Till The Cows Come Home
If you are raising Elsie, your cow, are you allowed to feed her non-kosher? The question would seem mostly non-sensical. However, care must be taken to avoid a prohibition, since the steaks may be high.
Kashrus
Animal Fattened on Non-Kosher Food in the Gemara
Whether meat from a kosher animal raised mainly on non-kosher feed may be eaten, and the views of Tosfos, the Rema, the Mordechai and the Rambam.