This is weird. My whole family is vegetarian, but our dog and cat most definitely are not. My mum very very briefly considered it for the dog when we got her (before the cat), mainly because of the stink of dog food I think! But she very quickly decided it would be cruel. She's even got the dog proper meat from the butchers when it's been ill (bloody spoilt dog :)).
I'm the only one who's vegetarian from birth, and I really dislike the smell of meat (smells like death to me) but I'm quite happy to feed it to the pets. The way I see it, I can be vegetarian, they can't. We have evolved enough to think about moral implications, etc, they just act on instinct. As for killing animals to feed other animals, pet food is usually made of leftovers that humans wouldn't eat anyway, so it's actually useful to use the waste...
www.dailymail.co.uk/news/article-1315145/Is-pet-food-poisoning-dogs.html
I know it's the Daily Mail, but it makes some very interesting points about feeding dogs food that isn't entirely meat. I was pretty horrified reading it.
'In North America, ?mammalian meat and bone meal?, a key animal component in pet food, has been shown to include the ground-up remains of euthanised cats and dogs ? flea collars, name tags, microchips and all.'
Hope no one just lost their dinner...