SEVERITY OF EXPERIMENTAL ESCHERICHIA-COLI MASTITIS IN KETONEMIC AND NONKETONEMIC DAIRY-COWS

The severity of experimental Escherichia coli mastitis in relation to in vitro chemotaxis of polymorphonuclear leukocytes was investigated i n cows during negative energy balance. The negative energy balance was induced by feed restriction. Cows were classified into two groups, ke tonemic and nonketonemic, based on the beta-hydroxybutyrate concentrat ion in the peripheral blood at the moment of inoculation. Bacterial gr owth in the inoculated quarter was used as a parameter to indicate the severity of experimental mastitis. In the nonketonemic cows, experime ntal mastitis ranged from moderate to severe. Severity of experimental mastitis was negatively related to preinfection chemotactic response of polymorphonuclear leukocytes. In contrast, the course of experiment al mastitis in the ketonemic group was relatively severe in all cows, regardless of preinfection chemotactic response.