Im now trying to convince my dad to let me adopt a neutered pig from a shelter by my house to be with my other guinea pig. But he's not convinced that its a 100% garentee that the pig is no longer furtal. Is there a chance that this could be true, could they mess something up during the opperation and the guinea pig could still reproduce? Or is it a 100% sure thing that if a guinea pig has been neutered that it will NOT reproduce what so ever?