Day 4

Like most grass farmers who practice rotational grazing, Joel moves his cattle onto fresh grass every day. The basic principle is "mob and move," he explained, as we bumped to a halt at the gate to the upper pasture. Eighty or so cattle were milling or laying around what looked like relatively tight quarters in a fenced-off section of a much larger pasture that sloped to the south.
"What we're trying to do here is mimic on a domestic scale what herbivore populations do all over the world. Whether it is wildebeests on the Serengeti, caribou in Alaska, or bison on the American plains, multistomached herds are always moving into fresh ground, following the cycles of the grass. Predators forced the buffalo to move frequently and stay mobbed-up together for safety."
These intense but brief stays completely change the animal's interaction with the grass and the soil. They eat down just about everything in the paddock, and then they move on, giving the grasses a chance to recover. Native grasses evolved to thrive under precisely such grazing patterns; indeed, they depend on them for their reproductive success. Not only do ruminants spread and fertilize seed with manure, but their hoof prints create shady little pockets of exposed soil where water collects--ideal conditions for germinating a grass seed. And in brittle lands during the driest summer months, when microbial life in the soil all but stops, the rumen of the animal takes over the soil's nutrient cycling role, breaking down dry plant matter into basic nutrients and organic matter, which the animals then spread in their urine and manure.

The Omnivore's Dilemma (page 192-193)

The ninety-nine cent 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-born 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 (as opposed to corn) than it now does.

The Omnivore's Dilemma (page 200-201)