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Silage: Production and Feeding – Part II

by Wyoming Livestock Roundup

A couple of weeks ago, I talked about silage – what is silage, what are silos, advantages and disadvantages of silage and crops commonly used for silage. Today, I will discuss the ensiling process of silage.

The ensiling process occurs after green, moist forage is placed in a silo. The process results in many changes in the forage as time advances. These changes maybe slow or fast depending on the type of crop, amount of moisture, length of chop and, finally, the type of silo. The entire process may be complete within 20 to 21 days if the conditions are favorable. Under good conditions, the process may result in silage with stable, high quality and pleasant smelling.

The goal of making high quality silage is to use oxygen and lower the pH. This will make the forage materials pickled or preserved. To achieve this goal, two types of bacteria are necessary. The first type of bacteria are oxygen-using bacteria called aerobic bacteria. These bacteria give off carbon dioxide and heat. In well-packed and finely chopped silage, these aerobic bacteria can utilize all oxygen in four to six hours. The heat released in this process can raise the temperature from 80 to over 100 degrees Fahrenheit.

The second type of bacteria are called anaerobic bacteria. These bacteria work in absence of oxygen and produce acetic acid. After that, lactic acid bacteria become active and continue producing lactic acid for 16 to 18 days. At this point, the pH drops very low – to between 3.6 and 4.2, and the silage is pickled.

At the other hand, at this time, all bacteria stop working. As a result, the silage becomes stable. This condition can remain for longer periods of time provided that no oxygen enter the silo.

Learning the basic process in ensiling is very important. This helps an understanding and appreciation of the importance of how to better manage ensiling practices. The process described above shows that finely chopped and good packing silage are very important. This favors elimination of oxygen quickly by aerobic bacteria before any acid production starts.

For a good ensiling process, a rapidly available supply of digestible energy is important as this helps anaerobic bacteria to produce acids. This is one of the good reasons why corn and other high-energy grain crops are considered as excellent silage crops.

I will continue discussion on silos, factors affecting silage quality and feeding silage in the Extension columns over the coming months. Please keep an eye on other parts.

Anowar Islam is an associate professor and the University of Wyoming Extension forage specialist in the Department of Plant Sciences in the College of Agriculture and Natural Resources. He can be reached at 307-766-4151 or

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