Your Guide to Equine Health Care

Problematic Behavior in Nonpregnant Mares: Is it Reproduction-Related?

Vets should perform a careful assessment of a mare’s hormonal status to determine whether there’s a definitive, repeatable relationship between it and her undesirable behavior.

No account yet? Register


During diestrus, high progesterone levels generally trigger behaviors such as agitated movement, tail-swishing, ear-pinning and tense facial muscles, urine-squirting, aggression, and vocalization toward stallions. | Photo: iStock

Reproductive behavior in sport horse mares can range from annoying to performance-limiting. For this reason, many mare owners and their veterinarians try to control or eliminate it. However, how do you really know if her reproductive system is to blame?

Dirk Vanderwall, DVM, PhD, Dipl. ACT, set out to address this concern and offer ways to manage undesirable behavior in his presentation at the 2017 American Association of Equine Practitioners convention, held Nov. 17-21 in San Antonio, Texas. Vanderwall is a professor of horse reproduction at Utah State University’s School of Veterinary Medicine, in Logan.

At the start of his presentation, he polled the veterinary audience and found that 79% believed that estrous behavior affects some mares’ performance. These results were similar to those from a survey of more than 750 veterinarians in which 90% believed the estrous cycle affects mares’

Create a free account with to view this content. is home to thousands of free articles about horse health care. In order to access some of our exclusive free content, you must be signed into

Start your free account today!

Already have an account?
and continue reading.


No account yet? Register

Written by:

Alexandra Beckstett, Managing Editor of The Horse and a native of Houston, Texas, is a lifelong horse owner who has shown successfully on the national hunter/jumper circuit and dabbled in hunter breeding. After graduating from Duke University, she joined Blood-Horse Publications as Assistant Editor of its book division, Eclipse Press, before joining The Horse.

Related Articles

Stay on top of the most recent Horse Health news with

FREE weekly newsletters from

Sponsored Content

Weekly Poll

sponsored by:

This poll is no longer accepting votes

Which hoof problem do you encounter most often in your horses?
342 votes · 342 answers

Readers’ Most Popular

Sign In

Don’t have an account? Register for a FREE account here.

Need to update your account?

You need to be logged in to fill out this form

Create a free account with!