This study was conducted to determine the optimum levels of silage additives on reed silage harvested at different maturity stages. Reed plants harvested at early boot (23% DM), late boot (24% DM) and early heading stages (26% DM) were chopped to an
average particle length of 1 cm and ensiled in 500 g mini silos, with and without additive treatment. The additives used were formic acid applied at 0.2, 0.4 and 0.6% of the fresh crop weight and molasses applied at 0.5, 1.0 and 2.0% of the fresh crop weight. Treatments were allocated in a randomized complete block design with three replicates. The silage pH, acid and NH₃-N/TN concentrations, and the situ DM disappearance at 0, 12, 24, 48 h of incubation in Korean beef cattle were examined. The silage fermentation quality and in situ digestibility were not affected by the different maturity stages. Silage treated with formic acid had the lower pH (4.5, 4.3 and 4.0 at 0.2, 0.4 and 0.6%, respectively) than the molasses (5.0, 4.8 and 4.4 at 0.5, 1.0 and 2.0%, respectively) and untreated (5.2). While the lactic acid concentrations increased with the higher levels of molasses, the higher levels of formic acid resulted in lower concentrations of lactic acid (p<0.05). The formic acid and molasses treatments were markedly effective for reducing the ammonia production which was similar at most addition levels (less than 10% NH₃-N/TN at all addition levels). Higher in situ digestibility resulted from adding additives, especially with formic acid treatment (about 10% at 0.2% level) (p<0.05). No significant difference was found between the addition levels of both additives. It is concluded that formic acid or molasses applied at ensiling produced better fermented silage and enhanced silage digestibility compared with untreated reed silage. The highest quality of reed silage was observed at 0.2% of formic acid and 2.0% of molasses, which are considered as the optimum levels of addition in this study.