Sleep Requirements of HorsesBy Kentucky Equine Research Staff · April 19, 2017
Horses certainly can and do sleep standing up, but at some point all horses must lie down to achieve a full sleep cycle and avoid sleep deprivation. In horses managed in herd situations, a variety of factors impact which horses lie down and for how long, potentially limiting the availability of the much-needed shut-eye.
Although sleep requirements in horses remain largely unknown, some facts gleaned from various research groups include:
- Horses spend most of their time either eating, resting, or sleeping;
- Approximately 5-7 hours of each day is committed to resting behavior, with actual sleep usually occurring after midnight in the dark hours;
- Horses can rest and achieve certain types of sleep (e.g., slow-wave sleep) while standing; however, the rapid eye movement (REM) phase cannot be entered without recumbency due to loss of muscle tone during this phase; and
- In a 24-hour period, horses require a minimum of 30 minutes for recumbency to fulfill their REM sleep needs.
Unsuitable environmental conditions (e.g., lack of available space, weather), social insecurity (low standing on the pecking order), and physical complaints (musculoskeletal discomfort) all limit the ability of some horses to lie down. In turn, these horses can suffer REM deficiency and excessive drowsiness. Affected horses may transition into REM sleep while standing and partially collapse before suddenly waking up.
To better understand factors impacting the willingness or ability of horses to lie down, one research group recorded recumbency in groups of horses with and without access to soft, bedded areas. Horses without access to a bedded area (they had only hard black rubber mats) rarely laid down, and less than 30 minutes of REM sleep was measured. As the dimensions of the bedded area suitable for recumbency increased, horses spent more time lying down. When large bedded areas were available, low-ranking horses could lie down as much as high-ranking horses. In contrast, when the bedded area was smaller, competition was fiercer and low-ranking horses experienced “forcedly terminated lying bouts.”
Ensuring adequate room for all horses to lie comfortably for at least 30 minutes every day and addressing underlying medical causes for decreased recumbency, such as osteoarthritis (OA), improves the quality of life of group-managed horses and minimizes welfare issues.
“Joint supplements that contain glucosamine and chondroitin sulfate, hyaluronic acid, and omega-3 fatty acids all support healthy joints. These types of products lubricate the joints and help decrease discomfort and inflammation associated with OA, potentially making it easier for horses to become recumbent and more easily stand after REM sleep,” advised Kathleen Crandell, Ph.D., a nutritionist for Kentucky Equine Research (KER).
Overweight horses may also find it difficult to lie down and rise from lying down, potentially limiting REM sleep. Be sure to maintain your horses in appropriate body condition.
*Burla, J.B., C. Rufener, I. Bachmann, et al. 2017. Space allowance of the littered area affects lying behavior in group-housed horses. Frontiers in Veterinary Science. 4:23.