COMPROMISE of the respiratory system is one of the main reasons for poor performance in the horse (Buechne-Maxwell et al, 1996). Recurrent Airway Obstruction (RAO) is an allergic, inflammatory and obstructive airway disease that is often associated with older horses.

The condition is like that of human asthma. It is mostly associated with horses that are stabled and fed on hay. It can result from the inhalation of dusts, such as those associated with hay and bedding materials. These dusts contain allergens, endotoxins, moulds and other small particles that can start the severe inflammation of the lungs associated with RAO. This condition affects between 10-15% of adult horses living in temperate climates (Hotchkiss, Reid and Christley, 2007).