Sleep is vital to a horse’s mental and physical well-being. However, the horse’s sleeping habits are not something we tend to think about, but it is essential to understand as it can affect their behaviour as well as an early indication of a health issue. Much depends on whether the animal is living in a stable, out at grass, or is wild. It is a myth that horses only sleep standing up as to achieve proper REM sleep a horse must lay down.
Horses do not sleep if they feel uncomfortable or unsafe in their environment. In a herd situation, you may notice that some horses lie down while others stay standing up to keep watch. Noisy and busy yards create a problem for the modern horse as well as a stable that is too small for their size. A stressed or unhappy horse will not lay down and sleep.
Horse sleeping habits are very different to ours and are typical of a prey animal. Whereas humans need around seven or eight hours of uninterrupted sleep, the horses’ sleep cycle is polyphasic, meaning they sleep several times throughout the day and night. The reason for this is because the horse is vulnerable to predators and must be ready to flee immediately to avoid danger.
There are four different stages of sleep.
During wakefulness, the horse is conscious and spends much of his time eating, being ridden or out at grass. A wild horse goes in search of food and water and may travel vast distances.
Many stabled horses relieve their boredom through dozing. The head and neck droops, the lips go floppy, and the ears are relaxed with the eyes closed. Usually, a horse stands on three legs, resting a hind leg so he can kick out instantly at any potential predators. This position is known as “stay apparatus” in which a group of muscles, tendons and ligaments lock the knees and stifles to prevent the horse from collapsing.
The horse must attain slow wave sleep before reaching REM sleep. At this stage, the brain is no longer functioning. The horse either remains standing up or lays down in a sternal recumbency position with the legs tucked underneath, and the head and neck remaining upright, away from the ground.
To achieve REM sleep, or paradoxical sleep as it is also known, the horse lays in lateral recumbency, where he is flat out on his side. The muscles rest but the brain is nearly as active as when the horse is awake and often dreaming occurs with involuntary movements of the limbs, eyes, tail and muzzle.
Horses only sleep between two to four hours over 24 hours lasting for just a few minutes at a time. A considerable amount of time is spent dozing and around two hours in Slow Wave Sleep (SWS) split into four or five short bursts, with REM occurring in between these stages. Foals, like other young animals or humans, sleep longer than adult horses, lying flat out on their side. Due to the herd instinct, a mare never leaves a foal while it is sleeping.
A horse sleeps for approximately 45 minutes in REM sleep, which usually occurs for around twenty minutes at a time. Horses are unable to lay down for too long because their large size places pressure on their organs and prevents the blood flow to specific areas of the body risking reperfusion injury. Plus, it is difficult for a horse to get up quickly when lying down, making it hard to escape a predator. However, the length, type and quality of sleep is also affected by the weather if living outside, diet, age, health and workload as well as the surrounding environment.
A horse can go up to two weeks without REM sleep before it has an adverse effect. A horse who lives in the wild and part of a herd is probably able to sleep more than a domesticated horse as each member take turns looking out for each other so feel safer.
Symptoms of sleep deprivation in a horse are:
Reasons for sleep deprivation include:
A horse who lacks REM sleep may overreact to situations by being extremely alert and spooky becoming a challenge to handle, or he may appear lazy and lethargic. If you think your horse is suffering from sleep deprivation, you need to consider the cause so that he can have some much-needed kip. If your horse is stabled, ensure the area is large enough to lie down with plenty of clean and comfortable bedding. Move your horse away from a noisy environment or aggressive horse if he is in a herd situation. A horse who lives outside needs a dry area to rest, otherwise bring him inside.
A horse suffering from a physical or medical issue that makes him unable to lie down requires veterinary treatment. Some horses find travelling to and staying at show grounds extremely stressful, so it may be better to allow him to sleep at home and travel on the day of the competition if possible.
A horse who wants to sleep excessively is a cause for concern, especially during the day. It may be that the horse is not having enough REM sleep, is depressed, isolated or possibly suffering from a neurological disease or endocrine disorder. It is vital that you consult your veterinarian so that they can carry out the necessary tests on the horse.
Observing your horse’s sleeping habits is vital for good health and performance as well as his happiness.