Related Experiment Video
Updated: Aug 22, 2026
Bovine Mammary Gland Biopsy Techniques
Published on: December 23, 2018
[Quantitative pathogen shedding in intramammary infections - a practical study with Bavarian dairy cows]
Klara Kalverkamp1,2, Wolfram Petzl2, Ulrike Sorge1
1Eutergesundheitsdienst und Milchhygiene, Tiergesundheitsdienst Bayern e.V., Poing.
Subject And Objective:
The objective of this Bavaria-wide cross-sectional field study was to describe the extent of selected quantitative bacterial pathogen shedding in quarter milk samples from lactating dairy cows. The association between pathogen shedding, udder health, and seasonal influences was evaluated.
Materials And Methods:
Randomly selected dairy farms (N=305) from all Bavarian administrative districts were visited once over the course of a year. A total of 58,108 quarter milk samples were taken from 14,700 cows and examined microbiologically. Pathogen shedding was determined semi-quantitatively (1-10 cfu/0.01ml to>200 cfu/0.01ml) per quarter. For the statistical analysis the 5 shedding classes were summarized into 3 categories.
Results:
The level of bacterial pathogen shedding varied depending on the health status of the udder quarter. Healthy quarters were more likely to show low or medium bacterial counts than subclinically or clinically affected quarters. For Staphylococcus aureus, the probability of low shedding (1-10 cfu/0.01 ml) was more than twelve times higher in healthy quarters than in clinically affected quarters. Streptococcus uberis and Streptococcus dysgalactiae were also predominantly shedded in medium concentrations in healthy quarters. For Staphylococcus aureus, there was also a seasonal effect with low pathogen shedding being observed less frequently in summer than in winter. For Escherichia coli and Streptococcus agalactiae, no reliable conclusions could be drawn due to overall low detection rates.
Conclusions:
The study showed that even clinically inapparent animals may shed relevant amounts of pathogenic bacteria. This confirms that milk somatic cell count alone is insufficient to fully assess udder health or infection status.
Clinical Relevance:
Targeted microbiological herd testing is a necessary supplement to somatic cell count analysis. It enables the detection of hidden sources of infection and may help in preventing spreading as well as new infections.
