Vital slumbers

A horse’s sleep patterns vary from our own, but their need for sufficient rest is the same. Rebecca Hamilton-Fletcher MRCVS explains equine sleep behaviour

- Rebecca Hamilton-Fletcher

MOST people recognise the benefits of a good night’s rest. It is therefore surprising that sleep is rarely raised as a welfare concern in horses, and there is little information available to owners on how best to ensure their horse is getting enough of it, in terms of both quantity and quality.

Sleep patterns differ between living species according to a range of biological and environmental factors, and it’s necessary to understand the basis of the equine sleep profile in order to maximise its potential.

Horses are “polyphasic sleepers”, engaging in multiple relatively short sleep episodes of around 20 to 40 minutes each, totalling approximately four hours, across each 24-hour period. This is considered a necessary adaptation by prey species for increased vigilance and survival. Each individual will have its own routine in preparation for sleep, usually involving circling or yawning, which progresses to a period of drowsiness – or quiet wakefulness – before eventually entering the sleep cycle itself.

Studies using electroencephalogram (EEG) profiling of brainwave activity, plus polysomnography, have shown that each sleep cycle can be broken into two primary interchanging states, the relative proportions of which are unique to each individual:

Non-rapid eye movement (NREM), or slow-wave sleep, constitutes more than 80% of daily sleep needs, and can be further subdivided into four categories. The horse remains standing, enabled by its unique stifle-locking mechanism, with a lowered poll and drooping, steady eyelids.