If these are kept as pets (as opposed to being reared for meat as Boer goats normally are), then I would only feed minimal concentrates and keep them mainly on hay, branches and in winter just a low protein concentrates like oats and sugar beet pellets (soaked). I assume they would still need access to a lick containing copper, like the (formerly) Red Rockies.
If these are the start of a herd for meat production, then you will get probably better advice from someone already doing them (I have dairy goats) or the Boer Goat Society.