Town of Stockton — An investigation is under way after 200 dead cows were found in a field in the Town of Stockton. The Portage County sheriff's office says the owner of the cattle has been working with a local veterinarian and it's believed the animals died from the IBR/BVD virus. The virus can cause respiratory and reproductive problems. WSAW reports samples from the dead cows have been sent to Madison for testing. Authorities say there is no threat to humans or other animals.