silage n : fodder harvested while green and kept succulent by partial fermentation as in a silo [syn: ensilage]

see Silage

English

Etymology

Alteration (probably by influence of silo) of ensilage (1881), itself from lang=fr, from ensiler, from ensilar.

Noun

1. Fermented green forage fodder stored in a silo.

Translations

For the Christian Alternative band, please see Silage (band)

Silage is fermented, high-moisture fodder that can be fed to ruminants (cud-chewing animals like cattle and sheep) or used as a biofuel feedstock for anaerobic digesters. It is fermented and stored in a process called ensilage, and usually made from grass crops, including maize or sorghum, using the entire plant, not just the grain. Silage can be made from many other field crops, and other terms (oatlage for oats, haylage for alfalfa) can be used.

It is sometimes a mix of two crops, such as oats and peas. Haylage means ensiled forages, made up of grass, alfalfa and alfalfa/grass mixes. This is used extensively in the Midwest and Northeastern areas of the United States. It is also used widely in Europe for dairy cattle diets.

Balage is another form of stored forage. In this case hay, alfalfa or grass is cut and baled while still fairly wet. That is, it is too wet to be baled and stored as hay. In this case the dry matter is around 60 to 70%. The bales are wrapped tightly in plastic wrappers. The material then goes through a limited fermentation in which short chain fatty acids are produced which protect and preserve the forage. This method has become popular on smaller farms.

Making silage

In California, Australia, and frequently in New Zealand, silage is placed in large heaps on the ground and rolled by tractor to push out all the air, then wrapped in plastic covers held tight by recycled tyres.

In New Zealand and Northern Europe the silo or "pit" is often a concrete bunker built on the side of a bank so that chopped grass can be dumped in at the top and drawn from the bottom in winter. This requires considerable effort to compress the stack in the silo to cure properly.

Fermentation

Silage undergoes anaerobic fermentation, which starts about 48 hours after the silo is filled. Traditionally, the fermentation is caused by indigenous microorganisms, but today, some silage is inoculated with specific microorganisms to speed fermentation or improve the resulting silage. The process converts sugars to acids and exhausts any oxygen present in the crop material. The fermentation is essentially complete after about two weeks. Silage inoculants contain one or more strains of lactic acid bacteria, and the most common is Lactobacillus plantarum. Other bacteria used in inoculants include Lactobacillus buchneri, Enterococcus faecium and Pediococcus species.

Silo effluent

The fermentation process releases liquid. Silo effluent contains nitric acid (HNO3), which is corrosive. It can also contaminate water courses unless precautions are taken. The high nutrient content can lead to eutrophication (growth of algae blooms).

Storing silage

Silage must be firmly packed to minimize the oxygen content, or it will spoil.

Anaerobic digestion

Silage is a useful feedstock for anaerobic digestion. Here silage can be fed into anaerobic digesters to produce biogas that in turn can be used to generate electricity and heat.

Safety

Silos are hazardous, and people die every year in the process of filling and maintaining them. There is a risk of injury by machinery or from falls. When a silo is filled, fine dust particles in the air can become explosive because of their large aggregate surface area. Also, fermentation presents respiratory hazards. Nitrogen dioxide gas is released in the early stages of fermentation, and can kill. Lack of oxygen inside the silo can cause asphyxiation. Molds that grow when air is allowed to reach cured silage can cause toxic organic dust syndrome. The silage itself poses no special danger.

Nutrition

The ensiled product retains a much larger proportion of its nutrients than if the crop had been dried and stored as hay or stover. Silage is most often fed to dairy cattle, because they respond well to highly nutritious diets.

Since silage goes through a fermentation process, energy is used by fermentative bacteria to produce volatile fatty acids (VFA), such as acetate, propionate, lactate, and butyrate, which preserve the forage. The result is that the silage is lower in energy than the original forage, since the fermentative bacteria use some of the carbohydrates to produce VFA. Thus, the ensiling process preserves forages, but does not improve the quality or the nutrient value.

See also

• Grain crimping

References

• Making and Feeding Silage, John Murdoch, B.Sc, Ph.D. Published by Dairy Farmer (Books) Limited, Lloyd's Chambers, Ipswich, U.K. (regret no date, probably 1960's)

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