There was no apocalyptic cause for the recent deaths of 200 cattle in Central Wisconsin. The steers succumbed in a Portage County feed lot earlier this month, and Doctor Peter Vanderloo at the Wisconsin Veterinary Diagnostic Lab said tests have shown that it was moldy sweet potatoes used in the animals? feed that did them in. ?The mold product that grows on sweet potatoes was present in the sweet potatoes,? said Vanderloo. ?All the clinical science, the death loss, the changes in the steers, are all compatible with this mold.