Cattlemen found that corn, being such a dense source of calories, produced meat more quickly than grass; it also produced a more reliably consistent product, eliminating the seasonal and regional differences you often find in grass-finished beef. Over time, the knowledge that went into growing grass good enough to finish cattle all the year round gradually was lost.

Along the way corn kept getting more plentiful and ever cheaper. When the farmer found that he could buy corn more cheaply than he could ever hope to grow it, it no longer made economic sense to feed animals on the farm, so they moved into CAFOs (Concentrated Animal Feeding Operations, aka factory farms). The farmer who then plowed up his pastures to grow corn to market found he could take off to Florida in the winter, not work so hard. To help dispose of the rising mountain of cheap corn farmers were now producing, the government did everything it could to help wean cattle off grass and onto corn, by subsidizing the building of feedlots (through tax breaks) and promoting a grading system based on marbling that favored corn-fed over grass-fed beef. (The government also exempted CAFOs from most clean air and clean water laws.) In time the cattle themselves changed, as the industry selected for animals that did well on corn; these animals, generally much bigger, had trouble getting all the energy they needed from grass. In dairy, farmers moved to superproductive breeds like the Holstein, whose energy requirements were so great they could barely survive on a diet of grass.

So feeding ruminants corn came to make a certain economic sense— I say “certain” because that statement depends on the particular method of accounting our economy applies to such questions, one that tends to hide the high cost of cheap food produced from corn. The ninety-ninecent price of a fast-food hamburger simply doesn’t take account of that meal’s true cost—to soil, oil, public health, the public purse, etc., costs which are never charged directly to the consumer but, indirectly and invisibly, to the taxpayer (in the form of subsidies), the health care system (in the form of food-borne illnesses and obesity), and the environment (in the form of pollution), not to mention the welfare of the workers in the feedlot and the slaughterhouse and the welfare of the animals themselves. If not for this sort of blind-man’s accounting, grass would make a lot more sense than it now does.