Using Facial Expressions to Assess Pain in Horses

Anyone who has witnessed a horse suffering from an acute episode of laminitis knows the heart-wrenching feeling of inadequacy, of being unable to help relieve the pain despite veterinary intervention. Sadly, laminitic episodes often turn into a waiting game to see if the horse will respond to therapies and begin to mend. One important way to assess the adequacy of treatment in cases of laminitis involves evaluation of pain.

Many pain-assessment tools and scales in horses, such as the Obel grading system, rely on the evaluation of movement. In cases of laminitis, this is neither feasible nor humane for many horses.

As all horsemen appreciate, horses communicate using a myriad of methods, including facial expressions. This realization led a group of researchers to determine whether an expression-based pain-coding system, dubbed the “horse grimace scale” or HGS, could be used instead of making painful horses walk and move.

In fact, observers need only assess six facial actions:

    1.Stiffly backward ears;
    2.Orbital tightening;
    3.Tension above the eyes;
    4.Prominent tightening of chewing muscles;
    5.Mouth rigidity and pronounced chin; and,
    6.Strained nostrils and flattening of the profile.

To validate the HGS, the research team took both video and still shots of 10 horses with acute laminitis on the day of admission to a referral hospital and again seven days later after treatment was instituted. The HGS determined from those pictures was compared with standard Obel scores.

Veterinarians blinded to time and treatment conditions assigned significantly higher pain scores using both the HGS and Obel scores. A significant correlation between the HGS and Obel scores was identified, suggesting that the HGS could prove to be an effective method to assess pain associated with acute laminitis.

“Having a tool to effectively monitor a patient’s pain without inducing additional pain associated with movement is a great asset. That said, avoiding bouts of acute laminitis is ideal,” observed Kathleen Crandell, Ph.D., an equine nutritionist with Kentucky Equine Research (KER).

Source: Equinews