Today’s culture fuels busy lifestyles with dwindling opportunities to sleep, so it should come as no surprise that a 2011 Center for Disease Control study estimated more than one third of American adults suffer from sleep deprivation. But did you know horses can suffer sleep deprivation as well? At the 2012 Western Veterinary Conference, held Feb. 19-23 in Las Vegas, Nev., one researcher presented an overview of this important, but not fully understood, equine health condition.

Before delving into sleep deprivation, however, it’s important to understand sleep in general. Joe Bertone, DVM, MS, Dipl. ACVIM, professor of equine medicine at Western University of Health Sciences in Pomona, Calif., reviewed with the veterinary audience the basics of equine sleep.

What is Sleep and What Influences It?

"Sleep is commonly defined as a period of immobility in which individuals seem unresponsive to their environment," Bertone explained. But even though it’s fact everyone needs sleep, the reasoning behind it isn’t yet clear: "Sleep is now accepted as a behavior with clear physiologic necessities that are not understood, but when lacking have clear dysfunctional impact."

So how much sleep is enough to prevent the dysfunctional impact? Bertone said that research, most of which was conducted in France in the 1960s and 70s by Dellaire and Ruckebusch, estimates that in a day horses fulfill approximately:

  • Two hours of diffuse drowsiness (during which the horse stands with full weight on both front legs and one rear leg while the other rear leg is cocked, or "primed,"