Milk

From Wikipedia, the free encyclopedia

Milk is an opaque white liquid produced by the mammary glands of mammals. It provides the primary source of nutrition for young mammals before they are able to digest other types of food. The early lactation milk is known as colostrum, and carries the mother’s antibodies to the baby. It can reduce the risk of many diseases in the baby. The exact components of raw milk varies by species, but it contains significant amounts of saturated fat, protein and calcium as well as vitamin C. Cow’s milk has a pH ranging from 6.4 to 6.8, making it slightly acidic.^[1][2]

Types of consumption

There are two distinct types of milk consumption: a natural source of nutrition for all infant mammals, and a food product for humans of all ages derived from other animals.

Nutrition for infant mammals

AnatomyMost goats naturally have two horns, of various shapes and sizes depending on the breed. While horns are a predominantly male feature, some breeds of goats have horned females. Polled (hornless) goats are not uncommon and there have been incidents of polycerate goats (having as many as eight horns), although this is a genetic rarity thought to be inherited. Their horns are made of living bone surrounded by keratin and other proteins, and are used for defense, dominance, and territoriality.^[6]

Goats are ruminants. They have a four-chambered stomach consisting of the rumen, the reticulum, the omasum, and the abomasum.

Goats have horizontal slit-shaped pupils, an adaptation which increases peripheral depth perception.^[7] Because goats’ irises are usually pale, the pupils are much more visible than in animals with horizontal pupils, but very dark irises, such as cattle, deer, most horses and many sheep.

Both male and female goats have beards, and many types of goats (most commonly dairy goats, dairy-cross boers, and pygmy goats) may have wattles, one dangling from each side of the neck.^[8]

Some breeds of sheep and goats look similar, but they can usually be told apart because goat tails are short and point up, whereas sheep tails hang down and are usually longer – though some (like those of Northern European short-tailed sheep) are short, and longer ones are often docked.

[edit] Reproduction

In some climates, goats are able to breed at any time of the year. In temperate climates and among the Swiss breeds, the breeding season commences as the day length shortens, and ends in early spring. Does of any breed come into heat every 21 days for 2 to 48 hours. A doe in heat typically flags her tail often, stays near the buck if one is present, becomes more vocal, and may also show a decrease in appetite and milk production for the duration of the heat.

Bucks (intact males) of Swiss and northern breeds come into rut in the fall as with the doe’s heat cycles. Rut is characterized by a decrease in appetite and obsessive interest in the does.

In addition to natural mating, artificial insemination has gained popularity among goat breeders, as it allows easy access to a wide variety of bloodlines.

Gestation length is approximately 150 days. Twins are the usual result, with single and triplet births also common. Less frequent are litters of quadruplet, quintuplet, and even sextuplet kids. Birthing, known as kidding, generally occurs uneventfully. Right before kidding the doe will have a sunken area around the tail and hip. Also she will have heavy breathing, a worried look, become restless and show great display of affection for her keeper. The mother often eats the placenta, which gives her much needed nutrients, helps stanch her bleeding, and parallels the behavior of wild herbivores such as deer to reduce the lure of the birth scent for predators.^[9][10]

Freshening (coming into milk production) occurs at kidding. Milk production varies with the breed, age, quality, and diet of the doe; dairy goats generally produce between 660 to 1,800 L (1,500 and 4,000 lb) of milk per 305 day lactation. On average, a good quality dairy doe will give at least 6 lb (2.7 l) of milk per day while she is in milk. A first time milker may produce less, or as much as 16 lb (7.3 l), or more of milk in exceptional cases. After the 305 day lactation, the doe will “dry off”, typically after she has been bred. Occasionally, goats that have not been bred and are continuously milked will continue lactation beyond the typical 305 days.^[11] Meat, fiber, and pet breeds are not usually milked and simply produce enough for the kids until weaning.

Male lactation is also known to occur in goats.^[12]

[edit] Diet

Goats are reputed to be willing to eat almost anything, even tin cans and cardboard boxes. While goats will not actually eat inedible material, they are browsing animals, not grazers like cattle and sheep, and (coupled with their natural curiosity) will chew on and taste just about anything resembling plant matter in order to decide whether it is good to eat, including cardboard and paper labels from tin cans. ^[13] Another possibility is that the goats are curious about the unusual smells of leftover food in discarded cans or boxes.

