Nova.. just read your post, sounds a lot like what we're going through.
I've had three calves die in the past month. The first two died about a month ago.. during the wet, crappy weather we've had this winter. Both were up and nursing after birth, seemed ok (other than cold and wet, like everything else) they didn't move around much the next day, but assumed that was because of the weather. (Brahman crosses) Found them laid out dead the next. (Two different times, within about a week)
We had four calves born on the 14th of this month. Weather is a little warmer, but pastures are a quagmire. Two days ago we started tubing one that wasn't looking good, found her dead this morning. Have another one, same age, that didn't look good this morning. Tubed her. Took the dead one to A & M, but it may be MONDAY before they can find anything. I'm about to load up the whole bunch and take them to the auction barn. I can't recall having seen a disease that would kill a newborn in two or three days, unless the calf hadn't nursed.
No scours, but a little bit of blood in the stools. I'm at a loss. Anyone have any suggestions?