From what I understand, the laws of "bechor behemah tehorah" (kosher first-born animal) are still in affecteffect today, both in Israel and outside. To avoid problems with this, we sell a share of the mother (I've always heard it explained as 'her ear') to a non-Jew, and therefore the firstborn offspring is permitted. Does that mean that the non-Jew who bought part of the mother owns a share in the offspring? Also, in today's huge meat-packing plants, does that end up being thousands of dollars a year? Does anyone supervise this today (such as the rabbanut in Israel)?