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Why Do Race Horses Bleed From the Nose After Running?

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We recently took our granddaughter to the Fairgrounds racetrack for a special day of horse racing. After one particular race, she noticed blood trickling from the winner’s nostrils and asked me why some of the horses bleed from their nose after they run?

Horses bleed from their nose when running because blood from a horse’s lungs blows out of their noses when pressure builds up, this condition is EIPH. The blood got into its lungs because pulmonary capillaries burst during the strain of running.

Most horseowners have owned or seen a horse bleed from its nose after strenous exercise, like running. But the cause is not always known.

Why do horses bleed from their nose after running?

Studies show that ninety-five percent of horses suffer from bleeding in their lungs after strenuous exercise. However, not all horses exhibit nasal bleeding.

A horses’ heart pumps a lot of blood when running.

As Thoroughbreds run, their heartbeat increases, pumping over 100 gallons of blood per minute. And with each stride, their lungs inhale approximately four gallons of air. This air moves in and out of each nostril.

Running creates pressure that leads to bleeding

Picture of racehorse running on a turf track,

Bleeding occurs because pressure builds inside their bodies, the blood-gas barrier, ruptures, and red cells flow into the lungs. This condition is EIPH. For horses that bleed extensively, the blood overflows their lungs and exit their nostrils.

Most competitive horses experience EIPH.

The vast majority, of performance horses, experience EIPH, and it generally starts soon after training begins, and gets worse as the horse ages. In the early 1980s, endoscopy confirmed that 70% of horses post-race had significant blood in their airways.

EIPH typically occurs in racehorses regardless of breed, and it’s also prevalent in other high-performance equine athletes, such as cutting, jumping, barrel, and dressage horses.

Racehorses with severe EIPH can be a problem. Their performance may decrease; they might need to be medicated before races; they could miss training or be banned from racing altogether.

However, there doesn’t seem to be a direct correlation between bleeding and performance. Throughout history, there have been some outstanding racehorses that were notorious bleeders.

Picture of a vet listening to the breathing of a horse with a stethoscope; she is checking for bleeding in the lungs,

But some animal healthcare professionals believe EIPH is an indicator that a horse is physically intolerant to exercise, and continued work will progressively damage the horse’s lungs.

Some scientists point to studies that show performance levels of horses with EIPH decrease in proportion to the number of races ran. Horses with severe conditions of EIPH that are left untreated are at risk of dying, although it is rare.

Horses have bled for centuries, but some aspects remain mysteries. One of the earliest recorded racehorses that suffered from nasal bleeding was appropriately named Bleeding Childers, and he was born about 1716.

It is defined as the presence of blood in the tracheobronchial tree (system of tubes in the lungs) following strenuous exercise.  EIPH generally occurs soon after training begins, and tends to increase in incidence with age.  

Not all horses with EIPH bleed from their nose.

Not every horse that has EIPH bleeds from their noses. The conditions that cause EIPH are:

A scope is used to diagnose EIPH

The best way to diagnose EIPH is via an endoscopic examination.

Endoscopic examination

Endoscopes are used to visualize the surface of organs, their vessels, and pathological changes without incisions. In 1974 they were used to confirm that lungs, rather than airways or other sites, were the source of blood coming from horses nostrils.

Endoscopic detection of post-race horses revealed 60 percent displayed EIPH symptoms, and upon subsequent examinations, discovery increased to 95%. However, the majority never bleed from the nose.

Picture of a vet performing a scope examination on a horse.

Lasix is used to treat horses with EIPH.

Furosemide (Lasix)

The most widely used treatment for EIPH is a diuretic called Furosemide, commonly known as Lasix. This drug has been used extensively for the treatment of bleeding in horses since the mid-1970s.

Lasix works by reducing the stress on horses organs by lowering the amount of fluid retained in the body just before the horse races. Lasix expels an average loss of twenty to thirty pounds of fluids.

Furosemide also reduces blood pressure in the aorta and pulmonary artery – and can enhance racing performance, particularly on first use in a horse starting a race.

Because Furosemide can enhance an equine’s sports performance ability, its use is controversial. How Lasix improves a horse’s performance, is not completely clear but may be related to weight loss caused by the medication.

By 1975 the drug was so popular and effective that the Daily Racing Form began listing the horses on Lasix for each race. The decreased pressure caused by the Laxis allows most horses to run without bleeding.

The success of the drug has resulted in approximately 92% of racehorses running on Lasix. Lasix has evened the field for horses that suffer bleeding. Before Lasix, horses that didn’t bleed had a much higher chance of winning, and now all horses seem to be on an even playing field.

Tracks that permit the use of Lasix require horseman to follow strict regulations. The typical rules are that the drug can only be given within twenty-four hours of the race and in a single dosage administered more than four hours before post time.

Eligible horses have to be approved by a licensed trainer or veterinarian that believes it’s in the horse’s best interest to run on the drug, and the dosage cannot be larger than 500 mg.

Lasix is often abused in the horse racing industry

Trainers use Lasix on horses that don’t bleed to make them run faster for their benefit, not for the health of the horses. Some horse racing enthusiasts estimate that only 2-3 percent of the horses on Lasix have EIPH severe enough to need the drug.

However, only a small percentage of horses may suffer severe EIPH; if Lasix is not used to keep the bleeding from cumulating, a horse’s EIPH can develop into a severe problem.

Many people believe that horse racing was thriving before the advent of Lasix use and would continue to thrive if it was no longer in use. One physical side effect of Lasix is it dehydrates the horse.

Some jockeys and opponents of the drug believe the high number of horse break downs on the track is related to dehydration. However, the Jockey Guild stated that Lasix is suitable for racehorses.

The International Federation for Horse Racing Authorities (“IFHA”) takes the stance that barring Lasix use is essential for the safety of horses and jockeys.

Another issue is the extended recovery time after a race on Lasix. Because horses lose so much weight while on Lasix, they typically extra time off between races to fully recover. Since the introduction of the drug, the average number of starts per year has decreased.

Lasix may be used to mask banned drugs. Diuretic drugs can wash other medicines out of an animal’s system. However, modern testing has advanced, and it is highly unlikely that Lasix is a useful masking agent any longer.

The most frequently used argument in support of banning Lasix is that the drug is a negative mark in the public eye. It is thought that the general perception is race-day performance-enhancing medications are unfair.

Nasal Strips are used to treat EIPH.

There are few options for EIPH treatment besides Lasix. However, nasal strips have been developed as a non-medical treatment option.

Horses are nasal breathers, and during forceful inhalation, the nasal strips support the nasal passage, thus preventing collapse and increased resistance to inhalation.

Keeping the nostrils open with the nasal strips allows better airflow and reduces the pressure on opposing sides of the blood-gas barrier. There are a few studies of nasal strips with a small sample of horses that have reported a possible reduction in EIPH.


Why do racehorses lead ponies?

Lead ponies help racehorses relax and focus before the run. It takes a special horse to work as a pony horse on a race track. They have to be calm, athletic, and alert. To learn more about the horses that accompany racehorses on the track check out this article: Pony Horses: 5 Reason Racehorses Have Another Horse With Them

Why do racehorses pee before they race?

Racehorse pee before they run because vets or trainers inject them with the diuretic Lasix, which is used to control bleeding in their lungs.
Lasix causes fluid to collect in the animal’s bladder and is expelled as urine. The timing of the injection is the reason they pee prior to racing. You can learn more about why horses have to pee so bad here: Why Do Racehorses Have to Pee so Bad? Fact, Fiction & Causes

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