The vegetarian Pied Pipers have the best of intentions. I’ll state right now that everything they say about factory farming is true: It is cruel, wasteful and destructive. But their first mistake is in assuming factory farming — a practice that is barely 50 years old — is the only way to raise animals. In my experience, their calculations on energy used, calories consumed and humans unfed are all based on the notion that animals eat grain. You can feed grain to animals, but it is not the diet for which they were designed. For most of human history, browsers and grazers haven’t been in competition with humans. They ate what we couldn’t eat (cellulose) and turned it into what we could (protein and fat). But our industrial culture stuffs grain into as many animals as it can. Grain will dramatically increase the growth rate of beef cattle and the milk production of dairy cows. It will also kill them. The delicate bacterial balance of a cow’s rumen may become acidic and turn septic. Chickens get fatty liver disease if fed corn exclusively. Sheep and goats, which are also ruminants like cattle, shouldn’t touch the stuff either.