agribusiness: Producers and manufacturers of agricultural goods and services, such as fertilizer and farm equipment makers, food and fiber processors, wholesalers, transporters, and retail food and fiber outlets.

amino acid: Any of a large number of compounds found in living cells that contain carbon, hydrogen, and nitrogen and join together to form proteins. Twenty of the naturally occurring amino acids are the building blocks of proteins, which they form by being connected to each other in chains. Eight of those twenty, called essential amino acids, cannot be synthesized in the cells of humans and must be consumed as part of the diet.

ammonia: Chemical formula NH3. A colorless alkaline gas that is lighter than air and has a strongly pungent odor. It is used as a fertilizer and refrigerant, and in making dyes, textiles, plastics and explosives. Ammonium ions are a toxic waste product of the metabolic process in animals. In mammals, ammonium ions are converted into urea and excreted in urine.

animal protein: Protein derived from meat, eggs or dairy products.

animal welfare: Animal welfare is the physical and psychological well-being of non-human animals.

antibiotic: A substance, such as penicillin, that is capable of destroying or weakening certain microorganisms, especially bacteria or fungi, that cause infections or infectious diseases. Antibiotics do not kill viruses.

artificial insemination (AI): The introduction of semen into the vagina or uterus without sexual reproduction.

average daily feed intake: The amount of feed consumed by an animal each day.

average daily gain: The amount of weight gained by an animal during its growing stages.


beef: The culinary name for meat from bovines (cattle). In parts of the United States, “beef” can also refer to living cattle.

biotechnology: The use of a living organism to solve an engineering problem or perform an industrial task. For example, using corn to produce biofuel.

boar: An uncastrated male swine.

bovid: Any of various hoofed, horned ruminant mammals of the family Bovidae, which includes cattle, sheep, goats, buffaloes, bisons, antelopes and yaks.

bovine: Relating to cows or cattle.

breeding stock: Sexually mature male and female livestock that are retained to produce offspring.

BST: Bovine somatotropin, commonly referred to as growth hormone. Produced naturally by the cow, stimulates metabolic functions related to growth and milk production.

bull: an uncastrated male bovine (cattle).


CAFO: Short for: concentrated animal feeding operation. A livestock operation defined by the federation government as “an animal feeding operation where more than 1,000 'animal units' (as defined by the regulation) are confined at the facility; or more than 300 animal units are confined at the facility and either one of the following conditions are met: pollutants are discharged into navigable waters through a man-made ditch, flushing system or other similar man-made device; or pollutants are discharged directly into waters of the United States which originate outside of and pass over, across, or through the facility or otherwise come into direct contact with the animals confined in the operation."

calves: The young of domestic cattle. The term is used for cattle of either sex from birth to weaning. Meat from a calf is called veal. Calf can also refer to young from animals like camels, dolphins, elephants, giraffes and  hippopotamuses.

camelid: any two-toed ruminant of the family Camelidae, including the camels, llamas and vicunas.

caprine: Relating to goats

carbohydrate: Any of a large class of organic compounds consisting of carbon, hydrogen and oxygen. Carbohydrates are produced in green plants by photosynthesis and serve as a major energy source in animal diets. Sugars, starches, and cellulose are all carbohydrates.

cecum: A large pouch forming the beginning of the large intestine. The appendix and the ileum of the small intestine both connect to the cecum. In plant-eating mammals, the cecum is important because it houses bacteria that aid in the breakdown of plant fibers.

Celsius: Relating to a temperature scale on which the freezing point of water is zero degrees and the boiling point of water is 100 degrees under normal atmospheric pressure.

cellulose: A carbohydrate that is the main component of the cell walls of most plants.

cow: A fully grown female animal of a domesticated breed of bovine, used as a source of milk or beef.

crossbreeding: The mating of animals of different breeds. For example, breeding a Hereford cow with an Angus bull.

crude fat: An estimate of the total fat content of feeds. The crude fat is estimated using ether extraction.

crude protein: An estimate for total protein content of feeds. A crude protein contains nitrogen from not only protein but non-protein sources as well. Crude protein is used for energy and helps build tissue.

cull: To select inferior animals from the herd for potential sale.

cud: Food that has been partly digested and brought up from the rumen to the mouth for further chewing by ruminants, such as cattle or sheep.


digestive tract: The series of organs in the digestive system through which food passes, nutrients are absorbed, and waste is eliminated. In higher vertebrates, it consists of the esophagus, stomach, small and large intestines, rectum and anus.

