Nature & Environment
Lost Hooves, Dead Cattle Before Merck Halted Zilmax Drug Sales
Staff Reporter
First Posted: Dec 31, 2013 03:42 PM EST
The U.S. beef industry's dependence on the muscle-building drug Zilmax began unraveling here, on a sweltering summer day, in the dusty cattle pens outside a Tyson Foods Inc slaughterhouse in southeastern 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 August 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," 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, 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 August 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 said 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 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 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 United States in 2007. In addition, Merck said, 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 said.
Tyson Foods spokesman 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 Tyson the use of Zilmax is a possible cause, he said.
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 said.
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.
Earlier this month, 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 has said that 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 told Reuters 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 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 hooves.
When animals delivered to slaughterhouses are unable to walk on their own, Agriculture Department regulations require such "downer" cattle be destroyed and their meat prevented from reaching consumers.
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 United States after being fed Zilmax since the drug was introduced in 2007. The FDA reports specify 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, reviewed by Reuters through a Freedom of Information Act request, at least 75 animals lost hooves 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. And a build-up of gas in bovine stomachs, referred to as 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.
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," said 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," said Abe Turgeon, a prominent livestock nutritionist, who had previously recommended Zilmax to some customers.
Merck Animal Health, the unit that 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 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.
Today, 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.
Merck has begun approaching cattle nutritionists, livestock academics and other professionals who influence opinion in an effort to gain industry insight and win support for the return of the drug, according to several people who have met with the company.
The FDA regulates livestock feed additives sold in the United States, and is charged with intervening when a pharmaceutical product it has approved causes harm when used as directed.
The agency said it has taken no action related to Zilmax. When asked for comment about the adverse-event reports filed by Merck, an FDA spokeswoman in a statement said the agency "has not reached any conclusions on the safety of Zilmax but the agency is continuing to receive and evaluate data. As part of this process, the agency is always interested in new information."
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.
PROFIT ON THE PLATE
Zilmax is a medicated feed supplement for beef cattle that belongs to a class of drugs known as beta-agonists, which are also used in humans to ease asthma symptoms. Zilmax, with its active ingredient zilpaterol hydrochloride, is a federally approved weight-gaining supplement. It is added to cattle feed in the weeks before slaughter to add extra pounds of profit-producing meat.
Zilmax was worth nearly $160 million in annual sales in the United States and Canada last year, and was a steady cash generator for Merck's animal health business, which has about $3.3 billion in global sales.
The additive served as a go-to solution for a troubled cattle industry, as one-fifth of the nation's feedlots went out of business over the last decade. With cattle herds in sharp decline, Zilmax worked along with improved animal genetics and feed to produce more meat with fewer animals.
The United States produced nearly 26 billion pounds of beef from a herd of 91 million cattle in 2012, according to USDA data. In 1975, when the nation's cattle herd hit a peak of 135 million head, the industry produced nearly 24 billion pounds of beef.
Last month, beef cattle walking into a U.S. packing plant on average weighed a record 1,346 pounds — up more than 20 percent in the last two decades.
Merck's Zilmax quickly developed a loyal customer base. Its popularity spread even to the show circuit, where ranchers' children today can win prizes exceeding $100,000 for raising big-girth bovines.
ADVERSE EVENTS
Tyson and rival beef processor Cargill Inc have told Reuters they will not accept Zilmax-fed cattle until Merck can provide a scientific vetting of Zilmax's safety to animals and the companies are confident any animal welfare issues are resolved. (Cargill says it didn't see the cattle lameness problems cited by JBS and Tyson.)
Both companies, too, have cited concerns about China and other nations that have barred the importation of meat produced from Zilmax-fed cattle. They fear that if such meat is accidentally sent to these countries, it could hurt their export businesses.
FDA records based on 59 adverse event reports filed since 2008 by Merck and Intervet Inc - the original developer of Zilmax before Merck acquired the firm in 2009 - chronicle incidents of Zilmax-fed cattle experiencing stomach ulcers, brain lesions and blindness. Merck also has reported incidents of Zilmax-fed animals showing signs of lethargy, bloody noses, respiratory problems and heart failure.
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 reviewed by Reuters.
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 the U.S. Agriculture Department show 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 prior 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 cattle 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, though, 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, said David Acheson, the agency's former Associate Commissioner for Food.
"I suspect that that's not going to trigger them to do much," Acheson said.
