When gilts or sows enter oestrus in their reproductive cycles (about 21 days long) they are ready to be bred. Farmers oversee breeding to ensure the sow is receptive and successfully bred.

• 小母猪和大母猪的发情期大概是21天，这是她们的生理循环周期。这时就要给她们配种，在配种时，农场主要仔细观察看母猪是不是能成功的配上。