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Glossary

Lupins
Lupins are a type of multipurpose annual legume grown throughout the world for use in feed and food and forage. The main cultivated lupin species are white lupins, yellow lupins, blue lupins and pearl lupins. White lupin seeds can be an alternative to soybean in all livestock species due to their high content of good quality protein.
Obligate aerobes
The microbes that absolutely need oxygen to grow.
Propionic Acid
A known mold inhibitor used to treat many feedstuffs to prevent molding. It can also be produced in the silage by fermentation of sugars and/or lactic acid by propionic acid-producing bacteria, such as Propionibacterium acidipropionici, and/or as a co-product in the conversion of lactic acid to acetic acid by Lactobacillus buchneri.
Relative feed value (RFV) and relative feed quality (RFQ)
Relative feed value was based on the concept of digestible dry matter intake relative to a standard forage. RFV has been widely used to ranking forage for sale, inventorying and allocating forage lots to animal groups according to their quality needs, and determining when to harvest. RFV assumes that acid detergent fiber (ADF) has a constant relationship to digestibility since digestibility is calculated from ADF. There is considerable variation in the digestibility of the dry matter relative to the ADF content. Relative Forage Quality was developed to include this variation.
Secondary Fermentation
Any fermentation that takes place after the primary fermentation (i.e. after the lactic acid production). However, some use secondary fermentation only to refer to clostridial fermentation in the silage. Others use the term only to describe fermentation of the silage by yeasts and so the onset of aerobic instability. Technically both are correct, provided there has been an initial lactic fermentation.
Shredding Processors
A processor that shreds the corn stalk into longer pieces than with a kernel processor, providing more physically effective fiber.
Shrink
DM loss is often called silage “shrink”.
Silage
The crop after it has been ensiled (e.g. corn silage, pea silage, alfalfa silage).
Soluble Protein
Produced by the breakdown of proteins into amino acids, etc. High levels of soluble protein indicate excessive protein degradation and may also be accompanied by high ammonia levels and other indicators of a bad fermentation (e.g. the fermentation acid profile).
Sub Clinical Ruminal Acidosis (SARA)
Rumen pH drops below 5.8 and remains below this threshold for three or more hours within a 24-hour period.
Volatile Fatty Acids (VFAs)
These are acids that are produced by microbes in the silage from sugars and other carbohydrate sources. By definition, they are volatile, which means they will volatilize (evaporate) in air, depending on the temperature. Lactic acid is NOT a volatile fatty acid, unlike acetic, propionic and butyric acids.
Wholecrop silage
Wholecrop cereal silage is made from cereal crops harvested before full ripeness and stored under anaerobic conditions. The term wholecrop denotes that grain and stalks (stem and leaf) are harvested and stored in a mix.
Wilting
The process where forage is left in the field to dry down, usually in windrows, to raise the dry matter level in the crop, prior to being chopped and ensiled.
Windrow
Forage collected into loose piles, ranging from inches to several feet in width, running along the length of the field in rows, allowing the wind to pass through the forage and help the forage dry down.
Yeasts and Molds
Both are fungi. Yeasts generally grow as single-cell organism while molds grow as multicellular filaments. Both occur widely in soil, water and on vegetation, increasing in numbers on vegetation as the crop ages or gets damaged (e.g. frost, hail, drought) and during wilting. In addition to being able to grow on free sugars, both yeasts and molds secrete extracellular enzymes, which break down the complex plant materials into simple sugars, which can then be used for growth. Many of the yeasts found on plant material contain carotenoid (orange to red) pigments to protect them against UV exposure and so can be responsible for some of the colors seen on silage faces. While yeasts can grow aerobically, they can also grow fermentatively (anaerobically), with ethanol being one of the major products. Other products that yeasts can produce in anaerobic growth conditions include n-propanol, iso-pentanol, acetic, propionic, butyric and iso-butyric acids, as well as small amounts of lactic acid. In the presence of air, yeasts will oxidize sugars fully, producing carbon dioxide and water and generating heat. Many yeasts can also use lactic acid for growth, again oxidizing it fully and generating heat. Yeasts are responsible for the vast majority (>95%) of heating silages. A yeast population >100,000 CFU/gram in the silage will almost certainly mean that the silage will heat as it is exposed to air during feedout. Yeast growth can be inhibited by acetic acid. The conditions normally associated with stable silage, low pH and anaerobic conditions, do not favor growth of molds. Generally, molds are only a problem where air exposure has occurred, e.g. at the top and on the sides of bunkers or piles, where there have been air leaks into the silage, where packing has been poor (e.g. localized lumps of moldy silage), at surfaces left exposed during filling and at the surface of the silage during feedout. As the silage moves towards the surface, if there are high numbers of yeasts present, these can grow on the lactic acid present, raising the pH and the silage temperature, promoting the subsequent growth of molds. Mold growth is undesirable, since the molds will fully oxidize both sugars and lactic acid, and will also break down (hydrolyze) and fully oxidize cellulose and other cell wall components, resulting in huge dry matter and energy losses. In addition, many of the molds commonly found in silages can produce mycotoxins, which can cause significant health and/ or reproductive problems and dramatically reduce performance. Finally, molds produce spores that become airborne when the silage is disturbed and can cause respiratory problems if they are inhaled (both for the cows and for the producer and farm workers). Mold growth can be inhibited by propionic acid.