In the EU at least, there's a legal requirement to make pet food safe for human consumption.
This isn't because the EU wants people to eat pet food, it's because they don't want all the inedible crap from the slaughterhouse industry to end up in pet food.
Probably the same in the US and Canda, but who knows. They wash their chickens in bleach because they can't be bothered cleaning the factories :P