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A Breath of Fresh Air

Equine Respiratory Health

If you’ve spent any significant time with racehorses, you’ve spent time thinking about their breathing and the challenges they sometimes face.

Dr. Reynaud Léguillette is very serious about equine respiratory health and he sat down with TROT to talk about the past, present and future of research on the topic. By Melissa Keith

In June 2016, University of Calgary’s Faculty of Veterinary Medicine announced the appointment of Dr. Reynaud Léguillette to its first Chair in Equine Sports Medicine. The position was created with encouragement and a starter donation from the Calgary Stampede, but expanded to include many small yet significant financial contributions from various corners of the multi-breed, multi-discipline Western Canadian industry. “I am quite involved with clinical and research work with the community in Alberta, around Calgary,” says the veterinary specialist. “The Dean thought that the best service to the community would be to do a Chair, so that I would focus on more research.”

Léguillette defines his branch of equine sports medicine as “really, exercise physiology.” While interested in musculoskeletal topics, he’s devoted much of his career to what he considers “the limiting factor to performance in horses”—the cardiovascular system. “I have done a lot of studies on the respiratory side, the lower airways and the lungs, this has been my focus for many years and how I started my training. I’ve done clinical and field studies on the lungs and lung inflammation in horses. My other interest is also exercise physiology […] so it’s kind of natural: if you have an interest in the equine lungs, then you have an interest in exercise physiology - you know, they kind of go hand in hand together.”

The busy veterinarian works with a variety of breeds, from draft horses to barrel racing quarter-horses, and thoroughbred runners to thoroughbred chuckwagon horses. Standardbreds evoke memories of his training and early career at the former Hippodrome de Montreal. “Not in studies, but I’ve done lots of clinical work with them,” Léguillette clarifies. “I’ve done a lot of what we call over-the-ground or dynamic endoscopies on standardbreds. I have done a little bit of fitness testing in standardbreds too; during my residency and internship, I was at the University of Montreal, where in these times, 50% of the caseload was standardbreds, basically. I’ve done high-speed treadmill tests on these standardbreds when I was a clinician at the University of Montreal. I basically started the exercise physiology and fitness tests with [them].”

Upon arrival in Calgary ten years ago, Dr. Léguillette found himself with some harness racing clientele, yet too few standardbred racehorses to undertake statistically-adequate field studies. Stampede Park closed as a harness racing venue in 2008 with no local replacement until last April. Since the debut of Century Downs, “we have a lot more of these horses and it’s definitely on the way up,” he remarks with delight. “I am definitely interested. I really like these horses, because they are easy to work with and the type of exercise they do is very unique.”

The recently-named Chair considers one unusual attribute of standardbred racehorses a very worthwhile starting point for further studies. “The standardbreds are actually very unique in the way they breathe,” explains Léguillette, citing work by other researchers. “From the reading and the study and literature reviews I’ve done, my understanding is that thoroughbreds have a perfect synchrony [i.e. match-up] between breathing rate and their strides, so every time their hooves hit the ground, they start expiring [i.e. breathing out], so this is why thoroughbred horses running at full speed have […] oxygen content in their blood much lower than at rest [i.e. hypoxia] and their CO2 [carbon dioxide] content is much higher. What this means is that they are at the edge of what their lungs can do, and that’s why we think that the lungs are the limiting factor to performance in galloping thoroughbreds. And why is that? I think it’s because these horses are stuck with synchrony between the gait and breathing rate. They breathe as fast as their strides in frequency.”

Remarkably, this trait is not shared by trotters or pacers in training and competition. “What I’ve read on standardbreds is actually that they’re quite unique, because they are not synchronized as much as the thoroughbreds,” Léguillette continues. “They have more control on their breathing strategy when they race. This is fascinating, for me, because the thoroughbreds are hypoxic and hypercapnic [i.e. low in blood oxygen and high in blood CO2] when they race. So they kind of tolerate the lack of oxygen, but they would benefit from breathing a little bit slower, with a little bit more volume.” This kind of respiration, he notes, is not a problem for their harness racing counterparts: “[thoroughbreds] don’t do it because we think it would cost them more energy to do so, versus a standardbred. Standardbreds are actually doing that, actually breathing a little bit slower, with a little bit more volume, and they are a little bit less hypoxic when they run.”

