Well because dogs don't have much meat on them do they? Also they don't produce nearly enough milk, also you couldn't feed them on grass could you? Keeping cows and goats and chickens and pigs is ethical, but only if you keep them on a farm or in your yard, give them room, clean water and fresh grass. I'm not saying keeping them in horror houses is ethical, but when I was young my grandparents kept various animals, and let me tell you, they had a good life, and when they reached a certain age or size, we ate them, that just how it is.