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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.Electronic supplementary materialThe online version of this article (10.1186/s12917-018-1636-4) contains supplementary material, which is available to authorized users.

Few data on cytokine profiles in bronchoalveolar lavage fluid (BALF) are available for racehorses with mild/moderate equine asthma (EA); cytological diagnosis being most frequently made from only one lung. The purpose of the study was to compare cytokine mRNA expressions and protein concentrations in BALF from both lungs. As part of a larger study, 250 ml saline was randomly instilled in one lung and 500 ml in the contralateral lung of 30 clinically healthy Standardbred racehorses. This procedure was repeated 72 h later, inversing the volume per lung. Cytological cutoff values for diagnosis of mild EA was neutrophil proportions > 10% when instilling 250 ml. Eleven horses that exhibited unilateral mild inflammatory cytology [i.e., normal cytology (<10% neutrophils) in the other lung] were enrolled. Protein concentrations were not significantly different between lungs, for any of the investigated cytokines. Relative mRNA expression of IL-1β (3.887 ± 0.929) and IL-10 (3.225 ± 0.516) were significantly higher in BALF from mild inflammatory lungs when compared with non-inflammatory ones (1.408 ± 0.337 and 1.488 ± 0.420, respectively); and also significantly correlated with neutrophil proportions (R = 0.45 and R = 0.58, respectively). These findings suggest that specific inflammatory response and/or regulation locally occurs within the lower airways.

Reasons for performing study Little data on BALF cytokine profiles are available from racehorses with IAD; cytological diagnosis being most frequently made from one lung only per horse. Objectives To compare cytokine mRNA expressions and protein concentrations in BALF from both lungs of horses with unilateral IAD‐consistent cytology. Study design Cross‐sectional study. Methods As part of a larger study, 250 ml saline was randomly instilled in one lung and 500 ml in the contralateral lung of 30 clinically healthy Standardbred racehorses. This procedure was repeated 72 h later, inversing the volume per lung. Cytological cut‐off values for IAD diagnosis was neutrophil proportions >10% when instilling 250 ml. For these samples, mRNA expression and concentrations of IL‐1β, IL‐4, IL‐8, IL‐10, IL‐17, TNF‐α and IFN‐γ were determined by RT‐qPCR and ELISA. Results Eleven horses had BALF with IAD‐ and CTL‐consistent cytology from, respectively, each lung, and were enrolled in the study (22 samples). Data were not significantly influenced by the sampling day, and BALF total cell counts or cytokine concentrations were not significantly different among lungs. Relative mRNA expression of IL‐1β (3.887 ± 3.082; P = 0.01) and IL‐10 (3.225 ± 1.710; P = 0.005) were significantly higher in BALF of IAD‐ compared to CTL consistent lungs (respectively 1.408 ± 1.118 and 1.488 ± 1.393); and also correlated to neutrophil proportions (respectively r = 0.54; P = 0.01 and r = 0.65; P = 0.001). Conclusions Differences in cytokine mRNA expression were associated with IAD‐ or CTL consistent BALF cytology in the same racehorses in training. These findings suggest that specific local immune reactions or regulation within the lower airways should be considered in IAD. Ethical animal research: The study was approved by the Regional Animal Ethic Committee, and informed consent was provided by all horse owners. Sources of funding: LABÉO, CISCO‐Oniris and AVEF (French Association of Equine Practitioners). Competing interests: None declared.