Aerobic Stability of Silage

Many factors affect the silage fermentation process. For example, the DM content and buffering capacity of the crop to be ensiled, the amount of fermentable sugar available at ensiling and the type and numbers of microorganisms that dominate the fermentation process can markedly affect fermentation. However, Woolford (1990) stated that “the single most important factor which influences the efficiency with which forage crops are conserved as silage is the degree of anaerobiosis achieved in the completed silo”. Rapid removal of air from the forage mass and the ability to prevent air from infiltrating the silage mass during storage and feedout can have profound effects on feed quality. Excessive exposure to air at the start of fermentation prolongs the metabolism of unwanted microbes that thrive in air and delays the growth of beneficial bacteria that produce lactic acid. This can lead to undesirable fermentations and a loss in nutritive value. Prolonged infiltration of air during storage or feedout into the silage mass can lead to aerobic spoilage. Silage that is unstable when exposed to air heats rapidly and spoils leading to a loss of DM and nutrients with the potential for production of undesirable compounds. Aerobic spoilage during storage often is responsible for the majority of total DM lost in forage conserved as silage and may be as high as 30-40%. Even short term exposure to air results in losses. For example, DM losses from corn silage exposed to air for just 1 to 2 d was measured to be as high as 6% (Ranjit and Kung, 2000). In addition, much of the readily spoiled DM is of high quality. Besides an economic loss of nutrients, feeding spoiled silage to ruminants depresses nutrient intake and decreases production (Hoffman and Ocker, 1997; Whitlock et al., 2000). Preventing silage from spoiling when it is exposed to air can improve the efficiency of a farm by preserving forage as high quality silage that is palatable to cows.