Sleep Deprivation in Horses Part 2 of 2

Is your horse getting enough sleep?

by Dave Sauter, DVM

As noted in last month's article, sleep deprivation will occur in horses if they are either prevented from lying down or unwilling to do so. Unlike humans, horses take several days or even weeks to develop symptoms of sleep deprivation. Symptoms include:

Excessive daytime sleepiness
Collapsing episodes, especially during relaxing circumstances (e.g., during grooming, while resting in a standing position)
Unexplained wounds or scars, especially on the front of the front fetlocks and the front of the knee—these injuries are caused by the collapsing episodes

Long term videotaping can assist in the diagnosis. It can help document an absence of recumbent sleep patterns and unobserved collapsing episodes.

Sleep deprivation is not the same as narcolepsy. Narcolepsy in horses, as in people, is rare (although there is a familial narcolepsy documented in miniature horses). With narcolepsy there is a sudden onset of uncontrolled sleep, a “sleep attack,” with complete loss of muscle tone. Play and startle reflexes have been reported as triggering factors in narcoleptic horses.

As prey animals, feeling safe and secure is of paramount concern before horses will allow themselves to enter such a vulnerable state as REM sleep. The natural setting for sleep in horses occurs in established herds. Often the members of the herd will be in various stages of sleep. This ensures a “sentinel” that is relatively more alert is on guard for any potential threat. Since they only need about 30 minutes of REM sleep, herd mates take turns performing the sentinel duties so everyone gets their opportunity.

Causes of Equine Sleep Deprivation

There are many causes of sleep deprivation in horses. Dr. Joe Bertone, a veterinarian board certified in internal medicine, has published several papers on the topic. To help organize and facilitate the diagnosis and treatment of sleep deprivation, Dr. Bertone has divided the causes into three categories:

--Pain-related

There are three basic components necessary to get REM sleep: what it takes to lie down, comfort while lying down, and getting back up again. If there is pain related to one or more of these components and the horse repeatedly experiences the difficulty, eventually it will avoid the painful process altogether. Here are some examples:

1. The most common situation is some musculoskeletal problem or combination of problems such as arthritis or old injuries. This is especially the case in older horses whose bodies have suffered wear and tear over the years and are less able to compensate for their aches and pains.


2. Thoracic pain in a horse that has survived pleural pneumonia but has lingering adhesions in the chest cavity.


3. Abdominal pain from something such as an enterolith (mineral deposit in the large intestine).


4. Late term pregnancy making all three steps more difficult and uncomfortable.


5. Neurological disease—in this case, it may be the distress, inability and struggle associated with getting down and back up again that results in the sleep avoidance behavior.

--Environmental/situational

Any environmental or situational condition that compromises the sense of security and safeness necessary for proper sleep can cause sleep deprivation. Examples:

1. Prey issues—lone horses may feel unsafe on with no sentinel to watch out for them. Wildlife, loose dogs, etc., can contribute to this.


2. Hierarchy issues—horses on the bottom of the pecking order may constantly feel threatened by herd mates, especially bully horses. Horses on the top are also at risk if they are constantly on alert in less safe environments in efforts to protect the herd. Another example of this is when new horses are introduced.


3. Loss of a companion.


4. Rigorous show and travel schedule.


5. Other environmental issues, such as stabling conditions, mud, ice, weather, noise, and travel that interfere with the sense of familiarity, safety and comfort can also be causes of sleep deprivation or avoidance.

--Monotony-related

This pertains to a horse that spends long hours in a fairly relaxed and boring situation, such as on the cross ties. As with humans, horses need activity during their waking hours to promote quality sleep.

There is no standard treatment or medicine that can be prescribed to treat sleep deprivation. The solution, if there is one, lies in identifying the cause(s) and addressing them individually. Although they don’t need nearly as much as humans do, horses need their sleep to be healthy. If your horse shows symptoms of sleep deprivation or you have concerns, discuss them with your vet.