Quality changes in alfalfa hay during storage in bales

This study quantified changes in forage quality and chemical composition that occurred in baled alfalfa hay. Conventional and laboratory-scale alfalfa hay bales of three densities (1.0, 1.5, and 2.0 times the density of the conventional bale) were made at two percentages of moisture (20 and 30%) and were stored for 60 d in small haystacks insulated with straw. Bale treatments were sampled before storage and at 4, 11, 22, and 60 d postbaling. These sampling times corresponded to specifically chosen temperature maxima and minima found in typical curves of temperature and time for baled alfalfa hay. Most changes in forage chemical composition (quality) appeared to be closely related to accumulated heating degree days >30 degrees C. The most active period of quality degradation, as measured by increases in NDF and ADIN concentration, generally occurred between 4 and 11 d postbaling. High moisture treatment combinations that favored extended microbial activity continued to depress forage quality (particularly increased NDF and ADIN) between d 11 and 22. Little change in quality occurred after 22 d, indicating that most changes in forage quality were completed within a month after baling. Strong linear relationships were observed between both NDF and artifact N concentrations and heating degree days >30 degrees C in high moisture treatments.