In medical school, I was dutifully dissecting a cadaver in my first year when a friend shuffled up beside me......
"can I ask you something" she asked, she took me aside. There are 200 people in a room the size of a school gym, all in white coats, goggles, gloves, all learning anatomy the best way there is.
at this point we were a good month or so into med school....
"my table are laughing at me" she said...... Already I knew it would be justified, she is an awesome and funny girl, but she would say the craziest things.
"I asked them where the meat layer was!" Is the very sentence she said and I remind her of it whenever I can. Her shock at realising meat was the same red stuff we were cutting up, did not go down well with her, unlike my burger that lunchtime. (Its true that for some reason, dissection made us all very, very hungry, so we always went to get a pub meal after it- wierd I know.)
so yeah, anything that we can digest with useful broken down parts is 'food for us' and likewise with other animals. But animals are NOT just our food source. They are equal to us, even if we don't treat them as such. Don't get me wrong, my burger was beef, but the reality is... A bullocks muscle and fat is no different to ours really.
I know, i know,,,,''why cant we just eat humans then' .... Prion diseases. No animal can eat its own kind, because it screws your DNA up.