BIOLOGY AND EFFECTS OF SPONTANEOUS HEATING IN HAY

The negative consequences of baling hay before it is adequately dried are widely known to producers. Frequently, these problems are created by uncooperative weather conditions that prevent forages from drying (rapidly) to concentrations of moisture that allow safe and stable storage of harvested forages. Negative consequences associated with baling hay before it is adequately dried include molding, spontaneous heating, undesirable changes in forage quality, and the potential for spontaneous combustion. The magnitude and duration of spontaneous heating is affected by numerous variables, including forage moisture content, bale size, bale density, climatic conditions, and use of preservatives. Most changes in nutritive value, including estimates of ruminal protein degradation and the associated ruminal decay rate, are related to spontaneous heating in surprising close linear relationships. Spontaneous heating has a profoundly negative overall effect on forage quality, and great care should be exercised to properly dehydrate forages prior to baling, thereby avoiding this undesirable phenomenon