Sleep Deprivation in Horses

By Dr. Lydia Gray on October 10, 2007 at 10:13 pm
Misc. Topics

I usually only pick one of many questions on a topic to “kick off” an entry, but these three questions on horses falling asleep were all so interesting and described the same problem so differently that I wanted to share them all.

After I girth my horse, he acts like he falls asleep, then his knee will buckle, and he sort of wakes himself up. OK I know it sounds funny, but the lady I bought him from said he is narcoleptic, not sure of spelling, it's just one of many issues he has. Can horses really have that disorder, or does he just have some type of nerve there that when pressure is applied, he zones out?
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I have a 12 yo TB mare. I have had her for two years now. She happens to fall asleep standing in her stall during the day, and then she almost falls on her knees. It looks really funny, when she dozes and her head starts to lower down, than her front leg becomes "soft", another leg "softens" as well, and she wakes up, when her nose touches the ground... I am finding her every day with new scratches. Besides her stall I didn't see her do it anywhere else. What could be the problem with her?
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I have a 26 year old Appaloosa gelding that is in good health and weight. He's on 24/7 turnout with a 3 sided shelter to use at his will. He sleeps a lot or should I say tries to sleep. He doesn't lay down much. He can get down to roll and get back up fine. When he's drifting off to sleep his eyes will close and his head drops lower and lower. When it's about at the lowest point he starts to sway backwards almost to the point of his legs giving out then he startles himself awake. This happens a lot. In your opinion do you think this is normal or something more to it or should I have my local vet check into? Thanks in advance for any help.

It’s always a good idea to have your veterinarian examine your horse when you notice anything abnormal. While I hope to offer a simple solution to the owners of these horses, it is possible something serious is going on. Conditions such as true narcolepsy, cataplexy (weakness or collapse), heart disease, epilepsy, EPM, HYPP and others could cause similar signs. An accurate diagnosis is the first step towards appropriate treatment.

Hopefully, these horses have nothing more than simple sleep deprivation. Yes, you read it right, sleep deprivation. But (you say), don’t horses sleep standing up? How could they become sleep-deprived?

I recently attended a lecture by Dr. Joe Bertone, Professor of Equine Medicine at Western University of Health Sciences, who is working on this theory of sleep deprivation. He has found that horses need between 30 and 60 minutes of REM sleep each day, and that after 7 to 14 days of being deprived of this sleep will begin to have sleep attacks as described in the questions above. What separates these sleep attacks from the sleep attacks of true narcolepsy is that sleep-deprived horses go through the first two stages of sleep—deep restfulness phase and slow wave sleep—before entering REM sleep and partially collapsing. Narcoleptic horses go from full wakefulness to full sleep (and back and forth) immediately, with no drowsiness or other sleep phases in between.

Why do horses become sleep-deprived? REM sleep can only be achieved when lying down, not standing, so sleep-deprived horses either can’t or won’t lie down. There are both physical and mental reasons for not lying down. If you never see your horse roll, or never see mud or shavings on him, he may not be physically able to get down and get back up. This would be another reason to have your veterinarian examine your horse, to see if there are any musculoskeletal or other reasons for pain. Once the pain is controlled, the horse may be able to lie down again and get REM sleep.

There are several mental reasons why horses won’t lie down. Once is the absence of a sentinel horse. Dr. Bertone shared stories of horses that suddenly found themselves alone or that lost the dominant horse in a herd and became sleep-deprived because they did not feel they could safely lie down and sleep soundly. Adding a companion, whether a watch mare or even a goat, usually resolves these situations.

Sometimes the environment is just not conducive to deep sleep. He related a story of a horse that was taken to the county fair for a show and started collapsing in the cross ties. By doing a little detective work, he was able to discover that, in addition to all of the (ab) normal sounds of a county fair, there was a fireworks display every night! This poor horse hadn’t sleep in over a week! When they took him home, he slept straight through one whole day and never collapsed again.

I encourage you to read the February 2007 issue of Equus magazine for more ideas on resolving sleep-deprivation in horses, and to visit their website to watch actual video of sleep-deprived horses: Click Here