Effect of dry matter content at baling on change in forage constituents during the storage of alfalfa hay

The purpose of this study was to evaluate the effect of DM content at baling on the pattern of forage constituent change and on DM and nutrient losses during storage. Alfalfa forage, baled at 64.1-66.2, 71.9-73.2, and 75.4-77.4% DM, was designated Low, Medium, and High DM treatments, respectively. Hay generated from each treatment was stored in a pole structure as two 74-bale stacks per treatment, using a bale wagon. Core samples were collected from bales on days 1, 4, 7, 14, 21, and 60 of storage. Bale temperature was monitored for eight bales per treatment daily for the first 35 d of storage and then on days 45, 50, and 60. Peak storage temperature reached was influenced (P < 0.05) by forage DM at baling; the highest peak temperature being associated with Low DM hay. DM losses also were higher (P < 0.05) in Low DM hay relative to either Medium or High DM bays, averaging 10.1, 4.5, and 3.0%, respectively. Dry matter (DM), neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent insoluble nitrogen (ADIN), and glucosamine contents increased in all forage treatments during storage; the extent of increase was more (P < 0.05) in Low DM hay than in High DM hay. Cellulose, lignin and crude protein (CP) concentrations followed a similar pattern during storage for hay baled and stored at the three DM contents. Soluble carbohydrate content loss was higher (P < 0.05) in Low DM hay relative to High DM hay. Forage DM content at baling will influence stack temperatures and extent of nutrient change during storage. Most changes in constituents of low DM hay occurred within the first 14 d of storage, a period within which peak temperatures were recorded in all forages. The study also showed that alfalfa forage can be stored at a DM content of 76% with minimal nutrient change and loss, which is lower than normally recommended.