DNA: Short for deoxyribonucleic acid. The nucleic acid that is the genetic material determining the makeup of all living cells and many viruses. It consists of two long strands of nucleotides linked together in a structure resembling a ladder twisted into a spiral.

duodenum: The beginning part of the small intestine, starting at the lower end of the stomach.

dry matter: Everything contained in a feed sample except water; this includes protein, fiber, fat, minerals, etc. In practice, it is the total weight of feed minus the weight of water in the feed, expressed as a percentage.

dry matter intake: The amount of (or prediction of the amount of) dry matter consumed by an animal. Typically, intake increases as the digestibility of the forage increases.


egg: The reproductive cell of most organisms that reproduce sexually. Eggs are haploid (they have half the number of chromosomes as the other cells in the organism’s body. During reproduction, the nucleus of an egg fuses with the nucleus of a sperm cell (the male reproductive cell) to form a new organism with a complete set of chromosomes. Some animals, like cows or humans, keep the egg inside the body as it develops into a fetus. Other animals, like chickens, incubate their eggs outside the body.

embryo: An animal in its earliest stages of development, before all the major body structure are represented. In humans, the embryonic stage lasts through the first eight weeks of pregnancy.

embryo transfer: The transfer into a recipient’s uterus of an egg that has been fertilized in vitro and is at the blastula stage of development.

enzyme: Any of numerous proteins produced in living cells that speed up or begin the metabolic processes of an organism. Enzymes can help break down food during digestion, or they can join nucleotides during the DNA replication process. In humans, the enzyme lactase breaks down the protein lactose found in milk.

EPA: The United States Environmental Protection Agency. In many states, the EPA monitors and regulates gas emissions and pollutant discharge from livestock operations.

erythrocyte: Any of the oval or disc-shaped cells that circulate in the blood of vertebrate animals, contain hemoglobin, and give blood its red color. The hemoglobin in erythrocytes binds with oxygen for transport and delivery to body tissues. Also called a red blood cell.

estrous cycle: The series of changes that occur in the female of most mammals from one period of estrus to another. The estrous cycle usually takes place during a period known as the breeding season, which ensures that young are born at a time when the chance of survival is greatest.

estrus: A regularly recurring period in female mammals during which the animal is sexually receptive. Estrus occurs around the time of ovulation. Also called heat.

estrus synchronization: When multiple females in a group go into estrus around the same time. This can be a natural occurrence caused by factors like seasonal changes or the presence of a male.

ether extract: The part of a complex organic material that is soluble in ether and consists chiefly of fats and fatty acids.

ewe: A female sheep of any age.

excreta: Substances produced by animals as waste after the metabolic process. Urine, fecal matter and carbon dioxide are all excreta.

exotic species: A non-native plant or animal species introduced by humans, either deliberately or accidentally.

external parasites: Organisms, like fleas, ticks, scabies, lice and horse flies, that feed off host animals. External parasites may feed off of a host’s blood, sweat, skin cells and even ocular fluid. External parasites are a concern in the animal industry because of their tendency to carry diseases. Also called an ectoparasite.


farrowing: Giving birth to a litter of pigs

fats: Oily compounds found in plant and animal tissues. Fats serve mainly as a reserve source of energy. Fat can also insulate organs from heat loss.

