The effects of various compounds on the aerobic stability of silages were evaluated. It has been observed that inoculation of whole-crop maize with homofermentative lactic acid bacteria leads to silages which have low stability against aerobic deterioration, while inoculation with heterofermentative lactic acid bacteria, such as Lactobacillus brevis or Lactobacillus buchneri, increases stability. Acetic acid has been proven to be the sole substance responsible for the increased aerobic stability, and this acid acts as an inhibitor of spoilage organisms. Therefore, stability increases exponentially with acetic acid concentration. Only butyric acid has a similar effect. Other compounds, like lactic acid, 1,2-propanediol, and 1-propanol, have been shown to have no effect, while fructose and mannitol reduce stability.Ensilage of green forage is a traditional way to conserve animal feed, and this process is gaining importance and is replacing hay production and direct feeding of green forage. The technology is simple and includes compression of the forage, followed by airtight sealing. Subsequently the autochthonous lactic acid bacteria convert the free sugars into lactic acid. Nowadays, the use of starter cultures is increasing in order to produce high-quality feed and to ensure that there is an immediate decrease in the pH to prevent growth of undesirable microorganisms, such as clostridia. Clostridia not only form butyric acid but are also responsible for the degradation of proteins to ammonia. An increase in pH and large decreases in feeding value are the results. Furthermore, clostridia form spores, which is an important criterion of hygienic quality of silages with respect to production of milk suitable for cheese processing, as the spores cause late blowing in hard cheeses.After silos are opened for feeding, air penetrates the silages and promotes the growth of aerobic, acid-tolerant microorganisms and the oxidation of fermentation products present in the silages. This so-called aerobic deterioration can cause spoilage of silages and may lead to potentially toxic substances or undesirable microorganisms.The stability of silages against aerobic deterioration (aerobic stability) can vary dramatically. However, the mechanisms that prevent aerobic spoilage are not well understood. Weinberg et al. (20) investigated several homofermentative lactic acid bacteria to determine their effects on aerobic stability when they were used as silage inocula. The inoculated silages tended to spoil even faster than the control silage. O'Kiely and Muck (15) stated that aerobic stability is not related to the silage dry matter content, pH, yeast number, or glucose addition at the time of ensiling, while the effects of organic acids, such as acetic acid, lactic acid, and propionic acid, have been described to some extent (1, 13). Other authors have described the positive aspect of the formation of acetic acid by heterofermentative lactic acid bacteria, which inhibits spoilage organisms (5,18,19).In silage experiments conducted at ...
