The prevalence of some microorganisms in cows' milk with regard to lactation number, lactation period and somatic cell count.

The aim of this study was to assess the effect of lactation number, lactation stage and somatic cell count (SCC) on the presence of pathogenic or opportunistic pathogens in cow milk. A total of 1712 milk samples were collected from the udder quarters of 428 lactating Holstein breed cows for bacteriological examination. Somatic cell count was taken from the controlled bovine records. The cows were divided into four groups according to the lactation number (viz. lactation numbers 1, 2, 3, 4 and above) and into three groups according to the lactation month (viz. 1-4, 5-8, 9 months and above). The statistical analysis was performed by SPSS 27.0 software (SPSS Inc., Chicago, Illinois, USA). Frequencies of microorganisms were calculated by determining their confidence intervals (Wilson Confidence Interval 95%, CI). Various farm pathogens were identified: CNS (Coagulase negative staphylococci), S. aureus, Enterococcus spp., Str. agalactiae, E. coli. It was found that CNS and S. agalactiae increased with somatic cell count, lactation number and lactation stage. E. coli increased at the end of the lactation stage (p≤0.05). Enterococcus spp. count in milk differed significantly between cows in lactations 1 and 4 and older (p≤0.05). Pathogen number also increased with milk fat, but decreased with increased protein content (p≤0.01).