The University of Wisconsin-Madison's vet lab ran tests on the cows. Its results show the cows died of a toxin that could be traced to rotten sweet potatoes. Peter Vanderloo, an associate director at the lab, tells AP the rotten veggies were mixed into the cattle's feed.
The cows dropped dead on a Portage County dairy farm earlier in January, not long after flocks of dead birds had rained down on Arkansas, and millions of fish carcasses had washed up on the Maryland shore.
We still don't know what caused that carnage (check here on that), but science has solved the mystery in Wisconsin.