Effect of microbial and chemical additives on the fermentation and aerobic stability of alfalfa silage ensiled at 2 dry matters and subjected to air stress during storage.

We evaluated the effects of different types of additives on the fermentation and aerobic stability of alfalfa (Medicago sativa) ensiled at 2 dry matters (DM). Alfalfa was untreated (CTRL) or treated with sodium benzoate, potassium sorbate, and sodium nitrite (SFE), or microbial inoculants (Lactobacillus plantarum MTD1 [LP] or L. buchneri 40788 and Pediococcus pentocaseus 12455 [LBPP]) at a moderate (38%) and high (46%) DM using a completely randomized design with a 2 × 4 factorial arrangement of treatments. High DM silage was higher (P < 0.01) in pH, had less lactic and acetic acid (P < 0.01) and had more yeasts (P < 0.05) and molds (P < 0.01) than moderate DM silage. Recovery of DM declined (P < 0.01) for CTRL and LP treated silages with increasing DM but was not different between LBPP and SFE treatments. Compared to CTRL, LBPP had a lower (P < 0.01) DM recovery at the moderate DM, but SFE had the greatest (P < 0.01) recovery of all treatments at the high DM. Treatment with LBPP increased (P < 0.05) the concentrations of acetic acid and 1,2 propanediol (PD) compared with other treatments (P < 0.01). Numerically, fewer yeasts were found in additive treated silages compared with CTRL, but they were statistically (P < 0.01) lower only when treated with SFE. Treatment with LP resulted in a small improvement in aerobic stability at the moderate but not high DM. In contrast, treatment with SFE and LBPP markedly improved (P < 0.01) the aerobic stability of alfalfa silage at both DM. Whereas SFE and LBPP were similar in their improvements in aerobic stability at the DM, LBPP was better (P < 0.01) than SFE at the high DM. A higher (P < 0.01) concentration of acetic acid in LBPP compared with other treatments was most likely responsible for better stability. This study showed that LBPP and SFE resulted in increases in the aerobic stability of alfalfa silage and it is the first study showing SFE, can markedly improve the aerobic stability of alfalfa silage.

Effects of a chemical additive on the fermentation, microbial communities, and aerobic stability of corn silage with or without air stress during storage.

We evaluated the effects of a chemical additive on the microbial communities, fermentation profile, and aerobic stability of whole-plant corn silage with or without air stress during storage. Whole-plant corn was either untreated or treated with a chemical additive containing sodium benzoate, potassium sorbate, and sodium nitrite at 2 or 3 liters/t of fresh forage weight. Ten individually treated and replicated silos (7.5 liters) were made for each treatment. Half of the silos remained sealed throughout a 63-d storage period, and the other half was subjected to air stress for 2 h/wk. The composition of the bacterial and fungal communities of fresh forage and silages untreated or treated with 2 liters/t of fresh forage weight was analyzed by Illumina Miseq sequencing. Treated silage had greater (P < 0.05) aerobic stability than untreated, even when subjected to air stress during storage, but the numbers of yeasts culturable on selective agar were not affected. However, the additive reduced the relative abundance (RA) of the lactating-assimilating yeast Candida tropicalis (P < 0.01). In air-stressed silages, untreated silage had a greater (P < 0.05) RA of Pichia kudriavzevii (also a lactate assimilator) than treated silage, whereas treated silage was dominated by Candida humilis, which is usually unable to assimilate lactate or assimilates it slowly. The additive improved the aerobic stability by specifically preventing the dominance of yeast species that can consume lactate and initiate aerobic spoilage. To the best of our knowledge, this is the first work that identifies the specific action of this additive on shifting the microbial communities in corn silage.