Surely "we do not have goat" should be accepted too? In english when "a" is dropped before an animal, it's implied you are asking for the meat. I've reported it.
'nyama ya mbuzi' is 'goat meat'. Just saying 'goat' to mean 'goat meat' is more of a colloquial thing
It should also be accepted though as it's also correct english
Not everything that makes sense in one language should (or does) make sense in another.
I should clarify that in English, goat has no term for meat, unlike beef or pork. So like duck or chicken, the meat is called goat aswell as the animal.