COMPARISON OF AIRWAY CYTOLOGY IN HEALTHY ADULT HORSES HOUSED EITHER ON PEAT BEDDING OR WOOD PELLET

Purpose of the study: Airborne particles are potential predisposing factors for equine asthma. The study investigates the effects of two bedding materials (peat, wood pellets) on equine airway health. Methods used: 29 clinically healthy adult horses were stalled on different bedding materials for 35 consecutive days (peat – wood pellet – peat) during November 2018– February 2019. Feeding, exercise or management did not change. Clinical examination was performed and tracheal wash (TW) and bronchoalveolar lavage fluid (BALF) samples obtained for cytological analyses at the end of each period. TW and BALF neutrophil percentages were compared with Related- Samples Wilcoxon Signed Rank Test using horses as their own controls. Significance was set at P < 0.05. Summary of the results: TW neutrophil percentage was lower after the wood pellet period (mean ± SD; 18.2 ± 17.5) compared to second (38.4 ± 25.8; P = 0.001) but not the first peat period. BALF neutrophil percentage was lower after the wood pellet period (1.9 ± 1.3) compared to second (4.8 ± 3.5; P < 0.001) but not the first peat period. Neutrophil percentage was higher in both TW and BAL after the second peat period compared to the first peat period. Conclusions: No consistent difference in airway neutrophilia was detected in tracheal secretions or BALF after peat or wood pellet period. However, neutrophilia increased after the second peat period compared to the first one possibly due to seasonal changes.