Self-heating of Hay and Grain in Dewar Flasks and the Development of Farmer's Lung Antigens

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Abstract
SUMMARY: In moist hay allowed to self-heat aerobically in Dewar flasks, the pattern of temperature change with time was affected considerably by the type of hay and duration of storage, but there was a relationship between water content and maximum temperature reached. Below 29% water content there was little heating or antigen production; in the critical range of 29-34% water content, different lots of hay self-heated to different temperatures between 33 and 55° and varied widely in their content of farmer's lung hay antigen complex (FLH), the wetter hays usually producing the more antigen; all samples with 40% water heated to c. 65° and produced FLH antigen, associated with the presence of Thermopolyspora polyspora. Progressively less antigen, especially in the lower regions of the flasks, was produced as water content increased from 47 to 68%. Moist barley and oat grain also self-heated and produced FLH antigen, usually only in the middle of the grain mass, where T. polyspora was most abundant; the drier upper layers and the lower regions where excess water accumulated were free from the antigen.