Cell function in the bovine mammary gland: a preliminary study on interdependence of healthy and infected udder quarters

Abstract

Udder defence mechanisms are not completely explained by current mastitis research. The anatomical construction of the udder implies that infection of one udder quarter does not influence the immune status of neighbouring quarters. To test this hypothesis, we compared the immune reactions of individual udder quarters in response to microbial attacks. In the course of immune reactions, polymorphonuclear leucocytes (PMN) release oxygen radicals, which can be determined by chemiluminescence (CL). Milk from 140 udder quarters of 36 cows was analysed for somatic cell count (SCC), differential cell count, viability and CL activity. Quarters with an SCC P=0·0012) lower in group A (72·6%) than in healthy quarters of group C (84·0%). Lowering the SCC limit of healthy quarters to (2929 CL units/million PMN) was markedly lower than that of the other groups (5616 in group A _{and 6445 CL units/million PMN in group C). These results allow the conclusion that the infection of one udder quarter influences the cell activity of neighbouring quarters. When the SCC threshold for healthy quarters was reduced to 50000 cells/ml, greater differences in cell activities were detected between healthy udders and healthy quarters of infected udders.}