RAO - Summer

Kate Hore RNutr(Animal). Snr Nutritionist at NAF

RAO, or recurrent airway obstruction, is commonly likened to asthma in humans and can be a difficult problem to manage. It is a chronic disorder which usually shows itself as a consistent cough with nasal discharge, and frequently limits the horses performance.

If the horse is only mildly affected then symptoms may only occur during or just after exercise, however even a mild cough should not be discounted as not a problem. Horses have a very low cough response compared to humans, therefore if a cough is seen then the horse is certainly experiencing respiratory stress. Sub-clinical respiratory stress is commonly found in working horses, and respiratory capacity is often considered to be the limiting factor for performance in elite equine athletes. Therefore maximising respiratory health should be considered for all working horses, and the as owners and trainers we ignore the occasional cough at our peril.

For those with more serious cases may wheeze almost constantly, with crackling being heard upon use of a stethoscope. These more severe cases may also be accompanied by heave lines, muscular lines around the area of the ribcage, caused by muscles having to work harder in order to exhale. Normally affected horses won’t demonstrate a high temperature, though if opportunistic bacterial infections take hold, then antibiotics may be needed. For those cases where impact on performance is mild, brochoalveolar lavage may be used to assess neutrophil levels, which indicate lower respiratory tract inflammation.

A number of allergens contribute to RAO, and in summer these can drastically increase. High levels of pollen and dust exist during the warmer months, a time when many horse owners like to turn out their horses. Here the condition becomes known as SPAOPD (Summer Pasture Associated Obstructive Pulmonary Disease). Pollen is a common trigger in respiratory disorders, along with mould spores, and their ubiquitous nature can make it very difficult, if not impossible, to avoid them. These allergens cause irritation and inflammation of the delicate lining of the lungs as well as bronchoconstriction; this inflammation leads to fluid production and hence the mucus discharge and crackling chest noises.