PHAGOCYTIC-ACTIVITY OF BOVINE POLYMORPHONUCLEAR NEUTROPHIL LEUKOCYTES

Two different investigations were conducted on the chemiluminescent ac tivity of bovine milk polymorphonuclear neutrophil leucocytes (PMN) ac tivated by different stimuli: zymosan, derived from the wall of Saccha romyces cerevisiae (Experiment A), and Streptococcus uberis and Escher ichia coli (Experiment B). In Experiment A, a quarter with a phagocyti c activity of PMN < 20 mV/1000 PMN following stimulation with zymosan was found to be 23 times more likely to be a clinical mastitis case th an a quarter with phagocytic activity above this threshold value. In E xperiment B, calculation of the odds ratio showed similar results foll owing stimulation with Str. uberis or Esch. coli. These results provid e evidence that immunocompromisation of mammary gland defences could p redispose to clinical mastitis. They also support the need to challeng e phagocytic cells with appropriate stimuli, and the Esch. coli test s eems to be the most sensitive.