Submitted to: University of Wisconsin Extension Family Living Website
Publication Type: Experiment Station
Publication Acceptance Date: 7/15/2008
Publication Date: 10/1/2008
Citation: Coblentz, W.K., Hoffman, P.C. 2008. Heat Damaged Forages: Effects on Forage Quality. University of Wisconsin Extension Family Living Website. Focus on Forage. 10(8). Available: www.uwex.edu/ces/crops/uwforage/HeatDamage-FOF.pdf
Technical Abstract: Traditionally, heat damage in forages has been associated with alterations in forage protein quality as a result of Maillard reactions, and most producers and nutritionists are familiar with this concept. However, this is not necessarily the most important negative consequence of spontaneous heating. In recent studies, concentrations of NDF increased by as much as 11 percentage units as a result of spontaneous heating, Generally, NDF is not actually generated during the heating process. Increases in NDF concentrations occur because cell solubles (most specifically, sugars) are oxidized preferentially during microbial respiration. Fiber components, such as NDF, ADF, and lignin, are generally inert during this process, but their concentrations increase because cell solubles are reduced during oxidation. This is particularly important because sugars and other cell solubles are essentially 100% digestible, while fiber components are not. As a result, spontaneous heating decreases the energy density of the forage. Recent research indicates that traditional guidelines defining heat-damage to forage proteins are reasonable, but concurrent reductions in energy density may be the most serious consequence of spontaneous heating.