The Effects of Collecting Bovine Milk Samples Premilking and Postmilking on the Results of Bacteriologic Analysis and Somatic Cell Count

Milk sample collection before attaching the milking cluster for bacteriological and cytological examination is a standard clinical diagnostic procedure in dairy production. Collecting samples premilking can be difficult under certain field conditions. Therefore, we aimed to determine the effect of the timing of milk sampling on the results of bacteriologic analysis and somatic cell count. The study was conducted on a dairy herd of 1520 German Holstein cows. From 110 cows selected because of previously high somatic cell count, paired milk samples (premilking and postmilking) were taken and submitted for bacteriological and cell count analysis. The somatic cell score (SCS) was significantly higher in postmilking samples than in premilking samples (p = 0.001). A total of 113 of 433 premilking and 69 of 433 postmilking samples had positive bacteriologic culture. Quarter samples with a positive bacteriologic culture had numerically higher SCS estimates than negative samples. Mammary quarters with positive premilking and negative postmilking cultures had a significantly lower SCS than quarters with positive premilking and postmilking cultures (p < 0.05). Our findings suggest that premilking and postmilking samples differ in bacteriological and cytological composition. Therefore, the sampling strategy has to be taken into account when making treatment and prevention strategy decisions based on milk samples.