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Published January 06, 2014, 09:34 AM

Lost hooves, dead cattle before Merck halted Zilmax sales

The U.S. beef industry’s dependence on the muscle-building drug Zilmax began unraveling on a sweltering summer day, in the dusty cattle pens outside a Tyson Foods Inc. slaughterhouse in southeast Washington state.

By: P.J. Huffstutter and Tom Polansek, Reuters

The U.S. beef industry’s dependence on the muscle-building drug Zilmax began unraveling on a sweltering summer day, in the dusty cattle pens outside a Tyson Foods Inc. slaughterhouse in southeast Washington state.

As cattle trailers that had traveled up to four hours in 95-degree heat began to unload, 15 heifers and steers hobbled down the ramps on Aug. 5, barely able to walk. The reason: The animals had lost their hooves, according to U.S. Department of Agriculture documents reviewed by Reuters. The documents show the 15 animals were destroyed.

The next day, the hottest day of the month, two more animals with missing hooves arrived by truck. Again, the animals were destroyed, the documents show.

The animals’ feet were “basically coming apart,” says Keith Belk, a professor of animal science at Colorado State University. Belk says he reviewed photos of the lame cattle, though he declined to say who showed them to him.

The 17 animals had a factor in common, according to an examination of U.S. government documents and interviews with people who had direct knowledge of the events. In the weeks before the cattle were shipped to Tyson’s slaughterhouse, outside the city limits of Pasco, all had been fed Merck & Co. Inc.’s profit-enhancing animal feed additive, Zilmax.

The day after the hoofless animals were euthanized on Aug. 6, Tyson told its feedlot customers it would stop accepting Zilmax-fed cattle. After Reuters reported the existence of a videotape of apparently lame Zilmax-fed animals — shown by an official of meatpacking giant JBS USA LLC at a trade meeting in Colorado — Merck itself temporarily suspended sales of the drug in the U.S. and Canada. The rest of the nation’s leading meatpackers soon followed Tyson, the largest U.S. meat processor.

Merck, in a statement to Reuters, stressed the safety of its product. It says the company investigates all reports of adverse reactions to its drugs, and did so after the deaths near Pasco.

“Several third-party experts were brought in to evaluate the situation, review the data and identify potential causes for the hoof issue,” Merck’s statement says. “The findings from the investigation showed that the hoof loss was not due to the fact these animals had received Zilmax.”

Merck declined to identify the names of the third-party investigators or provide more detail on the research findings.

After temporarily halting Zilmax sales, Merck continues to state Zilmax is safe when used as directed, with no welfare concerns discovered in 30 research studies since the product was introduced in the U.S. in 2007. In addition, Merck says, the company is planning more field evaluations of Zilmax, using “a well-designed collection and analysis of data by third-party industry experts.” A “prominent” epidemiologist and veterinarian will oversee the work, Merck says.

Tyson Foods spokesman Gary Mickelson says his company doesn’t know exactly what happened to the small group of cattle that were destroyed at the plant near Pasco. Some animal health experts have told Tyson the use of Zilmax is a possible cause, he says.

Tyson had seen some cattle mobility issues in the past, but “the issues at Pasco this summer were more severe” than the company had seen before, Mickelson says.

Questions arise

Scientists say they have yet to determine whether Zilmax causes ailments so severe that cattle must be euthanized. One theory is that the federally approved feed additive may compound the effects of common feedlot nutritional disorders such as acidosis, which can affect animals that consume too much starch (primarily grain) or sugar in a short period of time. Heat and animal genetics, too, may be factors.

Regardless, the episode at the Tyson plant — which hasn’t been publicly disclosed until now — is coming to light at a time of growing concern over risks to animal and human health posed by the increased use of pharmaceuticals in food production. Livestock pharmaceuticals use is expanding as part of the push to produce more meat at lower cost.

In December, in an effort to combat antibiotic-resistant bacteria that threatens human health, the U.S. Food and Drug Administration rolled out new policies to phase out the use of antibiotics that make cows, pigs and chickens plumper. The FDA says meat produced from cattle fed with Zilmax is safe for human consumption.