Aside from sampling many things, goats are quite particular in what they actually consume, preferring to browse on the tips of woody shrubs and trees, as well as the occasional broad-leaved plant. However, it can fairly be said that their plant diet is extremely varied, and includes some species which are otherwise toxic.^[14] They will seldom consume soiled food or contaminated water unless facing starvation. This is one of the reasons why goat rearing is most often free ranging, since stall-fed goat rearing involves extensive upkeep and is seldom commercially viable.

Goats prefer to browse on shrubbery and weeds, more like deer than sheep, preferring them to grasses. Nightshade is poisonous; wilted fruit tree leaves can also kill goats. Silage (corn stalks) is not good for goats, but haylage can be used if consumed immediately after opening. Alfalfa is their favorite hay; fescue is the least palatable and least nutritious. Mold in a goat’s feed can make it sick and possibly kill it. Goats should not be fed grass with any signs of mold.

The digestive physiology of a very young kid (like the young of other ruminants) is essentially the same as that of a monogastric animal. Milk digestion begins in the abomasum, the milk having bypassed the rumen via closure of the reticular/esophageal groove during suckling. At birth, the rumen is undeveloped, but as the kid begins to consume solid feed, the rumen soon increases in size and in its capacity to absorb nutrients.

[edit] Behavior

Goats are extremely curious and intelligent. They are easily trained to pull carts and walk on leads. Ches McCartney, nicknamed “the goat man”, toured the United States for over three decades in a wagon pulled by a herd of pet goats. They are also known for escaping their pens. Goats will test fences, either intentionally or simply because they are handy to climb on. If any of the fencing can be spread, pushed over or down, or otherwise be overcome, the goats will escape. Being very intelligent, once a weakness in the fence has been discovered, it will be exploited repeatedly. Goats are very coordinated and can climb and hold their balance in the most precarious places. Goats are also widely known for their ability to climb trees, although the tree generally has to be on somewhat of an angle. The vocalization goats make is called bleating.

Goats have an intensely inquisitive and intelligent nature: they will explore anything new or unfamiliar in their surroundings. They do so primarily with their prehensile upper lip and tongue. This is why they investigate items such as buttons, camera cases or clothing (and many other things besides) by nibbling at them, occasionally even eating them.

[edit] Life expectancy

Life expectancy for goats is between 15^[15] and 18 years.^[16] An instance of a goat reaching the age of 24 has been reported.^[17]

Several factors can reduce this average expectancy, however; problems during kidding can lower a doe’s expected life span to 10 or 11, and stresses of going into rut can lower a buck’s expected life span to 8 or 10.^[17]

[edit] Goats in agriculture

A goat is useful to humans either living or dead, first as a renewable provider of milk and fibre, and then as meat and hide. Some charities provide goats to impoverished people in poor countries, because goats are easier and cheaper to manage than cattle, and have multiple uses. In addition, goats are used for driving and packing purposes.

For instance, the intestine is used to make “catgut“, which is still in use as a material for internal human surgical sutures and strings for musical instruments. The horn of the goat, which signifies wellbeing (Cornucopia), is also used to make spoons.^[18]

[edit] Meat

The taste of goat meat is similar to that of lamb meat^{[citation needed]}; in fact, in the English-speaking islands of the Caribbean, and in some parts of Asia, particularly Pakistan and India, the word “mutton” is used to describe both goat and lamb meat. However, some feel that it has a similar taste to veal or venison, depending on the age and condition of the goat. The flavour of goat meat is said to be primarily linked to the presence of 4-methyloctanoic and 4-methylnonanoic acid ^[19]. It can be prepared in a variety of ways including stewed, baked, grilled, barbecued, minced, canned, fried, curried, or made into sausage. Due to its low fat content, the meat can toughen at high temperatures without additional moisture. One of the most popular goats grown for meat is the South African Boer, introduced into the United States in the early 1990s. The New Zealand Kiko is also considered a meat breed, as is the myotonic or “fainting goat”, a breed originating in Tennessee.

[edit] Milk, butter and cheese

Some goats are bred for milk, which can be drunk raw, although some people recommend pasteurization to reduce bacteria such as Staphylococcus aureus and Escherichia coli.^[20] If the strong-smelling buck is not separated from the does, his scent will affect the milk. Goat’s milk is commonly processed into cheese, goat butter, ice cream, cajeta and other products.

