The Cold, Hard “Hoof” About Zilmax

Image Source

By: Young-Eun Park, Staff Member

What does it feel like to have your toenails yanked off?[i] Ask the 75 cows that lost their hooves last year. It all started in August 2013, when employees at the Tyson Foods Inc. slaughterhouse noticed that 17 cows were hobbling down the ramps of the cattle trailer.[ii] The reason? Their hooves were “basically coming apart.”[iii] All seventeen animals were euthanized.[iv]

The seventeen animals had one aspect in common: in the weeks before the cattle were shipped to the slaughterhouse, all had been fed Merck & Company’s feed additive, Zilmax.[v] Zilmax is a supplement that makes cattle gain extra weight.[vi] During its manufacture, an estimated 70 to 80 percent of the US cattle herd was being fed Zilmax or its substitute.[vii] However, shortly after discovery of the crumbling hooves, Merck suspended sales in the US and Canada and promised to do research to determine whether Zilmax was the cause of these disturbing side effects.[viii]

This January, after a third-party investigation, Merck announced that it will resume sales of Zilmax since the “hoof loss was not due to the fact these animals had received Zilmax.”[ix]

Merck’s study draws a sigh of relief until the evidence is actually analyzed. First, Merck declined to identify the name of the third-party investigators or provide more detail on the findings[x], which makes a mysterious study backed by a company with $160 million in sales at stake[xi] completely useless. In fact, statistics point very convincingly towards Zilmax as being the culprit for cattle’s crippling side effects: in the two years after Zilmax was introduced, the number of cattle euthanized before slaughter rose nearly 175 percent from previous levels.[xii] The current plateau is at 1,600 to 2,300, well above the average of 670 a year in the four years before Zilmax’s 2007 debut.[xiii] Meatpacking plants and other countries are calling Merck’s bluff, with Tyson and Cargill refusing to accept Zilmax-fed cattle until Merck can prove that it’s safe,[xiv] and China refusing to accept meat from cattle fed with Zilmax.[xv]

Both Merck and the FDA insist that Zilmax-fed cattle are perfectly safe to consume, but that is not the issue.[xvi] Whether safe or not, Zilmax causes severe and unnecessary suffering in cattle. Already banned for use in horses because of the severe side effects,[xvii] cows experiencing lost hooves take tentative steps, as if walking on glass, and even when prodded, they refuse to rise to their feet.[xviii] These cows are inevitably euthanized, and neither the wellbeing of the animal nor its purpose of human consumption is ever realized. Echoing this view, both Tyson[xix] and Cargill have stated that their refusal to accept Zilmax-fed cows is not a food safety issue, but linked to its commitment to ensure the welfare of cattle harvested in the industry.[xx]

In an already mechanized and industrialized food industry, some weight should be given to animal treatment, even if the end product is safe to consume. Animal welfare is an important and integral part of animal agriculture and should be considered when making decisions about what we feed to livestock. Furthermore, while Zilmax-fed cows may be safe to consume at the outset, there is no telling what long-term effects the drug will have on humans. In the meantime, meatpacking plants, farmers, and other involved industries should refuse to use Zilmax even after its reintroduction into the market. That way, we won’t ever have to wonder what it feels like to live without toenails, and thankfully, cattle won’t have to experience it either.
[i] P.J. Huffstutter and Tom Polansek, Lost hooves, dead cattle before Merck halted Zilmax sales, AGWEEK (Jan. 6, 2014),
[ii] Tracy Staton, Mulling a Zilmax relaunch, Merck faces reports of hoofless cattle and skeptical customers, FIERCE PHARMA (Jan. 2, 2014),
[iii] See Huffstutter, supra note 1.
[iv] See Staton, supra note 1.
[v] See Huffstutter, supra note 1.
[vi] Zilmax, Merck Animal Health (last visited January 22, 2014),
[vii] Cargill’s view on Zilmax being pulled from the market, Cargill (last visited January 22, 2014),
[viii] See Huffstutter, supra note 1.
[ix] Lance Turner, Reuters: Lost Hooves Prompted Tyson Foods to End Use of Zilmax, ARKANSAS BUSINESS (Jan. 6, 2014),
[x] See Huffstutter, supra note 1.
[xi] See Staton, supra note 1.
[xii] See Huffstutter, supra note 1.
[xiii] Id.
[xiv] See Staton, supra note 1.
[xv] Id.
[xvi] See Huffstutter, supra note 1.
[xvii] Dr. Mercola, Merck Continues Promoting Zilmax, Despite Cattle Losing Their Hooves, (Jan. 15, 2014),
[xviii] See Huffstutter, supra note 1.
[xix] Mercola, supra note 1.
[xx] Cargill, supra note 1.