“Moody Mare Syndrome” Revisited: A Scientific Reappraisal

Richard Merriner

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The Data vs. The Myth

In a study of over 14,000 mares, researcher A.M. Kareskoski found that behavioral problems were not repeatably verified to be associated with estrus. In fact, 56.8% of mares presented for “strong estrous behavior” were actually in diestrus (the phase where they are not in heat) at the time of examination.

This suggests a significant “misinterpretation of equine behavior”. If more than half of these mares weren’t even in heat, their “moodiness” wasn’t hormonal—it was likely a signal of physical discomfort.

If Not Hormones, Then What?

The research highlighted a crucial link between behavior and underlying health issues:

  • Orthopedic Pain: Aggressive behavior was significantly associated with orthopedic diagnoses, such as limb lameness or back pain.
  • Internal Medicine: Symptoms like recurrent colic or non-specific pain were often tied to gastrointestinal issues, gastric ulcers, or inflammatory bowel disease.
  • Urogenital Discomfort: Conditions like pneumovagina can cause urogenital irritation that mimics “moody” behavior.

Interestingly, the study found that recurrent colic and non-specific pain were actually more common in geldings than in mares, further challenging the idea that these are “mare-specific” hormonal issues.

A Strategic Framework for Owners

From an MBA perspective, efficiency comes from accurate diagnostics. We shouldn’t invest in “solutions” (like ovariectomy or hormone therapy) without first identifying the root cause. The study proposes a Tiered Diagnostic Framework:

  1. The Symptom Diary: Keep an objective record of behavior for 3-4 weeks without assuming it’s cycle-related.
  2. Veterinary Verification: Use transrectal ultrasonography to confirm the actual stage of the estrous cycle when the behavior occurs.
  3. Comprehensive Work-up: Pursue lameness exams and internal medicine diagnostics alongside reproductive checks.

My Takeaway

At Richdel, we believe in supporting equine health through science, not stereotypes. When a mare is “moody,” she isn’t giving you a hard time; she is having a hard time. By moving away from the “Moody Mare” myth and toward data-driven veterinary care, we can ensure our horses get the specific relief they truly need.”

Call to Action: Stop guessing and start tracking! Download a behavior ethogram today and begin a 30-day symptom diary for your mare to share with your veterinarian at your next check-up. See these links:

References & Additional Research

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Published by Richard Merriner

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