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Glossary of Nutrient Terms

General Terms

Moisture – the percent water in a sample.

Dry matter – equals (100% – Moisture) and represents everything in the sample other than water including protein, fiber, fat, minerals, etc.. Animals consume feeds to meet their dry matter needs, because it is the dry matter that contains all of the nutrients. Therefore, animals will have to consume more feed with higher moisture content to receive the same amount of dry matter as they would from a drier feed. For example, if an animal consumes 10 lbs. of hay at 90% dry matter, it consumes 9 lbs. of dry matter (10 x .90). If pasture at 20% dry matter is substituted for the hay, it would have to consume 45 lbs. of pasture (9/.20) to receive the same amount of dry matter.

Thus, it is very important to know the dry matter content of a feed to establish feeding rates and ensure that livestock receive the proper amount of feed to meet their daily needs.

As Sampled Basis – nutrient results for a sample in its natural state including the water. Also known as as fed or as received.

Dry Matter Basis – nutrient results for the sample with the water removed. There is considerable variation in the moisture content of forages. Removing the water eliminates its dilution effect, thereby enabling direct comparisons of nutrient contents across different forages. For example, suppose that you wanted to compare the protein content of a hay testing 90% dry matter to a pasture testing 20% dry matter. On an as sampled basis the hay tested 14% crude protein (CP) and the pasture 5% CP. The hay appears to have the higher CP level. However, removing the dilution effect of the water reveals that the hay is 15.5% CP (14/.90) and the pasture is 25% CP (5/.20) on a dry matter basis. Thus, removing the dilution effect of the water revealed that per pound of dry matter, the pasture is higher in protein. Animals eating the pasture will consume more protein per pound of dry matter than they will from the hay.

Livestock nutrient requirements may be expressed on either an as sampled or dry matter basis. It is important to use analytical results expressed on the same basis as the nutrient requirements. In general, most livestock requirements are expressed on a dry matter basis, therefore the forage results on a dry matter basis should be used to balance the ration. Again, the key point is to make sure that the requirements and results are expressed on the same basis.


Crude Protein (CP) – the total protein in the sample including true protein and non-protein nitrogen. Proteins are organic compounds composed of amino acids. They are a major component of vital organs, tissue, muscle, hair, skin, milk and enzymes. Protein is required on a daily basis for maintenance, lactation, growth and reproduction.

Amino Acids (AA) – organic nitrogen containing compounds that serve as the building blocks of protein.

Lysine (Lys) – an indispensable amino acid required for growth in the young horse.

Acid Detergent Insoluble Crude Protein (ADICP) – also known as heat damaged or unavailable protein. Typically caused by heating during fermentation or drying, a portion of the protein reacts with carbohydrates to form an indigestible complex rendering it unavailable for digestion.


Neutral Detergent Fiber (NDF) – a measure of hemicellulose, cellulose and lignin representing the fibrous bulk of the forage. These three components are classified as cell wall or structural carbohydrates. They give the plant rigidity enabling it to support itself as it grows, much like the skeleton in animals. NDF can be negatively correlated with intake.

Acid Detergent Fiber (ADF) – a measure of cellulose and lignin. Cellulose varies in digestibility and is negatively influenced by the lignin content. As lignin content increases, digestibility of the cellulose decreases. ADF is negatively correlated with overall digestibility.

Lignin – indigestible plant component. As lignin content increases, digestibility of cellulose decreases thereby lowering the amount of energy potentially available to the animal.

Crude Fiber (CF) – historical method of fiber analysis used to divide carbohydrates into digestible and indigestible fractions. Crude fiber accounts for most of the cellulose and only a portion of the lignin. It is not the most accurate method for quantifying fiber, particularly for forages. However, given that grains are low in lignin, it is a reasonable estimate of fiber in grains and is still used today as the legal measurement of fiber in grains and finished feeds.

Pectin – a cell wall polysaccharide that functions as “cellular glue”. It is also known as “soluble fiber”.

Starch – a polysaccharide found primarily in the grain or seed and/or root portions of plants. Starch is a good source of energy.

Water Soluble Carbohydrates (WSC) – carbohydrates solubilized and extracted in water. Includes monosaccharies, disaccharides and some polysaccharides (mainly fructan). Fructan is a major storage carbohydrate in grasses.

Ethanol Soluble Carbohydrates (ESC) – carbohydrates solubilized and extracted in 80% ethanol. Includes primarily monosaccharides and disaccharides.

Non Fiber Carbohydrates (NFC) – a mathematical estimate of non-cell wall (non-fiber) carbohydrates consisting of starch, sugar, pectin and fermentation acids that can serve as energy sources for the animal. NFC is calculated as 100% – (CP% + NDF% + Fat% + Ash%).


Fat – typically determined by ether extraction. In addition to fat, ether extraction may solubilize plant pigments, esters and aldehydes. This is why the measurement is called crude fat. Fat is an energy dense nutrient and contains 2.25 x the energy found in carbohydrates. Fat is added to rations to boost energy levels when intake may be limiting.

