Silage

Last updated November 16, 2024

Silage is fodder made from green foliage crops which have been preserved by fermentation to the point of souring. It is fed to cattle, sheep and other ruminants.^[1] The fermentation and storage process is called ensilage, ensiling, or silaging. The exact methods vary, depending on available technology, local tradition and prevailing climate.

Silage is usually made from grass crops including maize, sorghum or other cereals, using the entire green plant (not just the grain). Specific terms may be used for silage made from particular crops: oatlage for oats, haylage for alfalfa (haylage may also refer to high dry matter silage made from hay).^[2]

History

Using the same technique as the process for making sauerkraut, green fodder was preserved for animals in parts of Germany since the start of the 19th century. This gained the attention of French agriculturist Auguste Goffart of Sologne, near Orléans. He published a book in 1877 which described the experiences of preserving green crops in silos.^[3] Goffart's experience attracted considerable attention.^[4] The conditions of dairy farming in the United States suited the ensiling of green corn fodder, and was soon adopted by New England farmers. Francis Morris of Maryland prepared the first silage produced in America in 1876.^[5] The favourable results obtained in the US led to the introduction of the system in the United Kingdom, where Thomas Kirby first introduced the process for British dairy herds.^[6]

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.^[7]

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.^[4]

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.^[8]

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, clovers, alfalfa, vetches, oats, rye and maize.^[4] Many crops have ensilaging potential, including potatoes and various weeds, notably spurrey such as Spergula arvensis . 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, but not exceeding 75%. Weather during harvest need not be as fair and dry as when harvesting for drying. For corn, harvest begins when the whole-plant moisture is at a suitable level, ideally a few days before it is ripe. For pasture-type crops, the grass is mown and allowed to wilt for a day or so until the moisture content drops to a suitable level. Ideally the crop is mowed when in full flower, and deposited in the silo on the day of its cutting.^[4]

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.^[4]

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 baler, making balage (North America) or silage bales (UK, Australia, New Zealand). 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 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.^[9]

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.^[9]

Fermentation

Silage undergoes anaerobic fermentation, which starts about 48 hours after the silo is filled, and converts sugars to acids. Fermentation is essentially complete after about two weeks.

Before anaerobic fermentation starts, there is an aerobic phase in which the trapped oxygen is consumed. How closely the fodder is packed determines the nature of the resulting silage by regulating the chemical reactions that occur in the stack. When closely packed, the supply of oxygen is limited, and the attendant acid fermentation brings about decomposition of the carbohydrates present into acetic, butyric and lactic acids. This product is named sour silage.^[10] If the fodder is unchaffed and loosely packed, or the silo is built gradually, oxidation proceeds more rapidly and the temperature rises; if the mass is compressed when the temperature is 60–70 °C (140–160 °F), the action ceases and sweet silage results. The nitrogenous ingredients of the fodder also change: in making sour silage, as much as one-third of the albuminoids may be converted into amino and ammonium compounds; in making sweet silage, a smaller proportion is changed, but they become less digestible.^[4] If the fermentation process is poorly managed, sour silage acquires an unpleasant odour due to excess production of ammonia or butyric acid (the latter is responsible for the smell of rancid butter).

In the past, the fermentation was conducted by indigenous microorganisms, but, today,^{[ when? ]} some bulk silage is inoculated with specific microorganisms to speed fermentation or improve the resulting silage. Silage inoculants contain one or more strains of lactic acid bacteria, and the most common is Lactobacillus plantarum . Other bacteria used include Lactobacillus buchneri , Enterococcus faecium and Pediococcus species.

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.^[11]

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 eutrophication (hypertrophication), the growth of bacterial or algal blooms.^[12]

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.^[13]

Storing silage

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

Silage goes through four major stages in a silo:^[14]

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.^[15] 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.^[16] 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.^[17]

Silage itself poses no special danger however the improvement in legislation to regulate the animal food industry has reduced the problems concerning food-related human diseases by improvement of the hygienic quality of silage.^[18] Milk from cows fed with silage containing clostridial spores could represent a risk in hard cheese production.^[19] A special focus has to be directed to zoonotic pathogens like listeria, mycotoxins, clostridia, and E. coli bacteria as a result of deficient hygiene in silage production and could end in dairy products.^[20]

Nutrition

Ensilage can be substituted for root crops. Bulk silage is commonly fed to dairy cattle, while baled silage tends to be used for beef cattle, sheep and horses. The advantages of silage as animal feed are several:

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.^[21]^[22])
Several of the fermenting organisms produce vitamins: for example, lactobacillus species produce folic acid and vitamin B12.^[23]
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.

Anaerobic digestion

Silage may be used for anaerobic digestion.^[24]

Fish silage

Fish silage^[25]^[26] 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.^[27]^[28] 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.^[29]

Similar practices employed by cattle farmers are believed to have caused an outbreak of bovine spongiform encephalopathy (BSE; known as "mad cow disease") in British cattle herds in the 1980s. The outbreak led to significant losses of human life, cattle, and agricultural exports.

