Summer Pasture-Associated Heaves

Most horse owners have heard of heaves, an asthma-like condition caused by irritation of the respiratory system when dust and mold spores are inhaled. Heaves is most often found in horses that spend a lot of time in stalls, where they come in contact with fine particles contained in hay.

Combined with irritating ammonia fumes from wet bedding, these particles cause tissues in the respiratory passages to swell, making it more difficult for horses to breathe. The name “heaves” comes from the audible wheeze and contraction of the horse’s flank as it struggles to move air out of its lungs.

Horses with heaves usually have a normal body temperature and may show a thin, clear nasal discharge. Some heavey horses exhibit worse signs in winter when they are confined to the barn, improving when they are turned out in milder weather.

Summer pasture-associated heaves, on the other hand, affects turned-out horses that are sensitive to pollens and molds found in pastures. Signs of illness are the same between the two conditions, but the triggering factor is different. These horses may be more comfortable if they are kept indoors during the warmer seasons.

A nutritional supplement that has gained widespread attention in the fight against heaves is omega-3 fatty acids, which have well-known anti-inflammatory properties. Fish oils are direct sources of DHA and EPA, which are the most useful omega-3 fatty acids in terms of conferring health benefits. Other oils may contain ALA, which must then be converted to DHA and EPA, a complicated and inefficient process. For optimal omega-3 supplementation, use a marine-derived source such as EO-3.

Owners should contact a veterinarian for a diagnosis and treatment program if their horses have trouble breathing or become exercise intolerant during any season of the year.