Surprise? From Fast Food Nation, p202:
About 75 percent of the cattle in the United States were routinely fed livestock wastes – the rendered remains of dead sheep and dead cattle – until August of 1997. They were also fed millions of dead cats and dead dogs every year, purchased from animal shelters. The FDA banned such practices after evidence from Great Britain suggested that they were responsible for a widespread outbreak of bovine spongiform encephalopathy (BSE), also known as “mad cow disease.” Nevertheless, current FDA regulations allow dead pigs and dead horses to be rendered into cattle feed, along with dead poultry. The regulations not only allow cattle to be fed dead poultry, they allow poultry to be fed dead cattle. Americans who spent more than six months in the United Kingdom during the 1980s are now forbidden to donate blood, in order to prevent the spread of BSE’s human variant, Creutzfeldt-Jakob disease. But cattle blood is still put into the feed given to American cattle. Steven P. Bjerklie, a former editor of the trade journal Meat & Poultry, is appalled by what goes into cattle feed these days. “Goddamn it, these cattle are ruminants,” Bjerklie says. “They’re designed to eat grass, and maybe, grain. I mean, they have four stomachs for a reason – to eat products that have a high cellulose content. They are not designed to eat other animals.”