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Care of the Pregnant Mare


Both absence of physical activity and over-exertion can be potentially harmful to your pregnant mare. Moderate exercise increases the flow of blood to the uterus through the utero-ovarian artery and thereby increases the supply of oxygen and nutrients to the fetus. In addition, a physically fit mare is more likely to foal without complications and recover quickly for the following breed season. Mares confined to a stall may have an increase in edema (swelling) of the lower legs and abdomen during the late stages of gestation due to lack of exercise. Strenuous exercise during the last two months of gestation should be avoided. Most mare owners simply continue with the mare’s usual pre-pregnancy routine during pregnancy.


Nutritional requirements vary with the mare’s age, size, physical activity, stage of pregnancy and whether she is lactating. Excellent quality hay and/or pasture grazing and free access to a mineral salt block should be included in your nutrition program. Pastures should be free of fescue or other potentially harmful plants to your mare and her developing fetus.

Plenty of clean, fresh water should be available at all times and should be prevented from freezing.

Your veterinarian can assist you in assessing any specific nutritional requirements of your mare. Grain supplementation should be discussed, as too much supplementation can lead to problems with the mare and her developing fetus; including leg abnormalities in the foal and post-foaling colic in the mare. The majority of pregnant mares do not need any supplements when they have access to excellent quality hay, grass and a mineral salt block.

A thin mare may produce a poorly developed foal or may abort. Obese mares tend to produce smaller foals, as the uterine capacity is decreased due to the compression by fat layers. Therefore, mares should maintain good condition at all times.


Pregnant mares should be kept on a regular de-worming program until one month prior to foaling. De-worming with Ivermectin 4 to 6 weeks prior to foaling and then within 12 hours after foaling has been noted to prevent foal scours (foal diarrhea). Manufacturer precautions pertaining to pregnant mares should be carefully noted before administration.


Vaccination recommendations vary among geographical locations. Your veterinarian can advise you on the specific vaccination recommendations for your area, your horse’s potential for exposure and any current outbreaks.

I use the following schedule for the southwestern United States:

  • 3rd month of pregnancy..........
    • Rhinopneumonitis
  • 5th month of pregnancy..........
    • Rhinopneumonitis, Influenza (Fall)
  • Fall...........................................
    • West Nile (for areas with mild winters)
  • 7th month of pregnancy..........
    • Rhinopneumonitis
  • 9th month of pregnancy..........
    • Rhinopneumonitis
  • Spring......................................
    • West Nile, Streptococcus Equi
  • 4 weeks prior to foaling..........
    • Rhinopneumonitis, Influenza, Encephalomyelitis, Tetanus

Foal vaccination programs also vary among geographical locations; therefore, Veterinarian assistance may be applicable once the foal is born. First foal vaccines usually begin at 4 months of age with some of the vaccines starting at 6 months of age provided the mare was properly vaccinated during pregnancy. The foal’s first vaccines will require a repeat administration (boosters) 3-4 weeks later.


Many factors may cause a mare to loose her foal. These include viral, bacterial and fungal infections. Hormone imbalances, cervical incompetence and uterine incompetence are believed to be important causes of habitual abortion in mares. A thorough pre-breed check and regular vaccinations are the best defense against these.

Twinning is a common cause of abortion in mares. Early detection by ultrasound, 15 to 18 days from the last breed date, followed by the “pinching” of one embryo increases the chances of a successful pregnancy, as healthy, full-term twins are uncommon among horses.

Poor nutrition as well as toxic plants or chemicals are known causes of abortion. Mental stress, heavy exertion, breeding during pregnancy, twisted umbilical cord, genetic abnormalities, trauma, certain medications and certain de-wormers may also result in abortion.


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