Winter Racing – The Breath of Cold Air

As I was flipping through channels watching the recently concluded Sochi Winter Olympics, I landed on the image of a Nordic skier coughing just after he finished his race.

Coughing is not something typically seen in Olympic-level competitors, but it is certainly not uncommon in winter athletes and, in particular, cross country skiers. In fact, up to 50 percent of them have some degree of exercise-induced bronchoconstriction. This is due largely to the effect of drawing in large amounts of cold, dry, unconditioned air into the lungs under athletic extremes.

So why is this relevant to racehorses? Ontario has been experiencing one of the coldest winters in a long time and people are asking; does racing in the extreme cold have a damaging impact on a horse’s health?

In the mid-2000’s, Dr. Mike Davis and his colleagues from Oklahoma State University evaluated the impact of inhaling cold air on the lung function of thoroughbred horses. Under laboratory conditions, they found that horses travelling at 20 miles/hour in a 5⁰C environment had lungs that became significantly cooled (5⁰C lower than body temperature) and, in the process, showed signs of injury to the lining of the airways. This airway cooling also caused a dysfunction in some of the airway cells leading to an increase in tracheal mucous production. It is thus important to remember that some (2/5) clear mucous after a race may be a normal consequence of cold weather racing. Horses that exercised at lower intensities (comparable to jogging) in -5⁰C temperatures developed bronchoconstriction (narrowing of their airways) 48 hours after exercise.

Given that the typical Standardbred jogs daily in subfreezing temperatures, there is the potential that they will be affected by ongoing bronchoconstriction. The researchers also found that exercising horses in -15⁰C temperature affected airway immunity, potentially increasing the susceptibility to respiratory pathogens such as viruses and bacteria and also to the development of asthma.

Why do these problems occur? During less intense exercise, the horse, an obligate nose-breather, can warm and humidify the air before it reaches the lungs. But when the exercise intensity is increased to that of racing, the volume of air passing through the upper airway becomes too great to adequately condition. When this unconditioned air reaches the lungs, there is a loss of heat and water from the surface of the lower airways in its attempt to condition it. The end result is a cold and dehydrated lower airway prone to cell injury. Some of the markers of inflammation produced are similar to those seen in asthmatics suggesting that repeated racing in cold weather can initiate or perpetuate chronic airway inflammation. The bronchoconstriction that ensues may lead to poor performance as the only sign (without a cough or nasal discharge). Sometimes pulmonary bleeding will occur secondary to airway inflammation or it may result from a reflex increase in blood pressure caused by exposure to the cold. Horses racing in colder temperatures reportedly have twice the risk of Exercise Induced Pulmonary Hemorrhage (bleeding) as those racing in warmer climates (Hinchcliff 2010).

Typically airway disease is thought of as a summer issue, mostly related to allergies, but it is important not to forget the cold as a source of airway malaise. In fact, since cold air is always dry, the burden on the lower airway to condition the inspired air is greater in the winter than summer and the loss of heat and water during expiration of air is also greater in the winter. This loss of water from the airway is a poorly recognized contributor to dehydration in the horse and dehydration is a major cause of fatigue and poor performance.

Therefore, it requires extra effort in the winter to ensure that your horse is drinking well. Offering warm water, salt (loose or oral with applesauce), steamed hay or soaked hay cubes are common ways to increase water consumption, keeping in mind that a horse that does not drink well will not eat hay well and vice versa. Of course there may be medical reasons why your horse is not drinking well so always consult your veterinarian.

How can racehorse airways be managed in the cold?

• Using equine appropriate nose masks while jogging may help keep the airway warm and hydrated, much like a face mask does for people.

• Beta2-agonist inhalers, used under veterinary supervision, can help treat the bronchoconstriction. Since the use of inhalers are not permitted on race day, nebulized saline may be used as an alternative, again under veterinary supervision, and is a therapy used by elite speed skaters before and after competition.

• Wait for a warmer part of the day if you need to train a mile, and consider your training plan for seasoned racehorses, do they need the speed work between races?

• Ensure that your horse is up to date with vaccination for equine respiratory diseases.

• Take the horse’s temperature on a daily basis as an increase in temperature may be the earliest sign of an infectious problem.

Winter racing is a long-standing pastime in the horse racing industry and Ontario’s horses thrive in the cold. Awareness of some of the effects of the cold weather on the horses, though, will help improve their health and extend their racing career.

Dr. Alison Moore is a Board Certified equine internal medicine and sports medicine specialist from Cambridge, Ontario who has been involved in the Standardbred industry as an owner, breeder and veterinarian. Over the last 14 years she developed a specialty practice that focused on performance problems in racehorses and sport horses. She has been appointed to a number of equine working groups, task forces, and committees concerning equine veterinary issues over the years and has been committed to ensuring that practicing veterinarians remain at the forefront of regulatory decisions regarding the health and welfare of racehorses. Recently, she joined the Animal Health and Welfare Branch of the Ontario Ministry of Agriculture where she continues to provide veterinary expertise to the Province.

The views presented in Trot Blogs are those of the author and do not necessarily represent those of Standardbred Canada.