Goat’s milk can replace sheep’s milk or cow’s milk in diets of those who are allergic.^[21] However, like cow’s milk, goat’s milk has lactose (sugar), and may cause gastrointestinal problems for individuals with lactose intolerance.^[21]

Goat’s milk naturally has small fat globules, which means the cream remains suspended in the milk, instead of rising to the top, as in raw cow’s milk; therefore, it does not need to be homogenized.

Many dairy goats, in their prime, average 6 to 8 pounds (2.7 to 3.6 kg) of milk daily (roughly 3 to 4 US quarts (2.7 to 3.6 liters)) during a ten-month lactation, producing more after freshening and gradually dropping in production toward the end of their lactation. The milk generally averages 3.5 percent butterfat. A doe may be expected to reach her heaviest production during her third or fourth lactation.^[22] It is also said that “formula derived from goat’s milk is unsuitable for babies who are lactose intolerant as it contains levels of lactose similar to cow’s-milk-based infant formulae.”^[23]

Goat butter is white because goats produce milk with the yellow beta-carotene converted to a colorless form of vitamin A.

Goat cheese is known as chèvre in France, after the French word for “goat”. Some varieties include Rocamadour and Montrachet.^[24]

[edit] Fiber

The Angora breed of goats produces long, curling, lustrous locks of mohair. The entire body of the goat is covered with mohair and there are no guard hairs. The locks constantly grow and can be four inches or more in length. Angora crossbreeds, such as the pygora and the nigora, have been created to produce mohair and/or cashgora on a smaller, easier-to-manage animal. The wool is shorn (cut from the body) twice a year, with an average yield of about 10 pounds.

Most goats have softer insulating hairs nearer the skin, and longer guard hairs on the surface. The desirable fiber for the textile industry is the former, and it goes by several names (down, cashmere and pashmina). The coarse guard hairs are of little value as they are too coarse, difficult to spin and difficult to dye. The cashmere goat produces a commercial quantity of cashmere wool, which is one of the most expensive natural fibers commercially produced; cashmere is very fine and soft. The cashmere goat fiber is harvested once a year, yielding around 9 ounces (200 grammes) of down.

In South Asia, cashmere is called “pashmina” (from Persian pashmina, “fine wool”). In the 18th and early 19th century, Kashmir (then called Cashmere by the English), had a thriving industry producing shawls from goat down imported from Tibet and Tartary through Ladakh. The shawls were introduced into Western Europe when the General in Chief of the French campaign in Egypt (1799-1802) sent one to Paris. Since these shawls were produced in the upper Kashmir and Ladakh region, the wool came to be known as “cashmere”.

[edit] Goat breeds

Goat breeds fall into overlapping, general categories. They are generally distributed in to those used for dairy, fiber, meat, skins, and as companion animals. Some breeds are also particularly noted as pack goats.

[edit] Showing

Goat breeders‘ clubs frequently hold shows, where goats are judged on traits relating to conformation, udder quality, evidence of high production, longevity, build and muscling (meat goats and pet goats) and fiber production and the fiber itself (fiber goats). People who show their goats usually keep registered stock and the offspring of award-winning animals command a higher price. Registered goats, in general, are usually higher-priced if for no other reason than that records have been kept proving their ancestry and the production and other data of their sires, dams, and other ancestors. A registered doe is usually less of a gamble than buying a doe at random (as at an auction or sale barn) because of these records and the reputation of the breeder. Children’s clubs such as 4-H also allow goats to be shown. Children’s shows often include a showmanship class, where the cleanliness and presentation of both the animal and the exhibitor as well as the handler’s ability and skill in handling the goat are scored. In a showmanship class, conformation is irrelevant since this is not what is being judged.

Various “Dairy Goat Scorecards” (milking does) are systems used for judging shows in the US. The American Dairy Goat Association (ADGA) scorecard for an adult doe includes a point system of a hundred total with major categories that include general appearance, the dairy character of a doe (physical traits that aid and increase milk production), body capacity, and specifically for the mammary system. Young stock and bucks are judged by different scorecards which place more emphasis on the other three categories; general appearance, body capacity, and dairy character.