As promised in my recent social media stories, my blog post this week is about the fermentation process, or otherwise known as ensiling, of silage (in the case of our ranch, corn silage).

First the basics:  Silage is the feedstuff produced by the fermentation process of a crop.  Ensiling is the name given to the process.

Desired silage of high nutritional value is achieved by:  1) harvesting the crop at the proper stage of maturity; 2) minimizing activities of plant enzymes and undesirable microorganisms; and 3) encouraging the presence of lactic acid bacteria (LAB).

Desired traits of a crop for optimal ensiling include:

·         dry matter (DM) content

·         sugar content

·         resistance to acidification

Based on these traits, corn is nearly the perfect crop for ensiling.  A key goal when ensiling corn is to reduce oxygen and raise acidity rapidly so that LAB can stabilize and preserve the silage.

The majority of the ensiling process is complete after three weeks of proper storage, but the full ensiling process isn’t complete until after approximately four months of storage.

This process takes place in 4 phases:  1) aerobic phase, 2) lag phase, 3) anaerobic fermentation phase, and 4) stable phase.

Aerobic Phase

Cells in the forage and aerobic bacteria use the oxygen in this phase to create carbon dioxide, water, and heat.  This phase takes 0 to 2 days depending on rapid and firm packing of the silage and properly sealing the silage.  Longer aerobic phases result in lower quality and quantity of silage content.  During this process, the pH will drop from 6.5 to 6.0.

Lag Phase

After oxygen is used up, plant enzymes break down complex carbohydrates, starch and fiber into simple sugars.  Enzymes also break down plant proteins making them more soluble.  Lactic acid bacteria will use the cell juices produced during the lag phase to grow during the anaerobic fermentation phase.  Silage pH drops to approximately 5.7 to 5.5 at this time.

Anaerobic Fermentation Phase

Anaerobic lactic acid bacteria use cell juices to grow, multiply, and make lactic and acetic acid to further increase silage acidity.  Lactic acid helps drop the acidity and preserve the silage.  Well-preserved silage should consist of at least 70% lactic acid.  This phase takes around 2 weeks after which the silage cools to near ambient temperature of 75-85°F and reaches a pH of about 4.0.

Stable Phase

Little biological activity occurs during this phase. so long as the silage has been packed and sealed properly.  Oxygen entering the silage can result in pathogen formation and deterioration of the silage.  Otherwise, desirable corn silage contains approximately 30-35% DM and digestible protein and fiber constituents.

Feeding

With the introduction of oxygen to the silage when opening the silage pile or silo, care needs taken during the feeding process of the silage to minimize losses of DM and nutrients that can occur because of aerobic microorganisms involved in deterioration of the silage.  Preventing mold during the feeding process is also important to keep toxic compounds that can affect livestock and human health from forming.  All of this is achieved by proper management of the silage face during feeding.

Thank you to Progressive Forage, University of Kentucky Agriculture, Food, and Environment Department of Animal & Food Sciences, and Hubbard® for the articles that provided information for this blog post.