GENETIC ASSOCIATION BETWEEN PARAMETERS OF INNATE IMMUNITY AND MEASURES OF MASTITIS IN PERIPARTURIENT HOLSTEIN CATTLE

Relationships between genetic measures of mastitis (somatic cell score , score for clinical mastitis, and scores for IMI with major or minor pathogens) and immunological parameters (physiological and molecular m arkers) were examined for periparturient Holstein cows. Physiological markers included 11 in vitro immunological assays. Molecular markers i ncluded the second exon of the DRB3 locus of the bovine major histocom patibility complex, the IgG2 isotype genotype, and the CD18 genotype(t he locus responsible for bovine leukocyte adhesion deficiency). A gene substitution model was used to estimate the additive genetic effects of alleles of the three molecular markers on estimated breeding value (EBV) for mastitis measures. Pearson correlation coefficients between EBV for immunological assays and EBV for mastitis measures were comput ed. Molecular markers explained up to 40% of the variation in EBV for measures of mastitis. The presence of allele DRB3.216 was associated with higher EBV for SCS. Allele DRB3.28 was associated with increased EBV for clinical mastitis, as was the IgG2(b) allele and the normal C D18 allele. Alleles DRB3.211, *23, IgG2(a), and the recessive allele for bovine leukocyte adhesion deficiency were associated with decrease d clinical mastitis. A positive genetic association was found between allele DRB3.224 and EBV for IMI by major pathogens and between DRB3.2 3 and IMI by minor pathogens. Several correlations between EBV for im munological assays and EBV for mastitis measures were significantly di fferent from 0. Cows with low EBV for SCS tended to have neutrophils t hat had greater functional ability at maximal immunosuppression, low s erum IgG(1), and high numbers of circulating mononuclear cells. Immuno logical parameters, including physiological and molecular markers, are useful aids to understand the genetics of resistance to mastitis.