Started out with 18 angora goats, 5 years later had 80. You feed goats more than pasture, once a day they get grained, and always have hay in the barn for munchies. All on a 10 1/0 acres, but that was about the limit...put up a couple thousand bales of hay in the spring and summer. Mostly for winter. It was fun.....but they were not milking goats, only had milk for their kids and were weaned at about 3-4 months and mama dried up...
The milk is healthier to drink if the animals never get any grain.
The seeds in green grass contain enzyme inhibitors, so that they are not digested, while dry grains have very little inhibitor, and thus get digested. This means that the milk will be low or bereft of omega3, and CLA if they get grain.