Hi Jacob,
A gilt can start to come into season from approx 6 months of age, but as previously said you wouldn't put them with the boar until at least 10 months old. Although the season is usually every 21 days it lasts between 12-36hours which is why doing AI can be difficult to catch and why you get three lots of semen to do morning, afternoon, morning OR afternoon, morning, afternoon as soon as she comes into season.