Omega Fatty Acids – essential fatty acids that play an important role in the function and structure of cell membranes, prostaglandin synthesis, preventing dry, flaky skin and reducing inflammation.


Energy is the nutrient required in the greatest amount. Energy is used in all biological processes and is essential for life. For livestock, energy requirements are determined for maintenance, growth or gain, lactation, reproduction and activity level. Failure to supply adequate energy will result in poor performance. Energy values are not measured, rather they are predicted using equations and relationships with other nutrients. Equi-analytical uses a multiple component summative approach in its energy prediction system. Energy contributions from protein, fiber, nonstructural carbohydrates and fat form the foundation of the system. Discounts are applied to reflect energy available for productive purposes.

Gross Energy – the total energy value of a feed before accounting for losses due normal digestive, metabolic and productive functions.

Digestible Energy (DE) – the energy that is apparently digested and absorbed by the animal. It is determined by subtracting the energy contained in the feces from the gross energy. In horses, the fecal energy loss is typically 35 – 40% of the gross energy. The DE is used to balance the energy portion of the equine diet. Energy requirements are expressed as megacalories (Mcal) in the nutrient requirement tables.

Total Digestible Nutrients (TDN) – denotes the sum of the digestible protein, digestible nitrogen-free extract (NFE), digestible crude fiber and 2.25X the digestible fat. TDN is estimated from digestible energy (DE).


Ash – a measure of the total mineral content. Samples are weighed and incinerated at 600oC for two hours. This burns off all of the organic material (protein, fiber, fat, etc.) leaving behind the minerals.

Calcium (Ca) – bone and teeth formation, blood clotting, muscle contractions, milk component, transmission of nerve impulses, cardiac regulation, activation and stabilization of enzymes.

Phosphorus (P) – bone and teeth formation, key component of energy metabolism, milk component, body fluid buffer systems.

Magnesium (Mg) – enzyme activator, found in skeletal tissue and bone, neuromuscular transmissions.

Potassium (K) – osmotic pressure regulation and water balance, electrolyte balance, acid-base balance, enzyme activator, muscle contraction, nerve impulse conductor.

Sodium (Na) – acid-base balance, muscle contraction, nerve transmission, maintenance of body fluid balance, osmotic pressure regulator, cellular uptake of glucose, amino acid transport.

Iron (Fe) – hemoglobin and oxygen transport, enzyme systems.

Zinc (Zn) – enzyme activator, wound healing, skin health, immune system.

Copper (Cu) – required for hemoglobin synthesis, coenzyme functions.

Manganese (Mn) – growth, bone formation, enzyme activator, fertility.

Molybdenum (Mo) – part of enzyme xanthine oxidase, antagonistic and interactive effects with copper and sulfur.

Sulfur (S) – present in insulin, biotin, thiamin, heparin and chondroitin sulfate.

Chloride (Cl) – acid-base balance, osmotic pressure regulation, component of gastric secretions.

Cobalt (Co) – required for vitamin B12 synthesis.

Selenium (Se) – component of glutathione peroxidase enzyme, antioxidant properties, prevention of white muscle disease and retained placenta.

Iodine (I) – essential for the synthesis of the thyroid hormones thyroxine (T4) and triiodothyronine (T3) that regulate basal metabolism.


Vitamin A – derived from carotene in green plants, it is important for normal eye and nerve function, maintenance of tissues in the reproductive and urinary tract, cell differentiation and required for normal growth, reproduction and lactation.

Vitamin D – exposure to sunlight generates the synthesis of vitamin D in the skin. Vitamin D acts in conjunction with calcium and phosphorus to promote and maintain proper bone formation and integrity.

Vitamin E – acts in conjunction with selenium as powerful antioxidants.


Relative Feed Value (RFV) – an index for ranking forages based on digestibility and intake potential. RFV is calculated from ADF and NDF. A RFV of 100 is considered the average score and represents an alfalfa hay containing 41% ADF and 53% NDF on a dry matter basis. The higher the RFV, the better the quality.

Due to the inherent variability of measuring ADF and NDF, absolute RFV values should not be used for making direct comparisons or pricing of forages. Rather a range of RFV values should be used to classify a forage. For example, if a RFV of 150 is the target value, any forage testing between 145 to 155 should be considered to have an equivalent value. A good rule of thumb is to accept anything within at least +/- 5 points of the target value.

Relative Forage Quality (RFQ) – an index for ranking forages based on a more comprehensive analysis than RFV. RFQ is calculated from CP, ADF, NDF, fat, ash and NDF digestibility measured at 48 hours. It should be more reflective of the feeding value of the forage. RFQ is based on the same scoring system as RFV with an average score of 100. The higher the RFQ, the better the quality.

Nitrates (NO3) – can become a problem when fed in high amounts. Nitrate accumulator plants include sorghum, sorghum sudangrass, sudangrass, weeds and small grain forages. Drought, frost, fertilization and manure application practices are factors that can lead to high nitrate levels. When nitrate is converted to nitrite, it impedes the uptake of oxygen by the blood resulting in death due to lack of oxygen. Blood becomes brownish in color and exterior membranes may become bluish in color.