What is the ruling on eating chicken that has been fed feed mixed with shed blood?

The gushing blood is impure by scholarly consensus, as are carrion and its parts. If gushing blood is mixed into animal feed, then the feed is impure.

If animals whose meat is permissible to eat are fed with impure feed, those animals become jallalah and their meat is not permissible to eat, unless they are subsequently fed with pure feed for a period sufficient to purify their flesh, and then slaughtered.

Jallalah refers to animals whose meat is permissible to eat, but which consume impurities until their smell changes.

Therefore, chickens that have been fed with feed mixed with gushing blood or other impurities have impure meat, and if slaughtered, their meat is not permissible to eat.