Understanding the process of fermentation in silage can help you identify critical control points for assuring feed quality. Lynn Reed is managing director for Ecosyl Products Inc., which produces a silage inoculant widely used in beef and dairy operations. Mr. Reed describes the following stages in the process of producing high-quality silage.

Aerobic breakdown of nutrients: This results from the presence of oxygen in the silo. Plants will continue to let off oxygen for several hours, or days if the silage is poorly packed, and plant enzymes are active until the oxygen is gone. Excess oxygen can lead to protein breakdown, excessive heating, and the growth of yeast and molds. Producers can eliminate oxygen with quick packing, even distribution of forage, chopping to a correct length and ensiling at recommended dry matter content. Oxygen must be eliminated before optimal fermentation can take place.

Anaerobic activity: Desirable microbes become active after oxygen is eliminated. During this stage, bacteria should produce lactic acid, which lowers the pH in silage. However, the natural populations of lactic acid producing bacteria in plants are often very low, and the addition of a fast growing bacteria speeds pH drop and results in a higher quality silage. The faster the pH drop, the more nutrients and dry matter are preserved.

Stabilization: At below pH 4.0 the anaerobic bacteria are inhibited, lactic acid production stops, fermentation is complete and the silage is stabilized.

Feedout: During feedout the silage is re-exposed to oxygen. Good silage will remain stable and not change in composition or heat during the third and fourth stages, provided silos are airtight, the crop is well packed and a sufficient quantity is removed each day to prevent spoilage.