Bovine Neutrophil Functions and Periparturient Disorders

Abstract

Neutrophil functions in periparturient normal cows (n = 46), and their relationship with the occurrence of retained placenta and metritis complex (RPM, n = 20), metritis (n = 18) and mastitis (n = 13), were studied by collecting blood samples via jugular vein twice weekly from 1 week before to 4 weeks after parturition. Seasonal variation of neutrophil function assays (n = 4 ovariectomized cows) and modulation of neutrophil functions in normal and abnormal postpartum cows (RPM, metritis or mastitis, n = 5 per group) were investigated in vitro by using arachidonic acid metabolites ($\rm PGE\sb2:$ 10$\sp{-6}$ M, PGF$\sb{2\alpha}:$ 10$\sp{-7}$ M, LTB$\sb4:$ 10$\sp{-8}$ M, and lipoxin B: 10$\sp{-8}$ M), and recombinant human colony-stimulating factors (rhG-CSF: 1000 and 6000 units/ml, and rhGM-CSF: 5 and 15 ng/ml). The results of these experiments suggest the following conclusions: (1) Random migration and ingestion activity of neutrophils increased, but ADCC and myeloperoxidase activity decreased, which may increase susceptibility to infections; (2) Neutrophils, monocytes and eosinophils decreased after calving; (3) There were seasonal variations in bovine neutrophil functional assays; (4) Neutrophil functions were impaired in abnormal cows after calving. A prepartum defect was noticed in term of superoxide production (metritis) or chemotaxis (mastitis), suggesting the defect of neutrophil function as a predisposing factor in the occurrence of these disorders; (5) Neutrophils decreased after parturition in cows with RPM or metritis, but not with mastitis. Immature neutrophils increased in cows with RPM or mastitis, but not with metritis; (6) In vitro treatment of neutrophils with AA metabolites and rhCSFs did not affect functions of neutrophils from either normal or abnormal postpartum cows; (7) Incubation of neutrophils in a 37$\sp\circ$C water bath for 30 minutes might restore the functions of neutrophils from cows with RPM or metritis, and further impair the functions of neutrophils from cows with mastitis.