Very Common
Less Common
You also might be observing
Observation
What you see. The starting point for addressing any equine health related issue is your observation.
YOU ARE OBSERVING
Aggressive or Stallion-Like Behavior in Mare
Summary
Occasionally mares may show aggressive or stallion-like behavior. Abnormal hormone production may be the cause. Rarely, otherwise normal mares (with normal ovaries), can show stallion like behavior toward the end of their heat cycle.
Several abnormal conditions are known to cause this kind of behavior. The most common of these is an ovarian tumor (granulosa-thecal cell tumor) which produces testosterone and other hormones in excess. These hormones cause changes in the mare's behavior. Some mares that have had anabolic steroids may behave this way too. This behavior is more common in mares that have been on the race track. In rare cases, mares are hermaphrodites and may have testicular tissue causing testosterone production.
Several abnormal conditions are known to cause this kind of behavior. The most common of these is an ovarian tumor (granulosa-thecal cell tumor) which produces testosterone and other hormones in excess. These hormones cause changes in the mare's behavior. Some mares that have had anabolic steroids may behave this way too. This behavior is more common in mares that have been on the race track. In rare cases, mares are hermaphrodites and may have testicular tissue causing testosterone production.
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Code Orange
Call Your Vet at Their First Available Office Hours- If this problem seems severe and has come on suddenly.
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Code Yellow
Contact Your Vet at Your Convenience for an Appointment- If this seems mild or occasional and the horse seems normal otherwise.
your role
What To Do
Assess the horse's general health using the Whole Horse Exam (WHE), paying particular attention to changes in your mare's general body appearance that might correspond to changes in behavior. Check the vulvar area for growths or abnormalities. Share your findings and concerns with your vet.
Skills you may need
Procedures that you may need to perform on your horse.
your vet's role
Your vet can evaluate the reproductive tract of a mare showing this behavior and perform necessary blood hormonal tests. Once those diagnostics are done, management plans can be considered. When evaluating these sorts of behaviors, always consider management and handling issues as these factors also affect behavior.
Questions Your Vet Might Ask:
- When did you first notice the behavior?
- What is the mare's age, breed and history?
- When do you seem to notice this behavior?
- What are the specific behaviors the mare is showing?
- When was the last time you felt that the mare's behavior was "normal"?
- What are the results of the Whole Horse Exam (WHE)?
- Does the horse have a history of having been on the race track?
- How old is the mare?
- What is the mare's reproductive history?
- Do you notice moodiness of your mare during the winter also?
Diagnostics Your Vet May Perform
Figuring out the cause of the problem. These are tests or procedures used by your vet to determine what’s wrong.
Very Common
Diagnoses Your Vet May Consider
The cause of the problem. These are conditions or ailments that are the cause of the observations you make.
Very Common
Treatments Your Vet May Recommend
A way to resolve the condition or diagnosis. Resolving the underlying cause or treating the signs of disease (symptomatic treatment)
Related References:
Gastal MO, Gastal EL, Beg MA, et. al. Stallion-like behavior in mares: Review of incidence, characteristics, ovarian activity & role of testosterone. J Equine Vet Sc Sept 2007 27(9): 390-93.