Pain in Horses Frequently Overlooked

By Jennifer Coates, DVM on May 26, 2014

Determining whether a horse is hurting is not always easy. Experienced horse people get pretty good at reading equine body language and facial expressions, but to the uninitiated, horses can be hard to decode. Unfortunately, this leads to an under-appreciation and under-treatment of pain in horses.

First, let me get one of my pet peeves out of the way. When a horse is limping, he or she hurts … end of story. I cannot tell you how many times I have heard owners say something along the lines of, “He’s not putting much weight on that back leg, doc, but it doesn’t seem to hurt him.” Of course he is in pain, why else would he be limping? (We’re talking true “limping” here, not neurologic dysfunction.) Put yourself in the horse’s shoes, so to speak. Have you ever limped for any reason other than pain? I didn’t think so. The same is true for animals.

Now let’s move on to the more subtle signs of pain in horses. With regards to body language and behavior, I look for four things:

A decrease in normal activity — A painful horse may not keep up with the rest of the herd when out on pasture, stop rolling in a favorite dirt patch, not self-groom, etc.
A lowered head — Horses who are hurting tend to hold their heads lower than do non-painful horses. Take particular note if the horse’s head is lower than its knees.
A hundred mile stare — Painful horses may stare off into the distance and take little interest in the goings on around them.
Stiffness and a reluctance to move — A horse who is in pain may stand very still and resist being led out of a stall or being moved in any other way.

Researchers have also begun developing something called a “grimace scale” to help identify horses who are in pain. In a study that was recently published in the online journal PLoS One, 46 horses were divided into three groups:

Group A (19 horses) underwent “routine surgical castration under general anaesthesia” and received “a single injection of Flunixin [a pain reliever] immediately before anaesthesia.”
Group B (21 horses) underwent “routine surgical castration under general anaesthesia” and received “a single injection of Flunixin immediately before anaesthesia and then again, as an oral administration, six hours after the surgery.”
Group C (6 horses) underwent non-invasive, indolent procedures, received the same [anesthesia and Flunixin treatment] as group A, but did not undergo surgical procedures that could be accompanied with surgical pain.”

According to the PLoS One publication:

Images of each subject before and 8-hours after surgery were compared to identify changes in facial expressions associated with these procedures by a trained treatment blind observer experienced in assessing facial expressions in other species (MCL). Based on these comparisons, the Horse Grimace Scale (HGS) was developed, and comprises six facial action units (FAUs): stiffly backwards ears, orbital tightening, tension above the eye area, prominent strained chewing muscles, mouth strained and pronounced chin, strained nostrils and flattening of the profile (see Figure 2).

With new tools like these, we’re running out of excuses for not adequately addressing the problem of pain in horses.

Dr. Jennifer Coates

Reference

Development of the Horse Grimace Scale (HGS) as a pain assessment tool in horses undergoing routine castration. Dalla Costa E, Minero M, Lebelt D, Stucke D, Canali E, Leach MC. PLoS One. 2014 Mar 19;9(3):e92281.

Image: Monkey Business Images / Shutterstock