Zilmax: The cattle growth drug that’s making beef more like chicken.

The Cattle Growth Drug That’s Making Beef More Like Chicken

The Cattle Growth Drug That’s Making Beef More Like Chicken

What to eat. What not to eat.
Feb. 14 2013 4:55 AM

Why Beef Is Becoming More Like Chicken

Cheap, uniform, and bland.

Beef Steak on wood table.
The beef industry has been shrinking for decades

Photo by Pablo H. Caridad/iStockphoto/Thinkstock

A new cattle drug called Zilmax is being widely used in the industrial feedlots where most of America’s beef comes from, but not because it produces a better sirloin. In fact, it has been shown to make steak less flavorful and juicy than beef from untreated cattle. Many feedlot owners, big meatpackers, and at least one prominent industry group resisted the drug, worrying that the beef industry would turn off consumers if it started churning out lower-quality steaks.

So what accounts for the sudden popularity of Zilmax? Zilmax is a highly effective growth drug, and it makes cattle swell up with muscle in the final weeks of their lives. And despite concerns within the industry, the economics of modern beef production have made the rise of Zilmax all but inevitable.

The beef industry has been shrinking for decades, a problem that can be traced to cheap chicken. Poultry companies like Tyson Foods figured out in the 1930s and ’40s how to raise chickens in a factory-like system. Using a business model called vertical integration, poultry companies like Tyson began to control every aspect of animal production, from the hatchery to the farm and the slaughterhouse. After the dawn of vertical integration, chickens were raised in barn-like warehouses on the farm, killed and butchered along assembly lines nearby, and, later, shipped out to big customers like McDonald’s and Wal-Mart—with every step of the process dictated by the same company. In the 1990s, the same model was widely applied to pork production, cutting out the middlemen and leading to a drop in pork prices (after adjusting for inflation).


As chicken got cheaper, it took top billing on fast-food menus. Beef got pushed aside. Some companies have tried to vertically integrate cattle production, but it has never panned out economically, thanks to the stubborn biology of cows. Chicken and pigs have offspring in big numbers, which lends itself to industrial-sized barns. (Hens lay a steady supply of eggs that yield full-grown chickens in about two months; sows bear big litters of piglets that reach maturity in about six months.) But a cow can only have one calf at a time, and the gestation period lasts nine months. After that, a calf suckles from its mother for about four months. It would be exorbitantly expensive to confine that life cycle in a warehouse, since the cow and calf would have to be sheltered and fed for over a year, just to get one full-grown heifer out of the deal. As a result, the vast majority of calves are still born and reared on wide-open ranchland, where herds of them eat free grass and stick by their mother’s side.

But cattle producers still imitate the heavily industrialized chicken industry to compete. Zilmax is part of a new regime for raising cattle that emphasizes higher production and cost-cutting wherever possible. This regime is what created the modern-day feedlot, where thousands of cattle, after being raised on open ranchland, are corralled on muddy hillsides to spend the last few months of their life eating corn. It is also what necessitates the battery of pharmaceuticals and feed additives that cattle must consume to stay healthy and gain weight—as Michael Pollan and others have noted, cattle didn’t evolve to digest corn, so they easily become sick on feedlots without careful monitoring.

Even with these advancements, the cattle business is still divided in half: On one side are independent ranches and feedlots that raise cattle; on the other side are big meatpackers that buy cattle from feedlots, slaughter them, and sell the beef. The relationship between cattlemen and meatpackers veers between amiable and adversarial. Neither can succeed without the other, but both are desperate to increase profits.

Enter Zilmax. Originally developed to treat asthma in humans, it was later found to be a “repartitioning agent” in cattle, changing the animals’ metabolism so they produce more muscle instead of fat. While this can boost the amount of meat per carcass, it can remove the very qualities that people like about beef, like the fatty marbling that adds juiciness and flavor. In 2006, Intervet Inc., the company that originally made Zilmax, won approval from the U.S. Food and Drug Administration to use it in the food supply, even after noting in its application to the FDA that “overall tenderness, juiciness, flavor intensity and beef flavor were all statistically different [in Zilmax-treated beef] compared to controls.” (Intervet’s application also said consumers probably wouldn’t notice the lesser quality.) The drug was launched commercially in the United States in 2007 and is now sold by Merck Animal Health.

At first, meatpackers greeted Zilmax with skepticism. Early research showing the harmful effects on beef quality scared off many feedlot owners who would have purchased it. By the late summer of 2011 only two of the major meatpackers, Tyson Foods Inc. and JBS SA, accepted cattle treated with Zilmax, according to feedlot managers and the companies. Cargill, which was concerned about quality, didn’t accept Zilmax-treated cattle until 2012. National Beef Packing Co. refused to comment on its Zilmax practices for this article, but according to feedlot managers, that company also began accepting Zilmax-treated animals last year. Those four major meatpackers control roughly 85 percent of the market, so when they decide to accept a new practice, as they now have with Zilmax, its implementation is swift across the entire beef supply.

As Zilmax gains popularity, it is creating a kind of positive feedback loop. As more feedlots use it and more meatpackers accept it, more of their competitors feel pressured to do the same just to keep up, even if they have concerns about Zilmax’s effects.