Cows exist for me to eat them. If you'd ever seen the utter idiocy (inconveniently and dangerously combined with great size) of a cow at close range, you'd understand this. Likewise sheep, which are even dumber, although thankfully much smaller. Chickens, Guineas, etc...all fall at about the same level, with domestic Turkeys being so abysmally stupid that they can drown in a rainstorm. No animal remotely approaching that level of idiocy would survive to reproductive age in the wild, where a great many things -still- don't, despite being smarter. Cats, dogs, horses, etc...are somewhat more intelligent, although I've met a few Irish Setters too dumb to find their way out of a phone booth. Added to this, they perform useful functions for us (hunting mice, gaurding the house, pulling things etc) and make lousy meat, so we keep them as companions rather than food. This suits me just fine, since I can't imagine dog tastes very good in any language other than Korean, and cats seem too stringy to be worth the effort. Horse is good, properly prepared, but is easy to get wrong.
As for hunting, this is what we call reality: humans are an evolutionary pressure, just like any other sort of predation. We're a part of nature, just like the animals are, and our nature is omnivorism tilted sharply to carnivorism. I hunt because I can spend $.75 on a bullet, or $75+ for the same amount of dead animal at the grocery store. I'm a human, the animals aren't. I'm at the top of the food chain, they're not. My ancestors evolved for 5 million years to get up here, theirs didn't.
As for wolves killing before they eat...you might wanna read up on that. Wolves commonly eviscerate and consume their prey alive.
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http://www.nytimes.com/books/97/06/0....01footet.html