The preservation of forage crops as silage depends upon the production of sufficient acids to inhibit the activity of undesirable microorganisms under anaerobic conditions. The epiphytic lactic acid bacteria (LAB) that naturally present on forage crops convey sugar into lactic acid in the ensiling process. It is well established that LAB play an important role in silage fermentation. LAB is a major component of the microbial flora which lives in various types of forage crops. The LAB commonly grow with other plant-associated microorganisms during silage fermentation, and they generally define the fermentation characteristics of silage. Moist dairy farm silage is based on natural lactic acid fermentation. The epiphytic LAB transform the water-soluble carbohydrates into organic acids during the ensiling process. As a result, the pH is reduced and the forage is preserved.

However, when the silo is opened and aerobic conditions prevail at feeding time, the silage is subject to aerobic microbial growth and is therefore potentially unstable. Furthermore, the deteriorated silage increases in dry matter loss and reduces in the nutritional value. Generally, the well-preserved silages are considered to be more liable to aerobic deterioration than poorly — fermented silages and some aerobic microorganisms can be harmful to the health of livestock. Therefore, the prevision of aerobic deterioration is an important task in making silage.