Harvesting goat milk leaves you with two resources, goat milk and a goat. Harvesting mutton is more difficult, because you're now subtracting from your brush-eating (so, 'breating') stock. If you have too many goats, there are millions of acres of forest waiting to feed them and make more milk. If you harvest them instead of use them, you'll run out of goats.

"In some parts of Asia, particularly India, Pakistan, Nepal, Sri Lanka and Bangladesh, the word mutton is sometimes used to describe both goat and sheep meat, despite its more specific meaning, limited to the meat of adult sheep, in the UK, US, Australia and other English-speaking countries."

A confusing use of the word on an international site.