From the Wall Street Journal, August 19, 2013:
What’s Ailing America’s Cattle?
Scientists Suspect Livestock-Feed Additives Are Behind Distress
Tyson Foods has suspended purchases of animals fed with the additive Zilmax. Shown, workers at a Tyson unit trimmed beef in Nebraska last year.
A growing number of cattle arriving for slaughter at U.S. meatpacking plants have recently shown unusual signs of distress. Some walked stiffly, while others had trouble moving or simply lay down, their tongues hanging from their mouths. A few even sat down in strange positions, looking more like dogs than cows.