Horse health and hygiene in the stable environment

On behalf of BEDMAX, Becky Windell, MSc Applied Equine Science, discusses the health and hygiene risks of the stable environment.

Whilst stabling is a common requirement for at least part of the year for most horses, not all stable environments accommodate a horse’s physiological needs.

Primarily stables often have unnaturally high dust levels and poor hygiene that can overwhelm the horse’s respiratory system leading to respiratory disease, allergies, and poor performance in horses. Improving air quality in stables is crucial for both equine and human health.

Air Quality

Air quality refers to how clean the air is, specifically to what extent harmful substances such as dust, gas (ammonia) and microorganisms are present.

Dust particles accumulate from a variety of sources, but mostly from the environment and management practices within the stable. The dust varies in size, with airborne respirable dust (less than 5 µm) being the most problematic as the smaller the particle, the deeper it can travel into the respiratory tract. Respirable particles are so small you can’t see them and have a 50% chance of being inhaled deep into the lungs.

Equine Asthma, an occupational disease

The number one risk factor for Equine Asthma is the environment.

Equine Asthma (EA) is a non-infectious respiratory condition triggered by inhaled allergens like dust, moulds, and pollen. It causes airway inflammation, thickening of airway linings, increased mucus production, and bronchoconstriction (airway narrowing). Symptoms range from mild poor performance to severe respiratory distress which needs medical intervention.

…Good news is it can be reversible when you manage the environment.

Dust Sources - Bedding

When you look at a stable, what is the main contributor to the space? Bedding.

The type of bedding used has a huge influence on the amount and type of dust produced. Straw is the biggest offender, and while straw quality can vary, even the best quality straw contains high concentrations of mould spores, bacteria and other respirable particles. Therefore, if straw is used as the bedding, then poorer air quality in the stable will result. Research found 1.5 times more respirable particles when horses were bedded on straw instead of sawdust. Another study showed horses bedded on straw had a 90% increased chance of having fungal elements in their airways and double the chance of being diagnosed with Inflammatory Airway Disease (IAD) (now referred to as mild Equine Asthma).

The same research showed horses bedded on wood shavings had a 40% reduced chance of having fungal elements in their airways and 30% reduced odds of being diagnosed with IAD in comparison to horses on other bedding types.

“In our study, straw bedding and dry hay feeding represented significant risk factors for IAD and for the presence of fungal elements in equine airways. Their use cannot be recommended in performance horses. Fungal spores naturally contaminate hay and straw during harvest. The storage of hay and straw can also lead to an exponential increase in fungal proliferation within the batches. The degree of contamination and proliferation is directly related to harvesting practices, initial levels of soil contamination, as well as storage conditions. On the contrary, wood shavings decreased the risk of IAD and the detection of fungal particles in the airways. This bedding type seems to be an appropriate solution to maintain equine respiratory health.” Dauvillier et al.

Wood shavings represent one of the most effective low-dust options available and can be further enhanced by selecting an appropriate wood species, optimal flake size, and suitable pre-use treatment to optimise hygiene.

Fresh Pine Shavings

It is well documented that pine has antibacterial properties. Literature suggests that stabling horses on pine-based bedding products can lead to improvements in equine health, particularly in terms of foot and respiratory well-being. These benefits may be attributed to pine’s pathogen-resisting properties.

A German research team confirmed the antibacterial effect of pine by inoculating wood chips of pine, spruce, larch, maple, beech, oak and poplar and analysing the survival of the bacteria. The bacteria had the lowest survival rate on pine compared with the other woods and even plastic.

Further research supports these findings, demonstrating that shavings derived from two types of pine trees showed significantly reduced levels of bacterial growth in laboratory conditions compared with spruce shavings, hemp, and straw. According to the studies conducted by Yarnell et al., pine shavings also display superior absorbency, with three times the absorbency of hemp and straw. Crucially, pine shavings not only absorb more urine initially but continue to do so for up to 24 hours, whereas other bedding materials, such as hemp and straw, reach their absorption limit after just eight hours.

This absorbency trait is hugely beneficial to hoof health. Continuous exposure from urine-soaked bedding can damage hoof keratin, causing cracks and weakening the horn structure, while also increasing hoof alkalinity and the risk of bacterial infections.

Flake Size

Large flakes minimise dust and allow urine to drain efficiently which helps keep the surface bedding dry and minimises ammonia levels.

Dust Extraction and Treatment

Thoroughly extracting dust from wood shavings before packaging leads to a reduction of dust entering the stable.

Drying the flakes at high temperatures to optimise moisture content, kill mould and bacteria will result in a hygienically clean bed.

Ammonia

The pungent gas ammonia is the result of the breakdown of urea (from urine) by bacteria found in bedding and the stable environment. (Side note: This is why the classic bad odour is worse in stables with straw compared to shavings as there is more bacteria in straw beds.)

Ammonia harms the mucous membranes of the eyes, nose and throat. It is a potent respiratory irritant that also heightens horses’ sensitivity to allergens like mould spores.

Dust Sources - Forage

Dry hay similarly to straw brings a huge amount of respirable dust into the stable so choosing a low-dust forage option is essential. Research has shown high temperature steaming hay/haylage prior to feeding will significantly reduce the airborne respirable dust burden.

How forage is fed is also important with evidence suggesting feeding from a haynet generates significantly more airborne respirable dust in a horse’s breathing zone compared to feeding from the ground.

Dust Sources - Organic Matter

Organic matter contributes to dust levels in stables so general housekeeping, removing cobwebs (which also indicate poor ventilation) minimising what loose hair and mud enter the stable by grooming the horse outside and being mindful of additional dust generating activities (sweeping or worse still leaf blowers on the yard). Research has demonstrated that stables located near the trainers’ office exhibit the highest levels of dust, which was attributed to increased activity in that area.

Ventilation

Replacing stale air with fresh air is the process of ventilation. It’s important to keep doors, windows, and vents open whenever possible to promote airflow.

Horse owners could also consider installing roof ridge vents and side eave vents to create a chimney effect.

Activity and Neighbours

Clements and Pirie found that cleaning stables caused a 19-fold rise in respirable particulates, with a 9-fold increase in adjacent shared-airspace stables. Daytime total and respirable particulate levels were almost twice those recorded overnight, regardless of management system, highlighting the effect of barn activity on particulate exposure. This is supported by Auger and Moore-Colyer’s work who found neighbouring stables contributed to dust levels in the stable when the same air space is shared.

Horse owners can seek to improve the stable environment and subsequent health and of their horses by considering air quality through stable design, ventilation, bedding and forage choices. Providing a clean, airy, comfortable and safe environment helps aid rest and recovery after exercise, promoting health and performance.