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.
It is not permissible for you to sell feed for those who use it to breed pigs because the means take the ruling of the objectives; what leads to something forbidden is itself forbidden. It is for this reason that the scholars stated that it is forbidden to sell grapes for a person who would squeeze it to be an intoxicant, because this is helping him in this prohibited act and Allaah Says (what means) {Help you one another in virtue, righteousness and piety but do not help one another in sin and transgression.}[Quran 5:2]
Allaah Knows best.