I think you are still mixing up the issues. If an animal can't give birth to humans, it doesn't imply that he/she has no right to survival and protection. Nature didn't give humans cow as a source of meat and milk. It is the carnists who started exploiting & slaughtering animals for their own selfish interest. Whether it's an animal or a human, everyone has a right to a dignified life.
I can't take your argument that cows can be replaced and humans can't. What are you talking of!!! No individual can be replaced once he / she is dead. Every life is precious. Whom you love more is your individual prerogative. It doesn't make any other life less valuable on this planet. Don't be a speciesist!