Equine Heaves is a condition that is characterized by inflamed airways in the trachea, bronchi and lungs. This can lead to a number of associated symptoms such as chronic coughing, excess mucous, poor performance and weight loss.

This condition also goes by several other names, including Recurrent Airway Obstruction (RAO), Equine Asthma, Equine Chronic Obstructive Pulmonary Disease, and Inflammatory Airway Disease (IAD).

Heaves is the most common respiratory condition affecting horses. Symptoms typically begin to appear around 9 to 12 years of age and both genders are equally affected.

Episodes of intense symptoms including severe cough and laboured breathing can last several days or weeks. These are often triggered by environmental allergens, most commonly due to prolonged exposure to dusty or moldy hay. This condition can also arise when horses are on pasture in hot, humid climates.

Heaves cannot be cured, but it can often be managed by controlling the horse’s environment. If needed, medications can be used to reduce inflammation in the lungs. [1]

Nutritional supplementation to support the immune system and respiratory health can also be beneficial for reducing symptoms.

What is Heaves?

Heaves is a chronic respiratory condition that is estimated to affect up to 20% of adult horses. [17]

It appears to be the result of an allergic reaction to inhaled environmental allergens which are usually found in hay, straw, or stall bedding.

When a horse inhales an allergen, an allergic reaction causes the airways in the lung tissue to narrow and become obstructed. [2]

Over time, this can affect the horse’s airways in three main ways:

  • Inflammation and thickening of tissue
  • Contraction of the smooth muscles surrounding the airways
  • Mucous accumulation

Consequences of Heaves in Horses

Due to the obstruction of the small airways in the lungs, horses with heaves must exert more effort to inhale and exhale. This increased respiratory effort forces the horse to use its abdominal muscles more.

Over time, this exertion can result in a visible ‘heave line‘ in the abdominal muscles, from an increased inspiratory effort. This is where the common name for the condition comes from.

As the disease progresses, horses may develop emphysema, irreversible lung damage, and permanent loss of lung function. Bacteria can also become trapped in the airways, leading to pneumonia – an infection of the air sacs.

Though researchers aren’t exactly sure how horses develop heaves all the time, they do know that the condition is similar to asthma in humans. Research has shown a link between dust exposure and heaves. [3]

The key to successfully managing horses with heaves is early diagnosis and vigilance of your horse’s environment and diet.

You can submit your horse’s diet for a free evaluation by our equine nutritionists. We can help you develop a nutritional plan that is appropriate for your horse and management situation.

Heaves is an allergen-induced respiratory condition that causes horses to exert greater effort when breathing. This can result in a ‘heave line‘ in the abdomen and lung damage.


Pasture-Related Heaves

Pasture-related heaves is also known as summer pasture-associated obstructive pulmonary disease (SPAOPD). It is most common in the southeastern United States where horses are frequently grazing in hot, humid weather.

This condition presents with identical symptoms to hay or barn-associated heaves. However, the symptoms appear when the horse is on pasture during the warmer months of the year.

Appropriate management for these horses will differ from that of horses suffering from hay or barn-associated heaves. For SPAOPD horses, removal from pasture during the summer months is best. They will also need to be kept in a low-dust environment.

As with hay or barn-associated heaves, researchers aren’t completely clear on what induces SPAOPD. A hypersensitivity to inhaled pollens or outdoor molds is suspected to trigger these horses, but air pollution may play a part as well. [7] Recently, a fungal component has been proposed as another mechanism contributing to the initiation of the disease. [18]

The most common clinical feature of SPAOPD is labored breathing (dyspnoea), which can be severe in some horses. This is characterized by an exaggerated and prolonged exhale with persistent nostril dilation.

These horses will have the characteristic heave line associated with laboured breathing. Chronic coughing and nasal discharge are usually present as well and horses with a severe condition may develop significant weight loss. [7]