The Dangers of Sleep Deprivation in Horses

The horses that collapsed had an altered and a very restless sleep profile – they spent notably less time in REM-sleep compared to those that did not collapse. Their REM sleep phases were shorter, they occurred while they were standing and in over 86 percent of cases were during, or immediately before the collapse.

Some of the horses in the study were not only suffering from physical issues but also from psychological problems. Stereotypic behaviours like weaving, cribbing, and box walking were present in 25 percent of the horses from the questionnaire. Of the examined horses, eight demonstrated altered behaviour after their collapses had begun – some became listless and others extremely anxious.

Two years after the assessments were made, seven horses from the study have been euthanized due to injuries or behavioural problems supposedly caused by the sleep deprivation.

Given the importance of sleep, it is clear that REM-sleep deprivation leads to behavioural changes and related collapses can cause severe injuries. Treatment for the condition should involve identifying the reason of the horse’s reluctance to lie down, treating any underlying medical conditions, and optimising their environment and management.

“We were amazed and shocked at how many horses seemed to suffer from these kinds of collapses,” says Fuchs. “Initially, we thought we might find 10 to 20 horses. To date, approximately 300 horse owners have contacted us and sought our advice.

It is amazing how easy it is to help some horses and how frustrating and difficult it can be to help others. The challenge is that every horse suffering from recumbent sleep deprivation is an individual and has its individual ‘reasons’ why it does not lie down. Horse owners need to be aware that the sleeping behaviour of horses is an important thing to consider. It is important to recognize the symptoms as soon as possible but prevention is essential.

“It was conspicuous that most horses seemed to have a problem after a change of stable. This is one thing we are looking at in a future study, especially the moving from a stable to an open communal barn. Open barns are obviously the most appropriate housing type for horses, but unfortunately, many of them have bad management and horses that were living in a stable for many years might not be able to cope with it.”

“It was great to see this important subject being researched,” says Janne Winther Christensen, Hon President of ISES. “Sleep is important for the welfare and performance of horses, and it would be very valuable to see more research on the various factors that influence sleep and sleep deprivation, for example, box sizes, flooring and bedding material, and the social environment. In nature, horses sleep within visual contact of each other and usually one horse remains standing whereas in the domestic environment, horses often sleep in single boxes with solid box walls where they are unable to see their neighbours while lying down.”