Relationship between mammary gland infections and some milk immune parameters in Sardinian breed ewes

Over the last few years an increased rate of intramammary infections caused by environmental and opportunistic pathogens has been observed in sheep farms. The presence of these microorganisms is mainly related to poor conditions of environmental hygiene and/or to decreased defenses of the mammary gland. The work we present here is a part of a project on the immune status of ewe mammary gland and its influence on mastitis development. In this paper, we have studied how intramammary infections caused by opportunistic pathogens reflect on immune parameters in ewe milk. Milk samples collected monthly before the morning milking, were screened for the presence of microorganisms and tested for somatic cell counts (SCC), polymorphonuclear neutrophil leukocytes (PMN), phagocytic activity, lysozyme content, and NAGase activity. Data showed that phagocytic activity was significantly higher in bacteriologically negative udders (156 mV/1000 PMNs) than in infected udders (10 mV/1000 PMNs). These results suggest that intramammary infection might be associated with a decrease of mammary gland immune status.