Variation in Serum Immunoglobulins in Canadian Holstein-Friesians

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Abstract
Variation and relation to pneumonia and mastitis, of IgG1, IgG2, IgM and IgA of blood serum, measured by radial immunodiffusion, was studied in a sample of 190 Canadian Holstein-Friesian females sired by 22 bulls in artificial insemination. Regression analyses indicated that combined effects of age, stage of lactation, parity and cow''s sire''s milk rating accounted for 6, 37, 2 and 3% of the total variation in IgG1, IgG2, IgM and IgA. The IgG2 increased significantly with age, parity and stage of lactation and decreased slightly with increasing sire milk ratings. Heritabilities by paternal half-sister correlation varied from 0 for IgG1 and IgA through 0.28-0.68 for IgG2 and 0.08-0.85 for IgM. IgG2 was positively correlated with clinical mastitis (0.24) and incidence of enzootic pneumonia (0.13) indicating further study of IgG2 and its relationship to disease is warranted. No significant correlations existed between other Ig and mastitis or pneumonia nor was a cow''s production related to Ig. Selection to alter Ig content and reduce disease may be feasible and should be examined further.