Hey man, nature is metal. Sometimes animals have to die.
We can point to any action and claim that "life is tough" and that we have justification for it. Stealing is now moral because "life in the hood is brutal". The fact that life is difficult (or a life that humans used to endure at some point) isn't justification.
Furthermore, lions eat their young, and numerous animals kill members of their own species. So if you want to be fully consistent, murder is now ethical.
It's odd to see someone point to vague appeals to "nature" as justification for putting slabs of fermented milk products from a refrigerator into a shopping cart under the fluorescent lights of a grocery store.