Equine Heaves is a condition that is characterized by inflamed airways in the 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 condition that affects adult horses. 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

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, hence the common name for the condition.

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 infection of the air sacs known as pneumonia.

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.

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]

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]

Symptoms of Heaves in Horses

The beginning stage of heaves typically presents with mild symptoms such as occasional coughing attacks and, in some cases, nasal discharge. The coughing usually occurs at the beginning of exercise or while eating.

As the disease progresses, the frequency and intensity of coughing increase. [4]

Aside from coughing and nasal discharge, other symptoms of heaves include:

  • Exercise intolerance
  • Increased respiratory rate at rest or following exercise
  • Abnormal lung sounds
  • Weight loss
  • Wheezing
  • Flaring of nostrils

In more severe cases of heaves, the horse’s mucous membranes may be pale. In extreme cases, cyanosis (a bluish tint to the mucous membranes) may appear. The horse’s foreskin or mammary glands may have swelling (edema), and exhalation is sometimes accompanied by pushing of the anus.

From a clinical standpoint, heaves can be categorized as being mild, moderate, or severe. Horses with severe hay or barn-associated heaves will show more signs when exposed to dust or mold. Symptoms also tend be worse in winter, especially if horses are housed indoors for extended periods of time. [3]

Heaves can affect a horse’s performance and reduce their quality of life. This condition is rarely fatal unless complications such as pneumonia develop.

Diagnosing Heaves in Horses

Heaves can be more difficult to diagnose in the early stages, but it’s important to have your horse evaluated by a veterinarian if you suspect the condition. A diagnosis is usually made based on clinical findings as well as history provided by the owner.

For example, if the horse has had reduced performance, episodes of coughing, or appears to be triggered by dust or pasture allergens, your veterinarian may recommend modifying the horse’s environment to see if symptoms can be reduced or eliminated.

For a more definitive diagnosis, endoscopy is the most common evaluation method. The procedure involves inserting a long, flexible tube with a small camera at the end into the horse’s esophagus.

Additional tests are often used for horses with mild to moderate heaves symptoms. Veterinarians typically evaluate the severity of the disease based on the presence and types of inflammatory cells in airway secretions.

These secretions are obtained through a process known as bronchoalveolar lavage (BAL).

Alternatively, a less invasive option is to evaluate fluid samples from the windpipe. However, this may be less accurate than BAL.

Blood work and chest x-rays don’t typically provide enough information to make a heaves diagnosis. However, these tests can be helpful to rule out other respiratory illness.

Ruling Out Other Conditions

Respiratory conditions that may look similar to heaves and need to be ruled out include:

Pleural effusion: a build-up of excess fluid between the layers of the pleura outside the lungs.

Tracheal collapse: common in older, small breed ponies, especially Shetlands.

Lungworm: a rare condition that can affect horses co-grazing with donkeys. The main symptom is chronic coughing, but the horse should have a positive response to anthelmintic drugs targeted at killing lungworms.

Idiopathic pulmonary easinophilia: an uncommon condition which results in chronic coughing and labored breathing.

Is there a Genetic Component to Heaves?

Though environmental factors can trigger heaves, researchers have also discovered that severe heaves appears to have a genetic component.

This has been documented in several equine breeds, including Warmblood and Lipizzaner horses. The risk for offspring to develop heaves is significantly increased when one or both parents are affected.

Researchers found that the presence of one or more major genes can play a role in the expression of heaves.

However, the major gene may differ between families of horses. For example, in one family, it may be a recessive gene, but in another family, a dominant gene may be responsible. [3]

To date, there are no genetic tests available to identify horses that might be susceptible to developing heaves.

Managing Heaves in Horses

Managing heaves requires making changes to the horse’s environment to lower exposure to triggering factors. This will vary depending on what causes a horse’s episodes.

For example, hay or barn-associated heaves will need different management than pasture-associated heaves.

