Farmers Fight Against Mandatory Cattle ID Tag (NPR) When the first U.S. case of Mad Cow disease was discovered six years ago, it prompted calls for a national system to track livestock from birth to slaughter. The Agriculture Department soon rolled out a voluntary program designed to identify animals and farms. So far, only about one in four cattle has an official ID tag, and the USDA says it needs more participation to make the program work. [News Source]