It takes 10x the amount of grain to feed one cow to get the same energy. Â Each step up the food chain divides the amount of energy by 10. Â Lets say that cow eats 10,000 lbs of grain in a life time, its only going to produce 100 pounds of steak (just an example). Â That's why you have fewer tertiary consumers (like lions, bears, or humans) than secondary level consumers (like any herbavore).
This is a great point and relays another great point, if we did not let the cow eat so much and get big and fat, then we would be killing it at an earlier age and therefore have better meat, Veal...better softer more supple shoes, because everyone here has to admit that calf skin feels so much better wrapped around your foot than does those hard hide Florsheims.
Although vegan/vegetarians have alot more to worry about with aedequate nutrient supplies, plus meat tastes very, very good.
Can you imagine if we had to rely on potato skins for shoes instead of that fine Prada leather?