The Influence of Delayed Sealing and Repeated Air Ingress during the Storage of Maize Silage on Fermentation Patterns, Yeast Development and Aerobic Stability

This study investigates the effects of delayed sealing and repeated air ingress on the formation of primary fermentation products and other volatile organic compounds (VOC), the development of yeasts and the aerobic stability (ASTA) of maize (26.8% dry matter, DM). After packing, the silos were sealed either promptly or with a delay of 24 h, with repeated air ingress after 27, 55 and 135 days of storage. Losses of DM, fermentation pattern, including VOC, yeast numbers and aerobic stability, were determined 6 times during storage for 142 days. Yeast numbers markedly increased during the first three fermentation days, with the effect being much stronger in silage sealed with a delay than in promptly sealed silage (log10 cfu/g FM 7.27 vs. 5.88, p < 0.002). Simultaneously, the concentrations of ethanol and ethyl esters and DM losses increased. The DM losses were closely correlated with the total concentrations of alcohols and acetic acid (delay: R2 = 0.71, p < 0.001; prompt: R2 = 0.91, p < 0.001, respectively). The repeated air ingress for 24 h during storage after completion of the main fermentation phase had only a minor effect on fermentation pattern, VOC formation and DM losses. The relationship between the counts of total yeasts and lactate-assimilating yeasts (LAY) was very strong (R2 = 0.995, p < 0.001), and LAY numbers were shown to be largely responsible for aerobic instability (R2 = 0.752, p < 0.001). This trial proved the detrimental effects of air on silage fermentation with delayed sealing to be much more deleterious than repeated short-term air ingress after about one month of storage.