Bovine blood neutrophil oxidative burst activity, the total leukocyte count and its differentiation, as well as progesterone, glucose and cortisol levels were studied on 10 cows from 1 week prior to calving until 8 weeks after parturition.
From day –7 before parturition a decrease in the metabolic oxidative burst activity of neutrophils was observed, reaching the lowest value 3 days after calving (0·28 (s.e. 0·06) nmol/l H2O2 per min 106 neutrophils) (P <0·01). Thereafter, values increased with a maximum of activity 26 days after parturition (0·57 (s.e. 0·05) nmol/H202 per min per 106 neutrophils). At the end of the experiment the neutrophils H2O2-productionwas 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 /A blood) (P <0·01) returning to normal levels about 3 weeks after calving. Lymphocytes and neutrophils showed a trend analogous to that of the total leukocytes. Eosinophils and monocytes did not change during the entire period. With the rapid increase of circulating neutrophils observed on the calving day, a marked left shift was observed with a maximum number of immature neutrophils (48·6%) observed on day +3 (1477 (s.e. 242) immature neutrophils per fjl blood) (P <0·01), reaching normal values about 4 weeks after parturition.
A significant increase (F < 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 days after calving (22·05 (s.e. 8·46) nglml plasma).
Progesterone levels averaged 4·07 (s.e. 1·21) jigll 7 days before calving, declining precipitously to 0·06 (s.e. 0·45) Hg/l 3 days after calving (F < 0·01), remaining very low for a period of about 3 weeks. Minimum and maximum anoestrus post-partum were 22 and 57 days, respectively.
Despite great hormonal variation observed in the peripartum period, no significant correlation was found between measured hormones and the oxidative burst activity of neutrophils.