The role of bedding for stabled horses….
Dr David Marlin
Comfort and Rest
Some owners pay little attention to bedding seeing it as just as an essential for keeping a horse partly or fully stabled. However bedding has at least four different and important roles to play for the stabled horse. One of the most important roles and perhaps one that is often forgotten is that bedding should provide a comfortable surface for horses to lie down on. Whilst we know that horses can and do often sleep standing up, studies of horses time budgets show that they spend a considerable amount of time lying down, both when at pasture and stabled. And a number of studies have shown that the type of bedding can influence how much time a horse will spend lying down. Encouraging horses to lie down is important for all stabled horses and ponies but particularly for injured or sick animals, young animals and those in work. Another feature of a bedding that may impact on how willing and for how long horses will lie on it is its ”sharpness”. Some beddings may have very sharp components which can cause discomfort, for example some larger woodchip beddings and some natural plant materials. Certain types of bedding can be prone to sticking to horses, for example small size shavings, making frequent grooming a necessity. Finally, beddings made from certain types of wood or treated with mould inhibitors or disinfectants can also lead to allergic skin reactions.
Air Quality & Respiratory Health
Many studies have shown that respiratory disease is common in horses and ponies and is usually the second most common reason for a vet to be called to see an animal after lameness. The true prevalence of respiratory disease in horses is also underestimated as horses and ponies can often have respiratory disease that the owner is not aware of as there are no outward signs. In veterinary terms these are referred to as clinical signs and include things such as cough, nasal discharge or increased respiratory (breathing) rate or increased effort. If a horse or pony does show outward signs of respiratory disease then if they have a veterinary investigation, which usually involves use of an endoscope (tube with a camera on) to look inside the lungs and collect samples of fluid for cell analysis and bacterial culture, then 9 times out of 10 respiratory disease will be confirmed. However, if they do not show any outward signs then we unfortunately cannot be sure they have a healthy respiratory system. For example, a study in Switzerland of 60 showjumpers and 50 dressage horses all competing, not showing any outward signs of respiratory disease and all considered to be healthy by their owners found that when they were examined by a vet, over half of them had respiratory disease which required treatment. There are two important reasons why horse owners should pay particular attention to respiratory health. Firstly, in trained horses, the respiratory system is the main limiting factor. Secondly, whilst all other systems generally get stronger and better with training, the respiratory system does not change with training and increased fitness. Therefore even low level respiratory disease and damage to the lungs can have a marked negative effect on performance.
From an owners perspective it’s clear that bedding serves to absorb urine. Some beddings are able to absorb urine better than others. For example, in one study it was found that shavings absorbed around 2/3rds more urine than straw. Using a highly absorbent bedding is advantageous for several reasons. Firstly, it prevents the horse from getting wet from lying in voided urine and if the bedding is highly absorbent it makes it easier to remove soiled bedding and urine from the stable. This is particularly important in stables where the floor is not sealed, as in most stables; even concrete floors are permeable to urine. One of the problems with urine in stables is that the protein in it is broken down by bacteria in both the bedding and on the floor releasing ammonia. Ammonia is a respiratory irritant and a good rule of thumb is that if you can smell ammonia then this is at a level that will cause irritation of the respiratory tract. Urine that makes contact with porous floors will result in production of both ammonia but will also encourage the growth of even more bacteria leading to a reduction in air quality. Bacterial toxins, referred to as endotoxin can also lead to development of allergic respiratory disease (as opposed to ammonia which leads to irritation rather than allergic reactions). Bacterial growth and ammonia production are related to the hygienic status of both the bedding and the flooring. Sealed non-porous rubber floors that are effectively cleaned 2-3 times per month combined with highly absorbent bedding material with low bacterial counts and removal of soiled bedding several times a day combined with good ventilation is likely to yield near perfect air quality. Conversely, bedding material with a high bacterial load which is poorly absorbent and used over porous floors with poor ventilation are likely to result in very poor air quality. Thus, where air quality is already compromised due to poor ventilation and porous flooring, using a good quality hygienic, absorbent and low dust bedding is essential to maintain respiratory health.
A number of studies have shown a relationship between the amount of respirable dust and respiratory disease in stabled horses. Respirable dust, defined as dust 5-10 microns (um), is dust that gets down into the deepest parts of the lungs and stays there causing allergic and or irritant reactions with the production of mucus and accumulation of inflammatory white blood cells; commonly cells known as neutrophils. Dust smaller than 5 micron in diameter is so small and light that it gets breathed in but doesn’t have time to “settle out” in the lung and so gets breathed out again. Larger dust particles (bigger than 10 micron) are filtered out in the nostrils. When it comes to dust in bedding, straw has had some bad press. However, some studies have shown that low quality wood shavings (usually the type that are a by product of the wood industry rather than shavings manufactured specifically for horse bedding) can have 5 times as much dust and bacterial endotoxin as a good quality straw bedding. Similarly, mould content can vary considerably between different types of beddings. Again, the mould counts in poor quality wood shavings may be considerably higher than in good quality straw and some beddings such as cardboard have been reported to be very low in moulds.
The amount of dust in a bedding is therefore clearly an important feature in terms of a horses respiratory health. However, whilst many beddings are marketed as “low dust” or even “dust free” there is currently no standard by which the consumer can judge what this means. A further confounding issue is that many beddings may be low in dust before packaging, but the process of packing and compressing the bedding for distribution can generate dust which stays within the packaging. Another significant issue is that whilst a bedding may be low in dust at the time of processing and packing, significant dust may be generated in use as the bedding is broken up by movement of the horse over it in the stable.
