Q. Are lactic acid bacteria active even when there still is oxygen in the ensiling environment?
A. Yes. In fact, there is always some oxygen remaining in the silage environment immediately after it is put into storage. This oxygen allows microorganisms to grow aerobically and produce carbon dioxide, which is defined as respiration. Additionally, until plant cells are dead, or have no oxygen available, they also respire. The respiration processes can generate heat and may contribute to yeast and mold growth. While oxygen is around, lactic bacteria grow, producing half as much lactic acid as they do when the material is anaerobic. This ability of the lactic bacteria is important, as it helps get rid of the trapped oxygen, begins the pH drop and also results in less heat production than if other aerobic organisms, like yeasts and Bacillus, are allowed free reign.
Once the oxygen supply is exhausted, the microbes that absolutely need oxygen to grow — obligate aerobes — cease to grow and the plant ceases respiration. Then, fermentation can begin.
Microbes that can grow without oxygen present — anaerobes and facultative anaerobes — begin to grow and produce various fermentation products, including:
- yeasts produce ethanol,
- lactic acid bacteria (LAB) produce predominantly lactic acid,
- propionic bacteria produce propionic acid,
- acetogenic bacteria produce acetic acid
- clostridia produce butyric acid.
An inoculant with LAB strains can help ensure silage pH drops rapidly and prevent growth of yeasts and clostridial fermentation. Even if you have no history of silage heating or spoilage, a proven inoculant can deliver dry matter savings.
I hope this information helps.
The Silage Dr.