Abstract
BackgroundAvoidance of antigenic stimuli was found to significantly reverse airway obstruction of horses with severe equine asthma (sEA). To date, no published study investigated the influence of steaming hay on lower airway condition of sEA-affected horses. The objectives were to determine the clinical, cytological and cytokine respiratory responses of both sEA and control (CTL) horses experimentally exposed to steamed or dry hay.ResultsA cohort of 6 sEA horses and 6 CTL horses was involved in this field study. On day 0, both groups were fed with steamed hay for 5 consecutive days, followed by a wash-out period of 26 days prior to be fed with dry hay for 5 consecutive days. Investigations performed 2 days prior to and 5 days after each challenge included clinical score, tracheal mucus accumulation, and bronchoalveolar lavage fluid (BALF) cytology and cytokine mRNA expression. Feeding steamed hay significantly decreased its mould content (P < 0.001). Mucus score significantly increased when feeding dry hay (P = 0.01). No significant influence of challenge type was found on clinical score. Percentages of neutrophils (P < 0.001) as well as mRNA expression of IL-1β (P = 0.024), IL-6R (P = 0.021), IL-18 (P = 0.009) and IL-23 (P = 0.036) in BALF of sEA affected horses were significantly increased after both (steamed and dry hay) challenges. Relative mRNA expression of IL-1β, IL-6R and IL-23 in BALF were also significantly correlated to neutrophil percentages and both clinical and tracheal mucus score.ConclusionsSteaming significantly decreased mould content but inconsistently influenced the respiratory response of sEA affected horses when fed hay. Based on BALF cytology and cytokine profiles, its relevance might be controversial as a non-medicinal therapy for sEA-affected horses.
Highlights
Avoidance of antigenic stimuli was found to significantly reverse airway obstruction of horses with severe equine asthma
Severe equine asthma is a chronic disease of adult horses characterised by frequent coughing and increased respiratory effort at rest, as well as marked lower airway inflammation and reversible airway obstruction [1]
While neutrophils involvement in the pathophysiology of this disease is well defined, controversies still persist in terms of T-helper (Th)-1 and/or Th-2 polarisation, as determined by cytokines Ribonucleic acid messenger (mRNA) expression in bronchoalveolar lavage fluid (BALF)-derived
Summary
Avoidance of antigenic stimuli was found to significantly reverse airway obstruction of horses with severe equine asthma (sEA). No published study investigated the influence of steaming hay on lower airway condition of sEA-affected horses. Severe equine asthma (sEA; previously known as recurrent airway obstruction) is a chronic disease of adult horses characterised by frequent coughing and increased respiratory effort at rest, as well as marked lower airway inflammation and reversible airway obstruction [1]. Soaking and high-temperature steaming of hay for 16 h and 50 min respectively, significantly reduced respirable particles exposure; endotoxin levels were not investigated [15, 16]. There is no published study that has investigated the potential influence of steaming hay on lower airway inflammation of sEA-affected horses
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