The following article is taken from http://www.huffingtonpost.com Thanks, Lenny, for the link.
The photo above has been extensively passed around today, and for good reason: it's a peak into the rarely-seen world of mechanically separated meat, or Advanced Meat Recovery (AMR).
Someone figured out in the 1960s that meat processors can eek out a few more percent of profit from chickens, turkeys, pigs, and cows by scraping the bones 100% clean of meat. This is done by machines, not humans, by passing bones leftover after the initial cutting through a high pressure sieve. The paste you see in the picture above is the result.
Michael Kindt continues:
There's more: because it's crawling with bacteria, it will be washed with ammonia, soaked in it, actually. Then, because it tastes gross, it will be reflavored artificially. Then, because it is weirdly pink, it will be dyed with artificial color.
But, hey, at least it tastes good, right?
The resulting paste goes on to become the main ingredient in many of America's favorite mass-produced and processed meat-like foods and snacks: bologna, hot dogs, salami, pepperoni, Slim Jim-like jerkys, and of course the ever-polarizing Chicken McNugget, where the paste from the photo above was likely destined.