alt Hacker NewsFeather meal is used in animal feed.
https://en.wikipedia.org/wiki/Feather_meal
Manure is also fed to cows.
https://extension.missouri.edu/publications/g2077
"Poultry litter can be used as a feedstuff... There are currently no federal or Missouri regulations governing the use of poultry litter as a feedstuff"
Sometimes EU regulations isn't that bad.
Poultry litter has been banned as cattle feed since 2001, partially due to mouth and foot disease and BSE and to some extent animal welfare.