פירוש על עבודה זרה 108:4

All rabbis agree that if one exchanges an idol for an animal, the animal is prohibited. The dispute is over animals exchanged for those animals. According to one opinion the prohibition continues. As we learn from the verse, anything that is derived from idolatry is accursed. The other opinion emphasizes that only “it,” the original animal is prohibited. The animal exchanged for the prohibited animal does not become prohibited.