Equine airway inflammation in loose-housing management compared with pasture and conventional stabling

Icelandic horses are often stabled in loose-housing systems, and to date this type of stabling has not been evaluated with regard to its potential impact on respiratory health. The objective was to assess if differences in management systems (eg, conventional stable, loose housing and pasture only) affect the degree of airway inflammation, evaluated by cytology of tracheal aspirate (TA) and bronchoalveolar lavage (BAL) fluid. In total, 84 Icelandic horses (aged 8.1±4.6 years) housed under three different management systems (conventional stables [n=29], loose-house systems [n=29] and pasture [n=26]) were included. Endoscopy including mucus scoring, TA and BAL was performed. TA and BAL cytologies were evaluated by performing both the total cell count (TCC) and the differential cell count (DCC). Significantly higher BAL neutrophil DCC (P=0.032, P=0.040) and TA TCC (P=0.007, P=0.028) were found for each of the two groups of horses with indoor access (conventional stable and loose housing) compared with the pasture group. Regardless of stabling environment, weak positive correlations were found between TA and BAL TCC (r=0.37, P<0.001), between TA TCC and TA neutrophil ratio (r=0.33, P=0.002), as well as between TA and BAL neutrophil ratio (r=0.39, P=<0.001). A larger proportion of horses with indoor access showed evidence of subclinical airway inflammation characterised by an increase in TA and BAL neutrophil ratios.