Cow
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In animal husbandry, the mature female of domesticated cattle. Commercial cow’s milk is commonly enriched with vitamins D and A before sale. Microorganisms contained in raw (unheated) milk or picked up from the environment will quickly sour and curdle the milk. Cooling to slightly above its freezing point keeps milk palatable for a longer time by reducing the multiplication of spoilage bacteria and the chemical changes that they induce. Many countries have laws requiring that milk be pasteurized as a protection against pathogenic (disease-causing) organisms. Pasteurization is a partial sterilization accomplished by raising the milk to a temperature high enough to destroy pathogenic bacteria and a large proportion of those causing spoilage. Pasteurized milk that is kept refrigerated in closed containers will remain consumable for approximately 14 days. Milk fat, being less dense than other milk components, can be efficiently removed in a cream separator by centrifugation, yielding low-fat milk and skim milk. Low-fat milk contains 1–2 percent fat, while skim milk contains less than 0.5 percent fat. Much of the milk sold as a beverage has undergone homogenization, a process in which the milk is forced under high pressure through small openings to distribute the fat evenly throughout the milk.
Cattle
Domesticated bovine farm animals that are raised for their meat or milk, for their hides, or for draft purposes. In the terminology used to describe the sex and age of cattle, the male is first a bull calf and if left intact becomes a bull; if castrated he becomes a steer and in about two or three years grows to an ox. The female is first a heifer calf, growing into a heifer and becoming a cow. Depending on the breed, mature bulls weigh 1,000–4,000 pounds (450 – 1,800 kg), and cows 800 – 2,400 pounds. Males retained for beef production are usually castrated to make them more docile on the range or in feedlots; with males intended for use as working oxen or bullocks, castration is practiced to make them more tractable at work. All modern domestic cattle are believed to belong to the species Bos taurus (European breeds such as Shorthorn and Jersey) or Bos indicus (zebu breeds such as Brahman) or to be crosses of these two (such as Santa Gertrudis). Many contemporary breeds are of recent origin. The definition of a breed is difficult and inexplicit, although the term is commonly used and, in practice, well understood. It may be used generally to connote animals that have been selectively bred for a long time so as to possess distinctive identity in colour, size, conformation, and function, and these or other distinguishing characteristics are perpetuated in their progeny.