If caught in the early stages, the prognosis is typically good and horse owners are often able to halt the progression of lung damage due to heaves. [5]

Remission of symptoms is typically seen 3-4 weeks after management changes are made. However, even a few minutes of exposure to contaminants may result in a recurrence of symptoms. [5]

The following have all been found to be helpful for managing hay or barn-associated heaves:

Turn Out:

Keeping your horse on pasture and in the fresh air is best as this will limit exposure to dust and other airborne particles that can trigger inflammation.

Good Ventilation:

If your horse must be stalled, ensure that the barn is well ventilated with open doors, windows, or fans. If you board your horse, try to get a stall near the end of the aisle where the airflow is better.

When hauling, make sure the trailer is well ventilated as well.

Carefully Assess Hay Quality:

Since feed can be a main source of dust, owners should pay strict attention to its quality. When choosing hay, assess the hay for signs of mould and avoid hays with excess moisture as these are prone to becoming mouldy.

Always store hay in a cool, dry, well-ventilated place to minimize mould growth.

Feed at Chest Height:

Though feeding at ground level can be good for many horses, it isn’t suitable for horses with heaves as they will be exposed to more dust that way.

Instead, install grain feeders at chest height and place hay in bags or racks also at that same height. Hay racks that are placed above the withers can also promote the inhalation of hay and dust particles.

Soak Hay and Feed:

Thoroughly wetting or soaking hay and feed can greatly reduce dust particles. Also, consider feeding a pelleted feed which is less dusty than many grains and is still palatable when moistened or soaked.

Use Hay Nets:

Hay nets make it easier to soak the hay and allow you to raise the hay to chest height.

They should also be used to cover round bales as this will help decrease dust in the air when horses are eating from these bales.

Change Stall Bedding:

If your horse must be stalled, even part-time, avoid using dusty stall bedding such as wood shavings or straw. Instead, use something such as shredded paper or cardboard, flax (newer on the market), sawdust, or peat moss.

These materials are significantly lower in dust if not, completely dust-free. If you must use shavings, spraying them down with a fine mist of water twice daily can help to reduce dust.

Avoid Dusty Barns and Arenas:

Do not clean or sweep barn aisles when your horse is in the barn. Also, avoid riding or working your horse in dusty arenas, especially those that are indoor

Nutritional Support for Heaves

Management of heaves first requires reduction or removal of the allergens that trigger the inflammatory response. Without that, further nutritional support or medications will have little impact.

However, once appropriate management adjustments have been implemented, nutritional supplements can play a role in supporting the immune system and healthy respiratory function.

Below are some additional nutritional considerations for horses with heaves:

Ensure their vitamin and mineral requirements are met

Several key vitamins and minerals are involved in supporting the immune system. This includes zinc, copper and manganese.

Selenium and vitamin E are also important antioxidants that help cells respond to stressors like allergens.

When choosing an equine vitamin and mineral supplement, look for one that provides adequate levels of these trace minerals. Trace minerals should always be supplied in organic forms for improved absorption and assimilation in the body.

Proteinates or polysaccharide complexes are common options for supplying organic forms of zinc, copper, and manganese. Organic selenium is best supplied as selenized yeast proteins which are a safe way to provide elevated levels of selenium.

Vitamin E comes in natural and synthetic forms. Of these, supplementation with natural vitamin E achieves higher levels in the blood, but is also more expensive.

Supplementation should provide at least 1000 IU of vitamin E per day to provide an anti-inflammatory and anti-oxidant benefit.

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Provide an omega-3 fatty acid supplement

Omega-3 fatty acids have anti-inflammatory properties that can modulate the immune response following allergen exposure to dampen hyper-reactions. In contrast, diets high in omega-6 fatty acids can have a pro-inflammatory effect and exaggerate inflammatory responses.

Common omega-3 fatty acids supplements used for horses are flax oil, camelina oil or fish oil.

