Over the years, the name of sleep deprivation has changed. It used to be lumped in with narcolepsy, but narcolepsy is quite rare, occurs at exercise or with activity, and has mainly been found in miniatures. Sleep deprivation, however, is much more common and occurs at rest or when things are quiet.
REM sleep is necessary for proper rest (in both humans and other animals). Horses need a very short amount of time in REM sleep but it MUST be done when the horse is laying down because they lose all muscle tone. Sleep deprivation investigation revolves around finding out why a horse is not laying down and getting REM sleep. Often a video is helpful for your vet.
REM sleep can look quite dramatic in horses – especially in horses that finally lay down after being sleep deprived. They can move their legs – some quite vigorously as if they are running a race; they can nicker, move their lips and ears, roll their eyes back in their head, etc. Sometimes they wake and are a bit confused since they were dreaming. They can look quite seizure-like. However, seizures are much more rare than sleep deprivation and the horse is otherwise normal. On sleep deprived horses, you will often find lesions on their front fetlocks – this is evidence that they have fallen and gotten back up. Sometimes this is your only evidence.
Here are a bunch of articles and some videos that will help identify sleep deprivation and help you and your vet work towards finding out why your horse is not getting enough sleep: By Dr. Karie Vander Werf
– https://thehorse.com/155696/six-types-of-sleep-deprivation-in-horses/
– https://thehorse.com/121155/understanding-equine-sleep-deprivation/
– https://thehorse.com/110342/the-otherwise-apparently-healthy-collapsing-horse/
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