Skip to content
Search Library
thumbnail

Broodmares are often checked 14 days after breeding to verify pregnancy. However, some mares that have conceived will not still be pregnant a few weeks later. Loss of pregnancy in the first 50 days after breeding is fairly common in broodmares. If the loss is noticed early enough that the mare can be rebred, the owner may still get a live foal in the spring, but mares that are at least seven weeks past their breeding date may not come back into season because of hormonal changes related to the formation of endometrial cups on the placenta.

While not all early pregnancy losses are easily explained, some factors are associated with a higher risk of a failed pregnancy. Some of these possible causes:

  • Age of the mare. In general, younger mares conceive and carry foals to term with more consistency than older mares. Aged mares may have abnormal eggs, uterine changes, or problems related to prior uterine infections.
  • Time between ovulation and fertilization. The oocyte becomes less capable of normal development as it ages. Early pregnancy might occur, but the embryo tends to be smaller than normal and the pregnancy is not maintained.
  • Reproductive health of the mare. Mares that have a history of pregnancy loss, chronic inflammation, infections, uterine cysts or scarring, tumors, or fibrosis are more likely to lose a pregnancy in the first few months.
  • Twin pregnancy. Mares usually can’t carry two fetuses to term and deliver healthy foals. If a twin pregnancy is allowed to continue, there is risk to the foals and to the mare. A veterinarian can eliminate one embryo, allowing the other to develop normally.
  • Hormonal imbalance. Some mares do not produce enough progesterone to maintain a pregnancy. Though the cause may be unknown, this may be due to illness, injury, adverse climatic conditions, poisoning, colic, laminitis, or other situations that cause stress.

Some factors such as weather stress and twin pregnancy are out of a breeder’s control. Other problems can often be avoided or corrected. If the owner schedules a breeding soundness examination by a veterinarian before the mare is bred, an endometrial biopsy can be done and some problems like uterine cysts or infection can be cleared up, improving the odds for an uneventful pregnancy.

X

Subscribe to Equinews and get the latest equine nutrition and health news delivered to your inbox. Sign up for free now!