Immunoglobulin (Ig) concentrations in serurn and in nasal secretions were
correlated with pneumonia and diarrhea during the first 12 wk of life of dairy
calves. The peak onset of pneumonia occurred between 2 and 4 wk of age when
the calves' serum Ig G1, Ig G2 and IgA concentrations were lowest. As IgG2
concentrations increased, fewer calves developed pneumonia. Peak onset of
pneumonia was also correlated with the lowest IgG and IgA concentrations in the
calves' nasal secretions. Diarrhea often preceded pneumonia.
