Dr. Melissa Mazan from the Tufts Cummings School of Veterinary Medicine in Massachusetts indicates 80% of stabled horses show evidence of inflammation in their airways. Also, a recent study at the school indicates that at least 25% of stabled horses show signs of inflammatory airway disease, such as coughing or exercise intolerance. Most of the time these symptoms are blamed on viral or bacterial diseases or allergies. However, even the cleanest of barns have large amounts of organic dust, including endotoxins and molds, that can lead to inflammatory airway disease and poor performance. People working in dusty areas like poultry barns have been shown to have a higher incidence of airway disease and asthma than people not exposed to this environment, even when there is only 0.3 mg dust per cubic meter. It has been shown that clean horse barns with good ventilation have three times that amount of organic dust in the air or about 1 mg dust per cubic meter. The reason these numbers are important is that when a horse is eating hay, the amount of dust can be as high as 12 mg per cubic meter, and some indoor riding arenas have levels as high as 60 mg dust per cubic meter. And we wonder why our horses cough all the time! All of these little particles cause significant inflammation in the lungs.
So what can you do to control this dust? First of all, you can wet down the barn aisle before sweeping and water indoor arenas before riding. Also, keep horses out of the stalls for 2 hours after the stalls have been cleaned to let the dust settle. Always keep horses outside rather than in the barn as much as possible.