DEATH IN THE HEAT
Tyson's plant, about 14 miles southeast of Pasco, is an integrated modern-day packing operation, stretching the length of several football fields. Five days a week, more than 1,300 workers arrive and walk past security guards toward a mechanical rumble emanating from the plant's gunmetal gray walls.
Tyson acquired the operation, one of its smaller plants, in 2001. It processes roughly 2,000 cattle a day, according to workers and local residents. Tyson would not comment on the number.
Washington state lies in the Pacific Northwest, with its soaring mountains and chilly rain. But the eastern flatlands around Pasco more closely resemble the Southwest's desert - and sometimes share its soaring summer temperatures.
To guard against the heat, Tyson has provided cover or shade for some holding pens at the plant. Overhead sprinkler systems help cool the cattle, too.
But 2013 saw one of the hottest summers in a quarter century, with at least three heat waves in which temperatures in the area topped 100 degrees, according to National Climatic Data Center. Temperatures were spiking on many of the dates when a total of 37 cattle were euthanized this summer due to lameness associated with Zilmax.
According to USDA documents and people knowledgeable about the events, some of the animals were shipped from Beef Northwest of North Powder, Oregon.
On August 5, of 17 cattle that were euthanized at Tyson's plant, the USDA inspector who condemned the animals noted that 15 had "lost toes." Two were destroyed for other reasons. The inspector identified at least one of the animals in the group that was put down as a heifer originating from Nyssa, Oregon.
Beef Northwest operates a feedlot in Nyssa. Animals making the trip to Pasco would have stood in a trailer for four hours on a 95-degree day as it traveled to Tyson's plant.
John Wilson, managing partner of Beef Northwest, confirmed that his company was using a Zilmax feed regimen this summer. About 40 of Beef Northwest's animals "developed lameness after arriving at a packing plant in two incidents in July and August of this year," he said. Wilson declined to identify the slaughterhouse and would not confirm the animals were destroyed.
Wilson said Beef Northwest had never faced lameness problems with its Zilmax-fed animals before this summer. While Beef Northwest was dispensing Zilmax, Wilson said, the company strictly followed Merck's dosage and other instructions.
Beef Northwest says it frequently conducted internal and third-party audits to ensure employees were not over-feeding Zilmax to the animals.
"In our cases, dosages were not an issue, never an issue," Wilson said in a phone interview. "I'd like to think that we were on the upper edge of the industry as far as heavy oversight of all of our protocols."
BELIEVERS AND NON-BELIEVERS
As feed-grain prices soared amid strong demand among livestock and ethanol producers in recent years, and with drought ravaging the U.S. crop belt, Zilmax seemed like an attractive solution. Some feedlot owners nicknamed it "Vitamin Z."
"We couldn't find feed cheap enough to make any money" on raising cattle, said Turgeon, the cattle nutritionist who works with Beef Northwest.
Many clients had adopted another beta-agonist - Optaflexx, made by Eli Lilly and Co's Elanco Animal Health unit. Elanco is Merck's biggest rival in the animal health business.
The two products use different active ingredients: Optaflexx is based on ractopamine, while Zilmax uses zilpaterol. But Zilmax added more weight to cattle than Optaflexx did, say industry nutritionists and feedlot owners. That perceived advantage helped Zilmax gain market share and sales faster than Optaflexx in recent years, say industry experts.
Turgeon had heard from his customers about lameness problems associated with Zilmax, and a colleague this summer showed him photos of animals with hooves peeling off, he said. Reuters has not seen any photos of cattle with missing hooves.
Merck is now trying to win the industry back. At a closed-door session of an Academy of Veterinary Consultants conference in Denver on December 5, some 300 cattle veterinarians sparred over Zilmax.
During the debate, they broke into informal camps of "believers" who think Zilmax hurts cattle, and "disbelievers" who discount its negative effects, according to Larry Moczygemba, president of the academy.
The veterinarians debated the effects of Zilmax and other beta-agonist drugs, Moczygemba said, without reaching a conclusion. Merck employees stayed in the room, mostly remaining silent.
"Few, if any, think this is just a beta-agonist problem all on its own," Moczygemba said. "But our role as vets puts animal well being first."
(© Reuters, reporting by P.J. Huffstutter in Pasco, Washington, and Chicago, and Tom Polansek in North Powder, Oregon, and Chicago.; Additional reporting by Eric M. Johnson in Pasco, Brian Grow in Atlanta and Lisa Baertlein in Los Angeles.; Edited by David Greising and Martin Howell.)
