After Cows' Feet Fall Apart, Feedlot Drug Is Questioned Reuters' special report zeroes in on Merck's muscle-building Zilmax By Kate Seamons, Newser Staff Posted Dec 31, 2013 6:38 AM CST Updated Dec 31, 2013 7:59 AM CST 41 comments Comments Read on, and you may find yourself vowing to go vegetarian in the New Year. (AP Photo/Tamara Lush) (Newser) – It's no surprise that America's cattle are pumped full of pharmaceuticals, but Reuters digs in to one particular drug—a muscle-building feed additive known as Zilmax that's manufactured by Merck and has been available in the US since 2007—whose alleged ill effects may be painfully visible. Using Department of Agriculture documents, Reuters pieces together what happened in early August at a Washington state slaughterhouse that serviced Tyson Foods, and reports on it publicly for the first time: Cattle were being trucked in, but some nearly couldn't make it off the ramps ... because their hooves had fallen off. Seventeen of the creatures had to be put down over two days, and according to documents and Reuters' sources, all had taken Zilmax. (And a review of FDA documents shows 285 cattle have been confirmed dead or euthanized since 2007 after ingesting Zilmax.) Their feet were "basically coming apart," says an animal science professor who was provided with photos of the affected cattle by an unnamed person. Tyson reacted quickly to the August incident, immediately saying it would no longer receive cattle that had taken Zilmax; other meatpackers followed suit, and Merck temporarily put all Zilmax sales on ice. Scientists have yet to prove a link, and Merck insists in a statement to Reuters that "several third-party experts were brought in ... [and found] that the hoof loss was not due to the fact these animals had received Zilmax." It's planning more "field evaluations" of Zilmax, which some feedlot owners have dubbed Vitamin Z for its ability to cheaply tack on 33 extra pounds of salable meat to a steer. Merck says it has every intention of bringing Zilmax back to the market; US and Canadian sales of the drug hit $160 million in 2012. Click for Reuters' full report, which shares some theories as to what could be going wrong with cattle who take Zilmax; one is that the additive could worsen common feedlot nutritional disorders present in cattle whose diet contains too much starch.