Boars become fertile at 6-7 months. Gilts can get pregnant as early as 5 months but it is recommended that they should not be mated until they are at least one year old giving them time to grow. Infertility is rare but is sometimes caused by boars and sows being too fat. If a male and female are brought up together they may not mate until they have been separated for a couple of weeks and put back together again. Litter numbers vary considerably. The piglets require access to a heat lamp in colder weather for best results. Piglets can be weaned at six weeks and the sow mated again after about a week of weaning her piglets.