However, not all omega-3 fatty acids are equal. Plant-based omega-3 oils, like flax or camelina, contain alpha-linoleic acid (ALA) which needs to be converted to either eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) to have beneficial, anti-inflammatory effects.

Unfortunately, this process is very inefficient in the horse’s body with only 5-15% of ALA being converted to these forms.

Consuming DHA directly from dietary supplements like microalgae or fish oil is the only practical way to increase serum omega-3 levels enough to obtain the physiological benefits.

DHA supplementation at a rate of 2.5 – 9 mg / kg (1250 – 4500 mg of DHA for a 500 kg horse) on a low-dust diet decreased coughing, improved lung function, and decreased inflammation in horses with recurrent airway obstruction (heaves) and inflammatory airway disease.

Horses given DHA had a 60% decrease in a clinical score of respiratory dysfunction after 2 months of supplementation. [16]

Mad Barn’s w-3 Oil is a combination of flax oil, soybean oil, microalgal DHA, and natural vitamin E.

The typical serving size of 100 ml provides 1500 mg of DHA as well as 1000 mg (1500 IU) of natural vitamin E. For horses that require caloric restriction for weight management, 30 – 60 ml can also be sufficient to provide the anti-inflammatory benefit.

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Spirulina and Jiaogulan

Spirulina is a blue-green algae that is a rich source of protein, vitamins and minerals.

It is high in antioxidants and has been shown to have anti-histamine effects. [14] This supplement is commonly used to support immune function and respiratory health.

Jiaogulan is a climbing vine that is used in horses to support circulatory healthy and overall well-being. [15] It is thought to support the normal opening of airways (bronchodilation).

In case reports, the combination of 2 grams jiaogulan and 20 grams of spirulina given twice per day was found to minimize coughing, headshaking, snorting, and sneezing that are often associated with poor respiratory health. [13]

Note that jiaogulan should not be fed to pregnant or lactating mares or to horses on non-steroidal anti-inflammatories (NSAIDs), such as bute, banamine, or previcox. Wait for a minimum of 7 days following cessation of NSAIDs before starting Jiaogulan.

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Medications for Treating Heaves

If your horse doesn’t improve with management changes alone, then your veterinarian may recommend medications to help control symptoms.

Several medications can be helpful in treating horses with moderate to severe heaves, but they should never be used as the sole therapy.

Multiple studies have shown that treatment with pharmaceutical drugs without environmental modification is not effective in improving symptoms of heaves. [6]

Medications for equine heaves commonly include the following:

Oral corticosteroids

These medications help to control inflammation in the airways and reduce airway thickening and mucous production.

The two most commonly used oral corticosteroids are dexamethasone and prednisone. However, dexamethasone may not be the best choice for horses prone to founder and should not be used long term in any horse.

Prednisone is safer but less potent than dexamethasone. Veterinarians often recommend it for long-term use after symptoms are under control.

Oral Bronchodilators

Bronchodilators help to relax muscles in the airways, keeping them dilated in order to make breathing easier. Clenbuterol is often prescribed as an oral bronchodilator.

Expectorants

These medications break down mucous, making it easier for the horse to expel it from the lungs. Expectorants can also help to eliminate bacteria trapped in the lungs.

These types of medications can be bought over the counter or stronger expectorants can be prescribed by a veterinarian.

Antibiotics

If a bacterial infection is present, your veterinarian may also prescribe antibiotics. The type of antibiotic needed will depend on the type of infection your horse has.

Aersolized Corticosteroids

For moderate to severe heaves, aerosolized corticosteroids such as beclomethasone diproprionate and fluticasone propionatecan may be required.

These medications can be given to horses via specialized masks such as the Equine AeroMask, Equine Haler, or AeroHippus. Because more medication is able to reach your horse’s lungs using this method, lower does of drugs are often effective.

Inhaled therapies require an initial financial investment but they target inflammation and allergies at the site of the problem: the lungs.

