Mad Cow Found in California

The fourth Mad Cow to be discovered in the U.S. was reported in California. It was a dairy cow presented for slaughter. It just happened to get caught in a random sample. California officials are saying that the meat did not enter the food chain and that there is no danger to the public.
The USDA reports the US has 90,800,000 cows and tests around 40,000 a year. How many Mad Cows are slaughtered and not caught in so few samples? Around 35,000,000 cows are killed each year. Testing 40,000 out of 35,000,000 leaves a lot of cows untested. Japan tests every cow they slaughter for Mad Cow Disease.
There is research that shows milk can transmit spongiform disease. I would like to see the test results the officials are reporting that tells us that Mad Cow Disease cannot be contracted from milk.