A regular goat has to spend 22 hours a day foraging for enough random weedy rifraff to keep itself alive. That's just to make meat. But a dairy goat that gets fed only has to spend 3 hours eating for subsistence - that means that the rest of the time, they're making milk. High summer in Khovsgol Province in Mongolia, powerbar slices of dried yak kurd solidify on a string over the stove. One window overhead in a yurt. Raw energy for some sunless frozen day.
I've been mending and gating a Tennessee goat's paradise lately. Expendable opposable thumbwork calories exchanged for portable goatmilk calories. We do the foraging for them, they make the juice that makes the cheese. Hurray for animal husbandry.