Similar to humans, horses need to be physically and emotionally comfortable to fall into deep sleep. Though they don’t require this deep sleep every night like humans do, their behavior and demeanor can change if they don’t get adequate rest.
Equine sleep has three distinct phases: it begins with the deep restfulness phase where the horse is relaxed, but easily roused; he can stand while in this phase. Next is slow-wave sleep where he is even more relaxed, but can still be standing. To enter the final sleep phase, paradoxical sleep, the horse must lie down. This phase of sleep is where a horse loses reflexed and muscle function; REM (rapid eye movement) occurs in this phase, as well. The horse’s brain is just as active in this phase as it is when the horse is awake.
Though people need two to three hours of paradoxical sleep each day, horses need only 30 to 60 minutes. Horses don’t have daily sleep cycles like humans, so they don’t need paradoxical sleep every day. They can typically only go between seven and 14 days without this type of sleep before becoming sleep deprived. A horse that desperately needs paradoxical sleep will begin having “sleep attacks” that may look similar to narcolepsy, but are not: Narcolepsy is where a horse has frequent, uncontrollable periods of deep sleep. It is a neurological problem typically brought on by stress, excitement or exercise.
Equine sleep deprivation can have physical causes, including pain. Some older horses may have difficulty lying down and getting up because their joints hurt. If a horse won’t lie down to roll, he is most often too painful to lie down to rest, as well. If a horse has enteroliths, stone-like formations in his colon, he may not lie down as the stones may press and pull on his colon, causing pain.
If the horse is uncomfortable in his environment he may be unwilling to lie down. He may be alone and fearful in his field, or he may feel unsafe as his herd is lacking a leader. Additionally, horses trying to enforce a specific pecking order in a herd may be too vigilant to sleep.
Three questions can be asked to help determine if a horse is having sleep issues:
- Has he rolled lately?
- Has his social situation changed?
- Is his environment noisy or somehow disturbing?
Read more at EQUUS magazine.
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