Effect of agricultural and environmental factors on the hay characteristics involved in equine respiratory disease

It is now widely recognized that an environmental approach to the prevention of equine Recurrent Airway Obstruction (RAO), resulting from recurrent exposure to dust and aeroallergens, requires closer consideration. The aims of this study were to quantify the dust and aeroallergens in hays in order to characterize the health quality of hay, to identify the most variable parameters and determine which climatic factors and agricultural practices improve the health quality of hay. Hays were experimentally produced from a homogeneous grassland by applying different agricultural practices and rainfall amounts. Treatment effects were evaluated by dust and aeroallergen quantifications and identifications. The highest fungal contamination in airborne particles and dust contamination during late harvest, occurred when hay moisture remained high during (rainfall after cut) or after the making process (baled at 75% DM). Eurotium amstelodami and Eurotium repens were mainly found in all hays, while Aspergillus fumigatus was mostly found in hays showing the highest colony forming units (CFUs). Barn drying increased dust content and haylages produced the lowest level of airborne particles. The highest levels of endotoxins were found in the hay harvested at 75% of dry matter and the hay exposed to a rainfall after cut. The presence of zearalenone was only detected in these two low quality hays. Overall results suggest that better agricultural practices for hay making can be adopted and may be used in combination to significantly improve the health quality of hay, leading to a lower long-term exposure of horses. (C) 2009 Elsevier B.V. All rights, reserved.