A barrow pig is a male pig that has been castrated before reaching sexual maturity. Castration is usually done when the pig is very young, at about two or three weeks of age, and it is performed to prevent the pig from becoming aggressive towards other males and to make it easier to handle and transport. Barrows are primarily kept for meat production, and they tend to gain weight quickly. In contrast, gilts are female pigs that have not produced a litter of piglets yet or are being used to grow out and finish to butcher. Gilts are kept primarily for reproduction, and they are fed, handled, and selected with the idea that they will produce the next generation of pigs. After breeding or having a litter, a gilt is called a sow.