You should study nutrition and biology! Geneticly, we are meat eaters. So it's the normal guys that eats meat.
Domestic animals, like cows, sheep, etc., doesn't survive without "our" help and they need to be slaughtered before they get to old. Anything else would be cruelty.
Who are you to say that cows are unhappy then they don't know what's facing them. The value of life (for a certain "individual") depends partly on his/hers expectations and plans for the future. The higher on "the evolution ladder" that a certain specimen is, the more is that specimens life worth. That's the only sane way to value life. Otherwise every growing object (even plants are alive) would have the same value. And that would mean that you can't eat anything. And that mean that you will die.
Best regards, Lars
McSpotlight: Actually, we're omnivores. However, given the current levels of population, there are not enough natural resources to sustain everyone on a carnivorous diet; if everyone in the world ate a Western diet, the natural resources left would last 13 years...