Roaring is a condition where a horse makes a distinct, loud breathing noise during exercise because one side of the airway has partially collapsed. The technical name is recurrent laryngeal neuropathy, and it happens when nerve damage causes a key muscle in the throat to waste away, leaving the airway unable to fully open when the horse needs it most. It ranges from a barely noticeable whistle to a full-on roar that limits performance.
Why the Airway Collapses
A horse’s larynx (the voice box) contains two flap-like structures called arytenoid cartilages. During exercise, a small muscle called the cricoarytenoid dorsalis pulls these cartilages open so the horse can move large volumes of air. That muscle is controlled by the recurrent laryngeal nerve, one of the longest nerves in the horse’s body. It runs from the brain all the way down the neck, loops around structures near the heart, and travels back up to the larynx.
In affected horses, this nerve degenerates. Without proper nerve signals, the muscle wastes away and can no longer pull the cartilage out of the airway. The left side is almost always the one affected, likely because the left recurrent laryngeal nerve takes a longer path than the right, making it more vulnerable to damage. As the cartilage sags inward, it partially blocks airflow, and the loose tissue vibrates with each breath in, producing the characteristic roaring sound.
Which Horses Are Most at Risk
Roaring overwhelmingly favors tall, long-necked breeds. Thoroughbreds are commonly diagnosed, but draft breeds carry the highest rates. A study of 183 competition draft horses found an overall prevalence of 35%. Belgians were hardest hit at 42%, followed by Percherons at 31% and Clydesdales at 17%. The pattern across breeds strongly suggests that longer nerve length (in taller horses) plays a role. Males are affected more often than females, and signs typically appear in young adult horses as they enter serious work.
Signs You Might Notice
The hallmark is an abnormal inspiratory noise, a roar or whistle that occurs when the horse breathes in during fast work. You won’t usually hear it at rest or at a walk because the horse doesn’t need to move enough air to expose the problem. It becomes obvious at a canter, gallop, or under heavy exertion.
Beyond the noise itself, you may notice:
- Decreasing exercise tolerance. The horse tires faster than expected or refuses to maintain speed.
- Labored breathing during or after work. Recovery from exercise takes longer than normal.
- Performance decline. A racehorse may fade in the final stretch, or a sport horse may struggle with intense efforts.
Some horses with mild cases never show obvious signs at lower levels of work and are only diagnosed during a pre-purchase exam or routine scoping.
How Veterinarians Diagnose It
Diagnosis starts with passing a flexible camera (endoscope) through the horse’s nostril to view the larynx. While the horse stands quietly, the vet watches how the arytenoid cartilages move. Veterinarians use a standardized grading system, called the Havemeyer scale, to classify severity from Grade I to Grade IV:
- Grade I: Both cartilages move symmetrically and fully open. Normal function.
- Grade II: Some asymmetry or delayed movement, but the cartilage can still achieve and hold a fully open position. Many Grade II horses perform without problems.
- Grade III: The cartilage cannot achieve or maintain full opening. This is where performance is typically affected, and surgery may be considered.
- Grade IV: Complete paralysis. The cartilage and vocal fold on the affected side do not move at all.
A resting exam doesn’t always tell the full story. Research comparing resting and exercising endoscopy in Thoroughbred yearlings found significant differences between what the scope shows in a quiet horse versus one at speed. Problems that looked minor or absent at rest sometimes became clearly significant during exercise, and other airway issues only appeared under exertion. Dynamic overground endoscopy, where a small camera is attached to the horse and records while it gallops, gives a much more accurate picture of what actually happens in the airway during work.
Surgical Options
For horses that need to perform at high intensity, surgery is the primary treatment. The most common procedure is prosthetic laryngoplasty, widely known as “tie-back” surgery. A suture is placed to permanently pull the paralyzed cartilage into an open position, mimicking what the wasted muscle can no longer do. This is often combined with a ventriculocordectomy, which removes the vocal fold and a small pouch of tissue on the affected side to further clear the airway.
The tie-back can be performed under general anesthesia or, in some cases, with the horse standing and sedated while a vet uses endoscopic guidance to adjust the suture tension in real time. The standing approach allows more precise positioning because the vet can see the airway on a screen and fine-tune how far open the cartilage is pulled.
Getting the tension right matters enormously. If the cartilage isn’t pulled open far enough, the horse still roars. If it’s pulled too far, the horse may have difficulty swallowing because food or water can slip into the airway. In a long-term survey of 200 horses that had tie-back surgery, 10% needed a second procedure to re-tighten a suture that had loosened, while 7% needed theirs loosened because swallowing problems were too severe.
For less severe cases or horses not in intense athletic work, a ventriculocordectomy alone (removing the vocal fold without the tie-back) can reduce the noise and modestly improve airflow. This can be done with a laser passed through the endoscope, making it a minimally invasive option.
What Recovery Looks Like
After tie-back surgery, horses typically start with stall rest and progress gradually to hand-walking, then light exercise, before returning to full work over several weeks to a few months. The exact timeline depends on the surgeon’s protocol and how the horse heals.
Coughing is the most common aftereffect. In the 200-horse survey, 43% of horses coughed at some point after surgery, and about half of those coughed specifically while eating. This happens because the tied-back cartilage holds part of the airway permanently open, which slightly compromises the larynx’s ability to protect itself during swallowing. For most horses the coughing is mild and temporary. Chronic coughing lasting more than six months occurred in about 14% of cases, and half of those turned out to be related to unrelated lung issues rather than the surgery itself.
Wound complications are generally minor. Swelling and small fluid pockets at the surgical site resolved within two weeks in most horses. Serious infections are uncommon.
Living With a Roarer
Not every horse that roars needs surgery. A pleasure horse or light trail horse with a Grade II or mild Grade III may never be limited by the condition. The decision to operate depends on what the horse is being asked to do. A racehorse or upper-level eventer that needs maximum oxygen intake is a much stronger candidate than a horse in moderate work.
For horses that do have surgery, the success rate for reducing noise and improving exercise tolerance is generally good, though some residual noise is common. Owners should be aware that feeding management can help post-surgical horses. Soaking hay, feeding from a raised position, and avoiding dusty or very fine feeds can reduce the chance of material entering the airway.
Roaring is not painful, and horses with mild cases often live full, productive lives without intervention. The condition does not typically worsen rapidly, but it also does not improve on its own since the underlying nerve damage is permanent.