Flap over milk – genetically engineered bovine growth hormone increases milk production in a glutted market, brings protests – special issue: 1994 – the Year in Science
American cows each churn out seven to eight gallons of milk a day, and together they produce 3 percent more milk than we consume. Yet this past February the St. Louis-based Monsanto Company began marketing a genetically engineered version of bovine somatotropin (BST), a cow hormone that increases a cow’s milk production by 10 to 15 percent. “The world’s population is going to double in the next 50 years or so,” says Lisa Watson, manager of health and consumer affairs at Monsanto, “so we have to use the best technologies we have.” American farmers buy BST in spite of the current milk surplus because it allows them to produce more milk with fewer cows.
The Food and Drug Administration approved BST in late 1993, saying that “milk and meat from BST-treated cows are safe to consume.” Not everyone sees it that way, of course. Protesters from the Pure Food Campaign – an international boycott against genetically engineered foods – took to the streets last year, dumping BST-treated milk outside supermarkets in 110 American cities. The protesters were angered by the FDA’s refusal to require labels on BST-treated milk. “The public has a basic right to know whether food has been genetically engineered or not,” says Ronnie Cummins, the campaign’s U.S. director.
There is no evidence, however, that BST is harmful to the public. Genetically engineered BST – also known as bovine growth hormone – is almost identical to that produced normaffy in the cow’s pituitary gland. Both versions of the hormone increase the amount of nutrients the cow’s mammary glands can absorb from the bloodstream and convert into milk But catde can produce only limited amounts of the hormone; Monsanto, on the other hand, can produce large amounts of the stuff by inserting the gene for the cow hormone into, bacteria. And farrners can produce larger amounts of milk by injecting their cows with Monsanto’s hormone every 2 weeks for 34 weeks. The FDA says BST poses no health risk to humans, because it’s structurally different from human hormones and can’t be used by our bodies. What’s more, the agency says, 90 pereent of the BST present in milk or meat – natural or not – is inactivated during pasteurization or cooking.
BST injections aren’t completely harmless to cows, diough. The FDA notes that cows treated with the hormone have shown an increased risk of mastitis, an udder infection. Monsanto puts the average increase at .1 case per cow per year.) And Monsanto’s own warning label on BST packets lists other possible side effects on cows, including ovarian cysts and an increase in somatic cell count (aka pus) in the milk. Finally, one study of several dozen holsteins at the University of Vermont found that BST-treated cows were twice as likely to suffer from hoof rot and leg injuries.
The increased risk of mastitis could conceivably have an indirect effect on human health: the infection must be treated with antibiotics, residues of which may make it into the milk. That might encourage bacteria in our bodies to become resistant to antibiotics. Under FDA rules, milk found to have antibiotic residues is supposed to be dumped, but that doesn’t reassure Cummins. “The average U.S. state tests for only 4 antibiotics,” he says, “and the average dairy farmer has access to 82.”
Some protesters may have been motivated less by a rational fear of genetic engineering than by a feeling that using BST is cruel and unnecessary. “Milk has got this image of a pure food,” says physiologist Ben Mepham of the Centre for Applied Bioethics at the University of Nottingham in England, where opposition to BST has also been strong. “It’s white md it’s pure, and you give it to your babies. People don’t really want other people shoving hormones – which they don’t understand anyway – into cows. The point is, why? We’ve got enough milk already, so why do we need cows to produce more?”
…AND TOMATOES TOO
Once upon a time a tomato ripened gently on the vine. But it’s a long truck ride to the supermarket, so today’s tomato is picked hard and green. Enter the Flavr Savr tomato, the first genetically engineered food to appear on the American market. The Flavr Savr, which hit the stores last May, can ripen on the vine because it has an “antisense” gene that dramatically slows the production of polygalacturonase, the enzyme that softensa tomato. So the tomato gets red and tasty but not too soft to ship. The FDA says it’s safe, but the Pure Food Campaign, which organized the BST-milk-dumping protest doesn’t like it: it organized a tomato-smashing campaign last year too.
The strongest reason for concern is similar in the two cases. To make the tomato plants that had taken up the antisense gene recognizable, biologists at Calgene, the California biotech firm that developed the Flavr Savr, linked the gene to a second gene that confers resistance to the antibiotic kanamycin; when the plants were exposed to the antibiotic, only those with both antisense and resistance genes survived. Some researchers worry that the resistance gene could spread into soil bacteria when the tomato plants are plowed under. From them it might conceivably spred into bacteria that infect humans or animals, making these bugs resistant to kanamycin as well.
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