The Respiratory System
Comprised of the lungs and the air passages through which the horse breathes, the respiratory system is obviously vital to life. The respiratory health of the horse is greatly impacted by its surroundings and the quality of equine management. Horses that spend a lot of time locked in closed stalls are subject to respiratory problems caused by constantly breathing urine odors. Whenever a horse is exposed to lots of dust — from hay, indoor arenas, dusty oats, and so on — chronic respiratory problems can develop.
Perhaps the most commonly known respiratory ailment is heaves. Heaves is a chronic problem usually caused by dust and mold in the feed. Many horses that develop heaves either have their hay soaked in water before eating it or have to avoid hay all together and instead eat commercially prepared complete feeds. Heaves is sometimes likened to COPD, or chronic obstructive pulmonary disease, in humans. It can be serious enough to cause permanent lung damage and is therefore considered unsoundness in the horse.
It is often shocking but not uncommon to see a racehorse bleed from the nostrils after a race. This is caused by tiny blood vessels that rupture in the lung tissue, usually as a result of strenuous exercise and exertion, such as high-speed galloping. Horses with this tendency are called “bleeders.” In most cases, these nosebleeds are not serious and usually stop within a few minutes. Lasix (Furosemide) is a much-disputed drug used to control such bleeding in horses.