Hilchos Issurei Mizbeiach 3:13

The preceding halacha (about animal offspring being as prohibited as their parents) is the case when the sin involving the animal or the animal killing a human occurred while the animal was pregnant. In such a case, the offspring was with the parent when it was invalidated and is considered to have been like one of its limbs. However, if the animal conceived after the sin or after killing a person, then its offspring is fit for the altar. If an animal was already consecrated when a human had relations with it and it only later conceived, the offspring is nevertheless fit for the altar. It should go without saying that the offspring is fit if a human had relations with its mother was while it was completely secular and only after was it consecrated and conceived. Similarly, a chick born from the egg of a treifah is fit to be brought on the altar.

Hilchos Issurei Mizbeiach 3:14

If someone bows down to grain, its kernels may be used for flour offerings because they have been changed. They are comparable to the offspring of animals prohibited for the altar, which are permitted. Similarly, an animal that was fattened with the fodder of idolatry is fit for the altar because the fodder has been changed.