Meat is animal flesh that is eaten as food. Humans have hunted and killed animals for meat since prehistoric times. The advent of civilization allowed the domestication of animals such as chickens, sheep, rabbits, pigs and cattle. This eventually led to their use in meat production on an industrial scale with the aid of slaughterhouses.

Meat is mainly composed of water, protein, and fat. It is edible raw, but is normally eaten after it has been cooked and seasoned or processed in a variety of ways. Unprocessed meat will spoil or rot within hours or days as a result of infection with and decomposition by bacteria and fungi.

Meat is important in economy and culture, even though its mass production and consumption has been determined to pose risks for human health and the environment. Many religions have rules about which meat may or may not be eaten, and vegetarian people abstain from eating meat because of concerns about the ethics of eating meat or about the effects of meat production or consumption.

The quality and quantity of usable meat depends on the animal’s plane of nutrition, i.e., whether it is over- or underfed. Scientists disagree, however, about how exactly the plane of nutrition influences carcase composition.

The composition of the diet, especially the amount of protein provided, is also an important factor regulating animal growth. Ruminants, which may digest cellulose, are better adapted to poor-quality diets, but their ruminal microorganisms degrade high-quality protein if supplied in excess. Because producing high-quality protein animal feed is expensive (see also Environmental impact below), several techniques are employed or experimented with to ensure maximum utilization of protein. These include the treatment of feed with formalin to protect amino acids during their passage through the rumen, the recycling of manure by feeding it back to cattle mixed with feed concentrates, or the partial conversion of petroleum hydrocarbons to protein through microbial action.

In plant feed, environmental factors influence the availability of crucial nutrients or micronutrients, a lack or excess of which can cause a great many ailments. In Australia, for instance, where the soil contains limited phosphate, cattle are being fed additional phosphate to increase the efficiency of beef production. Also in Australia, cattle and sheep in certain areas were often found losing their appetite and dying in the midst of rich pasture; this was at length found to be a result of cobalt deficiency in the soil. Plant toxins are also a risk to grazing animals; for instance, sodium fluoroacetate, found in some African and Australian plants, kills by disrupting the cellular metabolism. Certain man-made pollutants such as methylmercury and some pesticide residues present a particular hazard due to their tendency to bioaccumulate in meat, potentially poisoning consumers.

All muscle tissue is very high in protein, containing all of the essential amino acids, and in most cases is a good source of zinc, vitamin B12, selenium, phosphorus, niacin, vitamin B6, choline, riboflavin and iron. Several forms of meat are also high in vitamin K. Muscle tissue is very low in carbohydrates and does not contain dietary fiber. While taste quality may vary between meats, the proteins, vitamins, and minerals available from meats are generally consistent.

The fat content of meat can vary widely depending on the species and breed of animal, the way in which the animal was raised, including what it was fed, the anatomical part of the body, and the methods of butchering and cooking. Wild animals such as deer are typically leaner than farm animals, leading those concerned about fat content to choose game such as venison. Decades of breeding meat animals for fatness is being reversed by consumer demand for meat with less fat. The fatty deposits that exist with the muscle fibers in meats soften meat when it is cooked and improve the flavor through chemical changes initiated through heat that allow the protein and fat molecules to interact. The fat, when cooked with meat, also makes the meat seem juicier. However, the nutritional contribution of the fat is mainly calories as opposed to protein. As fat content rises, the meat’s contribution to nutrition declines. In addition, there is cholesterol associated with fat surrounding the meat. The cholesterol is a lipid associated with the kind of saturated fat found in meat. The increase in meat consumption after 1960 is associated with, though not definitively the cause of, significant imbalances of fat and cholesterol in the human diet.

The table in this section compares the nutritional content of several types of meat. While each kind of meat has about the same content of protein and carbohydrates, there is a very wide range of fat content.