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First Posted: Dec 31, 2013 03:42 PM EST
The U.S. beef industry's dependence on the muscle-building drug Zilmax began unraveling here, on a sweltering summer day, in the dusty cattle pens outside a Tyson Foods Inc slaughterhouse in southeastern 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 August 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," 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, 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 August 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 said 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 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 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 United States in 2007. In addition, Merck said, 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 said.
Tyson Foods spokesman 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 Tyson the use of Zilmax is a possible cause, he said.
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 said.
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.
Earlier this month, 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 has said that 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 told Reuters 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 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 hooves.
When animals delivered to slaughterhouses are unable to walk on their own, Agriculture Department regulations require such "downer" cattle be destroyed and their meat prevented from reaching consumers.
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 United States after being fed Zilmax since the drug was introduced in 2007. The FDA reports specify 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, reviewed by Reuters through a Freedom of Information Act request, at least 75 animals lost hooves 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. And a build-up of gas in bovine stomachs, referred to as 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.
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," said 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," said Abe Turgeon, a prominent livestock nutritionist, who had previously recommended Zilmax to some customers.
Merck Animal Health, the unit that 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 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.
Today, 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.
Merck has begun approaching cattle nutritionists, livestock academics and other professionals who influence opinion in an effort to gain industry insight and win support for the return of the drug, according to several people who have met with the company.
The FDA regulates livestock feed additives sold in the United States, and is charged with intervening when a pharmaceutical product it has approved causes harm when used as directed.
The agency said it has taken no action related to Zilmax. When asked for comment about the adverse-event reports filed by Merck, an FDA spokeswoman in a statement said the agency "has not reached any conclusions on the safety of Zilmax but the agency is continuing to receive and evaluate data. As part of this process, the agency is always interested in new information."
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.
PROFIT ON THE PLATE
Zilmax is a medicated feed supplement for beef cattle that belongs to a class of drugs known as beta-agonists, which are also used in humans to ease asthma symptoms. Zilmax, with its active ingredient zilpaterol hydrochloride, is a federally approved weight-gaining supplement. It is added to cattle feed in the weeks before slaughter to add extra pounds of profit-producing meat.
Zilmax was worth nearly $160 million in annual sales in the United States and Canada last year, and was a steady cash generator for Merck's animal health business, which has about $3.3 billion in global sales.
The additive served as a go-to solution for a troubled cattle industry, as one-fifth of the nation's feedlots went out of business over the last decade. With cattle herds in sharp decline, Zilmax worked along with improved animal genetics and feed to produce more meat with fewer animals.
The United States produced nearly 26 billion pounds of beef from a herd of 91 million cattle in 2012, according to USDA data. In 1975, when the nation's cattle herd hit a peak of 135 million head, the industry produced nearly 24 billion pounds of beef.
Last month, beef cattle walking into a U.S. packing plant on average weighed a record 1,346 pounds — up more than 20 percent in the last two decades.
Merck's Zilmax quickly developed a loyal customer base. Its popularity spread even to the show circuit, where ranchers' children today can win prizes exceeding $100,000 for raising big-girth bovines.
ADVERSE EVENTS
Tyson and rival beef processor Cargill Inc have told Reuters they will not accept Zilmax-fed cattle until Merck can provide a scientific vetting of Zilmax's safety to animals and the companies are confident any animal welfare issues are resolved. (Cargill says it didn't see the cattle lameness problems cited by JBS and Tyson.)
Both companies, too, have cited concerns about China and other nations that have barred the importation of meat produced from Zilmax-fed cattle. They fear that if such meat is accidentally sent to these countries, it could hurt their export businesses.
FDA records based on 59 adverse event reports filed since 2008 by Merck and Intervet Inc - the original developer of Zilmax before Merck acquired the firm in 2009 - chronicle incidents of Zilmax-fed cattle experiencing stomach ulcers, brain lesions and blindness. Merck also has reported incidents of Zilmax-fed animals showing signs of lethargy, bloody noses, respiratory problems and heart failure.
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 reviewed by Reuters.
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 the U.S. Agriculture Department show 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 prior 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 cattle 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, though, 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, said David Acheson, the agency's former Associate Commissioner for Food.
"I suspect that that's not going to trigger them to do much," Acheson said.
