An evaluation of the hygienic quality in single‐species hays and commercial forages used in equine nutrition

Pulmonary diseases such as recurrent airway obstruction have become a major concern in the horse industry. Airborne dust, including aeroallergens from forages, is suspected to be the main factor in its aetiology. Hypothesizing that grassland flora could affect hay hygienic quality, and therefore have implications for the respiratory health of horses, we compared five single‐species hays (Trifolium repens, Lolium perenne, Alopecurus geniculatus, Poa trivialis and Holcus lanatus). Multi‐species hay from Normandy, and different commercial forages (single‐species haylage, multi‐species haylage, Crau hay and hay from Swiss mixing), chosen to represent current horse forages, were also investigated. Dust, moulds, pollens and endotoxins were different among forage types, while mycotoxins were not detected in any of the forage types. Holcus lanatus hay was the dustiest among the single‐species hays but also the least contaminated by moulds. A particular mould profile was associated with each plant species. The four commercial forages appeared to have a better hygienic quality than the multi‐species hay. Among commercial forages, the single‐species haylage was the least dusty but also the most contaminated by moulds. Overall the results suggest that the hygienic quality of equine forages could be improved by an appropriate choice of grassland species.