Source                                  calories                protein                 carbs     fat

fish.                                            110–140                20–25 g                     0 g          1–5 g

chicken breast                          160                         28 g                            0 g          7 g

lamb                                           250                         30 g                            0 g          14 g

steak (beef top round)            210                          36 g                            0 g          7 g

steak (beef T-bone)                 450                         25 g                             0 g          35 g


Paleontological evidence suggests that meat constituted a substantial proportion of the diet of even the earliest humans. Early hunter-gatherers depended on the organized hunting of large animals such as bison and deer.

The domestication of animals, of which we have evidence dating back to the end of the last glacial period (c. 10,000 BCE), allowed the systematic production of meat and the breeding of animals with a view to improving meat production. The animals which are now the principal sources of meat were domesticated in conjunction with the development of early civilizations:

Sheep, originating from western Asia, were domesticated with the help of dogs prior to the establishment of settled agriculture, likely as early as the 8th millennium BCE. Several breeds of sheep were established in ancient Mesopotamia and Egypt by 3500–3000 BCE.Today, more than 200 sheep-breeds exist.

Cattle were domesticated in Mesopotamia after settled agriculture was established about 5000 BCE, and several breeds were established by 2500 BCE. Modern domesticated cattle fall into the groups Bos taurus (European cattle) and Bos taurus indicus (zebu), both descended from the now-extinct aurochs. The breeding of beef cattle, cattle optimized for meat production as opposed to animals best suited for work or dairy purposes, began in the middle of the 18th century.

A Hereford bull, a breed of cattle frequently used in beef production.

Domestic pigs, which are descended from wild boars, are known to have existed about 2500 BCE in modern-day Hungary and in Troy; earlier pottery from Jericho and Egypt depicts wild pigs. Pork sausages and hams were of great commercial importance in Greco-Roman times. Pigs continue to be bred intensively as they are being optimized to produce meat best suited for specific meat products.

Other animals are or have been raised or hunted for their flesh. The type of meat consumed varies much between different cultures, changes over time, depending on factors such as tradition and the availability of the animals. The amount and kind of meat consumed also varies by income, both between countries and within a given country.


Horses are commonly eaten in France, Italy, Germany and Japan, among other countries. Horses and other large mammals such as reindeer were hunted during the late Paleolithic in western Europe.

Dogs are consumed in China, South Korea and Vietnam. Dogs are also occasionally eaten in the Arctic regions. Historically, dog meat has been consumed in various parts of the world, such as Hawaii, Japan, Switzerland and Mexico.

Cats are consumed in Southern China, Peru and sometimes also in Northern Italy.

Guinea pigs are raised for their flesh in the Andes.

Whales and dolphins are hunted, partly for their flesh, in Japan, Alaska, Siberia, Canada, the Faroe Islands, Greenland, Iceland, Saint Vincent and the Grenadines and by two small communities in Indonesia.

Modern agriculture employs a number of techniques, such as progeny testing, to speed artificial selection by breeding animals to rapidly acquire the qualities desired by meat producers. For instance, in the wake of well-publicised health concerns associated with saturated fats in the 1980s, the fat content of United Kingdom beef, pork and lamb fell from 20–26 percent to 4–8 percent within a few decades, due to both selective breeding for leanness and changed methods of butchery. Methods of genetic engineering aimed at improving the meat production qualities of animals are now also becoming available.

Even though it is a very old industry, meat production continues to be shaped strongly by the evolving demands of customers. The trend towards selling meat in pre-packaged cuts has increased the demand for larger breeds of cattle, which are better suited to producing such cuts.Even more animals not previously exploited for their meat are now being farmed, especially the more agile and mobile species, whose muscles tend to be developed better than those of cattle, sheep or pigs. Examples are the various antelope species, the zebra, water buffalo and camel, as well as non-mammals, such as the crocodile, emu and ostrich. Another important trend in contemporary meat production is organic farming which, while providing no organoleptic benefit to meat so produced, meets an increasing demand for organic meat.