2008年11月28日星期五

Anatomy



Anatomy
Cattle have one stomach, with four compartments. They are the rumen, reticulum, omasum, and abomasum, the rumen being the largest compartment. Cattle sometimes consume metal objects which are deposited in the reticulum, the smallest compartment, and this is where hardware disease occurs. The reticulum is known as the "Honeycomb." The omasum's main function is to absorb water and nutrients from the digestible feed. The omasum is known as the "Many Plies." The abomasum is like the human stomach; this is why it is known as the "true stomach".

Dairy farming and the milking of cattle - once performed largely by hand, but now usually replaced by machine - exploits the cow's unique ruminant biology.
Cattle are ruminants, meaning that they have a digestive system that allows use of otherwise indigestible foods by repeatedly regurgitating and rechewing them as "cud." The cud is then reswallowed and further digested by specialised microorganisms in the rumen. These microbes are primarily responsible for decomposing cellulose and other carbohydrates into volatile fatty acids that cattle use as their primary metabolic fuel. The microbes inside of the rumen are also able to synthesize amino acids from non-protein nitrogenous sources such as urea and ammonia. As these microbes reproduce in the rumen, older generations die and their carcasses continue on through the digestive tract. These carcasses are then partially digested by the cattle, allowing it to gain a high quality protein source. These features allow cattle to thrive on grasses and other vegetation.
The gestation period for a cow is nine months. A newborn calf weighs 25 to 45 kg (55 to 100 lb). The world record for the heaviest bull was 1,740kg (3836lb) a Chianina named Donetto, when he was exhibited at the Arezzo show in 1955. The heaviest steer was eight year old ‘Old Ben’, a Shorthorn/Hereford cross weighing in at 2,140kg (4,720 lbs) in 1910.Steers are generally killed before reaching 750 kg (1,653 lb). Cattle usually live to about 15 years (occasionally as much as 25 years).
A common misconception about cattle (particularly bulls) is that they are enraged by the color red (something provocative is often said to be "like a red rag to a bull"). This is incorrect, as cattle are red-green color-blind. The myth arose from the use of red capes in the sport of bullfighting; in fact, two different capes are used. The capote is a large, flowing cape that is magenta and yellow. The more famous muleta is the smaller, red cape, used exclusively for the final, fatal segment of the fight. It is not the color of the cape that angers the bull, but rather the movement of the fabric that irritates the bull and incites it to charge.
Although cattle cannot distinguish red from green, they do have two kinds of color receptors in their retinas (cone cells) and so are theoretically able to distinguish some colors, probably in a similar way to other red-green color-blind or dichromatic mammals (such as dogs, cats, horses and up to ten percent of male humans).

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