Why does my horse cough when he is ridden?

Q: I have a gelding in his late-20s. He is still sound and healthy, except that he coughs when he is ridden. He always does it when he trots or canters, and sometimes even just at the walk. Is there something I can do to help him?

A: Have your vet out for a visit. She will listen to your gelding’s lungs and upper airways, take his temperature, and listen to your horse cough when you ride him. A coughing older horse is a common complaint and can have a handful of causes, some of which need to be ruled out by your vet before starting him on any medication.

One cause for a coughing horse is recurrent airway obstruction (RAO), commonly known as heaves. Like an equine version of asthma, RAO is caused by inflammation within your horse’s airways, usually caused by environmental irritants. This inflammation constricts the airways, causing labored breathing and coughing. In extremely bad cases, a horse suffering from heaves is barely able to breathe even while standing still; flared nostrils and hypertrophy of abdominal muscles (called a heave line) are classic signs of severe heaves. Milder cases can present as a cough during exertion, such as exercise.

Another cause for coughing is allergies, especially if this is a seasonal problem. Excess dust, pollen, spores, or even humidity can sometimes cause older horses to develop “flare ups” in their respiratory system and develop a cough. Sometimes older animals, including horses, merely develop “old” lungs, meaning chronic fibrosis slowly develops, making their airways less elastic over time. An older immune system can also cause a build up of inflammatory cells and general “gunk” in the airways, leading to a chronic cough.

I am assuming this is a dry, non-productive cough and your gelding is otherwise healthy. If the cough is moist, and the horse is running a temperature, an infectious cause may need to be pursued, such as a minor upper respiratory infection. Simple bloodwork will differentiate between infectious and non-infectious causes. Other diagnostics such as a transtracheal wash, where cellular samples from the horse’s trachea are collected and examined, may also be used.

Treatment for your coughing gelding will depend greatly on what your veterinarian finds, but you can start by altering your horse’s environment by removing dust and other particulates, keeping your horse out on pasture as much as possible, and wetting his hay before feeding. Medical treatments depend on your vet’s physical exam findings and other diagnostics, but may, if needed, include a course of antihistamines or steroids to help decrease inflammation that may be deep in your horse’s airways, and bronchodilators, which help open up the airways, allowing as much oxygen in as possible.