Dairy Cow Farmers love Barley - they roll it right before they feed it as the cows (who are also ruminants) get 25% more feed conversion that way.
You don't want to roll too much ahead of time as it doesn't store as well. Will he let you come back and do 4-5 bushels at a time and then take home in barrels to mix with your feed?
Barley helps increase your butterfat too.
Lastly, (and sure some will get upset with this!), but every dairy cow farmer we have discussed oats vs. barley (including our grain growing feed guy with PhD in animal nutrition) look at us like we have lost our minds when suggesting oats as a feed... The consensus is that oats are for horses.

A little in the ration for bulk is okay, but barley is better for your goats and the milk pail. Especially heavy producers.
BTW, we add a little barley to our dairy mix along with the BOSS. Our goats like both, milk well on both and show well on both - I think you will like it!