A “roarer” is a horse that makes a whistling or rasping noise as it inhales during strenuous exercise. The noise, which may be only a whisper or a much louder sound, is heard when weak or damaged muscles around the horse’s larynx fail to pull the arytenoid cartilages out of the way of incoming air traveling through the trachea. The airway may be only slightly blocked if the sound is fairly mild, while a louder noise generally signals more significant blockage.

The exact cause of this muscle weakness is unknown in many cases of roaring, although injury, infection, or a neurological condition may sometimes contribute to the problem. Horses at rest or performing mild exercise can breathe fairly normally, but the compromised airway impacts strenuous exercise because the horse can’t get enough air into its lungs. Recovery time after exercise is also slower because of reduced airflow.

Surgery to pull the cartilage into a permanently open position is the preferred treatment for a roarer horse. Suturing the cartilage out of the way (laryngoplasty, often called tie-back surgery) is usually effective in restoring free airflow, but the problem may recur if the sutures tear out or the tissues stretch in response to muscle movement around the larynx. In a study at the New Bolton Center to examine the effectiveness of severing nerves near the larynx (neurectomy) to limit post-surgical muscle movement, researchers concluded that laryngoplasty alone was helpful in 50-60% of horses, with neurectomy not increasing this percentage.