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 Nearly 18 months after Merck pulled the drug from the U.S. and
Canadian markets after videos and photographs surfaced showing
Zilmax-fed cattle turning up in a distressed state, either lame or
with hooves missing at slaughterhouses, scientists at Texas Tech
University are testing beef carcasses taken from cattle fed
different concentrations of Zilmax.
The Merck-funded field study and lab work, which have not previously
been reported, are designed to test Zilmax at its currently approved
dosage of 6.8 grams per ton of feed for a 20-day period prior to
slaughter, as well as dosages at about 60 percent and nearly 80
percent of that level, according to the title of the study. At the
time Merck pulled Zilmax off the market, it had only one dosage
level approved by the U.S. Food and Drug Administration.
Merck awarded $1.85 million to the Texas Tech team in October to
conduct the research, the university mentioned at the time in a
newsletter that got little attention outside of the school. The
research is ongoing and the specific time frame of the study was not
clear.
"This study is an example of the company's ongoing research efforts
to provide additional data on the use of Zilmax," the company said
in a statement to Reuters.
Merck, which says it still sells Zilmax in Mexico and South Africa,
declined to comment on why it was testing these particular levels or
whether it was collecting data to submit to the FDA. Merck also
declined to say how many cattle are being fed Zilmax as part of the
tests, or where the animals are being raised or slaughtered. It
declined to give any further details.
An FDA spokeswoman declined to comment on the study, citing
confidentiality regarding drug applications.
Texas Tech did not respond to requests for comment.
In November, federal regulators approved changes proposed by the
company in the way the drug is administered. The company has also
been working with cattle feed lot operators on how best to
administer the drug.
"It looks to me like they're doing studies to determine if the lower
dosages are efficacious in improving feed efficiency, growth rate
and carcass leanness," said David Anderson, former head of swine
research at Elanco Animal Health, a unit of Merck rival Eli Lily &
Co, when Reuters told him about the study.
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A similar product called Optaflexx, made by Elanco "has captured the
market," said Arizona cattle rancher Harvey Dietrich, co-founder of
advocacy group Beef Additive Alert, which is critical of growth-promotants
such as Zilmax. "Merck wants their market share back," he added.
At the time the videos of the distressed cattle surfaced in 2013,
some veterinarians argued that a key problem was that the drug, at
its approved dosage, was too potent for some animals.
The drug company does not need federal approval to return Zilmax to
the market. But all four of the nation's largest beef packers and
many meat producers have told Reuters they won't accept Zilmax until
Merck can scientifically prove the drug doesn't cause the animal
welfare issues seen in the past.
One option, say industry experts, would be for Merck to show the FDA
that Zilmax is effective and safe at helping cattle gain weight at
lower dosages, and petition the agency to alter the product's usage
label.
The multi-site study that Merck is funding could provide the data
needed to make such a petition, according to industry experts.
Current labeling covers both dosage and details about its
effectiveness on cattle.
Major meat packers like Cargill Inc and Tyson Foods Inc say they are
not processing any meat from Merck's study or slaughtering cattle
fed with Zilmax. Spokesmen for Cargill, Tyson, National Beef Packing
Co and JBS USA said their companies were not participating in the
study.
(Reporting By P.J. Huffstutter and Tom; Polansek in Chicago.;
Editing by Martin Howell)
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