All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
Feeding the animals whose meat is not lawful to eat with dead meat, which includes pork, is permissible. Therefore, it is permissible to carry the meat and take a fee for doing so unless the purpose of the factory in remanufacturing it is to sell it, because it is forbidden to sell it. Carrying it is helping in selling it so it is also forbidden to carry it. However, if the purpose of remanufacturing it is to feed the animals and not to sell it, then this is permissible because this use is like wasting it and it does not cause any harm. This was stated by Ibn Taymiyyah, in his Fataawa.
Even if the animals are fed animals whose meat we are allowed to eat, or whose milk we are allowed to drink, it is said that it is permissible to feed it with impurities according to the most preponderant opinion of the scholars. However, we are not allowed to eat its meat or milk it after feeding it with impurities until a given period of time passes so that its meat and milk become pure again. This is because when a ruling is confirmed for a given reason, then the ruling no longer applies when this reason does not longer exist.
Al-Mardaawi said in his book entitled Al-Insaaf, “It is permissible for a person to feed an animal with impurities if it will not be slaughtered (to be eaten) and will not be milked soon after.”
Allaah Knows best.