You're assuming all the food that goes to livestock is grown separately from human food. It's not. A great portion comes from leftovers (i.e. inedible for humans) from crops designed to feed people.
You're moving goal-posts from 'how much one eats daily' to 'how much time it takes to 'grow' said food'. It doesn't work that way. Otherwise we'd have to factor in the time it takes to grow produce to harvest time, as well as re-work that 'humans eat 6 lbs of food daily', since that number includes protein food in it, and a human would have to each much more than just six lbs of food per day if it was eating only produce.Secondly, as I've I already pointed out, a cow only produces less than 500lbs of meat after 2 years of eating 24 lbs a day. That's over 17,000 lbs of food to create less than 500lbs.