Chronic Obstructive Pulmonary Disease

Chronic Obstructive Pulmonary Disease (COPD), also known as heaves, and broken wind is a lung disease caused by allergic reaction to fungi found in hay and straw. When horses are confined to stalls, they are exposed to airborne irritants at much higher concentrations than those encountered at pasture.22, 87 Multiple studies have demonstrated that the concentrations of such particulate matter and endotoxin are heavily influenced by management practices within the barn, including feed and bedding used, activity within the barn, and barn characteristics. Though hay is considered a mainstay of conventional feeding programs, its use is associated with increased particulate matter exposures because of release of insect, fungal, and plant fragments as well as inorganic dust from even the best quality hay. Choice of bedding material also impacts endotoxin and particulate exposures within the stall. Respirable endotoxin concentrations measured at the breathing zone of horses bedded on straw were found to be roughly 1.5 times those measured while horses were bedded on sawdust.1

Chronic Obstructive Pulmonary Disease (COPD), also known as heaves, broken wind, alveolar emphysema and equine asthma, is a chronic respiratory condition caused by development of a narrow airway in the horse's lungs. It is caused by an allergic reaction to fungal infections. The condition is mostly seen in stabled horses and is associated with a dusty atmosphere and mold in hay and straw. Micropolyspora faeni (which causes farmer's lung in man and cattle) and Aspergillus fumigatus fungus appear to be the cause of COPD in most cases.

The disease affects horses of two years old and above, becoming more common as horses get older. Early signs may include mild cough, slight increase in respiratory rate and effort, thick yellow mucous, and exercise intolerance. Heaves-affected horses have normal temperature and appetite. An affected horse may show signs as rapidly as one hour after exposure, with the horse becoming increasingly breathless. Removal of the offending material allows most cases to improve gradually over a few days.

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The allergic reaction brings about serious changes in the lungs. These include inflammation of the very small airways, production of excessive, thick mucous and spasm of the airways which may result in their complete collapse. This makes exhalation difficult and an increased volume of air is retained in the lungs which have an overinflated appearance.

Three young horses

The changes in the lungs are reversible with a proper care, but once a horse becomes affected with heaves, it remains hypersensitive for many years if not for life.

The most important thing in treating heaves-affected horse is to provide minimum-dust environment together with medical therapy, if necessary. Use substitues for hay and straw. Bedding should be changed on a daily basis. The stable should be at least at least 70 yards to the windward side of the hay store, according to the direction of the prevailing wind. Dust should be removed from the stables on a regular basis.


  1. Investigating the Link between Particulate Exposure and Airway Inflammation in the Horse. K.M. Ivester,corresponding author, L.L. Cou√ętil, and N.J. Zimmerman

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