It has always puzzled me why horses, arguably as close to athletic perfection as you’re ever likely to see in an evolutionary sense, can be prone to exercise-induced bleeding in the lungs.
It seems to be a major failing in an animal capable of speeds we humans need a motor car to achieve.
The condition, known as exercise-induced pulmonary haemorrhage (EIPH) , is most prevalent among racehorses, who can pull up after racing with frothy, bright red bloody fluid showing at their nostrils.
EIPH is the justification in US racing for the common race-day use of the diuretic furosemide, which appears to reduce the chances of a horse suffering the condition.
Lung bleeding is an ailment linked to the upper limits of a horse’s physiological ability – when its heart-rate is approaching a dizzying 250 beats a minute, moving up to a litre of blood with every powerful contraction of the left ventricle.
Enter Dr Bob Cook, who proposes an explanation for not only EIPH, but the hitherto unexplained deaths that can occur in horses on the track, or within an hour of finishing their race.
Cook, an emeritus professor of veterinary surgery from the Cummings School of Veterinary Medicine at Tufts University in the United States, proposes that the problem lies with the bit. He argues that the presence of the bit spawns increasingly serious problems in the throat, lungs and heart.
The bit, he says, breaks the lip seal during strenuous exercise, destroying what should be a vacuum in the mouth. This releases the soft palate from its locked-down position and can lead to the airway in the upper throat collapsing.
Death follows from suffocation, waterlogging of the lungs and heart failure.
Cook, widely known for his development of a patented bitless bridle, has laid out his hypothesis in a study published online ahead of print in the peer-reviewed journal, Equine Veterinary Education.
Cook reasons that “bleeding”, as it is simply known in racehorses, is the same as an airway emergency in human medicine known as negative pressure pulmonary oedema.
The 84-year-old says the evidence is consistent with the bit being the cause of both EIPH and unexplained sudden deaths in racehorses.
There are few things that can kill a horse in a matter of seconds, he points out. Aside from asphyxia, only cardiac failure kills as quickly. While cardiac disease in the racehorse is rare, it it telling that cardiac failure can be a sequel to asphyxia.
Cook says that in the wild a horse runs with its lips closed, mouth shut, tongue immobile, poll extended, the head/neck pendulum unhindered, balance perfect, with no slobbering. This is not the picture we necessarily get with a racehorse running with a bit. Many gallop with their poll flexed, mouth agape, lips parted, tongue protruding, head/neck pendulum constrained, balance upset, and saliva streaming.
Such horses, he says, are denied the oral vacuum that keeps the soft palate in a locked-down position, and also are denied the ability to breathe, balance and conserve energy. Horses, he stresses, are nose breathers, not mouth breathers.
This failure to lock down the soft palate can result in obstruction of the airway of the upper throat and would account for abnormally intense and accumulating suction pressures in all ensuing sections of the airway when a horse takes each breath – up to two and half every second at full gallop.
Even transient airway obstruction can quickly cause serious consequences, he says.
In the lungs, where abnormal suction pressures are at their most intense in the tail-end small airways, this explains why heavily blood-stained oedema ﬂuid can be drawn from the lung into the airways.
He likens the effect to a hickey on human skin, but says the “sucks” are more brutal and more frequent. “Thirty strangulated breaths” may be more than enough to kill, he says.
Cook, in his journal article, is challenging an aspect of equitation – the bit – which a majority of riders use without question.
There is certainly a growing movement to go bitless, but the practice has a varying degree of acceptance across horse sport and the industry in general.
Needless to say, I am no position to judge the merits of Cook’s hypothesis more than any other layman involved with horses. But his journal report is thought-provoking, and he should be applauded for challenging the status quo.
Cook understandably wants racing administrators to investigate bitless racing and, unless the racing fraternity can come up with a definitive explanation for the unexplained deaths that still occur in the industry, it is hard to argue against that.
Cook proposes that removal of the bit will banish pain in the mouth and allow a racehorse to breathe freely during exercise. He predicts it will reduce the prevalence of asphyxia, lung bleeding, and sudden deaths.
His study focuses on racehorses, but his hypothesis is potentially more far-reaching.
Cook reminds us that unimpeded breathing is essential for optimum performance. Should it be ultimately proved that the bit does impede the dynamics of breathing during rigorous exercise, could we one day find that eventing horses actually perform better on cross-country courses when bitless? Or polo ponies play better? Or that bitless endurance horses are found to outperform those wearing bits? Or chuckwagon horses go that little bit faster?
I don’t know the answers, but I think we need to find out.
Read more on Bob Cook’s hypothesis here.
Bit-induced asphyxia in the racehorse as a cause of sudden death
The abstract can be read here.