Because of its subjective and complex nature, the severity of a horse’s pain is very difficult to assess. Recently, a comprehensive review was published by the University of Minnesota outlining the definitions of the types of pain and the difficulties associated with its assessment in animals.

Pain is broadly classified as acute (of short duration) or chronic (persisting over time), then further classified as superficial or deep within the body, and somatic (bone, muscle, ligament pain, etc.) or visceral (internal organ pain). But pain might not always fit a tidy definition. For example, an animal could have recurrent episodes of acute pain, or chronic pain with no obvious initiating cause. Researchers now recognize that some pain can even extend beyond the healing period, placing it into a new class called neurogenic pain. This type of pain can actually produce physical and functional changes in the nervous system.

It’s extremely important that veterinarians, horse owners, and all animal caretakers learn to recognize subtle signs of pain, including the emotional responses to pain that can influence its physical aspects. For example, a stoic mare with acute colic might be so stressed by the trailer ride to the hospital that she masks the extent of her pain out of fear. Another example would be a mare with chronic colic which appears only mildly affected by recurrent episodes, while actually suffering increasing emotional distress with each painful flare-up. In both cases, recognizing the extent of the animal’s pain would be very challenging. Veterinarians and horse owners need to put pain on their mental list of clinical signs of disease, and work together to help prevent unrecognized, and thus untreated, pain.

Sukumarannair, S.A.; Anil, L.; Deen, J. Journal of the American Veterinary Medical Association, 220 (3), 313-319, 2002