Is it permissible, Islamically, for Muslims to manufacture animal feed from animal waste that may contain impurities and blood, and is it permissible to consume the meat of animals that have been fed this feed, especially given the existence of studies linking it to certain diseases?

If the feed still has the characteristic of impurity attached to it after its manufacturing, then it is impermissible to sell it. The meat of an edible animal that was fed with it is not permissible to eat until it is fed with pure feed and thus becomes pure, because it takes the ruling of jallalah (an animal that feeds on impurities). If it is proven that its meat causes diseases even after being fed with pure feed, then it is not permissible to eat it to avert harm, based on the Prophet's (peace be upon him) saying: "There shall be no harm or reciprocating harm." This includes feed from which the characteristic of impurity has been removed but still causes the same harm; it is not permissible to manufacture or sell it. The questioner should beware of trading in it or eating its meat, and should advise Muslims accordingly.