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"
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.
reply
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"