On the day of his interview for TROT, the equine respiratory expert was excited about new research. “We just sent today for this grant [to investigate] why horses have EIPH [exercise-induced pulmonary haemorrhage or “bleeding”],” says Léguillette. “We have a few hypotheses: it’s basically a blood pressure problem. That’s the approach we’re taking. I want to understand why horses bleed [in a way that] makes sense for the barrel racing horses, makes sense for the standardbreds, thoroughbreds. Now let’s find a solution and tackle that. I think you can only find a good long-term solution once you understand the mechanisms of bleeding.” Although bleeders are found among most varieties of high-speed performance horses, the common condition remains poorly understood and there is no cure. A recent Yonkers Raceway card illustrated how prevalent Lasix treatment for EIPH is becoming among standardbreds: of 112 horses on the October 15th International Trot program, only 30 raced without the medication.

The University of Calgary veterinary researcher wants to take EIPH work beyond the obvious. “So the capillaries [i.e. tiny blood vessels] are breaking [in the lungs] and we all agree, absolutely; now the question is, why do they break?” he asks. “We know that these capillaries have a somewhat limited resistance to a change in pressure from both sides, so if you push too hard on them, they are going to break. We all agree on that, that these capillaries have a limit, and they have reached that limit when these horses are bleeding. And we don’t even know the number—we don’t know how much pressure they will tolerate before they break.” By investigating thoroughbred runners, Léguillette and his team hope to find a relationship between exercise-induced bleeding and possible sources of pressure that cause damage to fragile lung capillaries: “Now the question is, ok, what is generating this pressure? Is it because the heart is pumping too much blood? Is it because there is too much negative, or vacuum, pressure in the airways?”

The latter possibility—negative or vacuum pressure in bleeders’ airways—is one that taps into a consistent theme in Léguillette’s veterinary specialization. “I see that all the time. I do lots of what we call dynamic endoscopies, with a portable backpack endoscope on horses to look inside their throat as they are running on the track, and I can tell you 100%, if a horse had a throat obstruction, the horse has a narrowing of his throat while he’s running, I can guarantee you, if he’s a racehorse, he’s going to bleed.” But he stresses this explanation does not account for all or even most cases of EIPH: “If you have 80% of the horses bleeding in a race, you may see 5% with a throat problem. 75% of the horses bleed and have no reason to bleed, so you have to figure out why. We hope to know more answers within the next year and a half to two years; it’s a two-year [study grant].”

For unknown reasons, standardbred horses are especially prone to atrial fibrillation, an unusually fast and/or irregular heart rate. Léguillette says his clinical activities bring him into contact with harness racehorses affected by atrial fibrillation, whom he notes are at elevated risk for EIPH. Assessing bleeders, he follows a process of elimination to check for this and other problems often seen in standardbreds: “When I have an EIPH or bleeder case, I really rule out the problems first, so I look at the throat; I look at the heart; I look for atrial fibrillation or dynamic obstruction of the throat, and then if I have nothing, nothing, nothing, I say, ‘OK, you have a bleeder’- I can’t figure out why he’s bleeding, but most of the time you can help these horses by finding the primary cause of the bleeding.”

He finds airway obstructions in many standardbreds he visits and considers this subject ripe for research. “I don’t know if it’s because we have a [harness] racetrack now in Calgary or what, but I’m doing a lot of dynamic endoscopes on them,” Léguillette reports. “I find lots of problems on their throats. ‘Flipping the soft palette’, as people say. I actually think there is a link between this and atrial fibrillation, probably, but I have no evidence for it.” Activity at Century Downs means more standardbred field study possibilities for the Chair in Equine Sports Medicine. “Clearly the fact that the track is not far from us now is a big factor for sure, because it generates more clinical work for me, and the clinical work generates research ideas” with “more relevance, more pertinence” to his patients, their owners and trainers. Because the University of Calgary Faculty of Veterinary Medicine functions as a DTVH - a Distributed Teaching Veterinary Hospital - he practices out of a nearby referral centre, leading to more direct contact with regular racehorses, rather than the acute cases which predominate at on-site clinics.

