A sow, which is a female pig, is normally expected to farrow (give birth to piglets) twice a year. This is because the gestation period of a sow is about 3 months, 3 weeks, and 3 days, which means that a sow can have two litters of piglets in a year. However, the number of piglets in each litter can vary depending on various factors such as the breed of the sow, the health of the sow, and the quality of the feed.