Pregnancy-associated glycoprotein and decreased polymorphonuclear leukocyte function in early post-partum dairy cows

Phagocytosis and oxidative burst activity of polymorphonuclear neutrophil leukocytes (PMN) isolated from blood and pregnancy-associated glycoprotein (bPAG) concentrations in plasma were evaluated in two longitudinal studies in dairy cows from 3 weeks before until 5 weeks after calving, carried out in the United States and in Europe. Ingestion of Staphylococcus aureus by blood PMN increased during the first week after calving and normalised 3 weeks post-partum. Phagocytosis of Escherichia coli did not change in the early post-partum period. In both studies, a significant decrease in oxidative burst activity of PMN was observed between 1 and 3 weeks after calving. In all cows, a very significant increase in plasma bPAG concentration was found between 1 week before and 2 weeks after calving. The peak of bPAG concentration in plasma immediately preceded the alterations of blood PMN functions. These results suggest that bPAG may be associated with inhibition of PMN function of dairy cows during the early post-partum period.