Obviously, we want to provide the best possible and most hygienic environment for both horses and humans – but that is not all: Molds in stables pose a serious threat to the health of horses. They are often relevant for respiratory diseases and can even have a toxic effect. Discover how the dangerous spores enter a stable, what health problems they can cause and how mold growth can be prevented. 

Read about the extent to which the use of rubber mats in looseboxes or lying areas with reduced bedding can contribute to mold prevention and how the microbial environment both on and beneath the mats is affected.

How do molds enter a horse stable?

Most of the time we are the ones responsible for bringing molds into the stable along with the bedding. Molds cannot be fully eliminated in hay either. When straw and hay are harvested, they are normally dried directly in the field. If the weather is bad or the next thunderstorm is on its way, the straw or hay is sometimes stored somewhat sooner, even before it is completely dry. A less-than-optimum drying process, which occurs frequently with herb-laden hay, creates an ideal breeding ground for molds. Yet no matter how much care is taken during feed and bedding production, it is impossible to fully avoid a certain amount of mold growth with this natural product.

Health hazards / Exposure to molds

Many horses are sensitive to "dust". We have all heard the telltale sound of a stable mate or our own horse coughing, trying to expel thick mucus from their irritated airways. In most cases, increased movement is not enough to facilitate mucus discharge, and regular inhalation or even drug treatment becomes necessary. What is sometimes referred to as an "allergy" is in fact a hypersensitivity reaction to molds and their spores. Molds, but also yeasts and other particles, can adhere to particles of dust and are, thus, easily transported. Specialists refer to such composite particles as "bioaerosols".

Some fungi also produce mycotoxins, toxic metabolic products that can be detrimental to horse health in the long term.

Ways to prevent mold growth

To minimize the negative health impacts of molds in a stable, many horse owners – especially those with more sensitive horses – use dedusted, cleaned shavings or other bedding materials for the loosebox or lying shed. To ensure the ground is comfortable at all times and to keep the required amount of the significantly more expensive bedding to a minimum, the looseboxes or lying sheds are equipped with rubber mats. As such, a thinner layer of bedding is sufficient to absorb moisture and to provide the horses with a layer of natural bedding. This also minimizes the workload required to clean the loosebox or lying area. The regular cleaning of surfaces, at least with a broom, reduces the amount of dust and, therefore, also molds in the stable. 

When using bedding, ensure that it is of high quality or use types of bedding that are less prone to mold growth. (Further criteria for choosing the "right" bedding may also be found here: Which bedding is the best for horses?) Appropriate storage can also help prevent mold growth.

It is also important to ensure that the hay or feed is a high-quality product. Storage is also a crucial factor here: All cereal-based feed should ideally be stored in a completely dry environment and protected against vermin. Old feed and feed residues must always be removed from containers before refilling them with new feed.

Bacterial load and mold growth both on and beneath loosebox mats

Horse owners are often unsure about the potential for germ proliferation, particularly molds, on the concrete floor, on the rubber mat or beneath the rubber mat due to the multi-layered floor structure (rubber mat on top of concrete) in the loosebox. Once installed in the stable, rubber mats are often no longer cleaned on most horse farms – at least not on their lower side. However, various studies have shown that there is no microbial environment for molds beneath the mats and that the bacterial load in a rubber mat system with reduced bedding tends to be lower overall than in looseboxes with conventional alternating bedding.

In-house testing has demonstrated that even after years of use, the lower sides of BELMONDO® mats display significantly less fungal contamination than the surfaces. Despite elevated levels of colonization on the surfaces, increased fungal growth was not detected beneath the rubber mats.

Three horse looseboxes with three different BELMONDO® mats were tested; all of the mats had been installed for more than ten years. The looseboxes were always swept clean and had been occupied until shortly before the sample was taken. Four swab samples were taken in each box: from a dry spot and a wet corner of the box and from the upper and lower sides of the mats. As a reference guide, three empty looseboxes (swept clean and without mats) were sampled; these looseboxes had been empty for several months or years. The samples were then analyzed by an ISO 17025-accredited specialist microbiology lab.1)

Even in damp areas, where a higher amount of mold is to be expected, the rubber mats keep the fungal load low.
While the surfaces, whether empty or covered with mats, show a higher concentration, the concentration of fungi and yeasts under the mats is significantly lower.
  • Very low incidence of fungi beneath the mats
  • Hardly any yeasts on the lower sides of the mats (two out of five samples)
  • No heightened fungal growth beneath the rubber mats despite colonization on all stable surfaces, both on the mats and in empty looseboxes (swept clean and without mats)

Studies carried out by Nürtingen-Geislingen University in 2013 on the bacterial load in horse looseboxes had shown that the rubber mat system with reduced bedding leads to a slight reduction in the bacterial load. Nürtingen-Geislingen University concluded from the measurement results that an installed rubber mat system actually improves stable hygiene due to the reduced amount of organic matter.

The comparison involved a conventional bedding system (concrete + 10 cm bedding) and an elastic rubber mat system with reduced bedding (3 cm rubber mat + 1 cm bedding). Germs, yeasts and molds were analyzed both on and beneath the mats. This led to the conclusion that a lower amount of organic matter in the bedding material tends to improve stable hygiene.2)

Summary: Mold prevention as the foundation for horse health

In conclusion, it can be stated that molds in horse stables can pose a risk to the health of your horses. Mold spores cannot be completely avoided in stables, as they enter the stable with the feed and bedding. Nevertheless, there are preventive measures that can be taken. By cleaning the stables at regular intervals, using high-quality bedding and feed and storing them correctly, it is possible to promote a healthy environment for your horses.

To keep the demand for high-quality and expensive bedding to a minimum, a solution combined with rubber mats in looseboxes or lying areas is also suitable.


1) Test report no. H 9952 of September 12, 2023

2) Prof. Dr. B. Benz et al. (2013): Weniger Einstreu bei gleichem Komfort. In: Pferde Zucht & Haltung 1/2013, S. 66ff 

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