pigs are vertebrates, mammals, domestic animals and ancient omnivorous mammals. It is divided into domestic pigs and wild boars. Nowadays, it is generally considered that pig is the abbreviation of pig family. Pigs have different physical characteristics according to different breeds. But it is usually characterized by big ears, long head, straight nose and narrow waist and back. Hair is thick and hard, and it can be divided into white, pink, black, brown and color according to different varieties. [1]

Domestic pig is a subspecies of wild boar domesticated by human beings, and its tusks are shorter than those of wild boar, so it is one of the domestic animals of human beings. Generally speaking, domestic pig refers to a kind of pig bred by human beings for food.