Are the GG's being milked and/or in-kid? If all are pets and fully grown I would more or less cut out concentrate feed as they don't need it. I would top up their hay with stuff like Alfa A or Readigrass and veg like cabbage, carrots, bananas, apples etc etc. Grass nuts are also being fed by some pet goat keepers. In the summer lots of branches, grass and hay will be enough to keep them well fed but not fat. If you want to feed concentrate, some soaked sugar beet shreds and a dusting of rolled oats will also be enough.