A friend of mine learned a very expensive lesson this week. He has some very high bred angus cattle from one of the local experimental college farms here, but more than that these were pets. He cleared some trees and pushed them up in a pile. The cows ate the oak leaves and were poisoned. He lost one bull in the back of the trailer at the vets. Also a mama cow due to calve and a heifer. They managed to save another heifer but not sure if she lives what the lasting effects might be. I have not heard of oak leaf poisoning before so I thought I'd pass this along. I've seen cows eat leaves before, so it must have something to do with the amount they ate.