PREINFECTION IN-VITRO CHEMOTAXIS, PHAGOCYTOSIS, OXIDATIVE BURST, AND EXPRESSION OF CD11 CD18 RECEPTORS AND THEIR PREDICTIVE CAPACITY ON THEOUTCOME OF MASTITIS INDUCED IN DAIRY-COWS WITH ESCHERICHIA-COLI/

Four to 6 wk after parturition, 12 cows in second, fourth, or fifth la ctation were experimentally infected in one gland with Escherichia col i. The capacity of chemotaxis, phagocytosis, oxidative burst, and expr ession of CD11/CD18 receptors to predict the severity of IMI was measu red. Bacterial counts in the infected quarter, expressed as area under the curve, and residual milk production in the uninfected quarters we re compared to determine severity of the infection. Although these two outcome parameters were highly negatively correlated, regression mode ls with preinfection tests for leukocyte function fitted best with bac terial counts as an outcome parameter. Of the preinfection tests for l eukocyte function, chemotaxis best predicted the outcome of the IMI th at had been experimentally induced by E. coli. The number of circulati ng peripheral leukocytes just prior to inoculation was used to predict 52 and 45% of the severity of IMI for bacterial counts and residual m ilk production, respectively. As a categorical variable, parity predic ted 75 and 56% of the severity of IMI expressed as bacterial counts an d residual milk production, respectively. Because of the strong effect of parity on the outcome of the experimentally induced mastitis, anal ysis was performed to discriminate between second parity cows and olde r cows. Significant differences were found for the number of circulati ng peripheral leukocytes and for the expression of CD11b/CDl8 and CD11 c/CD18 receptors between younger and older cows.