Humans have always considered sleep to be a vital part of life. Most people value having a good night's sleep of around 6-8 hours and perform poorly if they don't get sufficient resting time. Have we ever considered the effects of sleep on the performance and wellbeing of our horses?
Stages of sleep
Wakefulness
Wakefulness (AW) is the period during which a horse is fully awake and aware of the environment around him. They spend this time eating, playing, training or avoiding predators.
Total Sleep Time (TST)
Total Sleep Time is the portion of a 24-hour day that a horse spends asleep. Horses will experience 5 to 7 episodes of sleep of about 30 to 40 minutes each and is divided into two stages that will most likely occur at night between midnight and 4am:
Slow Wave Sleep (SWS)
During this sleeping stage, the horse's brain is not functioning at an active level, therefore it is also known as the "sleep of the brain". It is a shallow level of sleep that can be accomplished both standing up or lying in a sternal position.
Paradoxical Sleep (PS)
Throughout the PS, the horse will lie flatout, as they experience complete muscle relaxation with eye movement and closed lids. This stage is similar to the REM-sleep, during which dreaming will occur in humans. About 25% of Total Sleep Time is spent in Paradoxical Sleep.
Drowsiness
When a horse is resting indoors, they will be in a state of drowsiness about 8% of the time, as opposed to a horse resting indoors, who will achieve this state 13 to 14% of the time. However horses living outdoor will experience less SWS and PS than horses living indoor, this is to be related to survival factors.
Factors influencing sleep patterns
Familiarity with surroundings
Horses who are familiar with their surrounding will feel more comfortable and willing to indulge in sleep. This makes sense knowing that horses are prey animals that might feel exposed to predators in an unknown environment.
Peace and quiet
Studies have shown that the absence of sight and auditory stimuli result in an increase of Slow Wave Sleep and large increase of Paradoxical Sleep.
Travel
As stated previously, sleep deprivation can occur when horses are in an unfamiliar environment. This can be a problem for horses who travel often for competitions or other. Upon arrival at the horse's destination, it can be beneficial to be regularly checked up on by a familiar person. Companion animals, such as goats, chickens or pigs have been known to provide additional familiarity to horses and counter these sleep problems. However this might not be attainable in every situation, but stuffed animals have been admitted as alternatives.
Some horses might benefit from travelling to an event a few days early to allow them to recover from the sleep deprivation.
We can rule that sleep is just as important for horses as it is for humans. Although horses do not need as much of it as we do, they can experience sleep deprivation. Therefore, as horse carers, we must do everything in our power to try and diminish these effects.
