Questions & Answers about Nós não comemos a carne.
How do we get the word comemos from the dictionary verb comer?
Why doesn't the Portuguese sentence have a word for "do" like in "do not eat"?
Is it mandatory to include the word nós at the beginning?
No, it is completely optional. Because the verb ending -emos in comemos is only ever used for "we", the listener already knows exactly who you are talking about. It is very common to just say Não comemos a carne.
Why is there an a before carne? Can I just say não comemos carne?
You can, but it changes the meaning slightly. Including the a means you are talking about a specific piece of meat ("We do not eat the meat"). If you drop the a and say Não comemos carne, it means "We do not eat meat" in general, which is exactly what a vegetarian would say.