Milk by Anne Mendelson Page A

known that you can stimulatedairy cows to higher yields by keeping them on low-fiber, “high-energy” rations with large amounts of “concentrate” (mostly meaning grains, especially corn). Concentrate translates into more net caloric energy per pound than fiber, which siphons off more energy into the work of digestion. But at high levels it also changes the only slightly acid environment of a normal rumen to a lower pH. The unhappy animal often loses her appetite. She is constantly thirsty and tries to right matters by drinking more water, which means more (if thinner) milk and explains why one can speak of milk watered inside the cow. She may develop full-blownruminal acidosis.
    Here we arrive at one of several déjà-vu-all-over-again moments in recent dairying history: Cows may no longer be munching distillery wastes in hideous city sheds, but it still is in at least some people’s interest to feed them substances injurious to their health. In acute and even subacute acidosis, the walls of the rumen become ulcerated, releasing infectious bacteria that often travel to the liver, where they cause abscesses, or generating by-products thatmigrate to the interior of the hooves, where they cause a painful foot inflammation calledlaminitis. (This condition probably was the reason that the “downer cows” surreptitiously filmed by the Humane Society at a California slaughtering plant early in 2008 had to be goaded onto their feet by electric shock.) In addition, lowered ruminal pH is ideal for encouraging the growth of Escherichia coli bacteria that can survive through the entire digestive tract (ending up in manure and fertilizer made from it) and often include the virulent 0157:H7 strain.
    The elite, high-producing stars of dairy herds are the cows who suffer most drastically on large amounts of concentrate. Already pushed by genetic makeup to the threshold of negative energy balance, they are easily nudged over the edge by any loss of appetite. But the breeding-and-feeding stresses on high-producing cows don’t end there. Since the mid-1990s farmers have made them even higher-producing through injections of thehormone bovine somatotropin (BST), also called “bovine growth hormone” (BGH). Or more precisely, theMonsanto Corporation’s laboratory-engineered “recombinant” version of the cow original, known as rBST or rBGH. Much controversy rages around rBST—and we now reach another plus-ça-change moment. Adulteration scandals, it seems, didn’t end with the practice of dyeing the milk. An angry faction has denounced rBST as a harmful foreign substance. Monsanto reasonably enough points out that it is indistinguishable from the BST made by cows and naturally found in milk. Its detractors, also reasonably, want to know whether consuming it can increase human blood levels of a potential carcinogen that occurs at higher concentrations in treated cows’ milk, “insulin-like growth factor-1” (IGF-1).
    No clear medical consensus has emerged on these issues. On the other hand, it’s obvious that whatever increases milk production in already high-yielding cows also increases the physical stress on organisms that are stressed to begin with. Not only is rBST a serious additional risk factor formastitis (infection of the udder), to which today’s stressed-out cows are highly prone, but it tends to shorten the animals’ life expectancy—which in any case has been on a downward slope over the last half century. In 1950, farmers might have kept many or most cows milking for a dozen years after their first lactation at (usually) about age two. In 2007 a production span of three years before “culling” to be sold for cheap beef wasn’t uncommon. Forget the fact that in the Dark Ages of dairying a well-treated cow might often have lived out something close to the twenty-year potential of the species; enlightened modern management ensures that during their short term on this planet many of today’s cows will have to