Answer
(Fatwa: 2085/1593=B=1429)
It is neither lawful to eat carrion and unlawful and impure things, nor to feed them to animals and nor to supply them. Also, it is unlawful to do business of such things. However, if the animal food is prepared by adding lawful and pure things in a large quantity, and the nature of those things is changed through chemicals, then it will be allowable to prepare such animal food as well as to sell it.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband