I've never spent much time researching it Sally (put off by the need for licensing, ability to ensure all the right protiens etc are present and in the right amounts etc) but there are loads of articles on it if you google.
I think there's a bit in the Andy Case book about mixing straights.
One thing the chap at the QMS course said was that soya is the most efficent provider of protein in terms of the amount of protien -v- the amount of food stuff. For example, to gain the required amount from peas you'd probably end up giving your pigs the runs by the time they ate the required amount - so it would be a balancing act between the protien sources.
But having said all that, there's a guy in USA who's raising fatteners on pasture (specially selected & planted) with the addition of whey to their diet for lysine - it is possible, of course it is
it's just weighing up if the time, effort and expense is worth it
Look out for veg processing plants - is there somewhere that makes fruit salads & veggie bags ? Local allotment or orchard group ? fruit & veg wholesalers or markets ?
Grains need to be rolled I think, or else they pass straight though 'em
Let us know how you get on - if I find any other info I'll pass it on to you and congratulations on your first sale
Karen