RELATING SUGAR FLUXES DURING BALE STORAGE TO QUALITY CHANGES IN ALFALFA HAY

Negative quality changes that occur when alfalfa (Medicago sativa L.) is baled at moisture levels in excess of 200 g kg(-1) have been well d ocumented; however, relatively little is known about changes in nonstr uctural carbohydrate pools during bale storage and how these changes a re involved in depression of forage quality. The objectives of this st udy were to quantify nonstructural carbohydrate pools at specific time periods during bale storage and to relate these findings to accumulat ed heating degree days and traditional quality indices. Alfalfa forage was field-dried to high-and low-moisture concentrations of 299 and 19 7 g kg(-1), respectively, and packaged as conventional (CONV) and labo ratory-stale (LAB) bales. During the first 4 d of storage, reducing su gar concentrations appeared to increase in high moisture conventional bales and high-moisture laboratory bales made at twice the density of conventional bales (treatments that most favored spontaneous heating). Between 4 and 11 d in storage, reducing sugar concentrations for thes e treatments decreased sharply and continued a gradual decline thereaf ter, effectively mirroring the concurrent increases in acid-detergent insoluble N (ADIN). Nonreducing free sugar, total free sugar, and tota l nonstructural carbohydrate (TNC) concentrations declined rapidly dur ing storage; these responses were linearly related to increases in hea ting degree days >30 degrees C. For high-moisture treatments, ADIN con centrations were strongly correlated with total free sugar and TNC lev els (r = -0.90 and -0.90, respectively). Correlations between ADIN con centrations and reducing sugars (r less than or equal to -0.72) appear ed weaker. At the low moisture level, reducing sugar concentration was not related (P greater than or equal to 0.05) to ADIN concentration.