RELATIONSHIP OF EQUINE HOUSING TO LARGE AIRWAY INFLAMMATION

The pasture, as compared to stall confinement, has been considered a m ore desirable environment for maintaining the health of the respirator y system in the horse. This conclusion is based on reports which showe d that ventilation in most barns was generally poor, and that horses b edded on straw and fed hay were exposed to many forms of respirable de bris, In this study, six normal horses were evaluated for evidence of airway mucosal inflammation after being housed on pasture or stabled i n a barn for one month. The response of the horses' airways was measur ed by assigning scores for the degree of tracheal mucosal secretions t hat were observed by endoscopic visualization. Cytological examination of transtracheal wash secretions was also performed, as well as histo logic evaluation of tracheobronchial tissues obtained by a transendosc opic epithelial biopsy technique, Samples were collected at three time points; the initial collection occurred after the horses were housed on pasture for one month. The horses were subsequently moved to a barn for an equal length of time and samples were obtained at the end of t his period. The horses were then returned to their original pasture an d final sampling was performed after they were housed in this environm ent for two months. There were no significant changes in any of the pa rameters evaluated. regardless of the environment in which the horses were maintained. These findings indicate that housing horses in a barn for four weeks does not cause tracheobronchial mucosal inflammation i n a manner that could be detected using the methods employed in this s tudy.