Recovery is widely seen as one of the most important factors in training an athlete – and it matters for horses just as much.
For all those who choose to work with horses in sport there is a responsibility to help them live happily and in a way that maximises their welfare.
One issue that has been repeatedly raised is of the overnight stable closure at shows – we got in touch with Linda Greening, senior lecturer at Hartpury College and a researcher into equine sleep to understand more about how sleep matters for horses.
How has our understanding of horses’ sleep evolved in recent years?
While many horse owners are aware of sleep, there is generally less understanding of its detail and nuances, such as how long horses sleep on average and which sleep stages they can achieve in different postures.
Equine sleep research has been published since the 1970s, but in recent years there has been a growing volume of research in this area.
Historically, the cost and resources required to use electroencephalography (EEG) in horses have been a barrier. Much of the more recent research has therefore relied on behavioural observations, which have improved our understanding of sleep patterns, although this approach can have limitations, for example, when distinguishing between drowsiness and standing sleep.
At the same time, EEG technology has advanced, enabling greater accuracy in sleep research. However, cost and time constraints remain, and studies often involve small sample sizes, making it more difficult to generalise findings.
As a result, although increased research activity has improved our knowledge of equine sleep, there are still many unknowns. Importantly, the information we do have needs to be more widely shared with horse owners.
What is the importance of REM sleep for horses, and why can this be hard to achieve for some horses? *Note - REM sleep is only possible when a horse lies down
REM sleep is crucial for all mammals and is described as essential for brain function, supporting learning, memory consolidation, emotional regulation, and neural plasticity.
In horses, REM sleep is also considered an important indicator of welfare, as its occurrence largely depends on the ability to achieve safe and sufficient recumbent rest.
Horses that struggle to lie down may do so for a variety of reasons, including injury or pain (particularly in older animals), anxiety associated with individual housing, or lack of comfort due to stable size or insufficient bedding.
In what conditions are horses most likely to achieve both REM sleep and proper rest?
Optimal conditions for sleep include:
• A familiar environment with familiar conspecifics (other horses they know)
• A housing environment with sufficient height and floor space to allow the horse to safely and comfortably move into and out of a recumbent posture, ideally enabling the neck and limbs to stretch fully
• A floor or bedding surface that is largely dust-free and deep enough to support transitions from standing to recumbency (rubber matting alone is not sufficient unless it is of hospital-grade quality)
• A defined light-dark cycle, with no disturbances from light or noise once lights are turned off
• An environment where the horse is not left anticipating feed, as this can promote head-over-door behaviour rather than recumbency and rest
'Circadian disruption' is when there is misalignment between a person's internal 24-hour biological clock and their external environment. Does evidence suggest horses experience circadian disruption when travelling across time zones, and if so, what can grooms do to help?
There is currently limited research specifically investigating circadian disruption in horses travelling across time zones.
However, evidence from other species suggests that exposure to light at appropriate times can help shift the body clock and support adaptation to a new time zone.
When travelling east, where earlier sleep is required, reducing exposure to bright light in the evening may be beneficial. When travelling west, where later sleep is needed, increased exposure to light later in the day may help.
While this guidance is primarily based on human research, supporting the circadian adjustment of grooms may indirectly benefit the horses in their care.
Thank you to Linda Greening for answering our questions, and helping us better understand the importance of sleep for horses' health and wellbeing.