Related Research Articles

<span class="mw-page-title-main">Hay</span> Dried grass, legumes or other herbaceous plants used as animal fodder

Hay is grass, legumes, or other herbaceous plants that have been cut and dried to be stored for use as animal fodder, either for large grazing animals raised as livestock, such as cattle, horses, goats, and sheep, or for smaller domesticated animals such as rabbits and guinea pigs. Pigs can eat hay, but do not digest it as efficiently as herbivores do.

Alfalfa, also called lucerne, is a perennial flowering plant in the legume family Fabaceae. It is cultivated as an important forage crop in many countries around the world. It is used for grazing, hay, and silage, as well as a green manure and cover crop. The name alfalfa is used in North America. The name lucerne is more commonly used in the United Kingdom, South Africa, Australia, and New Zealand. The plant superficially resembles clover, especially while young, when trifoliate leaves comprising round leaflets predominate. Later in maturity, leaflets are elongated. It has clusters of small purple flowers followed by fruits spiralled in two to three turns containing 10–20 seeds. Alfalfa is native to warmer temperate climates. It has been cultivated as livestock fodder since at least the era of the ancient Greeks and Romans.

<span class="mw-page-title-main">Lactic acid</span> Organic acid

Lactic acid is an organic acid. It has the molecular formula C₃H₆O₃. It is white in the solid state and it is miscible with water. When in the dissolved state, it forms a colorless solution. Production includes both artificial synthesis as well as natural sources. Lactic acid is an alpha-hydroxy acid (AHA) due to the presence of a hydroxyl group adjacent to the carboxyl group. It is used as a synthetic intermediate in many organic synthesis industries and in various biochemical industries. The conjugate base of lactic acid is called lactate (or the lactate anion). The name of the derived acyl group is lactoyl.

<span class="mw-page-title-main">Lactic acid fermentation</span> Series of interconnected biochemical reactions

Lactic acid fermentation is a metabolic process by which glucose or other six-carbon sugars are converted into cellular energy and the metabolite lactate, which is lactic acid in solution. It is an anaerobic fermentation reaction that occurs in some bacteria and animal cells, such as muscle cells.

Lactobacillus Bulgaricus is the main bacterium used for the production of yogurt. It also plays a crucial role in the ripening of some cheeses, as well as in other processes involving naturally fermented products. It is defined as homofermentive lactic acid bacteria due to lactic acid being the single end product of its carbohydrate digestion. It is also considered a probiotic.

Field corn, also known as cow corn, is a North American term for maize grown for livestock fodder, ethanol, cereal, and processed food products. The principal field corn varieties are dent corn, flint corn, flour corn which includes blue corn, and waxy corn.

Fodder, also called provender, is any agricultural foodstuff used specifically to feed domesticated livestock, such as cattle, rabbits, sheep, horses, chickens and pigs. "Fodder" refers particularly to food given to the animals, rather than that which they forage for themselves. Fodder includes hay, straw, silage, compressed and pelleted feeds, oils and mixed rations, and sprouted grains and legumes. Most animal feed is from plants, but some manufacturers add ingredients to processed feeds that are of animal origin.

A baler or hay baler is a piece of farm machinery used to compress a cut and raked crop into compact bales that are easy to handle, transport, and store. Often, bales are configured to dry and preserve some intrinsic value of the plants bundled. Different types of balers are commonly used, each producing a different type of bale – rectangular or cylindrical, of various sizes, bound with twine, strapping, netting, or wire.

A forage harvester – also known as a silage harvester, forager or chopper – is a farm implement that harvests forage plants to make silage. Silage is grass, corn or hay, which has been chopped into small pieces, and compacted together in a storage silo, silage bunker, or in silage bags. It is then fermented to provide feed for livestock. Haylage is a similar process to silage but using grass which has dried.

Malolactic conversion is a process in winemaking in which tart-tasting malic acid, naturally present in grape must, is converted to softer-tasting lactic acid. Malolactic fermentation is most often performed as a secondary fermentation shortly after the end of the primary fermentation, but can sometimes run concurrently with it. The process is standard for most red wine production and common for some white grape varieties such as Chardonnay, where it can impart a "buttery" flavor from diacetyl, a byproduct of the reaction.

Agricultural wastewater treatment is a farm management agenda for controlling pollution from confined animal operations and from surface runoff that may be contaminated by chemicals in fertilizer, pesticides, animal slurry, crop residues or irrigation water. Agricultural wastewater treatment is required for continuous confined animal operations like milk and egg production. It may be performed in plants using mechanized treatment units similar to those used for industrial wastewater. Where land is available for ponds, settling basins and facultative lagoons may have lower operational costs for seasonal use conditions from breeding or harvest cycles. Animal slurries are usually treated by containment in anaerobic lagoons before disposal by spray or trickle application to grassland. Constructed wetlands are sometimes used to facilitate treatment of animal wastes.

Corn stover consists of the leaves, stalks, and cobs of corn (maize) plants left in a field after harvest. Such stover makes up about half of the yield of a corn crop and is similar to straw from other cereal grasses; in Britain it is sometimes called corn straw. Corn stover is a very common agricultural product in areas of large amounts of corn production. As well as the non-grain part of harvested corn, the stover can also contain other weeds and grasses. Field corn and sweet corn, two different types of maize, have relatively similar corn stover.

