Merck to Study Health Risks of Zilmax Cattle Hormone

Following renewed concerns about the potential side effects of Zilmax given to cattle, Merck has announced that it will launch a study that is focused on the health risks of the popular cattle supplement.  

A week after Tyson Foods, the nation’s largest meat processor, announced that it will no longer accept beef from cattle treated with Zilmax, the manufacturer of the supplement has launched a study on the popular beef beta-agonist supplement. Merck & Co. announced the investigation on August 8.

Tyson said their decision came after cattle that had been given Zilmax were observed having difficulty walking and moving. The final decision was based on animal welfare, and not made for health concerns, reports the company. While they are not certain what causes of the reported lameness, some experts point to Zilmax.

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Zilmax is a popular beta-agonist, a class of drug used to add weight to cattle, pigs and turkey before slaughter. It is given to the animal for only 20 days, but Merck reports the product increases carcass weight by 24 to 33 pounds, while improving tenderness and flavor in the beef.

The FDA approved Zilmax and it has been used for nearly two decades in many countries around the world, including the U.S., Mexico, South Africa and South Korea. Merck promotes Zilmax as a way to produce more beef with fewer cattle, while conserving natural resources by using less water and energy.

“We are confident that, based on all of the available data on Zilmax, the experience reported by Tyson is not attributable to Zilmax,” Merck said in its announcement. “Indeed, Tyson itself points to the fact that there are other possible causes and that it does not know the specific cause of the issues it recently experienced.”

The announcement of the study into the potential Zilmax health risks includes a plan to increase quality control and proper customer use. Merck will launch an additional five part training program which will focus on answering questions regarding possible negative effects of the drug.

The program will require cattle feeders and feed lot operators to undergo additional training. Another part of the program is a scientific audit which will follow the cattle from feed yards to packing plants. Researchers hope to determine the potential causes of lameness in the cattle.

At a recent Denver conference, JBS USA, a large U.S. cattle processor, showed video of cattle with signs of lameness and having difficulty walking after being fed beta-agonist additives. JBS USA is also a large U.S. cattle processor.

Rumors mounted following the announcements, including allegations that many cattle companies are being offered premium prices by Tyson for cattle which have never been fed Zilmax. Tyson representatives say they only offer premium prices for cattle which meet criteria of their Open Prairie Natural Angus Beef Program. The program only accepts beef from cattle which did not receive hormones, antibiotics or beta-agonists.

Tyson suppliers will be given a choice to switch to a different beta-agonist or to stop offering cattle fed Zilmax completely. Critics say many rivals will likely follow suit and begin phasing out Zilmax as well.


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