Since you say you weren't trolling (and we have been bothered by such creatures here in the past), you may get a result if you just do a general search about protein in the poop of any mammals.
Someone (David I think) mentioned that a healthy cow shouldn't have a lot of protein in it's poop. If he is right, and past history indicates that he doesn't post unless he's either sure of his facts or puts in a qualifier, then perhaps the same principle would apply to all mammals.
Unless the animal was sick, most of the protein excreted would be in the form of bacteria. Most of the excreted nitrogen would be urea.
There have been news articles about synthetic food from manure. I took such reports as using manure as a source material for growth not as a direct source material for the chemicals.
Using manure as a source material for growth is normally called a garden. ;%) Using manure to feed a culture that makes meat-like-stuff is more direct but still the same general process.
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