Cows wait to be milked at the Fiscalini Cheese Co. in Modesto, Calif. The USDA confirmed today that Mad Cow disease was detected in a dairy cow in California, but also said consumers shouldn't worry. - 

This final note today, the first thing about which you need to know is that milk does not -- repeat not -- transmit Mad Cow disease.

That said, the U.S. Department of Agriculture announced today that it's found a dairy cow in California that has been infected with bovine spongiform encephalopathy. It's the fourth such cow found in the U.S. food chain in the past nine years.

The Department of Agriculture says there's no reason consumers should worry, but markets don't mess around with this kind of stuff. Cattle futures in Chicago traded down as far as they're allowed to go today.

Follow Kai Ryssdal at @kairyssdal