Effects of chemical additives on fermentation characteristics of high-moisture alfalfa silage

Alfalfa is sometimes harvested with a high moisture content that increases the chances for undesirable fermentations. The objective of these experiments were to determine the effectiveness of Safesil (SF; active ingredients: 10% potassium sorbate, 20% sodium benzoate, and 5% sodium nitrite) and Safesil Challenge (SC; active ingredients: 7.5% potassium sorbate, 15% sodium benzoate, and 10% sodium nitrite) from Salinity, Sweden, on improving the fermentation of high-moisture alfalfa silage. Alfalfa was directly chopped at 23% DM and used in two experiments. In Experiment 1, we evaluated the effect of SF on the characteristics of early fermentation. Four individual 1-kg replicates of untreated alfalfa or alfalfa treated with 4 L/t of SF were ensiled in vacuumed and heat-sealed, nylon-polyethylene bags for 1, 2, 4, and 7 d. Data were analyzed as a 2 x 4 factorial arrangement of treatments, with main factors of treatment, days of ensiling, and their interaction. In Experiment 2, the long term effects of SF or SC with and without air stress during storage were determined. Replicated silos (7.5 L) were packed (density of 224 kg of DM/m3) with the same forage described above and were untreated or treated with SF (3 and 4 L/t) or SC (2 and 3 L/t). Half of the silos were submitted to a 2-h weekly air stress. Data were analyzed by ANOVA as a 2 x 5 factorial arrangement of treatments with main factors of air stress, treatment, and their interaction. In Experiment 1, pH decreased and acids and ethanol similarly increased for untreated and treated silages as ensiling progressed. Compared with untreated silage, treated silages had fewer yeasts (P < 0.01) at 4 d of ensiling (4.52 vs. 2.96 log cfu/g) and less enterobacteria after 1 d (6.79 vs. 5.81 log cfu/g). Ethanol concentration was numerically lower for treated silages at all time points. In Experiment 2, for silos submitted to air stress, the DM recovery after 100 d was higher (P = 0.04) for SF- and SC-treated silage than for untreated silage. After 100 d, numbers of yeasts and molds were less than 2.00 log cfu/g for all treatments. These experiments showed that Safesil can quickly reduce harmful microorganisms, such as yeasts and enterobacteria, in high-moisture alfalfa and that Safesil and Safesil Challenge can improve DM recovery in silage submitted to air stress.