As long as no harm comes to the animal as a result of the food, they may be fed any type of food. The prohibition of pork, carrion, impurities, and other foods only applies to humans, since animals are not obligated to follow the Islamic Law which was revealed for human beings.
 Imam Abū Ḥanīfah gave a ruling that that it is permissible to feed dogs flour which had been mixed with impure water. [Badāiʿ aṣ-Ṣanāiʿ 1:78]
God knows best,
Imam Mustafa Umar