FDA: The United States Food and Drug Administration. Monitors and regulates many aspects of food safety.

feed: Animal foodstuffs. For example: corn can be an important ingredient in cattle feed. Sometimes referred to as fodder.

feed efficiency: The measure of a unit of meat or milk produced per unit of dry matter consumed. Animals with increased feed efficiency may gain more weight than animals with low efficiency, even if both animals consume the same amount of feed.

feeder cattle: Cattle past the calf stage that have weight increased making them salable as feedlot replacements.

feedlot: A confinement facility where cattle are fed to produce beef for the commercial trade. May be under a roof or outdoors.

fertility: The natural capability to produce offspring. In animals, this refers to the female’s ability to produce viable eggs or the male’s ability to produce viable sperm.

fertilization: The process by which two gametes (reproductive cells each having half a set of chromosomes) fuse to become a single cell called a zygote, which develops into a new organism. Among many animals, like mammals, fertilization occurs inside the body of the female.

fiber: 1. The parts of grains, fruits and vegetables that contain cellulose and are not digested by the body. Fiber helps the intestines absorb water, which increases the bulk of the stool and causes it to move more quickly through the body. 2. One of the elongated, thick-walled cells, often occurring in bundles, that gives strength and support to tissue in vascular plants.

forage: Herbaceous plants or plant parts fed to domestic animals

frozen semen: Semen collected from animals and stored at a temperature that preserves the cells. Frozen semen is useful in artificial insemination, in vitro fertilization and cloning.

feed:gain: The ratio of unit of feed consumed to unit of mass gained by an animal.


gain: As a verb: to acquire as an increase or addition: to gain weight; to gain speed. As a noun: an increase.

gain:feed ratio: The ration of unit of mass gained by an animal to unit of feed consumed.

gene: A segment of DNA that is the basic unit of heredity. Genes can regulate expression of hair color, height, etc.

genetic engineering: The science of altering and cloning genes to produce a new traits in an organism or to make a biological substance, such as a protein or hormone

genetics: The scientific study of the principles of heredity and the variation of inherited traits among related organisms

genome: The total amount of genetic information in the chromosomes of an organism.

gestation: The period of time spent in the uterus between conception and birth. Gestation in humans is about nine months.

gilt: Sexually mature female hog, prior to having her first litter.

global food security: the goal of producing enough food for the world population.


hatch act: To emerge from or break out of an egg.

heifer: A young female bovine that has never given birth.

hereditary: Passed or capable of being passed from parent to offspring by means of genes.

hermaphrodite: An organism, such as an earthworm or flowering plant, having both male and female reproductive organs in a single individual.

hog: 1. A hoofed mammal of the family Suidae, order Artiodactyla, comprising boars and swine. 1. A domesticated swine weighing 120 pounds (54 kg) or more, raised for market.

hormone: A chemical substance secreted by an endocrine gland or group of endocrine cells that acts to control or regulate specific physiological processes, including growth, metabolism and reproduction. Most hormones are secreted by endocrine cells in one part of the body and then transported by the blood to their target site of action in another part. Hormones include endorphins, androgens and estrogens.

horse: 1. A large, solid-hoofed, herbivorous quadruped, Equus caballus, domesticated since prehistoric times, bred in a number of varieties, and used for carrying or pulling loads, for riding, and for racing. 2. A fully mature male animal of this type; stallion. 3. Any of several odd-toed ungulates belonging to the family Equidae, including the horse, zebra, donkey, and ass, having a thick, flat coat with a narrow mane along the back of the neck and bearing the weight on only one functioning digit, the third, which is widened into a round or spade-shaped hoof.


implantation: To become attached to and embedded in the maternal uterine lining. Used for a fertilized egg.

inbreeding: The breeding or mating of related individuals within an isolated or closed group of organisms or people. Inbreeding can something results in a loss of vigor or health in offspring. However, In agriculture and animal husbandry, the continued breeding of closely related individuals can help to preserve desirable traits in a stock.

incubation: 1. The act of warming eggs in order to hatch them, as by a bird sitting upon a clutch of eggs in a nest. 2. The act of keeping an organism, a cell, or cell culture in conditions favorable for growth and development. 3. The maintenance of an infant, especially one that is ill or born before the usual gestation period, in an environment of controlled temperature, humidity, and oxygen concentration in order to provide optimal conditions for growth and development. 4. The development of an infection from the time the pathogen enters the body until symptoms first appear.

