Reply To: Parah Aduma is invalid :(

I thought that we Pasken that the very fact that it was mounted by a bull Pasels it (“Alal Aleha Ol” – see second Perek of Parah), and the birth – or for that matter, the pregnancy – merely proves what had happened beforehand to Pasel it. Either way, why wasn’t it kept separate from bulls? This doesn’t seem to be rocket science.