Diagnostic of mastitis risks: interpretation of somatic milk cell count

A somatic cell count (SCC) which is higher than 100000/ml in a quarter milk sample indicates a mastitis.Bacteriological findings have a highly significant influence on the SCC. In our investigations, quarters without pathogens always showed geometric mean values of the SCC around 50000/ml, quarters with pathogens isolated showed a three to five fold higher mean SCC, These great SCC differences also could be demonstrated in a comparision between the quarters of single cows. Different mastitis pathogens cause different SCC rises. Our investigation could underline the differentiation between minor pathogens (coagulase negative staphylococci) and major pathogens (Staphylococcus aureus). Only high herd SCC values allow a real interpretation of the udder health situation of a dairy herd, whereas low SCC values can be paralleled by quite a high incidence of clinical cases of mastitis. Herds with SCC mean values between 250000/ml and 400000/ml include about 30 per cent of cows with SCC > 250000/ml independent from the size of the herd. So the legal rules for the milk quality are not at all valuable from the point of view of mastitis control. The stage of lactation is also of high statistic significance for the SCC in bacteriologically negative quarters as well as in positive ones. Nevertheless, only the development in the positive quarters was of practical relevance for the herd SCC. As a consequence of our investigations, udder health can be scored as good, if there are less than ten per cent cows of a herd showing a SCC of > 250000/ml in three following milk controls, and less than eight per cent showing > 400000/ml in one control.