Genetic Association between Parameters of Innate Immunity and Measures of Mastitis in Periparturient Holstein Cattle

peer reviewedRelationships 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 markers) were examined for periparturient Holstein cows. Physiological markers included 11 in vitro immunological assays. Molecular markers included the second exon of the DRB3 locus of the bovine major histocompatibility complex, the IgG2 isotype genotype, and the CD18 genotype (the 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 computed. Molecular markers explained up to 40% of the variation in EBV for measures of mastitis. The presence of allele DRB3.2*16 was associated with higher EBV for SCS. Allele DRB3.2*8 was associated with increased EBV for clinical mastitis, as was the IgG2b allele and the normal CD18 allele. Alleles DRB3.2*11, *23, IgG2a, and the recessive allele for bovine leukocyte adhesion deficiency were associated with decreased clinical mastitis. A positive genetic association was found between allele DRB3.2*24 and EBV for IMI by major pathogens and between DRB3.2*3 and IMI by minor pathogens. Several correlations between EBV for immunological assays and EBV for mastitis measures were significantly different from 0. Cows with low EBV for SCS tended to have neutrophils that had greater functional ability at maximal immunosuppression, low serum IgG1, and high numbers of circulating mononuclear cells. Immunological parameters, including physiological and molecular markers, are useful aids to understand the genetics of resistance to mastiti

Breed and season influence on milk quality parameters and in mastitis occurrence

The aims of the present study were to evaluate the performance of Jersey and Holstein cows under different rainfall conditions (dry and rainy seasons) by monitoring aspects related to subclinical mastitis (somatic cell count, microbiological isolation, type of isolated pathogen), milk quality (lactose, protein, fat, total solids) and production (mean milk production) of both breeds. The study was carried out in a dairy farm located in the state of São Paulo, Brazil. Eight visitations were done to the farm, four in a period of high rainfall and four in a period of low rainfall. Milk samples were collected from 79 Holstein cows and 37 Jersey cows for electronic somatic cell count and determination of the main milk components (protein, fat, total solids, lactose). Milk fat, protein, total solids and production were influenced by breed and the season, with similar tendencies for both breeds in both seasons. Somatic cell count (SCC) showed similar results for both breeds. Holstein cows with intramammary infections (IMI) presented a higher increase in SCC when compared to Jersey cows (P<0.001). In the dry season, 53 animals had IMI in at least one month during the study, which 32 were Holstein and 21 were Jersey cows. In the rainy season, 65 animals had intramammary infection, being 43 Holstein and 22 Jersey cows. The frequency of IMI cases was larger in the rainy season than in the dry season. Jersey cows had a lower chance of showing IMI signs and symptoms than Holstein cows in the rainy season (odds ratio=0.52). The larger number of IMI cases in the rainy season may have led to a lower milk lactose rate for both breeds, thus milk lactose rate can be considered an indicator of IMI status. There was prevalence of contagious pathogens overall in the study. The applied model showed that environmental pathogens were more frequently isolated from the breed Jersey, regardless of the study season. There seems to be differences in the immune response of Jersey and Holstein breeds