A recent study investigated the night time behaviour of horses stabled with a bedding of either straw or wood shavings. The researchers were particularly interested in how long the horses spent lying down, either with their feet tucked under them (sternal recumbency) or lying down flat (lateral recumbency).
Horses were observed between the hours of 10pm and 5.30am using time-lapse video recordings. Data was collected on lying down and rising behaviour, as well as the frequency and duration of periods spent lying down.
Most time spent lying down was the period from midnight until early morning. The most significant finding from this study was that the time spent lying down flat was 3 times longer for horses bedded on straw than for those bedded on shavings. There was no difference in the time spent in sternal recumbency between those horses bedded on straw and those on shavings.
Previous studies have shown that sleep can be divided into 2 stages, slow wave sleep (SWS) and paradoxial sleep (PS). Horses normally fall asleep while standing up and they enter SWS during which the muscles gradually relax. If the horse is feeling comfortable in its environment it will lie down in sternal recumbency and drift further into SWS with further relaxation of the muscles. The horse may then lie down flat to enter PS where the muscles are totally relaxed, that is, there is virtually no muscle tone. An important point about sleep cycles is that the horse must lie down flat to complete a sleeping cycle that includes PS. If a horse cannot, or choses not to lie down then it can rest in SWS but cannot achieve the total relaxation of PS. Paradoxial sleep is sometimes termed the sleep of the body because of the general muscular relaxation whereas SWS is known as the sleep of the mind.
Could less time spent in PS sleep for horses bedded on wood shavings have welfare or performance effects? This study indicates that horses bedded on straw are likely to be more well rested than those bedded on shavings and it would be interesting to determine whether this extra rest is of benefit to the horse.
Reference: GR Pedersen, E Sondergaard, and J Ladewig (2004) The influence of Bedding on the Time Horses Spend Recumbent, Journal of Equine Veterinary Science, Vol. 24, No. 4.
Findings from Other Studies Regarding Bedding
- When given the choice of straw or wood shavings as a bedding type, horses spend more time on straw.
- Horses appear to spend more time performing bedding-directed behaviours on straw and this seems to reduce boredom in stabled horses
- The use of beddings other than straw may increase the risk of abnormal behaviours such as weaving.
- Both straw and wood shavings are economical and easy to obtain.
- Horses may eat straw bedding which is not desirable.
- Wood shavings are good for minimising respiratory problems in horses, as straw can sometimes be dusty and contain fungal spores.
- Straw is generally warmer bedding than shavings because it traps air
Taken From USYD