Breathing Easy Key to Equine Performance and Health

Photo: Erica Larson, News Editor

The equine respiratory system can be a major cause of poor performance or premature retirement from competition. Let's look at some of the key factors:

The Nose: Horses are "obligate nasal breathers" which means that during intensive exercise the nose is the only way air reaches the lungs. A significant portion of the horse's nasal passage is unsupported by bone or cartilage. This portion of the nasal passage collapses in all horses when breathing-in during exercise, reducing the size of the airway and greatly increasing resistance to airflow.

At rest, more than 50% of resistance to air flow comes from the nasal passages. This percentage increases to 80% during exercise. In addition, pathological upper airway obstructions (haryngeal hemiplegia, or roaring, for example) and functional obstructions (such as significant head flexion) create additional increases in the work of breathing. This makes it more difficult to move air to the lungs.

The Lungs: Resistance to airflow and high pulmonary blood pressure are known to cause lung bleeding. The lung tissue that separates the airways from the blood vessels is extremely thin--about 1/100 the thickness of a human hair. This ultra-thin membrane makes for efficient oxygen and carbon dioxide transfer, however, it also makes the membrane very fragile and it can rupture when exposed to high blood pressures and the enormous suction-like airway pressures generated during intensive exercise. This is referred to as exercise induced pulmonary hemorrhage (EIPH).

Numerous studies show that essentially all exercising horses experience some degree of EIPH during intensive exercise. However, less than 5% of these horses show blood at the nostrils. Symptoms of EIPH can include poor performance, coughing, extended cooling-out, and frequent swallowing. Moreover, each incidence of EIPH contributes to scar tissue formation and further bleeding. The lung damage from repeated episodes of EIPH can shorten a horse's competitive career.

Breathing in Stride: Horses are unique in that at the gallop, breathing and stride are linked. Horses take a single breath with each stride. At speeds beyond a hand gallop, a horse increases its speed by increasing stride length, not by moving their legs faster. When the horse lengthens its stride to increase speed, it also takes deeper, longer breaths providing the lungs with more air. A horse struggling to move air in and out of the lungs may shorten its stride and fatigue quicker. Conversely, when a horse breathes easier, stride adjustability or lengthening is easier.

The Treatments: There are a variety of treatments commonly used to combat EIPH and other breathing issues. Furosemide administration, bronchodilators, and corticosteroids are all used to treat specific respiratory conditions.

Recently, equine nasal strips have become a popular option for controlling respiratory resistance. Marketed by the FLAIR company, the drug-free Strips adhere to horses' noses, providing a spring-like force that gently supports the nasal passages and reduces soft tissue collapse during exercise. The strips reportedly reduce airway resistance, EIPH, fatigue and help horses recover quicker after exercise

Breathing easier helps maintain optimum performance. The benefits of breathing easier are important for horses competing at all levels of fitness and skill, as exercise is often a greater challenge for the less-fit animal.

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