Heaves In Horses: Symptoms, Causes, and Treatment

Last Updated on September 1, 2020

Although many horses breathe hard after running, you may notice your horse struggling to breathe after playing, walking, or while resting. It is usually an indication of a severe medical condition. The most common reason for a horse struggling to breathe is recurrent airway obstruction, also known as horse heaves.

What is Horse Heaves?

The heaves, which is formerly known as recurrent airway obstruction, or RAO, is a lung condition that usually affects horses over six years of age. It isn’t contagious, so if a horse has it, he cannot pass it onto others in the herd or a stable. The disease was once known as chronic obstructive pulmonary disease or COPD.

Symptoms of the Heaves

If you have older horses, it is important to be able to recognize the symptoms of the heaves to get them help and to manage their condition. Usually, the first symptom of RAO is a mild cough after or during activity like playing or exercise.

Sometimes when a horse coughs, there may be a white discharge, or mucus, that comes out of their nose. The nostrils will also tend to flare open as the horse tries to breathe and get more air into its lungs.

Although it will be easier to hear with a stethoscope, you may be able to hear the horse breath from across the barn if they have the heaves. Their breathing may be noisy because their windpipe, or trachea, may be full of secretions.

If a horse with heaves doesn’t receive treatment, the condition will worsen, and in a year or two, they may have difficulty breathing at rest. The condition will continue to deteriorate, and the horse will lose weight because he cannot breathe while eating. Muscular energy is also lost in the attempt to breathe.

Formation of a Heave Line

A horse with the heaves may develop what is known as a heave line. It is a visible line of abdominal muscles that develop as the horse tries to breathe and push air out of their lungs.

The lines run diagonally across the abdomen and sometimes the chest. Some of the lines appear as are indentions that indicate the horse’s muscles are trying to push air from their lungs.

What Causes the Heaves?

Exposure to environmental elements to which a horse is allergic is the main cause of the horse heaves. These elements may include dust and pollen in the air, poor quality feed, hay that may be dusty or contain mold or weeds, or an allergic reaction to weeds or grass in their pastures.

The heaves are most often seen in older horses that are kept indoors, but it can also be found in horses kept in pastures throughout the year. When a horse breathes in the allergens, the cells in their lungs release chemicals that can cause air passages to swell, thicken and produce mucus.

As the horse breaths, the swollen passages trap the air, and the horse needs to make an extra effort to expel air from his lungs. The more exposure a horse has to allergens, the more sensitive its lungs are to them.

There is some indication that the heaves may be hereditary because of the link to allergies, but ponies are often fed poorer quality hay to prevent them from gaining weight. Sometimes, the heaves may be the result of a lung infection, but it and other factors are still being researched.

How Heaves are Diagnosed

When an owner suspects his horse may have the heaves and calls in a vet, the horse doctor will take a medical history and examine his patient. When he or she listens to the lungs through a stethoscope, they will often hear crackling and wheezing sounds.

Since a fever doesn’t normally accompany the heaves, the vet will take the horse’s temperature to eliminate other possibilities, such as pneumonia. An endoscopic examination of the airway may be done to get a test sample of the mucus. The tests will usually reveal the presence of inflammatory cells called neutrophils.

Although a blood test may not be conclusive, it can still help rule out infections within the horse. The veterinarian will also consider the horse’s history, such as being kept in a poorly ventilated stable, how often they are indoors, and the quality of their hay.

A lab test can be done on blood to determine the environmental factors to which the horse is allergic. Once it is known what the horse is sensitive to, then an anti-serum can be developed to help desensitize the horse to those triggers.

Treatments for Heaves

Once a diagnosis of the heaves has been made, including its severity, then the veterinarian can develop a treatment plan. For milder cases of the heaves, they may recommend treating it by:

• Taking the horse outside more often to expose him to fresh air.
• Stabling him in an area with good ventilation, such as an end stall.
• Leaving the doors and windows open more often to increase exposure to fresh air.
• Keeping the stall clean.
• Feeding him at chest level as feeding him on the ground or from a feed bag can increase their exposure to dust and hay particles.

If your horse as a moderate case of the heaves, then the vet will prescribe medications for him, such as:

• Oral corticosteroids like prednisone or dexamethasone to control the inflammation of the airways. These medications can help to reduce thickening of the airways and mucus production.
• Oral bronchodilators like clenbuterol help to dilate and open airways to make it easier for the horse to breath.
• Expectorants can break down mucus and make it thinner, so it is easier for the horse to expel from his lungs. Usually, an over-the-counter expectorant will work well, but a vet can prescribe potassium iodide if necessary.
• Antibiotics may be necessary if bacteria are complicating the heaves. The bacteria will be found in the mucus sample taken from the horse during its examination.

For severe cases of the heaves, the vet may prescribe:

• Inhaled corticosteroids to control inflammation of the airways.
• Inhaled bronchodilators to open airways so the horse can breathe better.

It should be noted that medications cannot “cure” the heaves, but only help to manage the disease. However, there are other things that owners can do to manage the disease as well.

Managing the Heaves

Along with receiving treatments from a veterinarian, there are several things that you can do to help your horse.

Examine the Hay

A horse should be feed good quality hay, so you should examine it before feeding it to your horse. If you see signs of mold, do not use it as feed or bedding. Good quality hay will have more leaves, finer or small diameter stems, it will smell fresh, and it should appear bright green.

Wet the Hay

Before giving hay to your horse, wet it down to reduce exposure to dust and mold spores. The amount of water you need to use will depend on the severity of their condition. Some horses with severe heaves may need to have the hay submerged or soaked in water before they are fed.

Learn how probiotics for horses can improve their overall health.

Switch to Pellets

If your horse has a moderate to severe case of the heaves, consider switching to cubed hay or pellets.

Switch the Bedding

If you’re using straw for bedding, consider switching to shredded cardboard or paper bedding. Straw readily molds, and it exposes the horse to more dust. Other options include placing pellets over stall mats or using sawdust, which is a better option than straw.

Don’t Clean Around Horses

When you clean out the horse’s stall, move him outside to avoid exposing him to dust and hay particles that may fly around while you’re working. The exposure to fresh air will be good for him, and you can quickly clean the stall without a horse in the way. 

Use an Omega 3 Fatty Acid Supplement

Omega 3 fatty acids are often given to humans to help control many inflammatory conditions, and there is evidence it can help horses too. In a clinical trial, horses with heaves who were given omega-3 fatty acids supplements showed significant improvements over the horses who didn’t receive them.

The study found that the supplements helped to improve lung function and airway inflammation. During the study, the horses were also fed a low-dust diet of pellets instead of hay.

Along with managing horse heaves in those that already have the disease, practicing some of these steps can help prevent horses from getting heaves. Always make sure your horse is fed good hay and that his stall is kept clean to reduce his exposure to possible allergens.

Also, exercising your horse and making sure he is frequently taken outside will help as well. Look to make sure the stable is well-ventilated, so fresh air is always available. By knowing what the heaves are, how they develop, and how to manage them, you and the vet can help your horse have a better quality of life.

For more horse health guides and tips read these articles:

• Hay for Horses Guide
• Toxic Plants for Horses
• Horse Joint Health Guide
• Arthritis in Horses
• What Causes Horse Shedding