All had been kept on pasture since weaning. For the study, seven of the horses were stabled and seven left at pasture for three months. At that time, the groups were switched and monitored for another three months. Every month, each horse underwent a complete airway examination. The nostrils were blocked to observe soft palate function, and mucus was graded on a scale of zero to five, with five indicating significant mucus build-up.
Neutrophils are the white blood cells that remove or kill bacteria.
In the lower airway, stabling was associated with a level of neutrophilic inflammation similar to that reported for racehorses with inflammatory airway disease. There was no correlation between upper and lower airway inflammation or the mucus score. To Holcombe's surprise, the pastured horses averaged a ranking of 1.6, while the stabled horses had an average rating of 0.2. In addition, the researchers found a trend in the data to indicate that horses displaced their soft palate more commonly while housed in the stable than while kept on pasture. Stabling, airway inflammation and dorsal displacement of the soft palate in young horses.