What you see. The starting point for addressing any equine health related issue is your observation.


Change in Personality, Strange Behavior


This is a very general statement but one that I hear fairly frequently from my clients. My first task is to engage the horse owner in a thorough history, asking as many relevant questions as needed to gather more specific information.

Occasionally, a horse will act in a mysterious or atypical way, a personality change that may be hard to describe. Change in environment, new handlers, riders or management, all can contribute to an apparent change in personality. Physical problems can also manifest as atypical behavior. The behavior might include aggression toward horses or humans, depression, eating less than usual, misbehavior under saddle, or dozens of other variations.

Behavior is mostly controlled by the forebrain. Forebrain disease therefore can cause all sorts of behavioral changes, depending upon the specifics of the condition. Forebrain function can be affected by diseases of the brain itself, toxins in the blood, low blood sugar, blood loss, and liver dysfunction, among many other problems.

Hormonal changes in stallions and mares affect behavior. Pain causes behavioral change too. If there is a possibility that physical issues could contribute to the behavior change, then your vet may be able to help you rule those out. If your vet has ruled out physical causes, and you do not feel confident identifying and changing the behavior, then you may want help from a qualified trainer.

  • Code Orange

    Call Your Vet at Their First Available Office Hours
  • Code Yellow

    Contact Your Vet at Your Convenience for an Appointment
    • If this seems mild or occasional and the horse seems normal otherwise.
You also might be observing
Very Common
Less Common
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your role


What To Do

Assess your horse's general health using the Whole Horse Exam (WHE), paying particular attention to attitude and appetite and the vital signs, including rectal temperature, heart rate and respiratory rate. Share your findings and concerns with your vet.

NOTE: This observation is associated with Rabies, which is very rare in horses but does occur. As a precaution, wear gloves when handling a horse exhibiting this sign.

your vet's role

Your vet takes a careful history and observes the horse's behavior. A thorough physical exam rules out certain conditions. Depending upon the results of these tests, they may suggest other diagnostics.
Questions Your Vet Might Ask:
  • When did you first notice the behavior?
  • When did you last notice the horse behaving normally?
  • When do you seem to notice this behavior?
  • Is the horse a mare, gelding or stallion?
  • Describe how your horse's behavior has changed?
  • What is the horse's age, sex, breed and history?
  • Do you notice any other problems with the horse?
  • Do you notice any signs of abdominal pain (colic)?
  • If your horse is a mare, is she showing signs of heat or estrus behavior?

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
Less Common
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Author: Doug Thal DVM Dipl. ABVP