intramuscular: Within a muscle.

intramuscular fat: Fat located throughout skeletal muscle. It is responsible for the marbling seen in certain cuts of beef. In humans, excess accumulation of intramuscular fat is associated with insulin resistance and type 2 diabetes.

internal parasites: Organisms that live inside their hosts and rob their hosts of food or blood. Internal parasites include hookworms, tapeworms, coccidia and blood parasites. Also called an endoparasite.

invertebrate: 1. An animal that has no backbone or spinal column. Most animals are invertebrates. Corals, insects, worms, jellyfish, starfish and snail are invertebrates.

ionaphore: A lipid-soluble molecule usually synthesized by microorganisms to transport ions across the lipid bilayer of the cell membrane.


Johne’s disease: A contagious, chronic and sometimes fatal infection that primarily affects the small intestine of ruminants. Also called paratuberculosis.


kidney: Either of a pair of organs that are located in the rear of the abdominal cavity in vertebrates. The kidneys regulate fluid balance in the body in the form of urine.


lactase: An enzyme that is found in the small intestine, liver and kidneys of mammals. This enzyme begins the process of breaking down the protein lactose, found in dairy products.

lactation: The time between calving that a cow produces milk, usually 10 months.

lamb: A young sheep, less than one year old.

land-grant universities: State colleges and universities started from federal government grants of land to each state to encourage further practical education in agriculture, home economics and the mechanical arts.

lipid: Any of a large group or organic compounds that are oily to the touch and insoluble in water. Lipids include fatty acids, oils, waxes, sterols and triglycerides. They are a source of stored energy and are a component of cell membranes.

litter: 1. Material used as bedding for animals. 2. Material used to absorb the urine and feces of animals. 3. The uppermost slightly decayed layer of organic matter on the forest floor. 4. The offspring at one birth of a multiparous animal. Example: A litter of puppies.

liver: 1. A large glandular organ in the abdomen of vertebrate animals that is essential to many metabolic processes. The liver secretes bile, stores fat and sugar as reserve energy sources, converts harmful substances to less toxic forms, and regulates the amount of blood in the body. 2. A similar organ in invertebrate animals.


manure: Organic matter used as organic fertilizer in agriculture. Manures contribute to the fertility of the soil by adding organic matter and nutrients, such as nitrogen, that are trapped by bacteria in the soil. Higher organisms then feed on the fungi and bacteria in a chain of life that comprises the soil food web. It is also a product obtained after decomposition of organic matter like cow-dung which replenishes the soil with essential elements and adds humus to the soil.

marbling: The pattern created by intramuscular fat in meat, especially red meat. The quality of marbling in meat can be influenced by selective breeding and feeding practices. In the U.S. “prime” cuts of meat have the highest marbling content.

mastitis: An infection and inflammation of the udder in cows.

mineral: 1. A naturally occurring solid, inorganic element or compound having a uniform composition and a regularly repeating internal structure. Rocks are made up of minerals. Many minerals have commercial value, such as iron ore, coal or petroleum. In animals, minerals like iron can be necessary nutrients.

monogastric: An animal with a stomach consisting of one compartment for digestion. Includes humans and pigs.

multiparous: 1. Having given birth two or more times. 2. Giving birth to more than one offspring at a time.

mutton: Meat from sheep that are over one year old.


neonatal: Relating to newborn animals

nitrogen: A nonmetallic element that makes up about 78 percent of the atmosphere by volume, occurring as a colorless, odorless gas. It is a component of all proteins, making it essential for life, and it is also found in various minerals. Nitrogen is used to make ammonia, nitric acid, TNT and fertilizers. Symbol N.

non-protein nitrogen: A term used in animal nutrition to refer collectively to components such as urea, biuret and ammonia, which are not proteins but can be converted into proteins by microbes in the ruminant stomach.

nutrient: A substance that provides nourishment for growth or metabolism. Plants absorb nutrients mainly from the soil in the form of minerals and other inorganic compounds. Animals mainly obtain nutrients from ingested food.

nutrition: The process by which living organisms obtain food and use it for growth, metabolism and repair.


omasum: The third division of the stomach in ruminant animals. It removes excess water from food and further reduces the size of food particles before passing them to the abomasums for digestion by enzymes.

oogenesis: The formation, development, and maturation of an ovum or egg cell.

