Horses can be prone to various respiratory problems, from temporary airway irritation to chronic lung disease. Many of these conditions have contributing factors that you can work to minimize. Here are common causes of respiratory issues in horses and what you can do to reduce their impact.
Airborne Dust
Exposure to airborne irritants like hay dust is one of the leading causes of chronic obstructive pulmonary disease, also known as severe equine asthma, in horses. As your horse inhales these particles, the immune system reacts by triggering inflammation within the airways. The airway walls swell and mucus accumulates, which restricts airflow and makes breathing more difficult over time.
Reducing dust in your horse’s forage limits this repeated irritation during meals. Your veterinarian can recommend properly steamed hay or a lower-dust replacement that meets your horse’s nutritional needs. These changes reduce exposure to the particles that aggravate the condition.
Mold Spores
Hay that retains excess moisture allows mold to grow within the bale. As that mold develops, it produces microscopic spores that escape into the air when someone handles the hay. Your horse then inhales those spores while eating, potentially triggering inflammation in sensitive airways.
Unlike a visible patch of mold, airborne spores aren’t something you can identify by looking across the stall. A bale may release them even when its outer surface doesn’t look heavily contaminated. Consequently, hay quality requires more scrutiny than a quick glance, and shaking out moldy forage won’t remove the respiratory risk.
Ammonia Buildup
Ammonia develops as microbes break down urine in stall bedding. Without adequate removal of soiled material, the gas accumulates and irritates the tissues lining your horse’s airways. Poor ventilation allows that irritation to continue by keeping contaminated air inside the building.
The problem begins underneath your horse, where urine collects in the bedding. Adding another layer over a wet patch may improve the stall’s appearance, but the material beneath it continues producing ammonia. Removing that wet bedding addresses the source, while fresh-air exchange reduces the amount of gas your horse breathes during time indoors.
Pollen Exposure
Pollen can irritate your horse’s airways if they’re sensitive to it. When they inhale pollen from nearby plants, their immune system triggers inflammation that narrows the airways. As a result, breathing takes more effort, and horses with asthma may experience flare-ups.
For these horses, spending more time outside can increase exposure instead of relieving symptoms. If your horse’s breathing worsens during turnout, your veterinarian can assess whether outdoor allergens contribute to the problem. They may recommend changes to turnout during periods of high pollen to reduce how much your horse inhales.
Smoke Inhalation
Smoke carries tiny particles that enter your horse’s respiratory tract with each breath. Some travel deep into the lungs, where they irritate tissue and interfere with normal respiratory defenses. Wind can carry wildfire smoke far from its source, so nearby flames aren’t necessary for exposure.
During exercise, your horse breathes more deeply and draws in a greater volume of air. If that air contains smoke, the increased intake also increases the amount of pollution reaching the lungs. For that reason, reducing exertion during poor air quality limits exposure while the horse’s respiratory system is already under strain.
Viral Infections
Equine influenza is a contagious viral infection that affects the respiratory tract. Infected horses release the virus in respiratory secretions, allowing it to pass to other horses nearby. Close contact at shared facilities gives the infection opportunities to spread through a group.
Once the virus infects the airway lining, inflammation produces symptoms such as a persistent dry cough. A fever can accompany that cough, suggesting an illness beyond irritation from the environment. Separating a sick horse from others reduces further exposure while your veterinarian investigates the infection and advises you on recovery before the horse returns to work.
Bacterial Infections
Bacteria can multiply in your horse’s lungs and cause pneumonia, producing inflammation that makes breathing more difficult. Some bacterial infections develop after a viral illness damages the airway lining. This damage reduces the respiratory tract’s ability to remove bacteria before they cause an infection.
Your horse may then develop a fever or begin breathing harder instead of improving as the viral illness passes. If their condition worsens, your veterinarian can investigate whether a bacterial infection has developed. Treatment may include antibiotics to control the infection while your horse recovers.
Aspiration During Swallowing
Aspiration happens when your horse inhales feed or liquid into the lungs. This can happen during choke, when food gets stuck in the esophagus, the tube that carries food to the stomach. With that passage blocked, feed and saliva can back up into the throat, where your horse may breathe them into the windpipe.
Material that reaches the lungs can cause an infection called aspiration pneumonia. Even after a veterinarian removes the blockage, that infection may develop. If your horse develops breathing trouble after choke, contact your veterinarian for another examination.
Laryngeal Dysfunction
The larynx opens as your horse breathes in, allowing air to enter the windpipe. With laryngeal hemiplegia, nerve damage prevents one side from opening normally. The affected cartilage partially obstructs the airway, limiting how much air passes through when the horse needs it.
That restriction becomes more evident during exercise because the horse needs greater airflow. You may hear a roaring sound as they inhale, even though their breathing sounds normal at rest. An examination of the larynx allows your veterinarian to assess the obstruction, with evaluation during exercise showing problems that a resting examination doesn’t fully reveal.
Strenuous Exercise
Intense exercise can cause small blood vessels in a horse’s lungs to rupture, resulting in exercise-induced pulmonary hemorrhage. During strenuous effort, extreme pressure changes stress the thin walls of these vessels. When they rupture, blood enters the airways and may contribute to reduced athletic performance.
Despite the bleeding, blood doesn’t always reach the nostrils. A horse can experience this condition without an obvious nosebleed, making it difficult to recognize from appearance alone. If your veterinarian suspects exercise-related bleeding, examining the airways after exertion can reveal evidence that wouldn’t otherwise be visible while you watch the horse recover.
Keep Your Horse Breathing Comfortably
You don’t have to wait for respiratory issues in horses to become severe before asking for advice. If something changes in your horse’s breathing, talk with your veterinarian about what you’ve noticed. Getting answers early lets you focus on the care your horse needs and make changes that support their comfort.