COMPARISON OF WILTED SILAGES OF ALFALFA CUT AT TWO STAGES OF MATURITY WITH FORMIC-ACID-TREATED SILAGE FROM EARLY-CUT ALFALFA

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Abstract
First cut alfalfa was harvested at early bloom and stored as early-cut formic-acid-treated silage (EFS) and early-cut wilted silage (EWS). Late-cut wilted alfalfa silage (LWS) was harvested 15 days later. Dry matter (DM) yields were 2.91, 2.82 and 3.12 tonnes/ha, respectively, for EFS, EWS and LWS. In the same order, for feeding in spring of the subsequent year, recoveries from storage were 79.8, 85.6 and 86.0% of DM; 84.1, 92.3 and 88.1 of energy; and 77.6, 91.5 and 92.2% of crude protein (CP). Ad libitum DM intakes were not significantly different (102.6, 99.7 and 99.1 g/Wkg0.75 for the three treatments, respectively). Late-cut forages (both fresh and wilted) were significantly (P < 0.05) higher in fiber fractions (lignin and acid detergent insoluble nitrogen) than the early-cut forages. Similar trends persisted among the silages at feeding time after 9 mo. of storage. Differences in the chemical composition and digestibilities of nutrients for EFS and EWS were small and statistically not significant (P > 0.05). When fed at maintenance level, the digestibility values for DM, energy and cellulose were significantly (P < 0.05) higher for EWS than for LWS but not for EFS. However, when fed ad libitum in combination with corn silage (1:1 DM basis), there were no significant effects of either harvesting date or wilting vs. formic acid treatments on the digestibility of nutrients.