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Home 9 Health & Science 9 What is the air quality influence on the racehorses’s performance and health?

Air quality influences the development of respiratory disorders. The respiratory system can be irritated, infected, and affected by dust, mold, germs, and ammonia. This can weaken the natural defenses of the respiratory system. These problems, which can be deadly, restrict horses’ performance and put their health in danger.

Minor daily adjustments can have a favorable influence on the health of an active horse. To lower horses’ possible danger, severity, and respiratory illnesses duration, thorough environmental management is required.

We have studied several studies regarding the environment’s influence, and we want to address the following question: what effect does air quality have on the racehorse’s health? First, we’ll go through several factors that determine air quality. Then, discuss their significance as well as potential remedies.

Ensuring efficient ventilation in the stable

Moisture, allergens, dust: what are the ventilation challenges?

Stable design and management are critical in reducing dust, noxious gases, and infectious agents, as well as their dilution in the air.

It is feasible to limit horses’ exposure to potential allergens. Buildings should be well-insulated, have enough of air volume, and isolate each horse as much as possible.

Respirable dust is the portion of airborne particles that enter the peripheral airways. It is mostly found in the horse’s nostrils. The respirable dust concentrations in stables vary from 0.15 to 9.28 mg/m3, with a maximum suggested value of 0.23 mg/m3. Dust appears to increase the incidence and severity of respiratory disorders such as chronic obstructive pulmonary disease (COPD) and the spread of other infections.

The horse also generates a significant amount of heat and water. Moisture condensation forms on the walls, floor, and ceiling as a result of poor ventilation. The regular infusion of fresh air raises oxygen levels, eliminates mold and mildew, and improves air quality.

How to improve air quality?

The different openings in the inside living spaces (windows, doors, etc.) provide natural ventilation. An effective air distribution system can help to remove excess heat and humidity. It limits pollutant loads and drafts, as seen in the graph below. The stale air (previously “used” essentially dirty air) rises to make the new air warmer and less dense. Thermal thrust is the name given to this phenomenon.

air quality

Source : IFCE

The air should be renewed 4 to 8 times each hour in the winter to provide thermal and sanitary comfort.

Here are some more simple pointers:

  • Allow horses to get enough fresh air by keeping them outside as much as possible or bringing them out regularly.
  • Encourage a sturdy structure that maximizes air exchange.
  • Reduce dust by keeping feed and bedding in properly constructed facilities (preferably 50 meters away from the stalls), as they produce dust whenever we manipulate them.
  • Clean the stables daily and, if feasible, remove the horses from the stalls while cleaning.
  • Because blowers scatter small particles in the air, they should be used sparingly (very painful for the horse when they settle deep in the respiratory tract).

Providing a suitable atmosphere for racehorses

The presence of an animal in a building raises the temperature tenfold and causes humidity. This combination fosters a favorable habitat for bacteria and molds (such as fungi). These bacteria can cause infections in the respiratory tract and on the skin, and in the gut.

The humidity impact

On average, a horse produces more than 8 liters of water per day, just for sweating.

Humidity plays a role in the survival, development, and virulence of pathogens. High humidity can lead to odor problems, pathogen development, mold, condensation, and rust.

It contains not only water but also micro-organisms such as ammonia. An accumulation of ammonia can affect the performance and vitality of the horse.

It is possible to measure the moisture content with a hydrometer. A level below 70% is better to limit the growth of pathogenic contaminants.

The temperature role

Temperature affects bedding, spores, and bacterial growth.

Horses’ temperature comfort zone is far lower than that of humans. The ideal temperature range should be between 5 and 28°C. Outside of this range, they must give the energy to cool or heat up. Owners should also avoid temperature changes.

Do not neglect the importance of bedding 

The litter importance

Food and trash are dust contributors. Poorly kept bedding can be a source of moisture and hazardous gases (CO2 or NH3 ammonia). These particles and gases can cause long-term lung damage. Similarly, dirt raises the likelihood of rotting hooves or skin diseases, and consuming contaminated straw increases the likelihood of ulceration. Finally, hay is an important source of tiny fungus spores (reproductive cells of fungi) found in stable air. If the bedding is not changed regularly, these spores can permeate it and grow.

A clean stall not only decreases respiratory issues, but also helps the horse’s overall health.

Limit ammonia levels

Ammonia is produced by horses’ urine (the average horse excretes 8 to 10 liters per day) and feces. The EPA (Environmental Protection Agency) advises individuals not to be exposed to levels higher than 1.4 ppm (parts per million).

The average stable ammonia level predominantly affects the horse’s upper respiratory system. If you can smell ammonia in the barn (typically around 20/30 PPM or more), it is already beyond the acceptable level for optimum air quality. Ammonia skips the upper airway in more significant amounts. It induces lower airway irritation and pulmonary edema at concentrations exceeding 500 ppm. The most extreme exposures, which cause pulmonary edema, can be deadly.

An NH3 gas detector may be used to test ammonia levels accurately. It is preferable to position the device in the horse’s respiratory zone.

Which litter to choose?

It is better to choose your litter with care. There are different alternatives on the market. There are two main parameters: the respirable dust produced and the viable spores concentration.

Limiting respirable dust from the litter

Research published in the Journal of equine veterinary science in 2008 by Fleming K., Hessel E.F., and Van den Weghe H.F.A. sought to discover the best appropriate bedding to provide a healthier environment for horses.

The TEOM 1400a gravimetric analyzer was used to quantify the concentrations of airborne particles identified in the presence of various materials. The outcomes are as follows:

Litter type Average particle generation
Straw pellets between 111,2 and 149,2 mg/m 3
Wheat straw between 227,5 and 280,8 mg/m 3
Wood shavings between140,9 and 141,9 mg/m 3

According to these figures, straw pellets seem to be more suitable because they improve the stable climate in terms of airborne particle formation. A second laboratory experiment, also measuring hemp and flax, showed that these two materials have the highest airborne particle generation for all fractions.
In conclusion, straw pellets seem to contribute to stable climate improvement.

