That's a very good idea.
We've got sub-boards (no longer called child boards, that label caused some confusion) on the Marketplace and Coffee Lounge, but it makes a lot of sense to have them on the more popular livestock boards too.
I'll have a look through the recent history and will try to come up with a list of relevant sub-boards, at the right level. We don't want them to be too obscure, otherwise you can see the tumbleweed, but at the same time we don't want to drain all of the subjects from the main board.
Will start with sheep, watch this space, and anyone who wants to contribute with suggestions please do.
Dan