Optiflex: A feed additive sometimes given to animals raised for meat.

organic: 1. Involving organisms or the products of their life processes. 2. Relating to chemical compounds containing carbon.

ovine: Relating to sheep.

ovulation: The release if an egg cell (ovum) from the ovary in female animals, regulated in mammals by hormones produced in the pituitary glands during the menstrual cycle.


pancreas: A long, irregularly shaped gland in vertebrate animals that is located behind the stomach and is part of the digestive system. It secretes hormones (insulin, glucagon and somatostatin) into the bloodstream and digestive enzymes into the small intestine or gut. The pancreas also secretes sodium bicarbonate, which protects the lining of the intestine by neutralizing acids in the stomach.

parasite: An organism that lives on or in a different kind of organism (the host) from which it gets some or all of its nourishment. Parasites are generally harmful to their hosts, although the damage they do ranges from minor inconvenience to debilitating or fatal disease.

parturition: The action or process of giving birth to offspring. In cows, parturition is called calving, and in pigs parturition is called farrowing.

pasture: A fenced area of forage, usually improved, on which animals are grazed.

pathogen: An agent that causes infection or disease, especially a microorganism, such as a bacterium or a virus.

Paylean: A product from the company Elanco Animal Health. Paylean can direct nutrients toward quality lean gain and away from fat deposition, resulting in an increase of high-value, lean cuts of meat in pork carcasses.

phosphorus: A highly reactive, poisonous nonmetallic element occurring naturally in phosphates, especially in the mineral apatite. It exists in white (or sometimes yellow), red, and black forms, and it an essential component of protoplasm. Symbol P.

photoperiod: The duration of an organism’s daily exposure to light.

phytate: The salt form of phytic acid, the principle storage form of phosphorus in many plant tissues. Phosphorus and inositol in phytate form are not, in general, bioavailable to nonruminant animals because these animals lack the digestive enzyme phytase required to remove phosphate from the inositol in the phytate molecule. On the other hand, ruminants readily digest phytate because of the phytase produced by rumen microorganisms.

phytase: any type of phosphatase enzyme that catalyzes the hydrolysis of phytic acid (myo-inositol hexakisphosphate) and releases a usable form of inorganic phosphorus. While phytases have been found to occur in animals, plants, fungi and bacteria, phytases have been most commonly detected and characterized from fungi.

placenta: The sac-shaped organ that attaches the embryo or fetus to the uterus during pregnancy in most mammals. Blood flows between mother and fetus through the placenta, supplying oxygen and nutrients to the fetus and carrying away fetal waste products. The placenta is expelled after birth.

porcine: Relating to pigs

pork: The culinary name for meat from swine.

poultry: Domesticated birds kept by humans for the purpose of producing eggs, meat, and/or feathers. These most typically are members of the super order Galloanserae (fowl), especially the order Galliformes (which includes chickens, quails and turkeys) and the family Anatidae (in order Anseriformes), commonly known as "waterfowl" (e.g. domestic ducks and domestic geese). Poultry also includes other birds which are killed for their meat, such as pigeons or doves or birds considered to be game, like pheasants.

processed meat: Meat that has been altered from its original state for flavor, preservation and/or convenience. The methods used for processing foods include canning, freezing, refrigeration, dehydration and aseptic processing. Sausages, jerky, cured meats, meat patties, bacon and salamis are all examples of processed meats.

protein: Any of a large class of complex organic chemical compounds that are essential for life. Proteins play a central role in biological processes and form the basis of living tissues. They consist of long chains of amino acids connected by peptide bonds. Enzymes, antibodies and hemoglobin are examples of proteins.

protein supplement: A feed containing protein, vitamins and minerals which is fed to livestock to provide a complete diet.

