Sows intramammarily inoculated with Escherichia coli.: Influence of time of infection, hormone concentrations and leucocyte numbers on development ofdisease

The aim of this study was to identify factors that influence the developmen t of disease in sows inoculated with Escherichia coli in the mammary gland. Ten cross-bred primiparous sows were intramammarily inoculated with living E.. coli bacteria at different time points before parturition: seven sows within 48 h before parturition and three sows approximately 96 h before par turition. Before and after inoculation, blood samples and mammary gland bio psy specimens were collected and clinical observations were made. All seven sows inoculated close to parturition developed a rectal temperature of > 3 9.5 degreesC during the first 48 h post-partum and two of them also showed other signs of clinical disease. In the sows inoculated 4 days before partu rition, the rectal temperature never exceeded > 39.5 degreesC during the fi rst 48 h post-partum and none of them showed any other sign of clinical dis ease. There was a tendency (P < 0.1) that histological signs of mastitis we re more frequent in the sows inoculated close to parturition. There were no overall differences between the two groups of sows in plasma concentration s of cortisol, oestradiol-17 beta and 15-ketodihydro-PGF(2 alpha) before in oculation. Before inoculation, the number of neutrophils in the blood was o verall higher (P < 0.05) in the group of sows that were inoculated close to parturition. In comparison, the number of lymphocytes before inoculation h ad a tendency (P < 0.1) to be lower in that group. The data suggest that th e time of infection of the mammary gland relative to parturition and the nu mber of circulating neutrophils at the time of infection influence the deve lopment of clinical coliform mastitis in the sow.