Silver, we have a few theories.  The cocci definitely opened the door for some other stuff to emerge, although some of the diseases that came through on calves that were vaccinated and boostered for the specific bug (eg: Mannheimia).  The other thing we have been working through is whether oilfield emissions or environmental sulfur (among other things) may be limiting the immune response to vaccines.  We changed our vaccination product this fall when we boostered the calves because our vet changed brands.  We will be special ordering the old brand ahead of time in the future.  This ecoli and cperf A we think is a likely culprit in the young calf sudden death stuff we ran into last summer.  We are going to booster calves with a shot of multi-min pre-weaning this fall as well when we do our boosters as we think it should encourage a better response to vaccination. Our weather also played a part as it was very bouncy and dry/wet/cold/warm etc.  We are looking at changing our weaning protocols as well, but are not sure yet just what that will look like.

I told our vet (who has 7 kids) that I expected my name on their gifts right beside Santa Claus.