Merck Continues Promoting Zilmax, Despite Cattle Losing Their Hooves

Story at-a-glance

  • The beta-agonist drug Zilmax has been used to promote muscle growth in American-grown cattle since 2007. Within the first two years, the number of euthanized cattle shot up by 175 percent
  • FDA records show that reported side effects of Zilmax include stomach ulcers, brain lesions, blindness, lethargy and lameness, bloody nose, respiratory problems, heart failure, lost hooves, and sudden death
  • Zilmax is already banned for use in horses due to severe side effects, including muscle tremors and rapid heart rates
  • According to previous research, Zilmax is about 125 times more potent than ractopamine—a similar growth-promoting drug that is banned in 160 countries due to its adverse health effects in cattle
  • Organic, grass-fed and finished meat that is humanely raised and butchered is really the only type of meat worth eating, if you want to maintain good health


This is an older article that may not reflect Dr. Mercola’s current view on this topic. Use our search engine to find Dr. Mercola’s latest position on any health topic.

By Dr. Mercola

While the beta-agonist drug Zilmax (Zilpaterol) has been used to promote muscle growth in American-grown cattle since 2007, news of the dramatic adverse effects of this drug didn't hit mainstream news—and hence public consciousness—until late last year.1

In early August, 2013, Tyson Food Inc issued a statement saying it would no longer purchase Zilmax-fed cattle for slaughter due to animal welfare concerns.2 The company had noticed that many of the cows that had been fed the drug had trouble walking. The cattle also displayed other behavioral issues.

Since then, Cargill Inc. has also decided to reject Zilmax-fed cattle until it is confident that any animal welfare issues associated with the drug have been resolved.

Merck, the maker of the drug, initially said it would halt US and Canadian sales of Zilmax, pending company research and review. It wasn't long however before Merck announced it had no plans to discontinue the product,3 saying the company stands behind the safety of the drug.

At present, Merck does not need approval from the Food and Drug Administration (FDA) to return Zilmax to market, as the FDA has not taken any action against the drug.

Agricultural drug use has become a major health concern for animals and humans alike, and in my view, organic, grass-fed meat that is humanely raised and butchered is really the only type of meat worth eating, if you want to maintain good health. 

It is important to understand that grass-fed animals not only produce better eggs, milk & meat - but the return to native perennial grasses is key to future.  We destroyed most of the grasslands and replaced them with monocultures like corn and soy.   We then produce hydrogenated vegetable oil and high fructose corn syrup for human consumption, and use much of the remainder for feed in concentrated animal feeding operations.

The grasslands act very much like forests, while deforestation is very well known the destruction of grasslands have similar effects.  Perennial grass farming produces more nutritious products, while work in a perfect cycle with nature.

Special Report Reveals Shocking Side Effects of Zilmax

Beta-agonist drugs such as Zilmax belong to a class of non-hormone drugs used as a growth promoter in livestock. As a class, beta-agonist drugs have been used in US cattle production since 2003. 

They're fed to cattle in the weeks prior to slaughter to increase weight by as much as 30 pounds of lean meat per cow. Due to the short window between administration of the drug and slaughter, as much as 20 percent of it may remain in the meat you buy. A recent special report by Reuters4 revealed some of the more horrific effects Zilmax has on cattle:

"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 US Department of Agriculture documents reviewed by Reuters...

The next day... two more animals with missing hooves arrived by truck... The animals' feet were 'basically coming apart,' said Keith Belk, a professor of animal science at Colorado State University."

Merck responded to Reuters with a statement saying that:

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

It would not, however, disclose the identities of these third-party experts; nor would they release any more details on the investigation. According to Reuters, Tyson Foods had noticed "cattle mobility issues" prior to the August 5 and 6 events that spurred the company to refuse Zilmax-fed cattle, but none of them had been quite this severe.

Increased Use of Livestock Drugs Is Cause for Concern

Merck is required by federal law to report all deaths occurring in treated animals, and Food and Drug Administration (FDA) records show at least 285 cattle have unexpectedly died or been euthanized after receiving Zilmax since the drug's introduction in 2007. At least 75 cows lost their hooves and were euthanized within the past two years. Other reported adverse effects in cattle following the administration of Zilmax include:

Stomach ulcers Brain lesions Blindness Lethargy and lameness
Bloody nose Respiratory problems Heart failure Sudden death


According to the featured report, it still has not been determined whether Zilmax is responsible for causing all these side effects—some of them so severe that cattle have to be euthanized. Some of the statistics are telling, however. Within the first two years of Zilmax's introduction to market, the number of euthanized cattle skyrocketed; shooting up by 175 percent compared to the pre-Zilmax range.

One working theory is that the drug might compound the adverse effects of ailments associated with confined animal feeding operations (CAFOs), such as acidosis, which results when a cow eats too many grains or sugar. Excessive heat may be another compounding factor, as well as animal genetics.

"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," Reuters5 says.

"Livestock pharmaceuticals use is expanding as part of the push to produce more meat at lower cost... 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."

Zilmax Banned for Use in Horses Due to Side Effects

Zilmax is already banned for use in horses due to severe side effects, including muscle tremors and rapid heart rates.6 According to a 2008 veterinary case report7 involving three horses that were given Zilmax:

"Within 90 minutes the horses had muscular tremors which began in the skeletal muscles of the neck, shoulder, and foreleg and spread throughout the visible skeletal muscles. Intermittent visible muscular tremors continued for up to 1 week after the initial dose of zilpaterol. They also all had certain changes to their blood chemistry, such as elevated BUN, creatinine, and glucose and mild hyponatremia and hypochloremia... Liver and kidney changes were also noted."

