Chemiluminescence of bovine polymorphonuclear leucocytes during the periparturient period and relation with metabolic markers and bovine pregnancy-associated glycoprotein

The respiratory burst activity of polymorphonuclear leucocytes (PMN) was ev aluated in eight Holstein cows from 8 weeks before until 6 weeks after calv ing by chemiluminescence (CL). The CL response started to decrease 1 week b efore parturition, reaching a minimum during the first 2 weeks after calvin g. From week 3 of lactation, CL increased again and returned to original le vels by week 6 of lactation. Plasma concentrations of 3-hydroxybutyric acid , total bilirubin and bovine pregnancy-associated glycoprotein started to i ncrease before parturition to reach a maximum during the first or second we ek of lactation. The concentrations of glutamic-oxaloacetic transaminase, l actate dehydrogenase, non-esterified fatty acids and bilirubin increased af ter calving, reaching a maximum during the second week. A small decrease in plasma cholesterol during the week before and after calving was followed b y an increase. The CL response of the PMN showed significant temporal relat ionships with the plasma concentrations of 5-hydroxybutyric acid, bovine pr egnancy-associated glycoprotein, bilirubin, glutamic-oxaloacetic transamina se, non-esterified fatty acids. that with cholesterol was nearly significan t. This means tl-lat the change in the CL response with time coincided with the changes in plasma concentrations of these substances with time and tha t these changes were significantly related with each other. The results: of this study show that the decreased respiratory burst activity of bovine PM N around parturition may be related to the extent of the metabolic and horm onal changes, although the causative relationships are not proven, these re sults support earlier results suggesting that S-hydroxybutyric acid and bov ine pregnancy-associated glycoprotein may directly affect neutrophil functi on, whereas non-esterified fatty acids, cholesterol, bilirubin, and liver e nzymes map have potential as diagnostic markers of impaired neutrophil func tion and consequently increased disease risk around parturition.