Veterinary advice should be sought before applying any treatment or vaccine.


Recurrent Airway Obstruction, Chronic Obstructive Pulmonary Disease

Equine heaves (also called recurrent airway obstruction (RAO)) is a common chronic inflammatory disease that affects adult horses in temperate climates. It is characterized by recurrent episodes of severe breathing difficulties that leads to poor quality of life, early retirement, and euthanasia. There is no cure for the disease, and the goals for treatment are aimed at improving lung function and inducing clinical remission. Current treatment strategies include the use of corticosteroids, bronchodilators, and decreased antigen exposure (reduced exposure to dust from barn conditions, feed, bedding, and stored hay).

RAO shares many similarities to asthma in humans. RAO-affected horses develop marked airway obstruction as a result of bronchospasm, inflammation, accumulation of mucus and remodelling. Clinical signs demonstrated in horses with RAO include coughing and difficulty breathing, triggered by hypersensitivity reactions to irritants and allergens in their environment.

Environmental risk factors are similar to those seen in humans with asthma, which include indoor and outdoor allergens (mites, pollens, dust, endotoxins, mold spores, mycotoxins) and irritants like lipopolysaccharides (LPS). Horses with RAO tend to be extra sensitive to exposure of dust and molds commonly found in stored hay. Noxious fumes and high humidity can also act as triggers.

The severity of airway obstruction, inflammation, and associated symptoms can vary widely among horses. Recent studies confirmed that the plasma cortisol concentration in the horse increases concurrently with the development of acute exacerbation of RAO. In RAO, haptoglobin is a marker of both acute and chronic systemic inflammation, whereas high concentrations of SAA indicate acute inflammation.


Wheezing, crackles, or tracheal rattles
Severe coughing (especially when exercised)
Nasal discharge
Flared nostrils
Weight loss
Exercise intolerance
Abnormal or difficulty breathing at rest
Abdominal heave line


  • History
  • Clinical signs
  • Physical exam
  • Bronchoalveolar lavage fluid (BALF)
  • Endoscopy
  • Ultrasound
  • Radiographs


Minimize exposure to dustWet hay thoroughly (different then soaking), switch to low-dust feed, increase pasture turnout, switch to low-dust bedding, maximize air flow through barn and ventilation
Nasal oxygen
Omega-3 polyunsaturated fatty acid (PUFA)) supplementationContaining 1.5-3 g docosahexaenoic acid (DHA) for 2 months provides an additional benefit to a low-dust diet


  • Reduce exposure to dust and molds and time spent in the stall.
  • Use a low dust bedding material
  • Maximize turnout outside
  • Feed square hay bales instead of round hay bales
  • Don't sweep barn aisles while horses are inside
  • Design barns with good ventilation
  • Regularly test air quality levels in barns
  • Never feed moldy hay to horses


Good if changes in management occur and the horse is less exposed to dusty environments

Scientific Research References

Good Overviews

Clinical Trials

  • Flaring nostrils icon

Age Range

It is most frequently seen in middle-aged to older adult horses (age 7 and older).

Risk Factors

  • Limited turnout
  • Exposure to dust
  • Horses with prior history of a respiratory infection early in life