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The domestic pig (''Sus scrofa domesticus'' or ''Sus domesticus''), often called swine or hog, is a large, even-toed ungulate; it is variously considered a subspecies of the wild boar, or a distinct species. Its head-plus-body-length ranges from 0.9 to 1.8 m (35 to 71 in), and the adult can weigh between 50 to 350 kg (110 to 770 lb). Compared to other artiodactyls, its head is relatively long, pointed, and free of warts. Even-toed ungulates are generally herbivorous, but the domestic pig is an omnivore, like its wild relative. Domestic pigs are farmed primarily for the consumption of their meat, called pork. The animal's bones, hide, and bristles are also used in commercial products. Domestic pigs, especially the pot-bellied pig, are sometimes kept as pets. ==Description== The domestic pig typically has a large head, with a long snout which is strengthened by a special prenasal bone and a disk of cartilage at the tip.〔(ADW: Sus scrofa: Information )〕 The snout is used to dig into the soil to find food, and is a very acute sense organ. The dental formula of adult pigs is , giving a total of 44 teeth. The rear teeth are adapted for crushing. In the male the canine teeth can form tusks, which grow continuously and are sharpened by constantly being ground against each other.〔 There are four hoofed toes on each foot, or trotter, with the two larger central toes bearing most of the weight, but the outer two also being used in soft ground.〔(Feral Pig / Hog / Pig / Wild Boar Hunting )〕 Most domestic pigs have rather a sparse hair covering on their skin, although woolly-coated breeds, such as the Mangalitsa, are raised.〔(Royal visit delights at the Three Counties Show. )〕 Pigs possess both apocrine and eccrine sweat glands, although the latter appear limited to the snout and dorsonasal areas.〔Sumena, K.B., Lucy, K.M., Chungath, J.J., Ashok, N. and Harshan, K.R., (2010). Regional histology of the subcutaneous tissue and the sweat glands of large white Yorkshire pigs. Tamilnadu Journal of Veterinary and Animal Sciences, 6(3): 128-135 ()〕 Pigs, however, like other "hairless" mammals (e.g. elephants, rhinos, and mole-rats), do not use thermal sweat glands in cooling.〔Folk, G.E. and Semken, H.A., (1991). The evolution of sweat glands. International Journal of Biometeorology, 35: 180-186〕 Pigs are also less able than many other mammals to dissipate heat from wet mucous membranes in the mouth through panting. Their thermoneutral zone is 16 to 22 °C.〔(Sweat like a pig? )〕 At higher temperatures, pigs lose heat by wallowing in mud or water; although it has been suggested that wallowing may serve other functions, such as protection from sunburn, ecto-parasite control, and scent-marking.〔Bracke, M.B.M., (2011). Review of wallowing in pigs: Description of the behaviour and its motivational basis. Applied Animal Behaviour Science, 132(1): 1-13〕 Pigs are one of four known mammalian species which possess mutations in the nicotinic acetylcholine receptor that protect against snake venom. Mongooses, honey badgers, hedgehogs, and pigs all have modifications to the receptor pocket which prevents the snake venom α-neurotoxin from binding. These represent four separate, independent mutations. Female hogs reach sexual maturity at 3-12 months of age and come into estrus every 18-24 days if they are not successfully bred. The gestation period averages 112-120 days. 〔(【引用サイトリンク】 title=Feral Hog Reproductive Biology )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「domestic pig」の詳細全文を読む スポンサード リンク
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