Another way of looking at it
When a pig’s life is not totally mechanised to meet the ends of mass production, he or she lives in close-knit groups where the main female has the say. Male pigs usually live as loners after their puberty. When they have proved themselves to their adversaries they gain access to females. The females however, are quite emancipated and decide when any mating will take place. Until this time a boar will court a sow by following her. He will find out if she is receptive by gently massaging her flanks with his head. Mating lasts several minutes (no comment!) and if the sow becomes pregnant, she will have her piglets after three months.