DEATH IN THE HEAT
Tyson's plant, about 14 miles southeast of Pasco, is an integrated modern-day packing operation, stretching the length of several football fields. Five days a week, more than 1,300 workers arrive and walk past security guards toward a mechanical rumble emanating from the plant's gunmetal gray walls.
Tyson acquired the operation, one of its smaller plants, in 2001. It processes roughly 2,000 cattle a day, according to workers and local residents. Tyson would not comment on the number.
Washington state lies in the Pacific Northwest, with its soaring mountains and chilly rain. But the eastern flatlands around Pasco more closely resemble the Southwest's desert - and sometimes share its soaring summer temperatures.
To guard against the heat, Tyson has provided cover or shade for some holding pens at the plant. Overhead sprinkler systems help cool the cattle, too.
But 2013 saw one of the hottest summers in a quarter century, with at least three heat waves in which temperatures in the area topped 100 degrees, according to National Climatic Data Center. Temperatures were spiking on many of the dates when a total of 37 cattle were euthanized this summer due to lameness associated with Zilmax.
According to USDA documents and people knowledgeable about the events, some of the animals were shipped from Beef Northwest of North Powder, Oregon.
On August 5, of 17 cattle that were euthanized at Tyson's plant, the USDA inspector who condemned the animals noted that 15 had "lost toes." Two were destroyed for other reasons. The inspector identified at least one of the animals in the group that was put down as a heifer originating from Nyssa, Oregon.
Beef Northwest operates a feedlot in Nyssa. Animals making the trip to Pasco would have stood in a trailer for four hours on a 95-degree day as it traveled to Tyson's plant.
John Wilson, managing partner of Beef Northwest, confirmed that his company was using a Zilmax feed regimen this summer. About 40 of Beef Northwest's animals "developed lameness after arriving at a packing plant in two incidents in July and August of this year," he said. Wilson declined to identify the slaughterhouse and would not confirm the animals were destroyed.
Wilson said Beef Northwest had never faced lameness problems with its Zilmax-fed animals before this summer. While Beef Northwest was dispensing Zilmax, Wilson said, the company strictly followed Merck's dosage and other instructions.
Beef Northwest says it frequently conducted internal and third-party audits to ensure employees were not over-feeding Zilmax to the animals.
"In our cases, dosages were not an issue, never an issue," Wilson said in a phone interview. "I'd like to think that we were on the upper edge of the industry as far as heavy oversight of all of our protocols."
BELIEVERS AND NON-BELIEVERS
As feed-grain prices soared amid strong demand among livestock and ethanol producers in recent years, and with drought ravaging the U.S. crop belt, Zilmax seemed like an attractive solution. Some feedlot owners nicknamed it "Vitamin Z."
"We couldn't find feed cheap enough to make any money" on raising cattle, said Turgeon, the cattle nutritionist who works with Beef Northwest.
Many clients had adopted another beta-agonist - Optaflexx, made by Eli Lilly and Co's Elanco Animal Health unit. Elanco is Merck's biggest rival in the animal health business.
The two products use different active ingredients: Optaflexx is based on ractopamine, while Zilmax uses zilpaterol. But Zilmax added more weight to cattle than Optaflexx did, say industry nutritionists and feedlot owners. That perceived advantage helped Zilmax gain market share and sales faster than Optaflexx in recent years, say industry experts.
Turgeon had heard from his customers about lameness problems associated with Zilmax, and a colleague this summer showed him photos of animals with hooves peeling off, he said. Reuters has not seen any photos of cattle with missing hooves.
Merck is now trying to win the industry back. At a closed-door session of an Academy of Veterinary Consultants conference in Denver on December 5, some 300 cattle veterinarians sparred over Zilmax.
During the debate, they broke into informal camps of "believers" who think Zilmax hurts cattle, and "disbelievers" who discount its negative effects, according to Larry Moczygemba, president of the academy.
The veterinarians debated the effects of Zilmax and other beta-agonist drugs, Moczygemba said, without reaching a conclusion. Merck employees stayed in the room, mostly remaining silent.
"Few, if any, think this is just a beta-agonist problem all on its own," Moczygemba said. "But our role as vets puts animal well being first."
(© Reuters, reporting by P.J. Huffstutter in Pasco, Washington, and Chicago, and Tom Polansek in North Powder, Oregon, and Chicago.; Additional reporting by Eric M. Johnson in Pasco, Brian Grow in Atlanta and Lisa Baertlein in Los Angeles.; Edited by David Greising and Martin Howell.)
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