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Commodities: Field Crops: Forages

Common Terms Used in Animal Feeding and Nutrition

Glossary: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z


Acid Detergent Fiber (ADF): The fibrous component represents the least digestible fiber portion of forage or other roughage. This highly indigestible part of forage and includes lignin, cellulose, silica and insoluble forms of nitrogen but not hemicellulose. Forages with higher ADF are lower in digestible energy than forages with lower ADF. That means, as the ADF level increase, digestible energy levels decrease. During laboratory analysis, ADF is the residue remaining after boiling a forage sample in acid detergent solution. ADF is often used to calculate digestibility, total digestible nutrients (TDN) and/or net energy for lactation (NEl).

Acid Detergent Insoluble Crude Protein (ADICP) or Acid Detergent Fiber-Crude Protein (ADFCP): It is the insoluble protein fraction remaining in the acid detergent fiber residue of a feed sample. ADICP escapes ruminal breakdown and represents the portion of the protein that is not degradable and is therefore unavailable to the animal. It also contains any heat damaged protein which may result from heating during storage or processing. In this case a portion of the protein reacts with carbohydrates (fiber) to form an indigestible complex rendering it unavailable for digestion. This parameter is also reported as acid detergent insoluble protein (ADIP%), acid detergent insoluble nitrogen (ADIN %) or acid detergent fiber protein (ADFP%). It is expressed as a percent of crude protein.

Although ADICP is an adequate measure of heat damage to forage-based proteins, it is NOT an accurate estimate of heat damage in non-forage proteins.

Aflatoxins: Fungal or mold growth in/on foods and feed can result in the production of many different types of toxic biochemicals. As a group, these toxic substances are commonly called mycotoxins. The term “Aflatoxins” refers to a particular group of mycotoxins produced by some species of the genus Aspergillus. There are four major aflatoxins named as B1, B2, G1, G2 plus two additional metabolic products known as M1 and M2 that are of significance as direct contaminants of foods and feeds.

Fungal (or mold) growth and aflatoxin contamination are the consequence of interactions among the fungi, the host (foods or feeds) and the environment. On a standing crop, aflatoxin contamination of peanuts and corn is favored by high temperatures, prolonged drought conditions, and high insect activity; while postharvest production of aflatoxins on corn and peanuts is favored by higher water content, warm temperatures, and high humidity. Forages are generally not analyzed for aflatoxins but in some situations (e.g., corn or sorghum silage that is at risk) this analysis may be warranted.

Presence of aflatoxins in feeds, forages, and foods is an important anti-quality factor and are associated with various diseases in livestock, domestic animals and humans that are broadly termed aflatoxicosis. Aflatoxicosis is primarily a hepatic (liver) disease. Liver damage, decreased reproductive performance, reduced milk or egg production, embryonic death, teratogenicity (birth defects), tumors, and suppressed immune system function are caused by aflatoxins even when low levels are consumed.

The FDA’s action level for human food is 20 ppb total aflatoxins, with the exception of milk which has an action level of 0.5 ppb for aflatoxin M1. The FDA action level for most feeds is also 20 ppb (Table 1).

Table 1. FDA action levels for aflatoxins§


Action level (µg/kg or ppb)

All products, except milk, designated for humans




Corn for immature animals and dairy cattle


Corn for breeding beef cattle, swine and mature poultry


Corn for finishing swine


Corn for beef cattle


Cottonseed meal (as feed ingredient)


All feedstuff other than corn


§According to compliance policy guides 7120.26, 7106.10, 7126.33.

If the level of aflatoxins in forage is higher than the action level, it may be fed in combination with other feeds containing low levels of or no aflatoxins.

Amino Acids: A class of nitrogen-containing molecules containing an amine group, a carboxylic acid group, and a side chain that varies between different amino acids. Amino acids are the building blocks from which protein is made in the body. There are 20 known standard amino acids forming various proteins. When taken up into the body in the diet, the 20 standard amino acids are either used to synthesize proteins and other biomolecules or broken down into urea and carbon dioxide. Of the 20 standard amino acids, 8 are called essential amino acids, while the other 12 are non-essential amino acids. Animals (including human) cannot synthesize the essential amino acids from other compounds at the level needed for normal growth, so they must be obtained from food (hence they are called essential amino acids).

Anti-quality Factors: Apart from nutrients, forages may contain various harmful compounds that can adversely affect animal performance, cause sickness, or even death. These compounds are called anti-quality factors and include tannins, nitrates, alkaloids, cyanoglycosides, estrogens, and mycotoxins. The occurrence and/or severity of these factors depend on the forage and weed species present, season, environmental conditions, and sensitivity of the animal. High-quality forages should be free from harmful levels of anti-quality components.

Ash: The residue containing inorganic mineral elements of a feed sample, determined in a laboratory by burning the sample at a high temperature (removing the organic matter) and weighing the residue (i.e., ash).

As-fed Basis: Feed analyses reports often have results stated based on the feed’s natural state (i.e., including water) and/or on a dry matter basis. The term “As-fed Basis” is used to alert the reader that the analytical results of a feed sample are based on its natural state including water. That means it is affected by the sample’s moisture level before drying. This may also be referred to by the terms: “As-is Basis” or “As-received Basis”. When comparing two or more analyses, it is generally best to utilize the data from the “Dry Matter Basis” rather than the “As-fed Basis” unless you are mixing a ration for feeding.