Fermentation

When the forage is put into the storage system it initially has some oxygen trapped in. This oxygen allows microorganisms to grow aerobically and produce carbon dioxide (respiration): the plant itself also continues to respire. Once the oxygen supply is exhausted the microbes that absolutely need oxygen to grow (obligate aerobes) cease to grow and the plant ceases respiration. Microbes that can grow without oxygen present (anaerobes and facultative anaerobes) begin to grow fermentatively, producing various fermentation products. Yeasts will produce alcohol, lactic acid bacteria will produce predominantly lactic acid, propionic bacteria produce propionic acid, acetogenic bacteria produce acetic acid, clostridia produce butyric acid.