Horses sleep standing up? And if they lie down, it means something’s wrong with them? Let’s have a look at sleep in horses to understand our equine friends’ needs properly.
by Rachele Malavasi
Many people believe horses sleep standing up – and there is some truth in that, but it isn’t the full story. Horses actually need to lie flat out (lateral recumbency) for a total of at least one hour out of every 24, which they normally do in 15-minute periods; they need to lie semi-flat (sternal recumbency, meaning they are on the ground but the head and neck are raised, the nose resting on the ground) for another 3 hours or so a day. Finally, they need to spend at least two hours just dozing, which they do standing up. This makes six hours of rest per day, and these periods are concentrated mainly between 8p.m. and 5a.m. (with widely differing seasonal variations).
Each sleep position is significant. While standing, horses are ready to flee at the first sign of danger, and thanks to a locking system in their joints they can rest standing up, but without overtiring their muscles. The sternum recumbent position prepares for the REM (Rapid Eye Movement) phase of sleep, which is the only position in which the neck muscles can rest fully from supporting the very heavy head.
The REM phase: full recumbency is fundamentally necessary
Getting sufficient REM sleep is absolutely basic: it is in this phase of sleep that dopamine is produced, and this creates a positive link between consolidation of memories, learning and psycho-physical wellbeing. The growth hormone GH is also produced in this phase – this hormone is indispensable for the growth of new tissues and the mobilisation of fats and glycogen for energy. Good REM sleep leads to the ability to sustain effort and good performance.
Horses can go without REM sleep for several days, but in the long run this can lead to undesirable consequences, such as when the horse will sway on its front legs and then collapse to the ground. If you notice grazes on a horse’s front fetlocks, this could indicate such a collapse; however, they could equally indicate something else, such as difficulty in getting up after lying down.
Narcolepsy is something entirely different. This is where the horse does not sway before collapsing but just drops, and this is caused by not passing through the pre-REM stage of slow-wave sleep. In general, it happens after a strong emotive event, positive or negative.
In order for a horse to relax into a deep sleep – a condition of vulnerability for a prey animal – it must feel safe, it must have adequate space, and a good surface to rest on. As we have seen in other articles, the four walls of a stable do not represent a safe place. Horses can get used to being in a stable, but it is still a small area where anyone can invade its personal space, where the horse cannot identify the origins of loud and worrying noises, and where perhaps artificial lighting disturbs the sleep-waking patterns. But even in more natural surroundings a horse can feel too unsafe to lie down – maybe there is a very aggressive member of the herd, or maybe s/he has been moved to a new place and just needs to get used to it: in such a case a horse can go for a month before feeling safe enough to lie down.
Obviously, there is no comparison between the two environments: both in the wild and in a more natural management system, sleep takes up 15-30% of a horse’s day, whereas in a stable this reduces to 7%. Recent research has shown that even just increasing stable size by at least 1.5 times (taking the size of the horse into consideration) can increase the percentage of lying-down time to that seen in natural management situations. Note that in natural management in hot weather, horses will need shady areas to rest in, where they are less likely to be attacked by insects, which is particularly relevant to dark-coloured horses.
Choice of bedding
Good bedding makes a difference, not just in sleep quality but also to general health. Factors to consider are: amount of dust in the bedding, the danger of endotoxins which might cause respiratory disease, convenience, and absorbency. 10-15 cm depth is the minimum, and less than 5cm is no better than none at all. No bedding at all, or rubber matting on its own, greatly reduce the tendency to lie down. Bedding is useful in a natural management setting, and essential in a stable, where over and above comfort, close attention has to be paid to ventilation, lack of which will increase the danger from dust and endotoxins. Thus, while a straw bed is among the most comfortable, much more so than shavings, wood pellets or peat, it can be one of the worst in terms of endotoxins. Shavings are the least comfortable for the horse, but contain 40% fewer species of endotoxin, especially if they are made from pine, which is also among the most absorbent. In any case the real difference in terms of bedding and respiratory problems lies in what the horse eats: concentrates (usually fed only a few times a day with resultant long periods of fasting) means a horse will maybe spend around 11.5% of its time with its nose in the bedding, hunting for dropped morsels of food, whereas this time is reduced to 1% if the main feed is forage, better still if hay is steamed first.
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OTHER ARTICLES BY RACHELE MALAVASI ON HORSE ETHOLOGY:
The five senses
The social life