Changes in IgG2 levels with age in British cattle.

IgG1, IgG2 and IgM levels were measured in serum samples from 282 cattle of various ages and the results analysed by least squares. There were marked increases with age in IgG2 levels in bulls, and in dairy cattle in the absence of culling for disease or low production traits. There was about a 300% increase between one year and eight years of age for IgG2 compared with the small increase of about 20% for IgG1 but there was no apparent effect of age on IgM levels. There were no differences between Hereford and Friesian bulls for any of the immunoglobulins but there were environmental differences, between AI centres, for IgG1 and IgM. No animals were found to be immunodeficient but IgG2 levels ranged widely from 1 mg/ml to 35 mg/ml in different bulls.