Meat
Meat is animal tissue, mostly muscle, that is eaten as food. Humans have hunted and farmed other animals for meat since prehistory. The Neolithic Revolution allowed the domestication of vertebrates, including chickens, sheep, goats, pigs, horses, and cattle, starting around 11,000 years ago. Since then, selective breeding has enabled farmers to produce meat with the qualities desired by producers and consumers. Meat is important to economies and cultures around the world.
Meat is mainly composed of water, protein, and fat. Its quality is affected by many factors, including the genetics, health, and nutritional status of the animal involved. Without preservation, bacteria and fungi decompose and spoil unprocessed meat within hours or days. Meat is edible raw, but it is mostly eaten cooked, such as by stewing or roasting, or processed, such as by smoking or salting.
The consumption of meat increases the risk of certain negative health outcomes including cancer, coronary heart disease, and diabetes. Meat production significantly harms the environment by contributing to global warming, pollution, and biodiversity loss. Some people choose not to eat meat for ethical, environmental, health or religious reasons.
Etymology
The word meat comes from the Old English word mete, meaning food in general. In modern usage, meat primarily means skeletal muscle with its associated fat and connective tissue, but it can include offal, here meaning other edible organs such as liver and kidney. The term is sometimes used in a more restrictive sense to mean the flesh of mammalian species raised and prepared for human consumption, to the exclusion of fish, other seafood, insects, poultry, or other animals.History
Domestication
evidence suggests that meat constituted a substantial proportion of the diet of the earliest humans. Early hunter-gatherers depended on the organized hunting of large animals such as bison and deer. Animals were domesticated in the Neolithic, enabling the systematic production of meat and the breeding of animals to improve meat production.| Animal | Centre of origin | Purpose | Date/years ago |
| Goat, sheep, pig, cow | Near East, South Asia | Food | 11,000–10,000 |
| Chicken | East Asia | Cockfighting | 7,000 |
| Horse | Central Asia | Draft, riding | 5,500 |
Intensive animal farming
In the postwar period, governments gave farmers guaranteed prices to increase animal production. The effect was to raise output at the cost of increased inputs such as of animal feed and veterinary medicines, as well as of animal disease and environmental pollution. In 1966, the United States, the United Kingdom and other industrialized nations, began factory farming of beef and dairy cattle and domestic pigs. Intensive animal farming became globalized in the later years of the 20th century, replacing traditional stock rearing in countries around the world. In 1990 intensive animal farming accounted for 30% of world meat production and by 2005, this had risen to 40%.Selective breeding
Modern agriculture employs techniques such as progeny testing to speed selective breeding, allowing the rapid acquisition of the qualities desired by meat producers. For instance, in the wake of well-publicized 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 that could improve the meat-producing qualities of animals are becoming available.Meat production continues to be shaped by the demands of customers. The trend towards selling meat in pre-packaged cuts has increased the demand for larger breeds of cattle, better suited to producing such cuts. Animals not previously exploited for their meat are now being farmed, including mammals such as antelope, zebra, water buffalo and camel, as well as non-mammals, such as crocodile, emu and ostrich. Organic farming supports an increasing demand for meat produced to that standard.
Animal growth and development
Several factors affect the growth and development of meat.Genetics
| Trait | Heritability |
| Reproductive efficiency | 2–10% |
| Meat quality | 15–30% |
| Growth | 20–40% |
| Muscle/fat ratio | 40–60% |
Some economically important traits in meat animals are heritable to some degree, and can thus be selected for by animal breeding. In cattle, certain growth features are controlled by recessive genes which have not so far been excluded, complicating breeding. One such trait is dwarfism; another is the doppelender or "double muscling" condition, which causes muscle hypertrophy and thereby increases the animal's commercial value. Genetic analysis continues to reveal the mechanisms that control numerous aspects of the endocrine system and, through it, meat growth and quality.
Genetic engineering can shorten breeding programs significantly because they allow for the identification and isolation of genes coding for desired traits, and for the reincorporation of these genes into the animal genome. To enable this, the genomes of many animals are being mapped. Some research has already seen commercial application. For instance, a recombinant bacterium has been developed which improves the digestion of grass in the rumen of cattle, and some features of muscle fibers have been genetically altered. Experimental reproductive cloning of commercially important meat animals such as sheep, pig or cattle has been successful. Asexual reproduction of animals bearing desirable traits is anticipated.
Environment
Heat regulation in livestock is of economic significance, as mammals attempt to maintain a constant optimal body temperature. Low temperatures tend to prolong animal development and high temperatures tend to delay it. Depending on their size, body shape and insulation through tissue and fur, some animals have a relatively narrow zone of temperature tolerance and others a broad one. Static magnetic fields, for reasons still unknown, retard animal development.Animal nutrition
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 about how exactly the plane of nutrition influences carcase composition.The composition of the diet, especially the amount of protein provided, is 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, 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 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, where the soil contains limited phosphate, cattle are 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 found to be a result of cobalt deficiency in the soil. Plant toxins are a risk to grazing animals; for instance, sodium fluoroacetate, found in some African and Australian plants, kills by disrupting the cellular metabolism. Some man-made pollutants such as methylmercury and some pesticide residues present a particular hazard as they bioaccumulate in meat, potentially poisoning consumers.
Animal welfare
Practices such as confinement in factory farming have generated concerns for animal welfare. Animals have abnormal behaviors such as tail-biting, cannibalism, and feather pecking. Invasive procedures such as beak trimming, castration, and ear notching have similarly been questioned. Breeding for high productivity may affect welfare, as when broiler chickens are bred to be very large and to grow rapidly. Broilers often have leg deformities and become lame, and many die from the stress of handling and transport.Human intervention
Meat producers may seek to improve the fertility of female animals through the administration of gonadotrophic or ovulation-inducing hormones. In pig production, sow infertility is a common problem – possibly due to excessive fatness. No methods currently exist to augment the fertility of male animals. Artificial insemination is now routinely used to produce animals of the best possible genetic quality, and the efficiency of this method is improved through the administration of hormones that synchronize the ovulation cycles within groups of females.Growth hormones, particularly anabolic agents such as steroids, are used in some countries to accelerate muscle growth in animals. This practice has given rise to the beef hormone controversy, an international trade dispute. It may decrease the tenderness of meat, although research on this is inconclusive, and have other effects on the composition of the muscle flesh. Where castration is used to improve control over male animals, its side effects can be counteracted by the administration of hormones. Myostatin has been used to produce muscle hypertrophy.
Sedatives may be administered to animals to counteract stress factors and increase weight gain. The feeding of antibiotics to certain animals increases growth rates. This practice is particularly prevalent in the US, but has been banned in the EU, partly because it causes antimicrobial resistance in pathogenic microorganisms.