We didn't have feedlots but we did have an abbatoir just down the road where cattle waited for their slaughter in somewhat raised panic. Once again anything remotely resembling the deaths of these cattle in the feedlots (as per this story) would have raised serious questions. So although I take your point that the simple answers like yours need to be ruled out first, I still find it highly unusual.
We didn't have feedlots but we did have an abbatoir just down the road where cattle waited for their slaughter in somewhat raised panic. Once again anything remotely resembling the deaths of these cattle in the feedlots (as per this story) would have raised serious questions. So although I take your point that the simple answers like yours need to be ruled out first, I still find it highly unusual.