A silo is a structure for storing bulk materials.

Lactobacillales are an order of gram-positive, low-GC, acid-tolerant, generally nonsporulating, nonrespiring, either rod-shaped (bacilli) or spherical (cocci) bacteria that share common metabolic and physiological characteristics. These bacteria, usually found in decomposing plants and milk products, produce lactic acid as the major metabolic end product of carbohydrate fermentation, giving them the common name lactic acid bacteria (LAB).

In food processing, fermentation is the conversion of carbohydrates to alcohol or organic acids using microorganisms—yeasts or bacteria—without an oxidizing agent being used in the reaction. Fermentation usually implies that the action of microorganisms is desired. The science of fermentation is known as zymology or zymurgy.

Food microbiology is the study of the microorganisms that inhabit, create, or contaminate food. This includes the study of microorganisms causing food spoilage; pathogens that may cause disease ; microbes used to produce fermented foods such as cheese, yogurt, bread, beer, and wine; and microbes with other useful roles, such as producing probiotics.

Lentilactobacillus buchneri is a gram-positive, non-spore forming, anaerobic, rod prokaryote. L. buchneri is a heterofermentative bacteria that produces lactic acid and acetic acid during fermentation. It is used as a bacterial inoculant to improve the aerobic stability of silage. These bacteria are inoculated and used for preventing heating and spoilage after exposure to air.

<span class="mw-page-title-main">Animal feed</span> Food for various animals

Animal feed is food given to domestic animals, especially livestock, in the course of animal husbandry. There are two basic types: fodder and forage. Used alone, the word feed more often refers to fodder. Animal feed is an important input to animal agriculture, and is frequently the main cost of the raising or keeping of animals. Farms typically try to reduce cost for this food, by growing their own, grazing animals, or supplementing expensive feeds with substitutes, such as food waste like spent grain from beer brewing.

Fructilactobacillus fructivorans is a gram-positive bacteria and a member of the genus Fructilactobacillus in the family Lactobacillaceae. It is found in wine, beer, grape must, dairy, sauerkraut, meat, and fish. They are facultative anaerobics and experience best growth in environments with 5-10% CO₂. Temperature for growth is between 2 °C and 53 °C, with the optimum temperature between 30 °C and 40 °C and a pH level between 5.5 and 6.2. The bacterium is rod shaped and can be found in the following forms: single, pairs, chains of varying lengths, or long curved filaments. F. fructivorans is non-motile. The main end product of the metabolic process is lactate, although ethanol, acetate, formate, CO₂, and succinate may also be produced.

This glossary of agriculture is a list of definitions of terms and concepts used in agriculture, its sub-disciplines, and related fields, including horticulture, animal husbandry, agribusiness, and agricultural policy. For other glossaries relevant to agricultural science, see Glossary of biology, Glossary of ecology, Glossary of environmental science, and Glossary of botanical terms.

References

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↑ Crisp, Howard L.; Patterson, H. J. (July 1908). "Silos and silage in Maryland: The construction of silos and the making and feeding of silage". Bulletin of the Maryland Agricultural Experiment Station (129): 1–78. 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. [p. 2]
↑ Obituary of Thomas Kirby, Bromley Record, 1901.
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↑ Chisholm, Hugh, ed. (1911). "Hay" . Encyclopædia Britannica . Vol. 13 (11th ed.). Cambridge University Press.
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↑ Kimberlee Schoonmaker (October 1, 2000). "Four ways to be safe around silage". Archived from the original on 2011-01-17. Retrieved 2010-01-02.
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↑ Kireeva, Irina (2015-11-27), "The new European Regulation on Quality Schemes for Agricultural Products and Foodstuffs", Research Handbook on EU Agriculture Law, Edward Elgar Publishing, ISBN 978-1-78195-462-1 , retrieved 2024-11-05
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↑ Heiman, Caley. The silage puzzle: Overcoming common challenges Archived 2018-08-23 at the Wayback Machine . The Progressive Dairyman.
↑ Buchanan-Smith, J. G. (2010). "An investigation into palatability as a factor responsible for reduced intake of silage by sheep". Animal Production. 50 (2): 253–260. doi:10.1017/S0003356100004700.
↑ Santos, F.; Wegkamp, A.; de Vos, W. M.; Smid, E. J.; Hugenholtz, J. (14 March 2008). "High-Level Folate Production in Fermented Foods by the B12 Producer Lactobacillus reuteri JCM1112". Applied and Environmental Microbiology. 74 (10): 3291–3294. Bibcode:2008ApEnM..74.3291S. doi:10.1128/AEM.02719-07. PMC 2394963 . PMID 18344331.
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↑ de Arruda, Lia Ferraz; Borghesi, Ricardo; Oetterer, Marília (September 2007). "Use of fish waste as silage: a review". Brazilian Archives of Biology and Technology. 50 (5): 879–886. doi: 10.1590/S1516-89132007000500016 .
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