PERFORMANCE COMPARISONS OF CONVENTIONAL AND LABORATORY-SCALE ALFALFA HAY BALES IN ISOLATED ENVIRONMENTS

Negative quality changes, including Maillard reaction damage, in alfalfa (Medicago sativa L.) hay frequently are associated with spontaneous heating resulting from packaging and storing forage at moisture levels in excess of 200 g kg-1. Forage at three moisture levels (268, 229, and 185 g kg-1) was packaged in laboratory-scale bales at 1.0, 1.3, 1.7, and 2.0 times the density of parent, conventional bales and subsequently incubated in two different isolated environments such that all measured heat accumulation was the result of self-generated heat. Laboratory-scale hay packages generated measurable heat and exhibited quality changes when incubated (i) between straw bales stacked in an open-air pole shed and (ii) in insulated incubator boxes in a storeroom the minimum ambient storage temperature was set at 25-degrees-C. Heat development and negative quality changes were greater in the box-incubation system, indicating a need to control ambient storage temperature. At the high and medium moisture levels, acid-detergent insoluble N (ADIN) fractions for high-density, box-incubated laboratory bales were at least similar (P > 0.05) to those of parent, conventional bales, despite large disadvantages in measures of accumulated heat. These responses in laboratory bales were consistent with those reported in previous haystack-incubated studies and suggest that the environmental heat component created by adjacent conventional bales in those studies may have had a limited direct effect on ADIN content. Increasing density of laboratory bales probably rendered alfalfa proteins more susceptible to Maillard reaction damage and/or allowed the reaction to proceed more efficiently with respect to self-generated heat than it did in conventional bales.