Agreed, Brin, and that's why if what your saying is correct, and calves are only fed serem, and not blood, it's pretty irresponsible to state 'blood'.
I am against feeding livestock anything that is not natural for them to eat. It doesn't have to be 'organic', but if cattle are intended to eat grass, grain, and the like, that is all they should be fed. As far as: "They really don't seem to care one way or the other what they're eating as long as it arrives in time every day." Just because they'll eat it doesn't mean we should feed it to them. I don't think you were necessarily saying the opposite, but I thought I'd address that anyhow. I'm pretty sure if I fed my daughter human meat without telling her what it was, she would eat it....of course that's pretty sick, but the principle is the same, albeit more extreme.
Animals that eat other animals, no problem - feed them as much meat as they should have.
Re:"I'm opposed to the practice simply because its an avenue to disease, which has been demonstrated with BSE." - I agree, but I come at from the opposite angle. I am opposed to it for ethical reasons stated above. I feel that the immoral practice of feeding herbivores food they would never choose to eat in the wild, thus causing wicked diseases is a sign that the practice is a perversion of the natural order, if you will. It serves us right for putting profit ahead of humanitarian practices, fairness, common decency, and above all, common sense.