Of course there is little point in using good quality bedding if you are going to spoil the air quality by using dusty forage. Even good hay may have around 50 times as much dust as good haylage. There are a number of options when it comes to low dust and high hygienic quality forage. The first is to use haylage which will have a considerably lower level of respirable dust (containing moulds spores, bacteria and dust) than dry hay. The second option is to soak the hay before use but this has an impact on the mineral, vitamin and water soluble carbohydrate (sugar and therefore energy) content of the hay. It can also be time consuming and messy although the water soluble carbohydrate reduction is good for managing horses that are overweight, good doers or prone to laminitis. A third option is to consider investing in a hay steamer. Steaming improves the hygienic quality dramatically, is quick and convenient but also preserves the nutritional content of the hay. When it comes to hard feed, there is also the potential for dust with bacteria and moulds to be inhaled, especially as the horse eats with its head in the feed bucket very close to the feed. For example, rolled grains may have dust levels several hundred times higher than a molassed feed. Pelleted feeds, molassed feeds and oiled feeds are generally lower in dust but any dry feed can have a small amount of water added to it at the time of feeding which will dramatically reduce the amount of dust the horse is likely to breathe in whilst eating.
Insulation from cold
Stable floors can be very cold in winter, particularly stone floors, concrete floors and earth floors. An important function of bedding is to act as insulation and reduce the rate at which the horse loses heat when it lays down. The transfer of heat between the horse and the floor is by a process referred to as conduction and is the fastest mechanism by which heat can be lost. This is particularly important for younger and older animals, for sick animals, for animals with low bodyfat or for animals that struggle to maintain weight during colder weather. The colder the floor, the more heat that will be lost when the horse lies down. In order to maintain condition the horse will then need to use up heat to keep warm. If the amount of heat lost in keeping warm or thermoregulating is greater than that being fed then over time the horse will lose weight. Thus, a bedding that helps to insulate the horse from the floor is advantageous. Contrary to what we might immediately think, its not the material that is necessarily important but more its ability to trap air within the bedding as its the latter which affords the best insulation.
Aesthetics – how does it look?
A feature of beddings that may be important to some users is the look. For example, paper was at one time a popular bedding for use where a low dust environment was required, such as in Thoroughbred racing yards and competition yards. However, unnatural and “clinical” paper beds, whilst low in dust, came nowhere near the same aesthetic appeal as a nice straw or shavings bed. Yards using paper also often looked “untidy” as it was impossible to control the spread of paper around the yard. The same problem often applies with small and light shavings. In the 1980’s a rubber company wanted to develop a new concept in horse bedding for a recycled rubber waste product. They came up with giant yellow “spaghetti” which was put down in the stable, taken out weekly, loaded into a giant sieve and steam cleaned before being put back. Zero dust, but unfortunately totally rejected by the grooms that had to work with it! Natural looking beddings seem to have a higher level of aesthetic appeal to horse owners.
Economics & Ease of use
For many owners another feature they will consider when choosing a bedding material is the ease of use of a bedding which will also relate to how cost effective it is. Beddings that take a long time to manage on a daily basis and or where there is a high level of wastage due to difficulty in removing only the minimal amount of soiled bedding are likely to be both time consuming and expensive and therefore less attractive.
Foot & Skin health
Any material that is in close and or prolonged contact with the feet has the potential to cause drying and or infection. The most common foot infections is thrush which typically develops in the frog and Mud Fever is common around the lower parts of the legs and affects the skin. One study showed that the amount of Fusobacterium necrophorum growth on the frog, a bacteria associated with thrush in horses feet, was similar in shavings and paper and around twice as high as when horses were stabled on straw. Similarly, a different study showed that that the risk of horses developing Mud Fever as a result of Dermatophilus congolensis infection varied with different beddings. Finally, bedding material also has also been shown to influence hoof growth rate, with horses maintained on deep litter having a slower growth rate than horses on straw, dust-extracted chopped straw or shavings.
Protection from hard floors
Rarely in the wild do horses stand on solid surfaces for 24h a day 365 days a year. In deserts horses stand n sand which can be both compacted and hard and soft. In temperate climates horses may stand on hard ground for some of the Summer and softer ground in the Winter. Thus, it is unnatural for horses to stand on very hard surfaces for long periods of time and this can adversely affect hoof health. Hard floors may also increase the risk of horses injuring themselves in the stable, particularly as they lie down, rest or roll and stand up. A good bedding can help reduce the risk of slipping or hard contacts with the floor surface.
The environmental aspects of bedding materials are becoming of increasing importance and this is likely to continue. An average horse may produce up to 10,000kg of manure and waste bedding a year. The ability of different bedding materials to be composted, which is an environmentally friendly option for disposal as opposed to landfill, has been studied. One study found that sawdust actually composted more readily than paper or straw. Some of the factors that were suggested to influence composting were porosity, oxygen supply (i.e. air spaces) and microbial activity.
Clearly there are many factors involved in choosing a bedding. In a study carried out by student Hannah Cooper at Hadlow College in 2007, a range of different beddings were evaluated. She reported that no single bedding came top in all the categories of tests. She also identified that there was a high degree of “personal preference” amongst horse owners when it came to choosing bedding and whilst many owners acknowledged that straw was not a particularly good bedding for horses, “cost” was the major factor identified as to why owners did not switch to something more suitable. She concluded that “there is a need for a bedding that is good for the horse but is affordable and easily maintained”.