Study Evaluates Cribbers' Sleeping Habits

Is worrying about your horse's cribbing habit keeping you up at night? It turns out that cribbing might keep your horse up at night, too. New research has revealed that the stereotypy could be related to a lack of certain kinds of sleep. Specifically, British researchers say, horses that crib spend less time in "standing sleep" mode than horses that don't.

Standing sleep is a form of "slow-wave" sleep in horses, said Jane Williams, PhD candidate and researcher in the equitation science department of Hartpury College in Gloucester, England. Another form of slow-wave sleep occurs when horses are lying down but upright. When horses sleep lying down completely on their sides, they enter a non-slow-wave sleep called paradoxical sleep.

In a recent study, Williams and fellow researcher Kirsty Roberts, BSc equine science graduate, studied 14 cribbers and non-cribbers from 10 p.m. to 6 a.m. for five nights in a row via video camera, without human intervention.

They found that "crib-biting" horses had a 48% reduction in standing sleep time compared to "non-crib-biting" horses, Williams said. In other words, horses that don't "crib-bite" are getting nearly twice as much standing sleep as horses that do. The study revealed no significant differences in the other kinds of sleep.

"The reduction in standing sleep in crib-biters is indicative of potentially reduced slow-wave sleep, which can impact restorative repair," Williams said during her presentation at the 2012 conference of the International Society for Equitation Science. "That's significant because a lack of sleep can certainly impact their welfare."

Research on other species--including humans and rats--have shown that reduced sleep can reduce performance and learning capacity. "These horses could be difficult to ride or difficult to home," she added.

Exactly why the horses sleep standing less, however, is still unknown, according to Williams. It could be that the lack of sleep led them to start cribbing. But Williams prefers the opposite hypothesis: she thinks they might be staying awake in order to crib.

"One theory is the horses are more motivated to crib than sleep as it releases dopamine (a "feel-good" organic chemical in the brain) which rewards the behavior," she told The Horse.

Still, further research is necessary to investigate the cause-effect relationship, she said, as well as whether the cribbers "make up" for the lost standing sleep during the day.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.