Also, horses that aren’t actively experiencing heaves symptoms may benefit from low dose, long term, aerosolized corticosteroid treatment.

Aerosolized Bronchodilators

Inhaled bronchodilators can help to open your horse’s airways and are often helpful if given before an aerosolized corticosteroid. These medications are also given through use of a specialized mask.

Other Treatments for Heaves

Several alternative treatments could also be beneficial for supporting respiratory function, including:

  • Vicks Vapo Rub, which can be applied below the nostrils or used in a humidifier
  • Cough remedies such as Equitussin, Wind Aid, and/or Air Power

Conclusion

Taking care of a horse with heaves will require some work on the part of the horse owner. The good news is that many horses can be successfully managed and experience a high quality of life with minimal symptoms.

Some horses with heaves can still be used for pleasure, trail riding, or even competition.

Careful management of your horse’s environment as well as medication and feeding practices can all play a part in successful treatment of horses with heaves.

Beyond lowering their exposure to allergens, horses with heaves often benefit from nutritional supplements to support the immune system, antioxidant capacity and respiratory health.

To formulate a diet plan for your horse, contact our equine nutritionists for free evaluation of your current program and recommendations.

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References

  1. Herteman, N. et al. Endoscopic Evaluation of Angiogenesis in the Large Airways of Horses with Heaves Using Narrow Band Imaging. J Vet Intern Med. 2016.
  2. Bullone, M. et al. Development of a Semiquantitative Histological Score for the Diagnosis of Heaves Using Endobronchial Biopsy Specimens in Horses.. . .
  3. Couetil, L et al. Equine Asthma: Current Understanding and Future Directions. Front Equine Vet. 2020.
  4. Bosshard, S. and Gerber, V. Evaluation of Coughing and Nasal Discharge as Early Indicators for An Increased Risk to Develop Equine Recurrent Airway Obstruction (RAO). J Vet Intern Med. 2014.
  5. Davis, E. and Rush, B.R. Equine recurrent airway obstruction: pathogenesis, diagnosis, and patient management. Vet Clin North Am Equine Pract. 2002.
  6. Bond, S. et al. Equine asthma: Integrative biologic relevance of a recently proposed nomenclature. J Vet Intern Med. 2018.
  7. Polikepahad, S. et al. Immunohistochemical determination of the expression of endothelin receptors in bronchial smooth muscle and epithelium of healthy horses and horses affected by summer pasture-associated obstructive pulmonary disease. Am J Vet Res. 2006.
  8. McGorum, B.C. and Dixon, P.M. Summer pasture associated obstructive pulmonary disease (SPAOPD): an update. Equine Vet Edu. 1999.
  9. Lavoie-Lamoureux, A. et al. Markers of systemic inflammation in horses with heaves. J Vet Intern Med. 2012.
  10. Gerber, V. et al. Mixed Inheritance of Equine Recurrent Airway Obstruction. J Vet Intern Med. 2009.
  11. Leclere, M. et al. Heaves, an asthma-like disease of horses. Respirology. 2011.
  12. Hudson, N.P.H. Management of a case of summer pasture associated obstructive pulmonary disease by inhaled corticosteroids and environmental control. Equine Vet Edu. 1999.
  13. Kellon, Eleanor Use of the Herb Gynostemma Pentaphyllum and the Blue-green Algae Spirulina Platensis in Horses. Equine Congress. 2006.
  14. Roughan, Grattan P.Spirulina: A source of dietary gamma-linolenic acid? J Sci Food Agri. 1989.
  15. Hinckley, KA et al. Nitric oxide donors as treatment for grass induced acute laminitis in ponies. Equine Vet J. 1996.
  16. Nogradi, N. et al. Omega-3 Fatty Acid Supplementation Provides an Additional Benefit to a Low-Dust Diet in the Management of Horses with Chronic Lower Airway Inflammatory Disease. J Vet Intern Med. 2015.