The Omnivore's Dilemma - Michael Pollan [41]
Bloat is perhaps the most serious thing that can go wrong with a ruminant on corn. The fermentation in the rumen produces copious amounts of gas, which is normally expelled by belching during rumination. But when the diet contains too much starch and too little roughage, rumination all but stops, and a layer of foamy slime forms in the rumen that can trap the gas. The rumen inflates like a balloon until it presses against the animal’s lungs. Unless action is taken promptly to relieve the pressure (usually by forcing a hose down the animal’s esophagus), the animal suffocates.
A concentrated diet of corn can also give a cow acidosis. Unlike our own highly acid stomachs, the normal pH of a rumen is neutral. Corn renders it acidic, causing a kind of bovine heartburn that in some cases can kill the animal, but usually just makes him sick. Acidotic animals go off their feed, pant and salivate excessively, paw and scratch their bellies, and eat dirt. The condition can lead to diarrhea, ulcers, bloat, rumenitis, liver disease, and a general weakening of the immune system that leaves the animal vulnerable to the full panoply of feedlot diseases—pneumonia, coccidiosis, enterotoxemia, feedlot polio. Much like modern humans, modern cattle are susceptible to a set of relatively new diseases of civilization—assuming, that is, we’re willing to put the modern feedlot under the rubric of civilization.
Cattle rarely live on feedlot diets for more than 150 days, which might be about as much as their systems can tolerate. “I don’t know how long you could feed them this ration before you’d see problems,” Dr. Metzin said; another vet told me the diet would eventually “blow out their livers” and kill them. Over time the acids eat away at the rumen wall, allowing bacteria to enter the animal’s bloodstream. These microbes wind up in the liver, where they form abscesses and impair the liver’s function. Between 15 percent and 30 percent of feedlot cows are found at slaughter to have abscessed livers; Dr. Mel told me that in some pens the figure runs as high as 70 percent.
What keeps a feedlot animal healthy—or healthy enough—are antibiotics. Rumensin buffers acidity in the rumen, helping to prevent bloat and acidosis, and Tylosin, a form of erythromycin, lowers the incidence of liver infection. Most of the antibiotics sold in America today end up in animal feed, a practice that, it is now generally acknowledged (except in agriculture), is leading directly to the evolution of new antibiotic-resistant superbugs. In the debate over the use of antibiotics in agriculture, a distinction is usually made between their clinical and nonclinical uses. Public health advocates don’t object to treating sick animals with antibiotics; they just don’t want to see the drugs lose their effectiveness because factory farms are feeding them to healthy animals to promote growth. But the use of antibiotics in feedlot cattle confounds this distinction. Here the drugs are plainly being used to treat sick animals, yet the animals probably wouldn’t be sick if not for the diet of grain we feed them.
I asked Dr. Mel what would happen if drugs like Rumensin and Tylosin were banned from cattle feed, as some public health experts advocate. “We’d have a high death rate [it’s currently about 3 percent, matching the industry average] and poorer performing cattle. We just couldn’t feed them as hard.” The whole system would have to change—and slow down.
“Hell, if you gave them lots of grass and space, I wouldn’t have a job.”
MY FIRST IMPRESSION of pen 63, where my steer is spending his last five months, was, Not a bad little piece of real estate, all considered. The pen is far enough from the feed mill to be fairly quiet and it has a water view of what I thought was a pond or reservoir until I noticed the brown scum. The body of water is what is known, in the geography of CAFOs, as a manure lagoon.