For the band, see Silage (band).
Cattle eating maize silage
Silage is fermented, high-moisture fodder that can be fed to ruminants (cud-chewing animals such as cattle and sheep)[1] or used as a biofuel feedstock for anaerobic digesters. It is fermented and stored in a process called ensiling or silaging, and is usually made from grass crops, including maize, sorghum or other cereals, using the entire green plant (not just the grain). Silage can be made from many field crops, and special terms may be used depending on type (oatlage for oats, haylage for alfalfa – but see below for the different British use of the term haylage).[2]
Silage is made either by placing cut green vegetation in a silo, by piling it in a large heap covered with plastic sheet, or by wrapping large bales in plastic film.
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Contents
- 1 Making silage
- 2 Fermentation
- 3 Pollution and waste
- 4 Storing silage
- 5 Anaerobic digestion
- 6 Safety
- 7 Nutrition
- 8 History
- 9 See also
- 10 Footnotes
- 11 References
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Making silage
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This section does not cite any references or sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (June 2008) |
Silage must be made from plant material with a suitable moisture content, about 50% to 60%, depending on the means of storage, the degree of compression, and the amount of water that will be lost in storage. For maize, harvest begins when the whole-plant moisture is at a suie level. For pasture-type crops, the grass is mowed and allowed to wilt for a day or so until the moisture content drops to a suitable level.
The plant material is collected, chopped into pieces about 0.5 in (1.3 cm) long and packed. In the early days of mechanized agriculture, 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. Current technology uses mechanical forage harvesters that 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 silage into the wagon via a chute at the rear or side of the machine. Silage may also be emptied into a bagger, which puts the silage into a large plastic bag that is laid out on the ground.
MB Trac rolling a silage heap or "clamp" in Victoria, Australia
In North America, Australia, northwestern Europe, and frequently in New Zealand, silage is placed in large heaps on the ground and rolled by tractor to push out the air, then wrapped in plastic covers held down by reused tires or tire ring walls.[3]
In New Zealand and Northern Europe, the silo or "pit" is often a bunker built into the side of a bank, usually made out of concrete or old wooden railroad ties (railway sleepers). 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 tire weights.
In an alternative method, the cut vegetation is baled, making balage (North America) or silage bales (UK).[clarification needed] The grass or other forage is cut and partly dried until it contains 30–40% moisture (much drier than bulk silage, but too damp to be stored as dry hay). It is then made into large bales which are wrapped tightly in plastic to exclude air. The plastic may wrap the whole of each cylindrical or cuboid bale, or be wrapped around only the curved sides of a cylindrical bale, leaving the ends uncovered. In this case, the bales are placed tightly end to end on the ground, making a long continuous "sausage" of silage, often at the side of a field. The wrapping may be performed by a bale wrapper, while the baled silage is handled using a bale handler or a front-loader, either impaling the bale on a flap, or by using a special grab. The flaps do not hole the bales.
In the UK, baled silage is most often made in round bales about 4 feet by 4 feet, individually wrapped with four to six layers of "bale wrap plastic" (black, white or green 25 micrometre stretch film). The dry matter can vary a lot but can be 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 (search for "tube liner" various makes).
Haylage is a name for high dry matter silage of around 45% to 75%. Horse haylage is usually 55% to 75% dry matter, made in small bales or larger bales. 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 rear three-point linkage, they incorporate a trip tipping mechanism which can flip the bales over on to the flat side/end for storage on the thickest plastic layers.
Fermentation
Before starting the anaerobic stage, there is an aerobic phase in which the trapped oxygen is consumed. After finishing that oxygen, the anaerobic phase starts. Silage undergoes anaerobic fermentation, which starts about 48 hours after the silo is filled. In the past, the fermentation was conducted by indigenous microorganisms, but, today, some bulk 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. 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.
Pollution and waste
The fermentation process of silo or pit silage releases liquid. Silo effluent contains nitric acid (HNO3), which is corrosive. It can also contaminate water courses unless collected and treated – the high nutrient content can lead to eutrophication (growth of bacterial or algal blooms).
Plastic sheeting used for sealing pit or baled silage needs proper disposal, and some areas have recycling schemes for it.
Storing silage
Silage must be firmly packed to minimize the oxygen content, or it will spoil. Silage goes through four major stages in a silo:
- 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; 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.
Silage underneath plastic sheeting is held down by scrap tires. Concrete beneath the silage prevents liquor leaching out.
Anaerobic digestion
Silage is a useful feedstock for anaerobic digestion.[4] 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 deaths occur 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. 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.[5] 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.[6] Silage itself poses no special danger.
Nutrition
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This section does not cite any references or sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (June 2008) |
The ensiled product retains a much larger proportion of its nutrients than if the crop had been dried and stored as hay or stover.[citation needed]
Bulk silage is commonly fed to dairy cattle, while baled silage tends to be used for beef cattle, sheep and horses.
Since silage goes through a fermentation process, energy is used by fermentative bacteria to produce volatile fatty acids (VFAs), such as acetic, propionic, lactic, and butyric, 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 VFAs. Thus, the ensiling process preserves forages, but does not improve the quality or the nutrient value. Although it does not increase the level of the plant matter ensiled, it does increase the digestibility and utilization of nutrient by ruminants.
History
Main article: Ensilage
Francis Morris of Maryland prepared the first silage produced in America in 1876.[7]
See also
- Grain crimping
- Artturi Ilmari Virtanen
- Grass
- ^ Wood, Brian J. B.. Microbiology of fermented foods Volume 1&2. Springer. pp. 73. ISBN 978-0-7514-0216-2. http://books.google.com/books?id=mKfpPwm5ceEC&pg=PA73&dq=fodder+fermented+silage#v=onepage&q&f=false.
- ^ George, J. Ronald (1994). Extension Publications: Forage and Grain Crops. Dubuque,Iowa: Kendall/Hunt. pp. 152.
- ^ www.4entech.com/tire_rings.php
- ^ http://www.adnett.org/dl_feedstocks.pdf
- ^ http://nasdonline.org/document/901/d000741/watch-out-for-silage-gas.html
- ^ http://www.dairyherd.com/directories.asp?pgID=724&ed_id=243
- ^ Bulletin of the Maryland Agricultural Experiment Station (Maryland Agricultural Experiment Station) (121-145): 6. 1907. http://books.google.com/books?id=gEvOAAAAMAAJ. Retrieved 2012-12-01. "The first silage made in America was prepared by Francis Morris of Ellicott City, Maryland, in 1876, by putting whole corn in a trench or pit dug in the ground and covered with earth."
References
- Making and Feeding Silage, John Murdoch, B.Sc, Ph.D. Published by Dairy Farmer (Books) Limited, Lloyd's Chambers, Ipswich, U.K. 1961)
- Feeding baleage to horses - the ultimate guide - Horsetalk.co.nz
- "The Owner-Built Homestead" by Barbara and Ken Kern, New York: Scribner, 1977. ISBN: 0684149222
