While horses can and do rest on the ground, the majority of a horse's rest is done while standing, for reasons described in our other article "Why do horses sleep standing up?"

To get into a deep REM sleep, horses do spend a brief amount of time laying down.

Horses often do lie down to rest for short periods of time if they feel comfortable doing so; they generally do not stay down for long periods of time, however, as their circulatory and respiratory systems are not designed for being on the ground. Horses that are stuck on the ground for some reason-- called being "cast", for example, their legs caught under a fence-- can suffer from brain damage or suffocation from lying down for too long. For more information, read "how to help a cast horse".

Horses are most often observed lying down during short periods of rest. Horses will lay down if they feel it is safe, for example if there are other horses standing around calmly. My own horses sometimes lay in the afternoon sun and take short naps.

Foals tend to lie down often, sleeping at their mother's feet during the day. As they grow older they will begin to sleep standing more often.

Other reasons for horses to lay down include disorders such as colic, in which a horse will lay down to try to stop the discomfort in their stomach, and may even roll or thrash the ground.
Horses suffering from founder may also lay down from the hoof pain, in addition to displaying other signs of lameness.

If you see your horse laying down, it's most likely taking a short nap. Horses don't sleep nearly as much as we do, and rely on short naps throughout the day to keep them going.