Silage

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Silage (

Silage can be made from many field crops, and special terms may be used depending on type: oatlage for oats, haylage for alfalfa (haylage may also refer to high dry matter silage made from hay).^[3] It can be made using several methods, largely dependent on available technology, local tradition, or prevailing climate.

History

Using the same technique as the process for making

The modern silage preserved with acid and by preventing contact with air was invented by Finnish academic and professor of chemistry Artturi Ilmari Virtanen. Virtanen was awarded the 1945 Nobel prize in chemistry "for his research and inventions in agricultural and nutrition chemistry, especially for his fodder preservation method", practically inventing modern silage.^[8]

Early^[when?] silos were made of stone or concrete either above or below ground, but it is recognized that air may be sufficiently excluded in a tightly pressed stack, though in this case a few inches of the fodder around the sides is generally useless owing to mildew. In the US, structures were typically constructed of wooden cylinders to 35 or 40 ft. in depth.^[5]

In the early days of mechanized agriculture (late 1800s), stalks were cut and collected manually using a knife and horsedrawn wagon, and fed into a stationary machine called a "silo filler" that chopped the stalks and blew them up a narrow tube to the top of a tower silo.^[9]

Production

Partially dried mown grass is formed into cylindrical bales in the field (above) and sealed in polywrap (below).

The crops most often used for ensilage are the ordinary grasses,

After harvesting, crops are shredded to pieces about 15 mm (1⁄2 in) long. The material is spread in uniform layers over the floor of the silo, and closely packed. When the silo is filled or the stack built, a layer of straw or some other dry porous substance may be spread over the surface. In the silo, the pressure of the material, when chaffed, excludes air from all but the top layer; in the case of the stack, extra pressure is applied by weights to prevent excessive heating.^[5]

Equipment

Forage harvesters collect and chop the plant material, and deposit it in trucks or wagons. These forage harvesters can be either tractor-drawn or self-propelled. Harvesters blow the chaff into the wagon through a chute at the rear or side of the machine. Chaff may also be emptied into a bagger, which puts the silage into a large plastic bag that is laid out on the ground.

In North America, Australia, northwestern Europe, and New Zealand it is common for silage to be placed in large heaps on the ground, rolled by tractor to push out the air, then covered with plastic sheets that are held down by used tires or tire ring walls. In New Zealand and Northern Europe, 'clamps' made of concrete or old wooden railway ties (sleepers) and built into the side of a bank are sometimes used. The chopped grass can then be dumped in at the top, to be drawn from the bottom in winter. This requires considerable effort to compress the stack in the silo to cure it properly. Again, the pit is covered with plastic sheet and weighed down with tires.

In an alternative method, the cut vegetation is formed into bales using a

In the UK, baled silage is most often made in round bales about 1.2 m × 1.2 m (4 ft × 4 ft), individually wrapped with four to six layers of "bale wrap plastic" (black, white or green 25-micrometre stretch film). The percentage of dry matter can vary from about 20% dry matter upwards. The continuous "sausage" referred to above is made with a special machine which wraps the bales as they are pushed through a rotating hoop which applies the bale wrap to the outside of the bales (round or square) in a continuous wrap. The machine places the bales on the ground after wrapping by moving forward slowly during the wrapping process.

Haylage

Haylage sometimes refers to high dry matter silage of around 40% to 60%, typically made from hay. Horse haylage is usually 60% to 70% dry matter, made in small bales or larger bales.^[10]

Handling of wrapped bales is most often with some type of gripper that squeezes the plastic-covered bale between two metal parts to avoid puncturing the plastic. Simple fixed versions are available for round bales which are made of two shaped pipes or tubes spaced apart to slide under the sides of the bale, but when lifted will not let it slip through. Often used on the tractor's loader as an attachment called a bale grabber, they incorporate a trip tipping mechanism which can flip the bales over on to the flat side or end for storage on the thickest plastic layers.^[10]

Fermentation

Silage undergoes

Before anaerobic fermentation starts, there is an aerobic phase in which the trapped

Ryegrasses have high sugars and respond to nitrogen fertiliser better than any other grass species. These two qualities have made ryegrass the most popular grass for silage-making for the last sixty years.^[timeframe?] There are three ryegrasses in seed form and commonly used: Italian, Perennial and Hybrid.^[12]

