What is a young female pig called?

a gilt.

A gilt is a young female pig that has not yet given birth to piglets. She is typically between the ages of 6 and 12 months, and is considered sexually mature. Gilt pigs are often bred for the first time once they reach a weight of around 100-120 kg, which usually occurs at around 8-9 months of age. Gilt pigs can have their first litter of piglets at the age of 12-15 months. During pregnancy, gilts require a special diet that is high in protein, vitamins, and minerals to support the growth of their developing piglets. Once the piglets are born, the gilt will nurse them for about 8 weeks before they are weaned and she is bred again. Gilt pigs are a valuable asset to the pig farming industry, as they are used to maintain and increase the size of the breeding herd.