Assessment of blood neutrophil oxidative burst activity in dairy cows during the period of parturition

Bovine blood neutrophil oxidative burst activity, the total leukocyte count and its differentiation, as well as progesterone, glucose and cortisol lev els were studied on 10 cows from 1 week prior to calving until 8 weeks afte r parturition. From day -7 before parturition a decrease in the metabolic oxidative burst activity of neutrophils was observed, reaching the lowest value 3 days afte r calving (0.28 (s.e. 0.06) nmol/l H2O2 per min 10(6) neutrophils) (P less than or equal to 0.01). Thereafter, values increased with a maximum of acti vity 26 days after parturition (0.57 (s.e. 0.05) nmol/H2O2 per min per 10(6 ) neutrophils). At the end of the experiment the neutrophils H2O2-productio n was comparable to values observed on day -7. The maximum total leukocyte count was observed on the day of parturition (8 ,108 (s.e. 370) leukocytes per mu l blood) (P less than or equal to 0.01) r eturning to normal levels about 3 weeks after calving. Lymphocytes and neut rophils showed a trend analogous to that of the total leukocytes. Eosinophi ls and monocytes did not change during the entire period. With the rapid in crease of circulating neutrophils observed on the calving day, a marked lef t shift was observed with a maximum number of immature neutrophils (48.6%) observed on day +3 (1477 (s.e. 242) immature neutrophils per mu l blood) (P less than or equal to 0.01), reaching normal values about 4 weeks after pa rturition. A significant increase (P less than or equal to 0.01) of plasma glucose was found on the day of parturition (91.4 (s.e. 6.8) mg per 100 ml plasma), while the levels of cortisol reached their maximum 3 clays after c alving (22.05 (s.e. 8.46) ng/ml plasma). Progesterone levels averaged 4.07 (s.e. 1.21) mu g/l 7 days before calving, declining precipitously to 0.06 (s.e. 0.45) mu g/l 3 days after calving (P less than or equal to 0.01), remaining very low for a period of about 3 we eks. Minimum and maximum anoestrus post-partum were 12 and 57 days, respect ively. Despite great hormonal variation observed in the peripartum period, no significant correlation was found between measured hormones and the oxid ative burst activity of neutrophils.