The cases of hoofless cattle also raise ethical questions about whether the drive by modern agriculture to produce greater volumes of food, as cheaply as possible, is coming at the cost of animal welfare.

Of the more than 30 million beef cattle slaughtered in the U.S. annually, most move smoothly through a mechanized system that is among the most efficient in the world.

Reports that Zilmax causes lameness in some animals have raised concerns about the tradeoffs associated with a drug that adds up to 33 pounds of marketable meat to a 1,300-pound steer and has helped some feedlots stay in business at a time of punishing industry consolidation.

Livestock nutritionists, veterinarians and cattle researchers say that cattle losing hooves would be in great pain. Animals that have lost their hooves may take tentative steps, as if walking on glass, they say. Even when prodded, they sometimes refuse to rise back to their feet.

Livestock researcher Temple Grandin, who has pioneered humane slaughterhouse practices as a consultant to major beef processors, says it would be like a person having their toe nails yanked off.

“It would hurt a whole lot,” says Grandin, who says she has not witnessed any of the incidents of Zilmax-fed cattle with lost hooves.

Preparing for a return

Some veterinarians and animal experts say there is no proof Zilmax was the chief cause of any cattle deaths.

“My assessment is that I do not see data supporting the concerns today, at least the data that I have reviewed and been aware of,” says University of Nebraska-Lincoln animal science professor Galen Erickson, in response to questions from Reuters about Zilmax’s safety.

But some previously staunch supporters of Merck’s innovative growth drug are beginning to question the product’s safety record.

“Maybe we found the point where we pushed the cattle just so hard in the sake of making a buck that we exceeded the biological limits of the cattle,” says Abe Turgeon, a prominent livestock nutritionist, who had previously recommended Zilmax to some customers.

Merck Animal Health, the unit that markets the additive, says proper use of Zilmax “does not affect the safety or well-being of cattle.” Moving beyond the 30 studies it cited at the time it suspended Zilmax sales, Merck in August launched an audit of how the product was being used in the field, created an advisory board to review management practices in the feedlot and animal nutrition industries, and provided new funds for field research on Zilmax-fed cattle.

The company says it plans to reintroduce Zilmax, but notes it is too soon to know when sales to U.S. and Canadian customers may resume.

The Merck suspension of Zilmax sales is voluntary and at this point, the company could return Zilmax to the market without seeking permission from the FDA.

Adverse events

In September 2011, an unidentified veterinarian at an Oregon feedlot reported “unusual hoof loss in cattle being fed Zilmax,” according to one adverse event report.

In August this year, Merck reported an additional five episodes involving 66 cattle in Oregon and Idaho that lost their hooves after a Zilmax feeding regimen. In some cases, a consulting veterinarian also cited high ambient temperature and a cement-and-rebar floor that may have exacerbated the hoof damage.

Also in August, one Nebraska cattle producer, who is not named in the FDA documents, reported he had more dead cattle when he used Zilmax than when he didn’t, according to the documents.

A Reuters review of data kept by USDA shows that euthanizations of cattle have risen substantially since Zilmax came on the market.

In the two years after Zilmax was introduced, the number of beef steers and heifers euthanized before to slaughter at U.S. packing plants rose nearly 175 percent from previous levels. The number of euthanized steers and heifers has ranged between 1,600 and 2,300 each year since then. That new plateau is well above the average of 670 a year in the four years before Zilmax came on the market in 2007.

The government data does not, however, draw a link between Zilmax or any other possible factors and the increase in euthanized cattle at meatpacking plants.

The number of euthanized cattle and the other reports of cattle dying is also quite small relative to the more than 30 million cattle slaughtered each year. It is small enough that it likely hasn’t raised significant red flags with the FDA, says David Acheson, the agency’s former Associate Commissioner for Food.

“I suspect that that’s not going to trigger them to do much,” Acheson says.

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