Casings generally refer to the small intestine. Casings are generally sold on consignment, and the length is generally 12~ 15 meters. The longest can be about 20 meters. As we all know, the small intestine of an animal body is closely related to the digestion and absorption of nutrients. The longer the small intestine is, the higher the absorption efficiency of nutrients will be, and the breeding benefits will naturally increase. According to the master who has many years of slaughter experience, the length of the small intestine of adult fattening pigs is generally 15- 17 meters.