Do grains sold as animal feed meet the safety standards for human food?
What is animal feed in one country is human food in another (E.g. "Polenta") but that's just one example, so:


Is all animal feed safe to eat raw? Definitely not!
Is all animal feed safe to eat cooked? Definitely not!
Is some animal feed safe to eat raw? Probably not!
Is most animal feed safe to eat cooked? Probably yes.
Is it legal to serve this food to other people? No in most countries, including Germany


However, that is just some and most and probably and the quality control between  maize for animal consumption and maize used for human consumption is different, so the quality of the food you'll be cooking out of chicken feed will be much lower than the one rated for human consumption.

I mean: I once made a stew out of dog food by adding pepper, allspice, nutmeg and some nice dark monk beer, but that was a drunken bet and the two other drunks absolutely loved it the night itself until we realised the next day it was mostly horse meat...