Salting is a traditional, empirical practice used commonly in dairy farming regions to prevent moulding and heating in hay. Our aim was to evaluate the effect of salting hay on the proliferation of microorganisms, particularly thermophilic actinomycetes and moulds involved in farmer's lung disease. Fifty-one pairs of salted and unsalted hay bales from 14 farms were produced during the haymaking season between March and July. Both the salted and the unsalted bales came from the same field, and were packed and stored under identical conditions. Sampling was performed by microbiological analysis including 6 culture media during the winter following salting (January-February). The use of salt did not significantly decrease the amount of Saccharopolyspora rectivirgula , the actinomycetes most commonly involved in farmer's lung disease, or that of Absidia corymbifera, Eurotium amstelodami and Wallemia sebi , three moulds responsible for farmer's lung disease in eastern France. Our results are important in that they can inform farmers and dispel the false sense of security induced by salting, which is reinforced by the misconception that palatable hay is healthy hay.