Bit & Bridle

Equine COPD & Heaves

Other Names

  • Heaves
  • Broken Wind
  • Recurrent Airway Obstruction (RAO)
  • Equine Asthma (current preferred umbrella term)
  • Severe Equine Asthma (SEA)

What is Heaves (Equine COPD) in Horses?

Heaves — formally known as severe equine asthma (SEA) or recurrent airway obstruction (RAO) — is a chronic, non-infectious inflammatory disease of the lower airways. It is the most clinically significant form of equine asthma, characterised by bronchospasm, mucus accumulation, and airway remodelling triggered by hypersensitivity to inhaled environmental allergens, particularly fungal spores and organic dusts found in hay and stable bedding.

The condition closely parallels human asthma in its mechanism, presentation, and treatment approach. Like asthma, it cannot be cured but can be very effectively managed. Without appropriate management — primarily environmental — affected horses will experience progressively worsening respiratory function and, eventually, irreversible structural changes to the airways and lung tissue.

The term “equine asthma” has been adopted by the equine respiratory community to encompass the full spectrum of lower airway inflammatory disease in horses, from mild to severe. Heaves/RAO represents the severe end of this spectrum.

What Causes Heaves in Horses?

Heaves is an allergic/hypersensitivity disease. Affected horses develop an exaggerated inflammatory response to specific airborne allergens, particularly:

  • Fungal spores: The most significant trigger. Aspergillus, Alternaria, Cladosporium, and Faenia rectivirgula (which thrives in mouldy hay) are common culprits. Even hay that looks and smells normal can have very high fungal spore counts.
  • Organic dusts and endotoxins: Particles from hay, straw bedding, and concentrated feeds contain bacterial endotoxins and other inflammatory stimulants.
  • Storage mite antigens: Mites found in stored hay and bedding contribute to allergic sensitisation.
  • Barn dust: The complex mixture of airborne particles in traditional stabling environments — even without obvious mould — can trigger airways in sensitised horses.

Chronic low-grade airway inflammation (mild/moderate equine asthma, previously called inflammatory airway disease or IAD) can precede the development of full heaves in some horses, particularly performance horses with subclinical airway inflammation affecting their athletic capacity.

Genetic Factors

There is a clear genetic component to heaves. Studies have shown familial clustering, and certain genetic markers have been associated with RAO susceptibility. The condition is not caused by poor stable management per se — some horses develop RAO despite excellent conditions — but management is the primary modifiable factor.

Signs and Symptoms

In the UK, heaves typically worsens in winter (when horses spend more time stabled on hay and straw) and improves dramatically when horses are turned out to pasture.

Mild to Moderate Episodes

  • Intermittent dry cough, particularly at the start of exercise or when entering the stable
  • Slightly increased respiratory effort at rest
  • Mild nasal discharge (clear to slightly cloudy)
  • Slight reduction in exercise tolerance

Established or Severe Disease

  • Laboured breathing at rest: Both the rate and effort of breathing increase. The horse appears to work harder to breathe.
  • Flared nostrils: The nostrils dilate to try to increase airflow.
  • Double expiratory effort (heave line): The characteristic clinical sign that gives the disease its common name. The horse develops a muscular ridge running from the flank to the anus (the “heave line” or “heave groove”) from chronic over-use of abdominal muscles to force air out of stiffened, obstructed lungs.
  • Persistent cough: Often with a characteristic thick mucoid discharge.
  • Exercise intolerance: Even mild exercise becomes distressing. Severely affected horses cannot be worked.
  • Wheezing and abnormal lung sounds: Audible wheezes, crackles, and prolonged expiratory sounds on auscultation (listening with a stethoscope).
  • Barrel chest: In chronic severe cases, the chest may become visibly over-inflated due to air trapping.

Diagnosis

  • Clinical examination: History and clinical signs — particularly the heave line and double-expiratory effort in a stabled horse — are often sufficient for provisional diagnosis.
  • Lung auscultation: Your vet will listen to the lungs at rest and after re-breathing (use of a plastic bag over the nostrils to increase respiratory effort). Abnormal sounds confirm lower airway disease.
  • Bronchoalveolar lavage (BAL): Fluid collected from the airways and examined cytologically confirms eosinophilic and neutrophilic inflammation characteristic of equine asthma. This is the gold standard for definitive diagnosis and differentiation from infectious respiratory disease.
  • Endoscopy: Allows visualisation of airway mucus and airway inflammation.
  • Response to treatment: Many horses show dramatic improvement when moved to pasture or when environmental management is improved — this is strongly suggestive of heaves in an appropriate clinical context.

