What is the ruling on poultry that feeds on chicken bones?

If the poultry's feed consists of carrion (unslaughtered chickens) that have not been industrially transformed from their original state, then they are considered "Jalalah" (animals that feed on impurities). Scholars have differed regarding the ruling on their meat and excrement. The preponderant opinion is that what has been transformed into something wholesome (like their meat, eggs, and milk) is permissible, while what has been transformed into something impure (like their excrement) is najis (ritually impure).

Ibn Taymiyyah said: "Induction indicates that everything which Allah transforms from one kind to another, such as changing wine into vinegar, blood into semen, and the impure meat of 'Jalalah' into something pure, as well as their eggs and milk, and crops irrigated with impure water if then irrigated with pure water—the ruling of impurity, the reality of impurity, and its name are all removed. This is essential."

It is stated in Al-Taj wal-Iklil, on the authority of Ibn Al-Mawaz: "There is no harm in eating chickens that consume foul things." Al-Kharashi said: "All birds are permissible to eat, whether they eat carrion or not, even the 'Jalalah'."

And if the bones and impurities that poultry feed on have undergone industrial processes that transformed them from their original nature into another substance, then the poultry are not considered "Jalalah."