The 2014 Zoetis Research Excellence Award winner conducted his first webinar in mid-October, answering questions from an audience of hundreds online. He says many participants wanted to know about a specific diagnosis: “Of course I had lots of questions on EIPH - that’s a big concern for the industry, that’s very clear. People are very aware of the problem.” Prevention was a common theme, he adds. “I had lots of questions on the nasal strips, questions on nebulising the horses for airway inflammation, questions on management - how to avoid the dust. People want to know more about these things and how they work. The big problems, I felt, were EIPH and dust management.”

EIPH may remain an unsolved mystery for now, but dust management is not. “As probably everyone knows, but we definitely know now, dust is really, really bad for the lungs of horses,” says Léguillette, a trace of frustration in his voice. “It only makes sense, but when you go outside, when you travel around and visit these barns, sometimes you wonder… I mean, you see some horses that are left 24-7 inside dusty, dusty barns.” He reminds owners, trainers and caretakers that one major source of dust problems is highly preventable. “My take-home lesson number one is that round hay bales are not very good for your horses, because they dig in them and you need to prevent the digging aspect of it. How do you do that? You either fence your bales or unroll them and fork out the hay, or you put some kind of net on them.” Then there’s the matter of dust exposure in horses travelling between farms and racetracks: “The dirt in a trailer is very bad and how do you prevent that? You don’t have a hay net hanging in front of the nose of your horse; you use maybe hay cubes or steamed hay. I like hay cubes, I like steamers, I like people to be careful with the bedding and careful with the round hay bales.”

Whether a horse is spending the majority of its time outside or indoors, the Calgary veterinarian notes that reducing dust exposure is crucial to health and performance. “When I diagnose equine asthma, I always tell my clients, think of your horse as a kid with asthma who is allergic to dust. That’s what you’re dealing with. Would you put your kid with asthma, allergic to dust, in the middle of a dusty barn? Probably not! The problem is it becomes very high-maintenance; it’s very difficult to do.” Basic strategies for limiting inhalation of airborne particles include cleaning stalls when the animals are outside in the morning and bringing them back in when the job is finished; wet-sweeping barn aisles; and using hay-steamers.

Winter racing, he adds, is not such a hardship for harness horses. “It reminds me of the standardbreds in Montreal […] I was coming from France and my first winter was like, ‘Wow - it’s really cold out there!’ They’re racing these standardbreds and it’s minus 15, minus 14 [degrees Celsius]. I was like ‘Wow, how do they do it? It must be bad for them!’” Yet was amazed to find that the local horses and horsemen endured the conditions with few complaints. Léguillette notes that research on the effect of cold on horses’ lungs during exercise has revealed that there is a definite “pro-inflammatory” response, but more investigation is required to learn whether there is lasting impact and what it might be. The type of cold encountered during peak Canadian winter wasn’t even part of the study cited, he observes with a laugh. “[The lead investigator] didn’t go to extreme cold because he was actually working in Oklahoma, and so he had to generate the cold, which was a challenge for him!”

From his base in Calgary, Dr. Léguillette admits he’s now as accustomed to Canadian winters as those standardbreds and harness horsepeople he first met at Hippodrome de Montreal.

His position as Chair in Equine Sports Medicine is five years in duration, which he would like to see extended indefinitely, but that would take investment by a major donor.

“I like evidence-based research, but the truth is equine research is quite poor,” he tells TROT. “There is not a lot of funding, so we don’t have a lot of studies and we don’t have a lot of answers. We have lots of questions, because people are very knowledgeable and they keep their eyes open and observe things. But we have very few studies overall in equine medicine, if you compare equine research to human or even small animal research. That’s where I’m trying to contribute for sure - trying to do research that’s relevant to the people, but there is probably one study available for a thousand questions, unfortunately!”

Léguillette says he enjoys being part of Calgary’s multi-faceted horse sport scene, from Century Downs to Spruce Meadows to the Calgary Stampede. “I think we are very lucky in Calgary because we have a very supportive industry,” he muses, on his way to teach a class of veterinarians-in-training. “The horses are very important in public opinion in Alberta. They are really part of the heritage here.”

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