HORMONAL AND IMMUNOLOGICAL CHANGES IN BLOOD AND MAMMARY SECRETION IN THE SOW AT PARTURITION

The purpose of the present study was to record possible variations of estradiol-17 beta (E2) and cortisol concentrations, and parameters rel ated to granulocyte phagocytosis in mammary secretions from healthy so ws at parturition. The study was comprised 8 primiparous sows (Landrac e x Yorkshire). Blood and mammary secretion samples were collected twi ce daily from 3 d before (only blood) until 3 d after farrowing. Estra diol-17 beta and cortisol concentrations were determined in plasma and in cell-depleted skimmed mammary secretions. Phagocytic capacity of p olymorphonuclear cells (PMN) was assessed in whole blood and in cell s uspensions derived from mammary secretions. Opsonic activity was asses sed in serum and in cell-depleted skimmed mammary secretions. The 2 as says were based on chemiluminescence. Estradiol-17 beta concentration in plasma decreased (P<0.001) directly after parturition. In skimmed s ecretions, the highest E2 concentration was recorded in the first samp le after parturition and decreased (P<0.01) thereafter. The highest co rtisol concentration in plasma was recorded in the evening before part urition (P<0.01). In skimmed secretions, there was no significant vari ation in cortisol concentration. The concentrations of both steroid ho rmones were lower in mammary secretions than in plasma. The phagocytic capacity of PMN in blood and mammary secretion, expressed as peak che miluminescence per PMN, showed no significant change. This was also tr ue for the opsonic activity in serum. In skimmed secretions the opsoni c activity increased (P<0.01) after parturition.These data emphasize t he differences between plasma and mammary secretion concentrations of steroid hormones as well as between systemic and mammary gland immune competence. Regarding the phagocytosis process in mammary secretions, the part directly related to the PMN function seemed not to be altered at parturition compared with later on in lactation, whereas the part related to opsonic activity seemed to be impaired at parturition. The latter may play a role in the development of coliform mastitis at this time. (C) 1998 by Elsevier Science Inc.