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Mare Returns to Heat after Breeding, Won't Get Pregnant

Code Yellow - Contact Your Vet at Your Convenience for an Appointment

Code Yellow - Contact Your Vet at Your Convenience for an Appointment

    Either your mare has returned to heat or your vet was not able to confirm the pregnancy (with palpation and ultrasound). Many healthy mares bred to healthy stallions conceive and have a healthy foal. But there are many reasons for mares not to conceive, everything from uterine infections and inflammation to hormonal abnormalities.

    Mares show signs of heat (estrus) because of increases in estrogen, which is usually associated with the development of a large ovarian follicle (egg).

    If your mare was bred, but she is now showing signs of heat, she may no longer be pregnant. However, heat-related behavior does not always coincide with a real heat cycle. Sometimes a pregnant mare will show estrus signs. Your vet should perform a thorough exam to determine whether your mare is still pregnant.


    Ideally, a mare is evaluated by a veterinarian before breeding. Repeatedly breeding a mare that is having trouble conceiving is often a waste of time and money. If a mare has returned to heat after breeding, the best course of action is to have her evaluated by your veterinarian. All mares should be evaluated at 14 days after the last day that they are in heat (receptive to the stallion). Be sure to record the breeding dates, reproductive history of the mare and stallion including a record of prior foals and the years they were born. Supply all that information to your vet.

    Note when your mare started to exhibit heat behavior. Look for vaginal discharge, and note its color. Assess rear limbs and hindquarters for soiling, indicating discharge. Share your findings and concerns with your vet.


    The vet exam usually starts with reproductive evaluation of the mare, using rectal palpation, ultrasound and possibly other diagnostics. Your vet determines whether the mare is pregnant, and if not, the stage of estrus cycle she is at. They assess the mare for abnormalities that could indicate a problem that needs treatment.

    Lack of conception could also be related to the stallion. Your vet may also want to perform a breeding soundness evaluation (BSE) on the stallion.

    What Not To Do

    Do not repeatedly attempt (more than 2-3 times) to breed a mare that fails to conceive, without seeking veterinary consultation and exam. There is likely a reason for reproductive failure and repeated breeding is unlikely to solve it.

    Author: Doug Thal DVM Dipl. ABVP


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