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Estrus or Heat Behavior in Mare Interferes with Work

Code Orange - Call Your Vet at Their First Available Office Hours

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

Code Orange - Call Your Vet at Their First Available Office Hours

  • If this problem seems severe and has come on suddenly.

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

  • If this seems mild or occasional and the horse seems normal otherwise.

Mares experience estrus cycles between April through September (Northern Hemisphere), although this season may begin earlier or end later depending on where the mare lives. During breeding season, mares experience a heat cycle once every 18-23 days and will “show heat” on average of 5 days during each cycle.

Signs that a mare is showing heat include irritability, lack of focus, reluctance to work, sensitivity to touch, aggression (kicking and biting), elevating the tail and opening and closing the vulvar lips (“winking”), and/or excessive squatting and urination. Hormonal changes and pain (from ovulation) may be involved in causing these behavioral changes.

Individual mares are very different. Some show radical changes in mood and performance, while others are even tempered regardless of their cycle. Ideally, mares respect their handlers enough so that they are respectful and attentive, regardless of hormonal influence. Good, consistent and firm horsemanship goes a long way toward dealing with this problem. If you are having difficulty, it may be wise to engage a trainer who knows how to address this behavior.

Keep track of the mare’s behavior on the calendar. The timing of behavioral changes is helpful information for your vet.

WHAT YOUR VET DOES

There are veterinary treatments that can help manage the hormonal changes that affect behavior, including heat suppression. Generally, vets want to evaluate a mare’s reproductive health before suppressing estrus with drugs and hormones. This might involve rectal palpation, ultrasound or more rarely hormonal profiles. In some cases, they may choose to perform a trial of a hormone that suppresses heat (oral progestin) to see how much difference it makes to the behavior. If it is very helpful, long term management options can be discussed.

Author: Doug Thal DVM Dipl. ABVP

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