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Glossary

Effluent
Effluent is the liquid squeezed out of forage after it is packed in an ensiling structure.
Ensiling
Describes the process where a forage is put into a storage structure, becomes anaerobic and is acidified by the production of acids due to the action of bacteria either on the crop at harvest or added as an inoculant.
Ethanol
Primarily produced by the fermentative activity of yeasts but is also produced by heterofermentative lactic acid bacteria. If the level of ethanol in the silage is relatively low and there are reasonable levels of lactic and acetic acids, the source is probably heterofermentative LAB. If the level is high, the source is probably from yeasts. In any event, look also at the bound protein level (ADICP). If ADICP is greater than 10% of the CP, then there has been heating and the ethanol most likely came from yeasts. However, the ethanol level may be low due to being volatilized because of the heating.
Feedout Rate
The rate at which the silage is fed out, generally expressed in term of inches, or centimeters, per day that the silage surface is removed. In practice, feedout rates should be maintained at whatever is necessary to keep the silage stable.
Fermentation
When the forage is put into the storage system, it initially has some oxygen trapped inside. This oxygen allows microorganisms to grow aerobically and produce carbon dioxide (respiration). The plant itself also continues to respire. Once the oxygen supply is exhausted, the microbes that absolutely need oxygen to grow (obligate aerobes) cease to grow, and the plant ceases respiration. Microbes that can grow without oxygen present (anaerobes and facultative anaerobes) begin to grow fermentatively, producing various fermentation products. Yeasts will produce alcohol, lactic acid bacteria will produce predominantly lactic acid, propionic bacteria produce propionic acid, acetogenic bacteria produce acetic acid and clostridia produce butyric acid.
Fermentation Aids
Fermentation aids are compounds that assist the natural occurring bacteria to grow (e.g. sugars or enzymes) or add bacteria specific bacteria to the forage. Bacterial forage inoculants are one type of fermentation aid, or fermentation stimulant. In general, bacterial forage inoculants provide a more predictable outcome than other fermentation aids.
Fermentation Analysis
In order to get an idea of the quality of the silage and the fermentation pattern we take samples and submit them to approved laboratories (e.g. CVAS, Dairyland, DairyOne, Rock River Labs, BLGG) for analysis. There are a number of features we can request in the analysis, all of which add to the cost, so it is important to understand what we are looking for from the analysis, so that we do not pay for things we do not need. If we have a good, well preserved silage and we are doing the analysis just to show the producer the feeding quality of the silage, then limit the analysis to the "Feed" analysis. This will show things like the dry matter of the silage, pH, fiber and lignin levels, starch, protein levels (including total crude protein, soluble and bound protein) and the derived parameters like net energy figures. If the producer is unhappy with silage quality, then in addition to the above, add ash (shows if there was soil, or possibly slurry, in the forage: take 7 off the ash and the rest is from something other than the plant, e.g. ash at 12%, 12-7 = 5%, which is 100 lb./ton of silage DM of ash coming from soil, or slurry, potentially sources of clostridia [soil] and/ or enterobacteria [slurry]). In addition, have the fermentation analysis done (include 1, 2-propanediol if it is a silage treated with Lactobacillus buchneri) and also consider microbial analysis (usually only if yeasts are the suspected cause).
Forage
The crop prior to ensiling (e.g. forage corn, forage peas, alfalfa forage and forage grass).
Haylage
Though the use of the term can vary, it is generally used for alfalfa or grass silage made at a higher dry matter level (>30% DM). Some refer to any grass or alfalfa ensiled material as haylage regardless of DM.
Homofermenters and Heterofermenters
Lactic acid bacteria (LAB) can be broadly categorized into two groups based on how they ferment hexose (6-carbon) sugars like glucose and fructose. Homofermentative LAB convert soluble sugars from the forage into lactic acid. These bacteria are used to speed up the initial fermentation, helping to quickly reach a low pH. Examples include Lactobacillus plantarum or Pediococcus acidilactici, P. pentosaceus, Enterococcus faecium and Lactobacillus salivarius. Heterofermentative bacteria produce acids with strong antifungal properties, such as acetic acid and propionic acid. They can improve silage aerobic stability and help reduce the risks of aerobic spoilage after opening. Examples include the strains Lactobacillus buchneri and Propionibacterium acidipropionici. Other strains such as L. hilgardii are being studied as well.
Inoculants
Inoculants are additives containing bacteria selected to grow quickly and dominate the bacterial population in the silage. Traditional inoculants contain homofermentative LAB, e.g. Lactobacillus plantarum, Pediococcus spp., to increase lactic acid production and so increase the rate of pH drop and decrease the production of acetic and butyric acids. Other inoculants have been developed containing bacteria proven as aerobic stability enhancers, e.g. Lactobacillus buchneri, either on their own or in combination with the traditional inoculant organisms.
Iso-Butyric Acid
An isomer of butyric acid, usually present because of the deamination of the amino acid valine by clostridia (though it is also known to be produced by Lactobacillus brevis).
Lactic Acid
Lactic acid is the most acidic of the common fermentation acids and so is the main driver of the initial pH drop responsible for “pickling” the crop and the initial ensilage of the crop. It is produced by lactic acid bacteria, which can vary dramatically in efficacy of production and in levels on the forage crops ensiled. Hence, it is important to inoculate a forage crop with high numbers of efficient homolactic lactic acid producers if a fast pH drop is required. However, lactic acid has no effect against yeasts and molds, beyond reducing pH, and many common silage yeasts can actually use lactic acid to grow on.
Lactic acid bacteria (LAB)
During the ensiling process, lactic acid bacteria (LAB) play the most important role in the fermentation. LAB convert water-soluble carbohydrates (WSC) into sufficient organic acids, mainly lactic acid, under anaerobic conditions. As a result, pH decreases and undesirable microorganisms are inhibited.
Length of Cut (LOC)
There is a setting on the forage harvester that allows the operator to set the theoretical length of cut (TLOC). The particle size distribution achieved should always be checked.