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Farmers often add drugs to cattle and hog feed to make the animals gain weight rapidly. But there's new evidence that some of these drugs may make animals suffer. Last week, the drug company Merck Animal Health announced it would temporarily pull one of those products off the market.
NPR's Dan Charles explains why.
DAN CHARLES, BYLINE: Temple Grandin is a legendary figure in the beef industry. She's a professor at Colorado State University and one of the world's authorities on how cattle respond to their environment. She's re-designed slaughterhouses to make them more humane.
And around the summer of 2006, she says she started seeing a new kind of problem, especially when the weather got really hot.
TEMPLE GRANDIN: You had animals that were stiff and sore-footed; animals that were reluctant to move.
CHARLES: Not all the animals, Grandin says, but as many as one out of every five.
GRANDIN: And they act like the floor is red-hot, they don't want to put their feet down. And I had never seen these kinds of symptoms before, ever, anywhere.
CHARLES: She's become increasingly convinced the problem may be a new feed additive, a class of drugs called beta-agonists. Beta-agonists are similar, chemically, to the adrenaline that our bodies produce. In humans they're used to treat asthma. But if you feed them to cattle or pigs, the animals grow more muscle.
GUY LONERAGAN: These beta-agonist drugs have a dramatic and profound and beneficial impact on production.
CHARLES: That's Guy Loneragan, a professor of food safety and public health at Texas Tech University.
LONERAGAN: They can add somewhere in the range of 15 to 30 pounds of beef to the animal's carcass in the last three to four weeks of the fattening period.
CHARLES: That makes a significant difference to a beef producer's bottom-line. These drugs now are widely used. And Loneragan also now thinks they may be causing problems. Several weeks ago, the issue came to a head during a meeting that the National Cattlemen's Beef Association holds every summer. Guy Loneragan presented data showing that cattle getting beta-agonists are dying more often in feedlots.
Temple Grandin gave a talk about her observations of cattle that seem reluctant to move. And an animal welfare expert from a big meat-packer, JBS, showed a video of cattle that appeared lethargic, unable to walk properly.
Temple Grandin says the images made people angry.
GRANDIN: You've got a lot of people in the cattle industry that care about cattle. And they don't like to see cattle that are lame.
CHARLES: That same day another big meat packer, Tyson Foods, announced it would stop buying cattle that had been fed one particular beta-agonist, probably the most powerful one, called Zilmax.
Tyson Foods later asked Guy Loneragan, from Texas Tech University, to evaluate some of the information the company had collected on the effects of beta-agonists.
LONERAGAN: As they pieced together their information, and as I have had the opportunity to review their information, they felt like they had to act and I felt like they made the right decision.
CHARLES: Just last week, the company that makes Zilmax, Merck Animal Health, announced that it is suspending sales of that drug temporarily. The company says it's still convinced that Zilmax is safe for animals. It expects to answer all the questions that people now have.
Temple Grandin said she doesn't think that beta-agonists have to be banned. She thinks it may be possible to use these drugs in ways that avoid causing harm.
GRANDIN: Maybe you just don't do it in the summer, when it's hot, and the doses are probably going to have to be cut back. But these problems have got to stop. And I've worked all my career to improve how animals are handled. And these animals are just suffering.
CHARLES: The Food and Drug Administration, which approved these drugs, hasn't taken any action so far. An FDA spokesperson says the agency has received a very small number of reports of problems with these drugs and will review any new information to see if there is a safety issue.
Meanwhile, feedlot operators still are using one other beta-agonist, sold by a different company.
Dan Charles, NPR News.
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