Comparison of two sampling approaches to determine the prevalence of mastitis pathogens in dairy herds.

Improving udder health on dairy farms requires knowledge about the prevailing mastitis pathogens in order to take appropriate measures. The aim of this research communication was to evaluate the association between two sampling approaches for determining the prevalence of mastitis pathogens in dairy herds. Sampling approaches tested included (a) bacteriological investigation of randomly selected cows independent from stage of lactation (random sampling) and (b) sampling of cows two weeks prior to drying off (dry-off sampling). Using linear regression, the prevalence of mastitis pathogens were compared on herd-level for groups of specific pathogens. Associations between the prevalence estimated by the two approaches were found for Staphylococcus aureus, Streptococcus dysgalactiae, Streptococcus uberis and Gram-negative bacteria but not for other esculin-positive streptococci. This study indicated that both sampling approaches provide farmers with an overview of the prevalence of mastitis pathogens in their herds, with the dry-off results also being used to target antibiotic use to infected quarters.