Walking through the barn, you hear a dry cough coming from one of the stalled horses. This is not uncommon, particularly for horses cooped up inside in a barn. Many respiratory irritants abound in the indoor environment, including dust in hay, dust stirred up in bedding or in an adjacent arena, endotoxin released from manure, or ammonia fumes from urine-soaked bedding.

At the 2019 AAEP Convention, updates from the Havemeyer Equine Asthma Workshop held in May 2019 in Custer, South Dakota, were summarized in one of the sessions. Previous terminology of inflammatory airway disease (IAD), chronic obstructive pulmonary disease (COPD) and heaves are now lumped under one heading of “equine asthma.” The differentiation now relates to severity of the horse’s respiratory dysfunction, i.e. mild, moderate or severe.

Some pertinent points were discussed that have relevance to horse husbandry practices over which horse owners have control through stabling improvements in air quality. 

For example, organic dust contains mold, bacteria, endotoxin and plant parts, all of which are substances that impact respiratory health. Particles around 100 microns (the diameter of human hair is 50 microns) are problematic because this small size is easily inhaled into the lower airways. But even more problematic are the invisible particles that are primarily responsible for airway inflammation. 

All of these particles and the ensuing inflammatory response in the airways can have an impact on equine performance.