Information about the rendering plants have been out for many years, but still some people tend to ignore the warnings. IF you do not believe this, then just call up the dog food companies and ask if they do tours to show how the dog food is made. You don't need to buy the book, there's a lot of information out there if you just look. Here is just a couple.
http://www.homevet.com/petcare/foodbook.html http://www.prwatch.org/prwissues/1996Q1/madcow13.html http://home.att.net/~wdcusick/03.html