PRRS: The acronym for porcine reproductive and respiratory syndrome. The result of a viral disease that causes reproductive failure in breeding stock and respiratory tract illness in young pigs.

puberty: The stage in the development of humans and other primates marked by the development of secondary sex characteristics, including the beginning of the menstrual cycle in females. In humans, puberty occurs at the onset of adolescence, between the ages of about 11 and 14 in girls and 13 and 16 in boys.



ractopamine: A drug that is used as a feed additive to promote leanness in pigs raised for their meat.

ram (or buck): A male sheep of any age.

rangeland: A large open land area on which livestock wander and graze. The native vegetation is mainly grasses and shrubs.

red meat: Meat which is red when raw and not white when cooked. In the nutritional sciences, red meat includes all mammal meat. Red meat includes the meat of most adult mammals and some fowl (e.g. ducks).

reticulum: The second division of the stomach in ruminant animals, which together with the rumen contains microorganisms that digest fiber. The reticulum’s contents are regurgitated for further chewing as part of the cud.

roughage: The coarse, indigestible constituents of food or fodder, which provide bulk to the diet and promote normal bowel function.

rumen: The first and largest division of the stomach in ruminant animals, in which the food is fermented by microorganisms.

ruminant: Any of various even-toed hoofed mammals of the suborder Ruminantia. Ruminants usually have a stomach divided into four compartments and chew a cud consisting of regurgitated, partially digested food. Includes cattle, sheep, goats, deer and others.


semen: A thick, whitish fluid that is produced during ejaculation by male mammals and carries sperm cells.

sex hormone: Any of various steroid hormones that regulate the sexual development of an organism and are needed for reproduction. Testosterone and estrogen are sex hormones.

sheep: Any of various usually horned ruminant mammals of the genus Ovis in the family Bovidae, especially the domesticated species O. aries, raised in many breeds for wool, edible flesh or skin.

silage: A crop that has been preserved in a moist, succulent condition by partial fermentation in a tight container (silo) above or below ground. The chief crops stored in this way are corn (the whole plant), sorghum, and various legumes and grasses. The main use of silage is in cattle feed.

sire: The male parent. To father or become the sire of.

small intestine: The long, narrow, coiled section of the intestine that extends from the stomach to the beginning of the large intestine. Nutrients from food are absorbed into the bloodstream from the small intestine. In mammals, it is made up of the duodenum, jejunum and ileum.

sperm: The smaller, usually motile male reproductive cell or most organisms that reproduce sexually. Sperm cells are haploid (they have half the number of chromosomes as other cells in the body).

sorghum: A cereal grass used mainly for feed grain or silage.

sow: A sexually mature female hog, after having her first litter.

stomach: 1. A saclike muscular organ in vertebrate animals that stores and breaks down ingested food. Food enters the stomach from the esophagus and passes to the small intestine through the pylorus. Glands in the stomach secrete hydrochloric acid and the digestive enzyme pepsin. 2. A similar digestive structure of many invertebrates.

superovulation: A term used to describe the drug-induced production of multiple eggs for use during assisted reproductive technologies.

swine: An animal commonly referred to as a pig or boar. Any of various omnivorous, even-toed ungulates of the family Suidae, including pigs, hogs and boars, having a stout body with thick skin, a short neck and a movable snout.


Total Maximum Daily Load (TMDL): a regulatory term in the U.S. Clean Water Act, describing a value of the maximum amount of a pollutant that a body of water can receive while still meeting water quality standards. Alternatively, TMDL is an allocation of that water pollutant deemed acceptable to the subject receiving waters. TMDLs have been used extensively by the United States Environmental Protection Agency (EPA) and state environmental agencies in implementing the Clean Water Act by establishing maximum pollution limits for industrial wastewater dischargers.

