Physiological and pathological factors influencing bovine immunoglobulin G1 concentration in milk.

Bovine immunoglobulin G1 concentration was determined by radial immunodiffusion in 349 milk samples of uninfected quarters, 95 of infected quarters, and 118 blood serum samples from 42 Holstein-Friesian cows taken at days 30, 150, and 270. In lactation, immunoglobulin G1 concentration in milk was not affected by immunoglobulin G1 concentration in blood serum or location of quarters. The immunoglobulin G1 concentrations increased at the end of lactation and in samples collected from cows beyond the third lactation. Uninfected quarters had a mean immunoglobulin G1 concentration of .46 mg/ml. This was less than means from quarters infected by minor or major pathogens. Quarter infection by Staphylococcus aureus resulted in an increase of immunoglobulin G1 concentration in blood serum (9.22 to 11.3 mg/ml). When Corynebacterium bovis was persistent throughout the lactation, immunoglobulin G1 concentration in blood serum was increased (11.26 mg/ml). There was no correlation between somatic cell count and immunoglobulin G1 concentration in uninfected quarters. There was a slight correlation between bovine serum albumin and immunoglobulin G1 concentration in identical quarters (.23). Infection of quarters increased in varying degrees the correlation between immunoglobulin G1 concentration and bovine serum albumin concentration or somatic cell count in milk.