Tagged cattle are gathered at Larson Farms/Midwest Feeders, one of the largest ranches in Illinois, Wednesday, April 25, 2012, in Maple Park, Ill. Owner Mike Martz, who raises 6,000 cattle a year, says the USDA system is working and that the discovery of mad cow disease in a lone cow in California is a prime example. (AP Photo/Charles Osgood)

Federal officials say the mad cow recently discovered in California had been euthanized after it became lame and started lying down.

The U.S. Department of Agriculture revealed the new information
from its investigation Thursday night and also said the cow was 10
years and seven months old. It came from a dairy farm in Tulare
County, the nation's No. 1 dairy-producing county.

Routine testing at a transfer facility showed the dead cow destined for a rendering plant had mad cow disease, or bovine spongiform encephalopathy.

It's the fourth case of BSE ever discovered in the U.S. and the
first since 2006.

U.S. health officials say there is no risk to the food supply.
The California cow was never destined for the meat market, and it
developed BSE from a random mutation, not tainted feed.