Bactericidal activity of bovine neonatal serums for selected coliform bacteria in relation to total protein and immunoglobulin G1 and immunoglobulin M concentrations.

Bactericidal activity for a serum-sensitive Aerobacter aerogenes strain was associated with antibodies present in immunoglobulin G1 (IgG1) and immunoglobulin M (IgM), with the greatest activity on a weight basis in IgM. Activity in immunoglobulin G2 was absent. A total of 118 serums were prepared from blood collected from neonatal calves on farms experiencing unusually high mortality from diarrhea. The serums were allotted to 4 groups on the basis of total serum protein concentrations as follows: group I=7.0 to 9.5 g/dl, group II=6.00 to 6.98 g/dl, group III=5.00 to 5.90 g/dl, and group IV=3.9 to 4.9 g/dl. Bactericidal activity for the serum-sensitive aerobacter strain was distributed approximately equally throughout the 4 groups. Activity for 3 strains of Escherichia coli was minimal to absent. Concentrations of IgG1 and IgM were determined in 82 of the serums. Concentrations of IgG1 ranged from 0 to 54.2 mg/ml, with overlapping among the 4 groups. Concentrations of IgM could not be determined in serums with concentrations greater than 1.6 mg/ml. However, bactericidal activity did not correlate with the immunoglobulin concentrations, since activity was present to the same degree in serums with small concentrations of immunoglobulins compared with serums with as much as threefold larger concentrations.