Horse Illustrated Magazine

Q: I have an 11-year-old mare that was diagnosed with heaves about a year ago. The vet prescribed some granules, but I can’t get her to eat them no matter what it is mixed in. I have tried molasses, grain mixes, grass, hay, and flax seed. I was wondering if you could tell me more about heaves and if there were other remedies I should try.

A: Heaves, also known as recurrent airway obstruction (RAO), is a common respiratory condition in horses that causes constriction of the airways, resulting in heavy, labored breathing (heaving), and coughing.  Very similar to asthma in humans, this condition is a chronic disease that is usually managed with medication and environmental changes rather than treated.  Heaves in horses can vary from mild occurrences that are triggered by season to extremely severe flare-ups, resulting in breathing so labored that the horse loses weight and develops a “heave line”, which is the excessive muscular development along the barrel of the horse’s chest.

Heaves begins as an allergic reaction to something in the horse’s environment that he has inhaled.  This usually involves mold or dust from poor quality forage, but can also be due to poorly ventilated barns and even un-identified allergens out in the pasture.  Like humans with allergies, some horses only develop reactions against a single allergen and others are highly allergic to multiple culprits.

This allergic reaction in the horse’s respiratory system causes inflammation and constriction along the airways which result in coughing, harsh lung sounds, and heavy breathing with flared nostrils.  Most horses with heaves are relatively straightforward to diagnose by a veterinarian on the farm, as the dry, harsh cough and history of heavy breathing are usually typical for the condition.  However, if you were to admit your horse to a veterinary hospital, internal medicine specialists would likely examine the horse with an endoscope (a narrow camera that can be placed down the trachea) and observe highly irritated airways congested with inflammatory white blood cells and mucus. 

Once the diagnosis of heaves has been made, as it has in your mare’s case, management of the condition must start immediately to prevent the condition from worsening.  The key point in successfully managing heaves, since its basis is allergy-dependent, is environmental management.  The more you can reduce your horse’s exposure to excessive dust, mold, and other air pollutants, the better.  This means try to keep your horse outside as much as possible.  Even the cleanest, most well-ventilated stalls have a much higher concentration of dust, ammonia, and other things than the pasture.  Good old-fashioned fresh air is the best thing for your horse (whether she has heaves or not!).  Other environmental management tips for horses with heaves include soaking hay to help reduce dust and feeding the hay from a hay net, so the horse doesn’t have to rummage around the ground next to the bedding.  Also, if possible, store hay and straw far away from your horse’s stall, ideally in another building altogether.  Keep windows and doors open as much as possible, even in the winter months. 

Most times, a horse with heaves will need medication at least at the time of diagnosis.  The reason for this is that simply improving the air quality will not decrease the airway constriction and inflammation in a timely manner.  For these clinical signs, anti-inflammatories and bronchodilators are commonly used medications.  Unfortunately, inflammation along the respiratory tract tends to warrant the use of fairly strong anti-inflammatory agents such as steroids, rather than the more innocuous non-steroidal anti-inflammatories (NSAIDs) such as phenylbutazone (bute) and flunixin meglumine (Banamine).  The granules you describe are most likely an antihistamine.  This also acts to help decrease inflammation, but again, isn’t as strong as a steroid such as dexamethasone or prednisone, especially if you mare isn’t eating any of it!  Depending on how severe your mare’s condition is, it may be worth it to have your vet out again to re-examine her and possibly prescribe a regimen of tapered doses of steroid along with a bronchodilator, which can be given as an oral liquid in a syringe.  Some cases of heaves are severe enough that medications given orally or IV aren’t powerful enough to reach the lungs in high concentrations.  When this is the case, inhalers made specifically for horses are used.

Many people think once a horse has heaves, her productive life is over.  This is not necessarily true, but the prognosis is greatly reliant on the severity of the disease.  If the condition is relatively mild and easily controlled by environmental management and occasional medications for flare-ups, horses with heaves can still be ridden, with the understanding that there may be some times of the year (such as dry, dusty summer months, or periods of heavy pollen count) that heavy working may not be possible.  Further discussions with your veterinarian will help you design a plan specifically tailored for your mare’s needs.

— Anna O’Brien

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