Well, it depends on what you mean by 'integrate'.
To me 'integrated' means they all live in the same physical space without being bloodied or bullied too much.
The youngers will still be lowest in the pecking order and tend to hang out and sleep together kind of apart from the older birds.
Once the youngers start laying they may rise in the pecking order and work their way onto the main roosts with the older birds.
I have a separate roost for younger birds, by the time they are all laying they are using the main roosts.
It's long slow process, with many variations, if you observe closely you'll begin to learn how it works.
