Glossary

The highly indigestible portion of forage that includes lignin, cellulose, silica and insoluble forms of nitrogen, but not hemicellulose. Forages with higher ADF are lower in digestible energy (in fact ADF is used to calculate the energy value of forages). During laboratory analysis, ADF is the residue remaining after boiling a forage sample in acid detergent solution.

ADICP is the insoluble protein fraction remaining in the acid detergent fiber residue of a feed sample. It is the component of protein that is unavailable to the horse. This parameter is also reported as acid detergent insoluble preotien (ADIP), acid detergent insoluble nitrogen (ADIN) or acid detergent fiber protein (ADFP). It is typically expressed as a percent of crude protein, but sometimes on a dry matter basis or both.

The building blocks from which proteins are made. There are 20 standard amino acids required to form proteins (actually 21 – selenocysteine is considered the 21^st amino acid as it is required by all mammals). Amino acids are used to synthesize proteins and other biomolecules. They can also be broken down and used to produce glucose through gluconeogenesis. This results in the nitrogen being removed from the amino acid. The body needs to detoxify this nitrogen, it does so in the liver by turning ammonia (free form of nitrogen) into urea, which is then excreted.

These are not normally measured in typical forage analysis. Apart from nutrients, forages may contain various harmful compounds that can adversely affect animal performance and cause sickness or even death. These compounds can include tannins, nitrates, alkaloids, cyanoglycosides, estrogens, yeast, molds and mycotoxins. The occurrence and/or severity of these factors depends on the forage and weed species present, season, environmental conditions, geographical region and sensitivity of the animal.

Feed analyses typically report results on an as-fed basis and dry matter basis. All feeds contain some level of water, which is typically designated as moisture. This will vary based on the type of feed. For example, ensiled forages and fresh pasture will contain high levels of water/moisture, 65 and 75 percent, respectively. Whereas, dry hay and common feed ingredients are typically only 10 to 12 percent moisture. The nutrient concentrations listed on all commercially available feeds are reported on an as-fed basis. It is important if entering values for nutrient concentrations of feeds or forages that you are using appropriate values.

The only functional role of vitamin C categorically established is its ability to prevent and/or cure scurvy. In this role, however, it affects to some extent every body function. For example, normal development of cartilage, bone, and dentine depends on an adequate supply of vitamin C. In addition, the basement membrane lining the capillaries, the “intracellular cement” holding together the endothelial cells, and the scar tissue responsible for wound healing all require the presence of vitamin C for their formation and maintenance. Ascorbic acid is an antioxidant, cofactor of hydroxylating enzymes involved in synthesis of collagen, carnitine, norepinephrine. Horses can produce endogenous vitamin C, there is no evidence supplementation is needed.

The residue containing inorganic mineral elements of a feed sample, determined in a laboratory by burning the sample at a high temperature and weighing the residue (ash).

Biotin functions in cells covalently bound to enzymes. These enzymes replenish oxaloacetate for Krebs cycle, necessary for gluconeogenesis; commit acetate units to fatty acid synthesis; provide mechanism for metabolism of some amino acids and odd-numbered chain fatty acids; and allows catabolism of leucine and certain isoprenoid compounds. Biotin is involved in CO₂ transfer reactions; carboxylation reactions.

Calcium is the most abundant divalent cation of the body, averaging about 1.5% of the total body weight. Bones and teeth contain about 99% of the calcium. The other 1% of the body’s calcium is distributed in both intracellular (inside the cell) and extracellular (outside the cell) fluids. Calcium is a structural component of bones and teeth, role in intracellular and hormonal secretion regulation, muscle contraction, blood clotting, and activation of some enzyme systems.

Carbohydrates are biochemical compounds composed only of the elements carbon, hydrogen and oxygen. They represent the single largest source of energy for horses. They come in many different forms, which will impact the overall response of the horse to feeding. Carbohydrates are polymers made of basic sugar units, such as glucose, fructose, galactose, etc. The two major classes of carbohydrates in plants are known as non-structural and structural. Those that serve as storage and energy reserves for the plant are available for more rapid metabolism to supply energy (e.g., sugars, starch and pectin) are referred to as non-structural. Those carbohydrate fractions that are not used for energy storage and provide fiber and anatomical features for rigidity and even water transport are known as structural carbohydrates (e.g., cellulose, lignin etc). Non-structural carbohydrates are more available for energy metabolism than the structural carbohydrates.

Cellulose is a major structural carbohydrate that is present in plant cell walls. It is the most abundant carbohydrate on earth. Cellulose is an unbranched chain of glucose molecules that are linked together by beta-1,4 bonds. Mammals do not contain the enzymes necessary to digest cellulose (break the beta-1,4 bonds between glucose molecules), but bacteria do. The microflora present in the hindgut of a horse are able to digest cellulose, allowing the horse to derive significant amounts of energy from cellulose, an example of the symbiosis between the horse and resident bacterial population. Cellulose is not generally measured in lab analysis, but can be estimated as follows:

Cellulose = ADF – (ADL + Ash), where ADF is acid detergent fiber and ADL is acid detergent lignin

Chloride is the most abundant anion in the extracellular fluid. Approximately 88% of chloride is found in extracellular fluid, and just 12% is intracellular. Its negative charge neutralize the positive charge of sodium ions with which it is usually associated. In this respect, it is of great importance in the maintenance of electrolyte balance. Chloride has important functions in addition to its role as a major electrolyte. It is require for the formation of gastric hydrochloric acid, secreted along with protons from the parietal cells of the stomach. Also, it acts as the exchange anion in the red blood cell. Chloride functions as a major anion, maintains pH balance, enzyme activation, and is a component of gastric hydrochloric acid

Choline is an essential material for building and maintaining cell membranes. It is a constituent of lecithins which are fatty substances (lipids) with one of the three fatty acid molecules replaced by choline which is joined to the glycerol part of the molecule through a phosphoric acid linkage. The free choline pools from which the neurotransmitter acetylcholine is synthesized are maintained through several mechanisms, one of which is the enzymatic hydrolysis of lecithin and sphingomyelin. Choline can be synthesized in liver providing there is a sufficient supply of methionine. Choline plays an essential role in fat metabolism in the liver. Choline is involved in neurotransmission, fatty acid metabolism in liver, and cell structure.

No Cr-dependent enzyme has been identified in the horse. However, Cr is an essential trace element due to its function as a cofactor involved in activation of insulin. The biological action of chromium is believed to be due to its complexing with nicotinic acid and amino acids to form the organic compound glucose tolerance factor (GTF). GTF is thought to initiate the disulfide bridging between insulin and the insulin receptor. The effectiveness of insulin is greater in the presence of chromium than in its absence. Thus the primary function of GTF is to potentiate insulin action, thereby affecting cellular glucose uptake, and intracellular carbohydrate and lipid metabolism.

Vitamin B₁₂ is considered a generic term for a group of compounds called corrinoids because of their corrin nucleus. The corrin is a marocyclic ring made of four reduced pyrrole rings linked together. The corrin of vitamin B₁₂ has an atom of cobalt in the center of it. Cobalamin is involved in methylation of homocysteine to methionine; conversion of methylmalonyl CoA to succinyl CoA

Cobalt must be supplied in the diet of monogastric animal species and humans in its active form, vitamin B₁₂. When these species receive adequate dietary vitamin B₁₂ there is no convincing evidence of a requirement for or benefit from dietary Co. Cobalt is, however, a dietary essential for ruminants; ruminal, microogranisms incorporate Co into vitamin B₁₂. The only known function of Co is its participation in metabolism as a component of vitamin B₁₂.