Wednesday, April 24, 2019

Mild asthma can separate winners from losers on the racetrack

Dr Laurent Couetil treats asthmatic horse with a nebuliser

A split second may be all that separates the winner and the rest of the field. Anything that limits peak performance reduces the chance of success. In many cases the problem lies in the lungs. 

A recent study has shown that mild equine asthma is common in racing horses and negatively impacts performance.

The study, led by Laurent Couëtil, director of Purdue University’s Equine Sports Medicine Center, found that approximately 80% of racehorses had evidence of low-grade inflammation in their lungs and that the greater the lung inflammation, the poorer horses performed. 

Couëtil explains: “Unlike the heart or muscle, the lung in the horse athlete is a limiting factor. Even in healthy horses, breathing is a limiting factor on performance. So, if you take a little bit away from that, the consequences can be severe.”

Thoroughbred horses, trained in eight separate yards, were recruited to the study, which was carried out at the Shelbyville, Indiana, racetrack. 

Horses were examined an hour after the race. The examination included endoscopy of the respiratory tract, and the collection of a sample of cells from deep within the lungs (bronchoalveolar lavage - BAL)

Then, within a week after the race, the research team measured the amount of dust in the breathing zone of the horses. Horses were fitted with sensors near their noses to measure how much dust they were inhaling. They wore the sensors while going about their daily business, and the findings show that most of the dust they inhaled was coming from hay.

The research team found that the greater the exposure to dust, the worse the lung inflammation. However, it was not just any type of dust, but “respirable dust” (particles that are less than 4 microns in diameter - too small to be seen with the naked eye, and so small that they can penetrate deep into the lungs) that was most important.

“We know dust is the problem, but now we’re trying to figure out how to reduce it. In our next study, we’re testing different types of hay to see if we can reduce the amount of dust horses are coming into contact with while they’re eating,” Couëtil said.

Some horses will be fed steamed hay, which incubates in a sauna-like case for an hour before being fed to horses. The final product is a little wet, but the process kills much of the mould and dust that accumulates in bales of hay. Other horses will be fed baled silage, or haylage, which is hay baled at a higher moisture content than dry hay and stored in a tightly sealed plastic wrap.

Previous work* by Couëtil and colleagues found that some supplements could also help horses recover from severe asthma. When fed together with a lower-dust feed option, Omega-3 fatty acid supplements were shown to enhance and hasten recovery.

“The horses that were fed the supplement improved much quicker and to a much greater extent. Many of them stopping coughing within a couple weeks,” Couëtil said. “The next step for us is trying to understand the mechanism that makes that happen.”

For more details, see:

An observational study of environmental exposures, airway cytology, and performance in racing thoroughbreds.
Kathleen M. Ivester, Laurent L. Couëtil, George E. Moore.
Journal of Veterinary Internal Medicine (2018) Vol 32, pp 1754-1762

*Omega‐3 Fatty Acid Supplementation Provides an Additional Benefit to a Low‐Dust Diet in the Management of Horses with Chronic Lower Airway Inflammatory Disease
N. Nogradi,  L.L. Couetil, J. Messick,  M.A. Stochelski, J.R. Burgess
J Vet Intern Med. (2015) 29(1): 299–306.

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