turkey: A large bird in the genus Meleagris. One species, Meleagris gallopavo, commonly known as the Wild Turkey, is native to the forests of North America. The domestic turkey is a descendant of this species. The other living species is Meleagris ocellata or the Ocellated Turkey, native to the forests of the Yucatán Peninsula.


umbilical cord: The flexible cord that attaches an embryo or fetus to the placenta. The umbilical cord contains blood vessels that supply nutrients and oxygen to the fetus and remove its wastes, including carbon dioxide.

urea: The chief nitrogen-containing waste product excreted in the urine of mammals and some fish. It is the final nitrogenous product in the breakdown of proteins by the body.

urethra: The duct through which urine passes from the bladder to the outside of the body in most mammals and some fish and birds. In males, the urethra passes through the penis and also serves as the duct for the release of sperm.

USDA: The United States Department of Agriculture

uterus: The hollow, muscular organ of female mammals in which the embryo develops. In most mammals, the uterus is divided into two saclike parts, whereas in primates it is a single structure. It lies between the bladder and rectum and is attached to the vagina and the fallopian tubes. During the menstral cycle (estrus), the lining of the uterus (endometrium) undergoes changes that permit the implantation of a fertilized egg. Also called womb.

uterine: Relating to the uterus.


veal: The meat of young cattle (calves), as opposed to meat from older cattle. Though veal can be produced from a calf of either sex and any breed, most veal comes from male calves of dairy cattle breeds

vitamin: An organic compound required as a nutrient in tiny amounts by an organism.[1] In other words, an organic chemical compound (or related set of compounds) is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. Thus, the term is conditional both on the circumstances and on the particular organism. For example, ascorbic acid (vitamin C) is a vitamin for humans, but not for most other animals, and biotin and vitamin D are required in the human diet only in certain circumstances. By convention, the term vitamin does not include other essential nutrients such as dietary minerals, essential fatty acids, or essential amino acids (which are needed in larger amounts than vitamins), nor does it encompass the large number of other nutrients that promote health but are otherwise required less often.

virus: Any of various extremely small, often disease-causing agents consisting of a particle containing a segment of DNA or RNA within a protein coat. Viruses are not technically considered living organisms because they are devoid of biological processes (such as metabolism and respiration) and cannot reproduce on their own. Viruses are the cause of diseases like the “common cold” and chicken pox.


warm-blooded: Having a relatively warm body temperature that stays about the same regardless of changes in the surroundings. Birds and mammals are warm-blooded.

water: A chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state (water vapor or steam).

white blood cell: Any of various white or colorless cells in the blood of vertebrate animals, many of which participate in the inflammatory and immune responses to protect the body against infection and the repair of injuries to tissues. White body cells are formed mainly in the bone marrow.

wool: The textile fiber obtained from sheep and certain other animals,[1] including cashmere from goats, mohair from goats, qiviut from muskoxen, vicuña, alpaca, camel from animals in the camel family, and angora from rabbits. Wool has several qualities that distinguish it from hair or fur: it is crimped, it is elastic, and it grows in staples (clusters). The term wool is usually restricted to describing the fibrous protein derived from the specialized skin cells called follicles in sheep.



yoke: A wooden beam, normally used between a pair of oxen or other animals to enable them to pull together on a load when working in pairs, as oxen usually do; some yokes are fitted to individual animals. There are several types of yoke, used in different cultures, and for different types of oxen. A pair of oxen may be called a yoke of oxen, and yoke is also a verb, as in "to yoke a pair of oxen". Other animals that may be yoked include horses, mules, donkeys and water buffalo.

yolk: The yellow internal part of the egg of a bird or reptile. The yolk is surrounded by the albumen and supplies food to the developing young.


zoonotic: Relating to a disease communicable from animals to humans under natural conditions. Example: rabies.

zygote: The cell formed by the union of the nuclei of two reproductive cells (gametes), especially in a fertilized egg cell.

Glossary compiled with the help of: New Mexico State University College of Agricultural, Consumer, and Environmental Sciences; The American Heritage Science Dictionary; The University of Georgia College of Agricultural and Environmental Science; and the Utah State University Cooperative Extension.