I realize that. 

I was simply highlighting there wasn't anything that came down and said "These animals only exist to serve humans". The idea that animals only exist for humans would be an idea/purpose that humans made/invented, and is definitely not nature's intention (especially since Nature has no intention, nature simply exists).

If you refer to species we specifically bred for ourselves then it does hold more weight. Those species specifically were made for the purpose of serving humans, but not all animal species over all.