Treatment

Environmental Management (The Most Important Treatment)

Without addressing the horse’s environment, all other treatments offer only temporary relief. The allergenic load must be reduced:

  • Move to pasture: For many horses, full-time turnout on pasture produces dramatic improvement within days. This is the most powerful environmental intervention available.
  • Switch from hay to haylage: Haylage (fermented forage wrapped at higher moisture content) has vastly lower fungal spore counts than dry hay. This often transforms respiratory health in affected horses stabled in winter.
  • Soak or steam hay: If hay must be fed, soaking it (30–60 minutes in fresh water) or steaming (using a hay steamer — which kills spores more effectively than soaking) significantly reduces spore content.
  • Replace straw bedding: Use dust-extracted shavings, paper bedding, or rubber matting. Straw is a major source of fungal spores.
  • Maximise ventilation: Stable design and management must prioritise airflow. Remove horses during mucking-out and hay feeding. Avoid adjacent hay/straw storage in the stable block. Open doors and windows.
  • Feed from the ground: Position hay at ground level rather than in a haynet — this reduces inhalation of particles into the lower airways.

Bronchodilators

Clenbuterol (Ventipulmin syrup or granules) is a beta-2 agonist licensed for horses in the UK. It relaxes bronchial smooth muscle and rapidly improves airflow. It is most useful as adjunctive treatment in horses with significant bronchospasm, in combination with — not instead of — environmental management and steroids. Overuse of bronchodilators without addressing the underlying inflammation can mask disease progression.

Corticosteroids

For moderate to severe disease, or when environmental management is insufficient, corticosteroids are highly effective at reducing airway inflammation:

  • Inhaled corticosteroids: Beclomethasone or fluticasone administered via a specially adapted equine inhaler (Aeromask) deliver drug directly to the airways with minimal systemic absorption. This is the preferred route for long-term management and closely mirrors asthma treatment in humans.
  • Systemic corticosteroids: Oral dexamethasone or prednisolone can be used for short-term management of acute exacerbations. Long-term systemic corticosteroid use in horses carries risks including laminitis (particularly in horses with concurrent EMS or PPID), immune suppression, and adrenal suppression.

Prevention

  • Year-round turnout where possible, particularly for horses with a history of respiratory problems
  • Low-dust stable management as standard practice: haylage or steamed hay, dust-extracted shavings bedding, excellent ventilation
  • Avoid storing hay and straw in the same building as horses
  • Regular airway health checks for performance horses — subclinical airway inflammation may reduce athletic capacity long before obvious heaves develops

When to Call the Vet

Contact your vet if:

  • A horse develops visible breathing difficulty at rest
  • You notice the characteristic double-expiratory effort or a developing heave line
  • A persistent cough does not resolve within 2–3 weeks despite improved stable management
  • An affected horse deteriorates despite environmental changes
  • You need guidance on an appropriate inhaler or corticosteroid protocol for a horse with established disease

Frequently Asked Questions About Heaves in Horses

Can heaves be cured?

No — heaves cannot be cured, but it can be managed very effectively. Many horses with heaves live comfortably with minimal signs when managed in the right environment (ideally full-time turnout on pasture) and with appropriate medication during flares. The key is identifying and removing the triggers rather than relying on medication alone.

Will a horse with heaves ever be able to compete?

It depends on the severity of the disease. Horses with mild to moderate equine asthma that is well-controlled with environmental management often continue in full work, including competition. Horses with severe established heaves may have permanently reduced lung capacity and lower exercise tolerance, limiting their use in high-intensity disciplines. Early diagnosis and management significantly improve the long-term outlook.

Is feeding haylage always better for a horse with heaves?

For most heaves horses, correctly produced haylage is significantly better than dry hay from a respiratory perspective. However, haylage is higher in energy and lower in fibre than hay, which can cause weight gain and carries a higher risk of spoilage if the wrapping is damaged. Horses prone to laminitis or EMS need their haylage intake carefully managed. Good-quality hay that is steam-treated is a viable alternative if haylage isn’t suitable.

Is stabling always bad for horses with heaves?

Traditional stabling with haynet hay and straw bedding is very bad for horses with heaves. However, modern stable environments with good ventilation, low-dust management, and haylage can dramatically reduce allergen exposure. Horses with heaves should ideally live out full time, but if stabling is necessary, environmental optimisation is essential.