The official title for an all-too-common respiratory ailment in horses is chronic obstructive pulmonary disease (COPD). For the average horse owner, however, that rather cumbersome title has been reduced to a single word: heaves. Other people call it broken wind.

In this article, we’ll stick with the acronym COPD. While there is some debate about the primary cause, it is the general consensus that COPD is caused by an exposure to dust, molds, and other air pollutants.

The reason for debate about primary cause is the puzzling fact that two horses might share the same environment and feed supply, with one suffering from COPD and the other showing no signs of the malady. Does this mean that heredity is involved? That some horses are predisposed to COPD and others are not? Additional long-term research will be necessary before those questions are answered with certainty.

What is known is that dust and mold, particularly, can bring on an episode of COPD. It is also known that unless the environment and/or feeding program are changed, the condition can become permanent and compromise the horse’s ability to perform.

While there are some therapeutic approaches that can assist the horse with COPD, there is no cure. Nor is there a vaccine that can prevent COPD since it is a non-infectious disease.

Before we can discuss just what COPD is and how it functions in a horse, we first must understand how the equine respiratory system works.

The Respiratory System

Basically, the respiratory system for equines and other mammals functions to exchange oxygen and carbon dioxide. Oxygen enters the lungs during inspiration, and carbon dioxide exits with expiration. Oxygen is the fuel to be burned, and carbon dioxide is the exhaust to be removed.

Air enters through the nostrils, then passes through the nasal cavity. A horse differs from many mammals in tha