How Does A Horse Sleep?

Horses are quite eloquently designed when it comes to sleep.

Sleep Mechanisms in the Horse

Stay Apparatus/Overview of Passive Stay Apparatus - Pelvic Limb - "The pelvic limb stay apparatus has three essential elements. The first element, the stifle joint locking mechanism, allows the weight of the caudal body to rest, essentially, on the locked joint. The second element, the reciprocal mechanism, ensures that the stifle and hock joints will move in unison, and the leg will move in a smooth, coordinated manner. The first and second elements work together. The third element involves other ligaments/tendons in the distal limb."

Stay Apparatus - University Penn.

When you hear the term stay apparatus it can seem confusing. Is it the front legs or the hind legs that have the stay apparatus? Or, do both the fore limbs and the hind limbs have this apparatus? What is it? The stay apparatus consists of both ligaments and tendons that stabilize the joints in the forelegs. Also, in the hind limbs lower joints the fetlocks and pasterns are stabilized. Sometimes the term "check apparatus" will be applied to the hind limbs."...Horses indeed sleep standing up. They use what's called "Equine Stay Apparatus", a system of tendons, ligaments and muscles in the horse's leg. The lower leg joints lock with assistance from the above and the suspensory apparatus.

These parts work together to keep the horse's legs in a standing, locked position. While your horse may appear to be awake, he is likely asleep enough to kick out at you if you were to approach him unexpectedly..." Does sleep affect a horse's behavior? Do they sleep standing up?

Note: Pictures of my horses coming soon. I have to take the images when I catch the horses napping. Thank you for your patience.

The check apparatus allows a horse to rest and relax without falling down. You may see horses with most of their weight on the forehand and one hind leg with the other hind leg cocked and the toe pointed. The hips are rotated and the stay function is activated. They will not look alert and their ears will be relaxed. The head, neck and sometimes lips may be drooped. Their eyes are closed. Some horses may snore or twitch. If lying down they may even move their legs as though they are running. Some horses do sleep stretched flat out on the ground. Some prefer to lie down at night some during the day. Many enjoy and seek out a sunny spot.

When horses sleep in the lying down position it puts a great amount of pressure on their internal organs. This is one reason a horse is down for only short periods of time. Also, of course, they are more vulnerable to predators in a down position. Sometimes horses will get "cast" and cannot get up. (Cast in this usage means stuck in a down position, unable to get up). If left that way for any long period of time a horse may die. It will be unable to breathe from the pressure of its body on the respiratory system. Most horses will lie down for a brief rest every day if they have a comfortable place to do so. They tend to sleep in packs with one horse always alert and standing guard--on the lookout for predators. Horses are awake the majority of hours in a 24-hour period. They take short periods of rest in a standing position. This light sleep in a twenty-four hour period may range from four hours to as much as fifteen hours. Lying down they may range from a few minutes to several hours. Diet, temperature, workload, gestation, health and gender all effect the amount of time a horse sleeps. Although individual to each horse, the period of each sleep phase is very brief, lasting only a few minutes at a time. In order to go into the REM sleep horses must lie down. Their REM (Rapid Eye Movement) sleep requirement is a few minutes to several hours. This is attained over a period of time, not all at once.

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