Meat - WikiHQ

thumb|upright=1.5|Raw meat (clockwise from left): [[chicken as food|chicken, beef, bacon, pork chops]]

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 (especially red and processed meat, as opposed to fish and poultry) 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 (vegetarians and vegans) choose not to eat meat for ethical, environmental, health or religious reasons.

Etymology

The word meat comes from the Old English word , 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 (pigs, cattle, sheep, goats, etc.) raised and prepared for human consumption, to the exclusion of fish, other seafood, insects, poultry, or other animals.

History

Domestication

Paleontological 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.

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|+ Major animal domestications

! 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. In 1990 intensive animal farming accounted for 30% of world meat production and by 2005, this had risen to 40%.

File:Lamb meat.jpg|A shoulder of lamb

File:Hereford bull large.jpg|A Hereford bull, a breed of beef cattle

File:SelectionOfPackageMeats.jpg|Supermarket meat, North America

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Animal growth and development

Several factors affect the growth and development of meat.

Genetics

{|class="wikitable floatleft col2right"

! 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 (e.g. cattle) 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

thumb|The welfare of farm animals such as hens in [[battery cages and other systems is debated.]]

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.

Composition

Biochemical

The biochemical composition of meat varies in complex ways depending on the species, breed, sex, age, plane of nutrition, training and exercise of the animal, as well as on the anatomical location of the musculature involved. Even between animals of the same litter and sex there are considerable differences in such parameters as the percentage of intramuscular fat.

Adult mammalian muscle consists of roughly 75 percent water, 19 percent protein, 2.5 percent intramuscular fat, 1.2 percent carbohydrates and 2.3 percent other soluble substances. These include organic compounds, especially amino acids, and inorganic substances such as minerals. Muscle proteins are either soluble in water (sarcoplasmic proteins, about 11.5 percent of total muscle mass) or in concentrated salt solutions (myofibrillar proteins, about 5.5 percent of mass). There are several hundred sarcoplasmic proteins. Most of them – the glycolytic enzymes – are involved in glycolysis, the conversion of sugars into high-energy molecules, especially adenosine triphosphate (ATP). The two most abundant myofibrillar proteins, myosin and actin, form the muscle's overall structure and enable it to deliver power, consuming ATP in the process. The remaining protein mass includes connective tissue (collagen and elastin). Fat in meat can be either adipose tissue, used by the animal to store energy and consisting of "true fats" (esters of glycerol with fatty acids), or intramuscular fat, which contains phospholipids and cholesterol.

Nutritional

Muscle tissue is high in protein, containing all the essential amino acids, and for example red meat is a good source of vitamin B<sub>12</sub>, selenium, niacin, vitamin B<sub>6</sub>, and iron. Several forms of meat are high in vitamin K. Muscle tissue is very low in carbohydrates and does not contain dietary fiber.

The fat content of meat varies widely with the species and breed of animal, the way in which the animal was raised, what it was fed, the part of the body, and the methods of butchering and cooking. Wild animals such as deer are 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 leaner meat. Small amounts – in the range – of fat deposited near the muscle fibers ("marbling") in meats can slightly improve perceived flavour, juiciness and tenderness, but contribute no more than about to overall palatability. Fat around meat further contains cholesterol. The increase in meat consumption after 1960 is associated with significant imbalances of fat and cholesterol in the human diet.

{|class="wikitable col2right col3right col4right col5right"

|+ Nutritional content of ; data vary widely with selection (e.g. skinless, boneless) and preparation

! Source

! Energy: kJ (kcal)

! Protein

! Carbs

! Fat

! Chicken breast

|

|25 g

|0 g

|2 g

! Lamb mince

|19 g

|0 g

|26 g

! Beef mince

|

|19 g

|0 g

|22 g

! Dog

|20 g

|0 g

|22 g

! Horse

|

|23 g

|0 g

|5 g

! Pork loin

|14 g

|0 g

|30 g

! Rabbit

|32 g

|0 g

|9 g

Production

File:World production of meat by main items.svg|World production of meat by main items

File:World production of main meat items by main producers (2023).svg|World production of main meat items by main producers (2023)

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