by predators. The mares that are healthy and reproductively sound produce offspring who are also likely to be healthy and reproductively sound. This reinforces strong pregnancy rates. In a domestic breeding program, it is far more likely for mares who have some problems to be bred. When this happens, the result may be a failed pregnancy or a foal who has inherited or congenital problems.

5. Does pregnancy in a horse always last 340-341 days?

Actually, the length of time a mare may safely carry a foal ranges from 320 to 370 days, and in some cases, it can last a little (or even a lot) longer. Healthy foals have been delivered after 400 days, and oddly these long term foals tend to be on the small side. A foal born prior to 300 days is considered premature and is unlikely to survive because its lungs will not be fully developed.

Final Words On Horse Pregnancy

How Many Mares Can A Stallion Breed In One Year

Hopefully now you know a little more about the reproductive cycle of the horse, and can answer the question how long are mares pregnant for.

Even if you don’t want to get into horse breeding techniques, the reproductive cycle is an interesting subject!

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