How bedding thickness affects the sleeping and resting behavior of horses – Master’s Thesis summary
The importance of the well-being of horses has been emphasized in recent years, and various parameters are being developed to measure it. While the impact of sleep on the well-being and health of humans is well-known, there is still relatively little research on equine sleep. Although it is understood that during sleep the body and tissues recover and regenerate, the comprehensive significance of sleep for various animal species, including horses and humans, is still unclear. Researchers are contemplating whether the brain is the only organ that requires sleep for recovery, while other tissues are believed to be able to recover solely through rest.
Equine Sleep
Primarily, horses rest while standing and go through sleep cycles while lying down whenever possible. Equine sleep can be roughly divided into non-REM and REM sleep. Horses can sleep partly also while standing up. However, they must lie down for REM sleep, because REM sleep requires complete muscle relaxation, known as muscle atony. Sleeping while standing is made possible by horses’ exceptional ability to lock their hind knee, which allows them to maintain a stable standing posture with minimal muscle effort. Despite the ability to sleep in a non-REM state while standing, horses generally prefer to lie down.
Equine sleep is easily disrupted, and many external factors, such as temperature, environment, living conditions, the age of the horse, and bedding choice, can affect it. As prey animals, horses only lie down in an environment they can trust. Horses may delay lying down and achieving REM sleep for weeks if they do not feel safe. This is important to consider during long-distance travel or clinic visits, as postponing REM sleep may have negative effects on horses’ recovery and well-being.
Horses require only a few minutes of REM sleep per day, but to achieve it, a horse must be lying down for at least 30 minutes daily. A lack of REM sleep quickly leads to sleep deprivation, which can cause fatigue, learning difficulties, and excessive drowsiness. In severe cases, horses may collapse or experience sudden physical breakdowns. To recover from sleep deprivation, horses sleep more frequently and for longer periods.
Research
The Faculty of Veterinary Medicine at the University of Helsinki is collaborating with the Finnish Horse Knowledge Center Suomen Hevostietokeskus and the Nord University in Norway on several studies related to equine sleep as part of the UNIHEPO research project. The purpose of the first study was to investigate how the sleep and rest behavior of horses change with different thicknesses of bedding in stall conditions. As part of this study, a master’s thesis in animal sciences titled “The effect of bedding softness on the sleeping and resting behavior of horses” was conducted, and it will be published in its entirety in the spring of 2024. A summary of the work is now available.
For the mentioned study, a bedding experiment was conducted at Ylä-Savo Vocational College in Hingunniemi in the autumn of 2022. During the experiment, the behavior of 16 horses was recorded on 5 cm and 15 cm thick beddings. There were two consecutive test periods, each lasting for 21 days, and peat was used as the bedding material. Video footage from both periods was analyzed, focusing on the first two and last two nights of each period. The number of different behavioral episodes were counted based on the analysis and the duration of these behaviors was measured.
Results
Horses can sleep either with their chest on the ground, with their neck and head either tense or relaxed, or they can sleep on their sides, lying completely on one side with their neck and head relaxed. According to the results, horses slept for longer periods on their chest on the thicker bedding, and they also had longer periods of their neck and head being relaxed, indicating a sleep state. On thicker bedding, horses were also observed to have longer periods of overall resting behavior when all the lying episodes and their durations were combined.
Horses slept on their sides equally often with both bedding thicknesses. However, horses spent longer periods on their sides on the thicker bedding, although this difference was not statistically significant. Somewhat surprisingly, it was observed that horses rolled after lying down almost exclusively on thicker bedding. This behavior was rarely observed with thin bedding. The connection between rolling behavior and bedding thickness should be further investigated.
These initial research findings provide valuable additional information about the factors affecting the sleep and rest behavior of horses. Horse sleep is a multifaceted phenomenon influenced by many factors. Based on the results, optimal conditions for horse sleep and rest behavior require a sufficiently thick bedding layer in the stall. A sufficiently soft bedding surface is an important part of equine welfare.
