Researchers offer advice on helping horses get quality sleep

Sleep provides horses an important rest and recovery period known to repair muscles, reinvigorate the immune system, and flush the brain of accumulated toxins.

Those are great benefits, but they come with a flip side: a significantly altered state of consciousness and physical readiness. And while horses can sleep standing up, they can only achieve rapid eye movement (REM) sleep while lying down—making these open-grasslands prey animals more vulnerable. That probably explains why horses evolved to need remarkably little sleep, says Linda Greening, PhD, senior lecturer in Hartpury University’s Equine Department, in the U.K.

Still, despite needing merely half the sleep we do—at least four hours will do—plus being able to take mini-naps throughout the day, researchers find it increasingly apparent that domestic horses lack sufficient sleep, Greening says. To better understand the problem, her team has just developed an equine sleep scoring system based on not only quantity but also quality.

What is good-quality sleep, and how much do horses need? How do you know if your horse is getting enough, and how can you improve it? In this article we’ll address those questions and more with helpful information and tips from leading equine sleep experts.

REM Sleep in Horses

A vital aspect of sleep quality is being able to achieve that dream-stage slumber known as REM sleep, says Katherine Houpt, VMD, PhD, Dipl. ACVB, professor emeritus at Cornell University’s College of Veterinary Medicine, in Ithaca, New York.

REM sleep is actually similar to wakefulness and tends to occur just before animals wake up, Greening explains. It’s during REM sleep that the brain “sorts out memories from the day,” selecting those to keep and those to delete, which “kind of frees up storage space,” she says. Horses need 40-45 minutes of REM sleep per 24 hours.

Standing horses can enter non-REM sleep—including a deep form of sleep—thanks to their stay apparatus that locks the legs. But because REM sleep induces a total loss of muscle tone throughout the body, it relaxes all soft tissues, including the stay apparatus. Horses can only safely enter REM sleep when lying flat on their sides (lateral recumbency) or up on their sternum (sternal recumbency), usually with their muzzle resting against the ground, Houpt explains.

The Seriousness of Sleep Deprivation in Horses

Although horses usually get their best quality sleep between midnight and 5:00 a.m., they don’t have to fulfill their sleep requirements all at once, our sources say. They can even go several days on reduced quantities of sleep