A second study by Vandenput S., Istasse L., Nicks B., and Lekeux P., published in the Veterinary Quarterly in 1997, investigated the quality of different types of bedding.

Dust particles were counted and sized with an optical particle counter, the Rion KC-01B, in different types of litter in the laboratory. The results are as follows:

Litter type

Respirable dust (in particles/liter of air)

Wood shavings

31 492 ± 12 910

Good straw

11 571 ± 4 897

Flax straw

9 251 ± 1 776

This study found that of all the bedding materials studied, wood shavings, even though specifically for horses, released significantly more respirable particles than most of the other materials. There was no significant difference between good quality straw and flax straw.

Viable spore concentrations

This same study measured the viable airborne particles number in the same materials. The experience tested the three allergens incriminated in COPD: A. fumigants, F. rectivigula, and T. vulgaris. The researchers used an Andersen sampler and an appropriate nutrient medium. The following are the results regarding the presence of these allergens:

Litter type


((in colony forming units (CFU)/42.45 L of air)

F. rectivirgula (in colony forming units (CFU)/42.45 L of air)

T. vulgaris

(in colony forming units (CFU)/42.45 L of air))

Wood shavings

710 ± 124

53 ± 29

79 ± 59

Good straw

402 ± 214

18 ± 17

33 ± 17

Flax straw

104 ± 23

10 ± 9

60 ± 13

 The values collected for wood shavings do not differ significantly from those for good straw. A. fumigants and F. rectivigula concentration are lower for flax straw litter than for the other sources. However, these measurements took place in the laboratory. So, they do not represent the variations in humidity and temperature present in the stables.

A delicate choice

The values collected for wood shavings are not considerably different from those contained for excellent straw. The concentrations of A. fumigants and F. rectivigula in flax straw litter are lower than in the other sources. These measurements, however, were conducted in a laboratory. As a result, they do not accurately replicate the fluctuations in humidity and temperature found in stables.

Finally, the litter selection is still sensitive. Owners should utilize highly absorbent materials while decreasing the concentration of dust particles and live spores. Commercial wood shavings are probably of higher quality, albeit they might be dustier than expected at times. Straw quality is challenging to measure and very changeable, mainly owing to storage conditions. More research is needed to discover which sort of bedding is best. Alternative materials, however, are available to decrease dust and allergies in the near horse area.

Contamination risks linked to the hay presence

Respiratory problems caused by fungi

The most common causes of respiratory difficulties are fungi and mycotoxins (especially the pathogenic fungus: Aspergillus Fumigatus, mentioned earlier in this article). Infections caused by fungi in the respiratory system can be infectious, poisonous, allergic, or all three.

Hay, haylage, straw, and oats are the most significant sources of this fungus. It is a storage fungus that spreads in foods that have been stored in excess or with a moisture level of morea than 14%. When the fungus contaminates feed or bedding, the horse has no alternative but to breathe in these dangerous spores into the stable. The fungus also causes immunosuppression, which is frequently a prelude to subsequent bacterial and viral infections.

qualité de l'air

Hay is a significant source of respirable dust and contaminants (bacteria and molds). Indeed, it was harvested and dried in the fields. As a result,  dust and particles (such as molds, bacteria, and parasites) naturally contaminate it, especially during humid and rainy summers.

Disinfecting hay

Hay should be stored carefully to limit the spread of harmful agents. Ideally, you should sanitize it as well to make it safer for the horse. It is possible to accomplish this by following the steps below:

  • Make use of probiotics. The probiotics increase in the water and consume little bacteria and fungus particles. You can combine them with the hay-soaking water. A 15- to 20-minute soak is plenty (when hay is soaked in water for an extended period, it loses some of its sugars). Furthermore, scientific investigations have shown that soaking hay in clean water for more than 30 minutes significantly raises its bacterial colony level.
  • Use a hay sprayer with a high temperature. It’s the most efficient way. It kills all bacteria, fungus, and viruses while retaining the nutritious characteristics of the hay, which is especially good for horses suffering from chronic lung illness or respiratory inflammation.

Furthermore, finding the most natural technique to provide hay to the horse is critical. One alternative is to feed on the floor, but this must be done in a hygienic environment. There are benefits to offering the hay in a hay net or slow feeder. It allows you to analyze the amount supplied objectively, allows the horse to eat slowly with little nibbles in a natural position (which is healthy for the stomach), and, most importantly, keeps the hay clean.

Alternatives to hay include alfalfa pellets, mixed concentrates, and whole grain. The prior study also included an examination of horse nutrition. It finds grass silages and alfalfa pellets to be suitable feed sources with low dust and allergy levels.


Horses are athletes and require a competitive respiratory system to enhance their performance. Forms of equine asthma and bleeding are respiratory concerns that are significant reasons for racehorses’ poor performance.

More and more practitioners and owners are realizing that strict control of the horse’s environment is necessary to decrease the potential risk, severity, and duration of respiratory diseases. Good air quality in the stables daily will be less costly in time and money than taking the horse to the veterinarian. Indeed, it is easier to prevent problems than to solve them.

 Several approaches can be taken to improve the air quality for horses in barns. Stable design and management are essential to minimize and dilute emissions of dust, noxious gases, and infectious agents (high air exchange, uniform temperature, and healthy atmosphere), but attention should also be paid to horse feed and bedding, which are the significant sources of dust and allergens in stables.

Keywords: air quality, stable management, dust, ammonia, hay, bedding, feed, temperature, moisture, performance, health