Horse & Hound
Winter respiratory health
Why reducing respirable particles indoors is important for horses
MOST horses spend more time indoors in winter, both at rest in the stable and during exercise in an indoor school.
Compared to being at pasture, this represents a major change in a horse’s lifestyle – in terms of the bedding underfoot, the surface he works on, the forage he eats and the air he breathes when confined to a smaller space. These factors can affect the airway health of all horses, but most significantly those with airway inflammation.
Equine asthma (EA) is the term used to describe horses with chronic, reversible airway inflammation. This can range from mild exercise limitation (mild EA, previously called inflammatory airway disease), to horses who cough, have nasal discharge and a raised breathing rate at rest (severe EA, previously called recurrent airway obstruction). Airway inflammation develops as a response to the quality of a horse’s breathing environment, in particular the levels of different “respirable particles” within his breathing zone – the area at nostril level. Organic dusts, mould spores, bacterial components
(in particular endotoxins) and chemical irritants such as ammonia are the key particles small enough to enter a horse’s airways and cause inflammation. Cold air may slow down the ability of the lungs to remove these irritants.
Horses with severe EA will have obvious signs after exposure to high respirable particle environments. Because mild EA is subclinical (not observable) at rest, a horse may appear “normal” even though his airways are inflamed; with ongoing exposure, however, poor performance will develop.
Recent studies have shown that an increased number of mast (allergic inflammatory) cells in the airways of racehorses makes them 1.5 times less likely to win a race. So while it is vital to understand how to improve the environment for a severe EA horse, it is just as useful in milder EA cases.
There is also an appreciation that high respirable particle levels can increase mucus production in the lungs without causing inflammation, yet leaving a sport horse less willing to perform. All horses could therefore benefit from an improved breathing environment, although those with EA need more specific changes.
A HORSE on a straw bed in a conventional stable, eating dry hay, could be breathing up to 15 times more respirable particles than he would if he was grass-fed at pasture. Since an outdoor life may not be an option in winter, it makes sense to clean up his indoor environment in these key areas…