MASTITIS OF PERIPARTURIENT HOLSTEIN CATTLE - A PHENOTYPIC AND GENETIC-STUDY

Environmental and genetic factors affecting somatic cell scores, clini cal mastitis, and IMI by minor and major pathogens were studied on 137 periparturient Holstein cows selected for milk production. Environmen tal effects were obtained by generalized least squares and logistic re gression. Genetic parameters were from BLUP and threshold animal model s. Lactation number affected the number of quarters with clinical mast itis and the number of quarters infected with minor pathogens. The DIM affected somatic cell score and number of quarters infected with majo r pathogens. Heritabilities for all mastitis indicators averaged 10%, but differences occurred among the indicators. Correlations between br eeding values of the number of quarters infected with minor pathogens and the number infected with major pathogens were antagonistic and sta tistically significant.