Pollution and waste

The fermentation process of silo or pit silage releases liquid. Silo effluent is corrosive. It can also contaminate water sources unless collected and treated. The high nutrient content can lead to

Plastic sheeting used for sealing pit or baled silage needs proper disposal, and some areas have recycling schemes for it. Traditionally, farms have burned silage plastics; however odor and smoke concerns have led certain communities to restrict that practice.[14]

Storing silage

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

Silage goes through four major stages in a silo:^[15]

• Presealing, which, after the first few days after filling a silo, enables some respiration and some dry matter (DM) loss, but stops.
• Fermentation, which occurs over a few weeks. pH drops, and there is more DM loss, but hemicellulose is broken down; aerobic respiration stops.
• Infiltration, which enables some oxygen infiltration, allowing for limited microbial respiration. Available carbohydrates (CHOs) are lost as heat and gas.
• Emptying, which exposes surface, causing additional loss; rate of loss increases.

Safety

Silos are potentially hazardous: deaths may occur in the process of filling and maintaining them, and several safety precautions are necessary.^[16] 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. The ensiling process produces "silo gas" during the early stages of the fermentation process. Silage gas contains nitric oxide (NO), which will react with oxygen (O₂) in the air to form nitrogen dioxide (NO₂), which is toxic.^[17] Lack of oxygen inside the silo can cause asphyxiation. Molds that grow when air reaches cured silage can cause organic dust toxic syndrome. Collapsing silage from large bunker silos has caused deaths.^[18] Silage itself poses no special danger.

Nutrition

Ensilage can be substituted for

• During fermentation, the silage bacteria act on the cellulose and carbohydrates in the forage to produce
  volatile fatty acids (VFAs), such as acetic, propionic, lactic, and butyric acids. By lowering pH
  , these produce a hostile environment for competing bacteria that might cause spoilage. The VFAs thus act as natural preservatives, in the same way that the lactic acid in yogurt and cheese increases the preservability of what began as milk, or how vinegar (dilute acetic acid) preserves pickled vegetables. This preservative action is particularly important during winter in temperate regions, when green forage is unavailable.
• When silage is prepared under optimal conditions, the modest acidity also has the effect of improving palatability, and provides a dietary contrast for the animal. (However, excessive production of acetic and butyric acids can reduce palatability: the mix of bacteria is ideally chosen so as to maximize lactic acid production.[19]^[20])
• Several of the fermenting organisms produce vitamins: for example, lactobacillus species produce
  folic acid and vitamin B12.^[21]
• The fermentation process that produces VFA also yields energy that the bacteria use: some of the energy is released as heat. Silage is thus modestly lower in caloric content than the original forage, in the same way that yogurt has modestly fewer calories than milk. However, this loss of energy is offset by the preservation characteristics and improved digestibility of silage.

Silage may be used for anaerobic digestion.^[22]

Fish silage

Fish silage^[23][24] is a method used for conserving by-products from fishing for later use as feed in fish farming. This way, the parts of the fish that are not used as human food such as fish guts (entrails), fish heads and trimmings are utilized as ingredients in feed pellets.^[25][26] The silage is performed by first grinding the remains and mixing it with formic acid, and then storing it in a tank. The acid helps with preservation as well as further dissolving the residues. Process tanks for fish silage can be aboard ships or on land.^[27]

See also

• Grain crimping
• Grain bin

References

Sources

• Making and Feeding Silage, John Murdoch, B.Sc., Ph.D. Published by Dairy Farmer (Books) Limited, Lloyd's Chambers, Ipswich, UK 1961)
• Feeding baleage to horses – the ultimate guide – Horsetalk.co.nz Archived 2012-10-21 at the Wayback Machine
• "The Owner-Built Homestead" by Barbara and Ken Kern, New York: Scribner, 1977.
  ISBN 0684149222

Further reading

• Zhou, Yiqin. Compar[ison of] Fresh or Ensiled Fodders (e.g., Grass, Legume, Corn) on the Production of Greenhouse Gases Following Enteric Fermentation in Beef Cattle. Rouyn-Noranda, Qué.: Université du Québec en Abitibi-Témiscamingue, 2011. N.B.: Research report.

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