Why Do Thoroughbred Horses Get Nose Bleeds?

If you're passionate about horse racing or considering re-homing a thoroughbred, understanding why some horses suffer nosebleeds is essential. This common issue, often seen during or following races, is mostly due to a condition called Exercise-Induced Pulmonary Haemorrhage (EIPH). While the sight of blood might cause alarm, this guide will walk you through why these nosebleeds occur, which horses are affected, and what you can expect if you welcome an ex-racehorse into your life.

Historically, it was thought that nosebleeds in racehorses stemmed from ruptured blood vessels in the nose. However, modern veterinary research has revealed the true culprit is actually in the lungs. Specifically, the small blood vessels in the lungs can burst due to the intense respiratory demands of high-speed exercise. It's important to differentiate between bleeding caused by exercise (EIPH) and nosebleeds at rest, which could signal other serious health problems needing prompt veterinary attention.

How Common is Exercise-Induced Pulmonary Haemorrhage?

Although actual visible nosebleeds in racehorses are relatively rare, studies from the 1980s found that up to 75% of racehorses had blood detected in their windpipes immediately after racing. This blood originates from the lungs, indicating widespread but often minor bleeding events. In the UK specifically, research suggests just over half of racehorses show signs of EIPH after competition.

The likelihood of a horse experiencing EIPH increases with age. This condition is not exclusive to British Thoroughbreds; other breeds such as Arabian, Appaloosa, and Standardbred horses can also be affected. Furthermore, performance disciplines like eventing, polo, and show jumping report cases, though endurance horses seldom show signs. Despite the high percentages, many horses have only mild bleeding that is easily overlooked by owners or trainers.

What Causes Nosebleeds in Thoroughbred Horses?

The exact cause of EIPH remains unclear but is generally believed to involve stress on the pulmonary capillaries—the tiny blood vessels in the lungs. During intense exercise such as racing, these capillaries may rupture due to the enormous pressures caused by high-speed breathing and blood flow, a phenomenon sometimes described as pulmonary capillary stress failure.

Besides EIPH, nosebleeds can also result from other causes, including trauma from falls or collisions, foreign objects irritating nasal tissues, infections, tumours like progressive ethmoid hematoma, and rare bleeding or clotting disorders. Such cases require immediate veterinary diagnosis and treatment to rule out life-threatening issues.

Does EIPH Impact a Horse's Performance?

Common sense suggests that bleeding lungs might hamper a horse’s performance, but scientific evidence is mixed. Many horses with mild EIPH perform well without noticeable detriment. However, severe or repeated episodes can reduce stamina and speed, leading trainers and owners to monitor affected horses carefully. The decision to retire a horse often depends on the severity and frequency of the bleeding episodes.

How is EIPH Treated?

Veterinarians usually assess how much EIPH affects a horse’s health and performance before recommending treatment. The most effective and commonly used treatment for severe cases is the administration of the diuretic frusemide (commercially known as Lasix). This medication reduces blood pressure in the lungs and can help prevent or lessen episodes of bleeding during strenuous exercise.

What Happens to Thoroughbreds That Bleed Frequently?

Horses that suffer severe or repeated bouts of EIPH are often retired from racing to preserve their welfare. Fortunately, many of these ex-racehorses lead fulfilling lives after rehoming, often excelling in less demanding equestrian activities or providing company as pleasure horses. Occasional mild nosebleeds in a rehomed thoroughbred are usually manageable, but it is crucial to maintain regular veterinary check-ups to monitor for any changes.

If you are considering adopting a thoroughbred or ex-racehorse known to be a "bleeder", consultation with a vet to understand the condition, its management, and what to watch for is invaluable. This will ensure your horse enjoys a happy, healthy new chapter outside the racecourse.

Conclusion

Rehoming a thoroughbred that has experienced nosebleeds due to EIPH is far from hopeless. While the condition requires awareness and management, most horses go on to live happy, active lives beyond racing. Understanding the nature of exercise-induced pulmonary haemorrhage and collaborating with your vet can help you provide the best care and ensure the well-being of your nouvel equine companion.