Anyone who’s suffered from chronic aches and pains will likely say the ever-present irritation can put a damper on their day, possibly even making them cranky. But is the same true for horses? A group of French researchers recently completed a study on the topic and, for the first time, demonstrated an association between chronic discomfort or pain and aggressive behavior in horses.

"Several studies have implicated that experiencing acute pain can affect the social behavior of humans and animals in that the risk of exhibiting aggressive or violent behavior is increased," said equine behavior scientist Carole Fureix, PhD, of the University of Rennes in Rennes, France, and lead researcher on the study.

Researchers on one study noted that 70% of human patients with chronic pain expressed feelings of anger. However, studies evaluating the link between chronic pain and aggression are lacking in animals. So Fureix and colleagues set out to determine if chronic discomfort or pain in horses was associated with increased aggression.

The researchers observed 59 horses (44 geldings and 15 mares that were 5 to 20 years old; mostly French Saddlebreds) residing at three different riding centers in France. The horses completed five different standardized behavioral tests that are commonly used in human-horse relationship studies (see sidebar). Subsequently, an equine chiropractor assessed the degree of back pain (or absence thereof) based on bony and soft tissue palpation and stiffness