[vinylengraver]

Quoting from Animal Planet:
"A pet food manufacturer made a mock product that had a guaranteed analysis of 10% protein, 6.5% fat, 2.4% fiber, and 68% moisture, similar to what you see on many canned pet food labels. The only problem, was that the ingredients were old leather work boots, used motor oil, crushed coal, and water!"
The breeder where I got my Phoebe showed me what happens when you dissolve a bunch of typical dogfood in water and let sit until it settles.
Floating on the surface there was a half-inch thick layer of finely ground hair. Human or animal, not quite sure which... still, legitimate protein source for your beloved pet according to a typical pet food label.

This is why I will NEVER feed my dog any commercially available dog food product. Period.