The last five, or so, years we have been hammered with pneumonia at weaning time.  For the first five years I was home from school and caring for the herd I had one with pneumonia.  I have mass treated the herd of weaned calves in four out of the last five years to get the infection stopped.  It doesn't seem to matter if the calves are in the lot or on pasture, they still get hit really hard with pneumonia at weaning.  This year I am giving everything Inforce 3 at birth when I work the calves.  We will see if it makes any difference.  It isn't cheap but neither is Micotil and Baytril.  It is also pretty hard to market the dead ones.