Can cattle growth efficiencies be pushed too far?

The tradeoff between beef production and animal welfare has put Zilmax in the hot seat

PASCO, Wash. (Reuters) — The U.S. beef industry’s dependence on the muscle-building drug Zilmax began unravelling here, on a sweltering summer day, in the dusty cattle pens outside a Tyson Foods slaughterhouse in south-eastern Washington state.

Fifteen heifers and steers hobbled down the ramps Aug. 5, barely able to walk, as cattle trailers that had travelled up to four hours in 35 C heat began to unload. The reason: the animals had lost their hoofs, according to U.S. Department of Agriculture documents. The documents show the 15 animals were destroyed.

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

The animals’ feet were “basically coming apart,” said Keith Belk, a professor of animal science at Colorado State University.

Belk said 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 near Pasco, all had been fed Merck & Co.’s profit-enhancing animal feed additive, Zilmax.

The day after the hoofless animals were euthanized Aug. 6, Tyson told its feedlot customers it would stop accepting Zilmax-fed cattle.

Merck itself temporarily suspended sales of the drug in the United States and Canada after Reuters reported the existence of a videotape of apparently lame Zilmax-fed animals, which an official of meat packing giant JBS USA LLC showed at a trade meeting in Colorado. The rest of the nation’s leading meat packers soon followed Tyson, the largest U.S. meat processor.

Merck released a statement that stressed the safety of its product, saying the company investigates all reports of adverse reactions to its drugs and had done 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 said.

“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 research findings.

After temporarily halting Zilmax sales, Merck continues to state that Zilmax is safe when used as directed, with no welfare concerns discovered in 30 research studies since the product was introduced in the United States in 2007.

In addition, Merck said it 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, it added.

Tyson Foods spokesperson Gary Mickelson said 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 the company that the use of Zilmax is a possible cause, he said.

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

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 eat too much starch (primarily grain) or sugar in a short period of time. Heat and animal genetics may also 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 pharmaceutical use is expanding as part of a push to produce more meat at lower cost.

The U.S. Food and Drug Administration rolled out new policies late last year to phase out the use of antibiotics that make cows, pigs and chickens plumper. The FDA said it made the move in an effort to combat antibiotic-resistant bacteria that threatens human health.

However, the FDA has said 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.

Most of the more than 30 million beef cattle slaughtered in the U.S. annually 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 lb. steer and has helped some feedlots stay in business at a time of punishing industry consolidation.

Livestock nutritionists, veterinarians and cattle researchers told Reuters that cattle losing hoofs would be in great pain.

Animals that have lost their hoofs may take tentative steps, as if walking on glass, they said. 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, said it would be like a person having their toe nails yanked off.

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

USDA regulations require that downer cattle be destroyed and their meat prevented from reaching consumers. U.S. federal law requires Merck to report all animal deaths, as well as any other adverse reactions, in connection with use of its products.

A review of reports submitted by Merck and others to the FDA shows at least 285 cattle have died unexpectedly or been destroyed in the U.S. after being fed Zilmax since the drug was introduced in 2007.

The FDA reports identify the ailments that led to the unexpected deaths but do not consistently state whether the animals expired on their own or were euthanized.

According to the reports, which Reuters reviewed through a Freedom of Information Act request, at least 75 animals lost hoofs and were euthanized after being fed Zilmax over the past two years.

The reports show pneumonia was a factor in the death of 94 Zilmax-fed cattle, while bloat was listed as a cause in 41 cases of cattle fed Zilmax. Of the 285 animals that died, 113 were fed either an animal-based antibiotic or another medication to boost weight, or both, in conjunction with Zilmax.

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,” said University of Nebraska-Lincoln animal science professor Galen Erickson, in re-sponse to questions from Reuters about Zilmax’s safety.

However, 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,” said Abe Turgeon, a prominent livestock nutritionist, who had previously recommended Zilmax to customers.

Merck Animal Health, which markets the additive, said 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 launched an audit in August 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 has said it plans to reintroduce Zilmax but noted it is too soon to know when sales to U.S. and Canadian customers may resume.



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