Horse Pregnancy Information

Delicate and complex animals, horses have equally delicate and complex reproductive cycles. A foal grows inside its dam for 340 days, while the mare gains up to 200 pounds. With nearly ten percent of equine pregnancies ending in miscarriage, horse owners must understand the changes their mares experience in order to protect both mother and baby.

  1. Breeding

    • Before mares become pregnant, they should be in sound health, without disease or defects.

      According to the Washington State University College of Veterinary Medicine publication "Equine News," every mare should undergo "a breeding soundness evaluation" before pregnancy.

      While many mares still become pregnant naturally, artificial insemination has become prevalent because of its safety and effectiveness.

      Embryo transplant and surrogate mares have also become widespread in the equine industry. Thanks to surrogates, valuable mares may produce more than one foal per year or produce foals late in life.

    Gestation and Fetal Development

    • A mare carries her foal for nearly a year before the birth.

      Les Sellnow's article "Fetal Development and Foal Growth" on the popular equine web site The Horse chronicles the progression of fertilized egg to live foal. By day 21 of a mare's pregnancy, the fetus develops a heartbeat. Sex becomes clear through an ultrasound after just two months, but the fetus remains about "the size of a cat" until its sixth month. By birth, it will weigh roughly 100 pounds.

    Dietary Needs

    • A pregnant mare needs additional nutrients while her foal develops.

      When a mare becomes pregnant, she needs 20 percent more nutrition than before her pregnancy, according to Washington State University's "Equine News.") Similarly, "Nutrition of the Broodmare," published by the University of Kentucky's Cooperative Extension Services, states that during latter stages of pregnancy, the foal's growth rate of one pound per day necessitates added supplements and nutrients for most pregnant mares.

    Veterinary Care

    • Regular veterinary checkups keep track of a mare's pregnancy ups and downs.

      Just as a mare needs a thorough checkup pre-pregnancy, she requires regular exams as she carries her foal. Ultrasounds allow the vet to track the fetus' development. The mare needs extra attention to her vaccination and worming schedules to ensure her fetus' safety.

    Complications

    • Pregnancy complications in horses can include colic and founder.

      The added weight a mare carries during her pregnancy elevates her risk for aggravating preexisting injuries. Colic and bacterial, viral and fungal infections are also extremely dangerous for pregnant mares, as they can lead to miscarriage or the mare's death. When a mare carries twins, only rarely do both foals survive.

    Labor and Birth

    • Most mares go into labor in the evening or early morning hours.

      Equine birth occurs in three phases, Sellnow writes. In the first phase, uterine contractions push the fetus into the proper position. During the second phase, the foal emerges. Finally, in the third phase, the mare's final contractions expel the placenta, and the mare's pregnancy ends.