Ractopamine, another beta-agonist, is yet another drug used in the US, even though it's been banned in 160 other countries due to its potential health hazards. The researchers also noted that Zilmax is about 125 times more potent than ractopamine, saying this may be why side effects were overlooked in connection with ractopamine studies.

It's worth noting that, in human medicine, the same class of drugs (beta-agonists) can be found in certain asthma medications, such as Advair. One long-acting beta-agonist called salmeterol was linked to an epidemic of asthma deaths in the 1960s. Weight gain is also a common complaint among Advair users—so much so that the manufacturer has added weight gain to the post-marketing side effects. Other adverse reactions to beta-agonist drugs include increased heart rate, insomnia, headaches, and essential tremor—eerily similar to those experienced by horses. So why wouldn't the drug affect cows in a similar fashion?

Might Beta-Agonists in Meat Pose Human Health Hazards?

According to Randox Food Diagnostics,8 which has created tests for Zilmax residue in beef, use of beta-agonists prior to slaughter is of particular concern "as this poses a risk to the consumer and may result in consumer toxicity." Research findings to this effect include:

  • A 2003 study in Analytica Chimica Acta:9 residue behaviour of Zilmax in urine, plasma, muscle, liver, kidney, and retina of cattle and pig was assessed. Two heifers and 16 pigs were treated with Zilmax and slaughtered after withdrawal times varying from 1 to 10 days. The drug was detectable at each point of time examined in all matrices except plasma after a withdrawal period of 10 days. It's worth noting that in the US, the recommended market window is three to 10 days after discontinuing Zilmax10
  • A 2006 study11 on residues of Zilmax  in sheep found detectable levels in liver and muscle tissues up to nine days after discontinuation of the drug

Even before it was approved, scientists expressed concerns that beta-agonists might result in increased cardiovascular risk for consumers.12 According to an article published in the Journal of Animal Science in 1998:13

"The use of highly active beta-agonists as growth promoters is not appropriate because of the potential hazard for human and animal health, as was recently concluded at the scientific Conference on Growth Promotion in Meat Production (Nov. 1995, Brussels)."

Not All Meat Is Created Equal

I believe the movement toward ethical and sustainable meat eating is an important one, both in terms of animal welfare and human health. Agricultural drug use is indeed becoming a major health concern for animals and humans alike, courtesy of factory farming methods where efficiency and low cost is the primary objective.

Besides beta-agonist drugs like Zilmax and Ractopamine (the latter of which, by the way, is banned in 160 countries), animals raised in American confined animal feeding operations (CAFOs) are also typically given a number of other drugs, including antibiotics and hormones.

You are essentially getting a concoction of drugs in every piece of meat you eat. The routine use of antibiotics alone now poses a significant threat to human health, as it has spawned a dramatic rise in antibiotic-resistant disease. Instead of their natural diet, which is plain grass, CAFO cattle are also fed a wholly unnatural diet consisting of pesticide-laden and oftentimes genetically engineered (GE) grains—primarilyGE corn and soy.

Organic, grass-fed and finished meat that is humanely raised and butchered is really about the only type of meat that is healthy to eat. By purchasing your meat from smaller farms that raise their animals in a humane fashion, according to organic principles, you're promoting the proliferation of such farms, which in the end will benefit everyone, including all the animals.

I've also previously written about the atrocities that take place in some U.S. CAFOs, where filthy, crowded conditions are the norm, and I think most people would agree that such animal abuse is inexcusable, even if they're "only" being raised for food. It would be foolish to think that the end result—the meat from these animals—would have any major health benefits.

In fact, the differences between CAFO beef and organic grass-fed beef are so vast; you're really talking about two different animals, and two separate industries with entirely different farming practices and environmental impact. The latter also tends to favor far more humane butchering practices, which is also a very important part of "ethical meat."

Rethink Your Shopping Habits, to Protect Your Family's Health

Whether you do so for ethical, environmental, or health reasons — or all of the above -- the closer you can get to the "backyard barnyard," the better. Ideally, you'll want to get all your animal products, including meat, chicken and eggs, from smaller community farms with free-ranging animals that are organically fed and locally marketed. This is the way food has been raised and distributed for centuries... before it was corrupted by politics, corporate greed, and the blaring arrogance of the food industry.

You can do this not only by visiting the farm directly, if you have one nearby, but also by taking part in farmer's markets and community-supported agriculture programs. The following organizations can also help you locate farm-fresh foods in your local area, raised in a humane, sustainable manner:

  1. Local Harvest -- This Web site will help you find farmers' markets, family farms, and other sources of sustainably grown food in your area where you can buy produce, grass-fed meats, and many other goodies.
  2. Farmers' Markets -- A national listing of farmers' markets.
  3. Eat Well Guide: Wholesome Food from Healthy Animals -- The Eat Well Guide is a free online directory of sustainably raised meat, poultry, dairy, and eggs from farms, stores, restaurants, inns, and hotels, and online outlets in the United States and Canada.
  4. Community Involved in Sustaining Agriculture (CISA) -- CISA is dedicated to sustaining agriculture and promoting the products of small farms.
  5. FoodRoutes -- The FoodRoutes "Find Good Food" map can help you connect with local farmers to find the freshest, tastiest food possible. On their interactive map, you can find a listing for local farmers, CSAs, and markets near you.

Where to Buy Locally Grown Food Infographic Preview


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