Mare Has Trouble Breathing

She often seems to be having an asthma attack. What is causing this and can be done to cure it?

Q: I have a 13-year-old blue roan Paint mare. Recently she’s begun having problems breathing. Not all the time, but frequently she seems to be having an asthma attack. We’ve been giving her an allergy/cough medication on her feed, but she’s still not getting much better. Any suggestions?


A: The problem that looks most like asthma in horses is something called COPD or chronic obstructive pulmonary disease, also known as “heaves.” A variety of spores or dust can cause this problem, and it leads to constriction of the bronchi—the airways in the lungs. An alternative diagnosis, given your horse’s symptoms, would be a chronic, low-grade respiratory infection.

Classic cases of heaves typically are seen in horses closed up in barns where hay is stored above the stall and the animals have little access to fresh, circulating air.

Your veterinarian can make a diagnosis of heaves based on a physical exam. Affected horses often dilate their nostrils noticeably and/or have a “double expiratory” (a two-phased exhalation). They also typically show a characteristic line in their abdominal muscle, created by their extra breathing efforts. A further test that your vet may recommend—both to help confirm the diagnosis and rule out a chronic, low-grade infection—is taking a sample of fluid from the lungs for examination by a pathologist. A lung-fluid sample can be collected by passing a tube up your horse’s nose and down into her lungs, or by inserting a needle through her trachea and then passing a tiny tube inside the needle down into her lungs.

Management of heaves often includes moving the horse into a more ventilated environment, such as from stall to pasture or from an enclosed barn to one with a more open design. Sometimes a change in bedding, or using less bedding along with rubber mats, is beneficial as well. 

Medications may also help. The airway-dilating drug Ventipulmin works well in many horses. Others may respond to corticosteriods administered orally, through an inhaler, or via injections. The best way to manage a particular horse depends on the horse and the situation; your vet can determine what will be most beneficial for your mare.

If it were a different time of year, your vet would need to rule out a summertime variant of COPD that results when a horse develops an allergic response to airborne pollens. This condition is known as summer-pasture-associated pulmonary disease. Both forms of the disease are often referred to as recurrent airway obstruction, or RAO.


Veterinary Care for Horses

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