Ensiling fermentation products and aerobic stability of corn and sorghum silages

Abstract

The objective of the present study was to determine the changes that occur in corn (Zea mays) and sorghum (Sorghum vulgare) silages during exposure to air, and to try to elucidate the factors that exert silage aerobic stability. Two corn and two sorghum ensiling experiments were performed in mini-silos. After a storage period of 5 months, the various silages were subjected to an aerobic stability test in bottle systems, which lasted 7 days. In these bottles changes in pH, production of CO2, numbers of yeasts and molds serve as spoilage indicators. Changes in chemical components during aerobic exposure were also followed. The first corn silage was aerobically stable, whereas the second corn silage spoiled; pH values for the unstable silage increased from 3.6 to 4.1 and 5.9, and the CO2 production was 38 and 48 g kg−1 DM, after 4 and 7 days of aerobic exposure, respectively. The first corn silage that was aerobically stable contained high concentrations of acetic acid, whereas the second corn silage that spoiled had low concentrations of VFA. The two sorghum silages were more stable upon aerobic exposure in spite of their low content of acetic acid, and other volatile fatty acids (VFA), which are known inhibitors of fungi.