Open Access

Franziska Nankemann, Yanchao Zhang, Janina Schmidt, Nicole Wente, Volker Krömker

• Cow-based calf rearing (dam- or foster cow-based) is gaining popularity as a relatively natural husbandry practice. However, direct udder contact by calves creates a bidirectional transmission route for pathogens. The objective of this cross-sectional study was to investigate the prevalence and concordance of mastitis-associated pathogens in the milk of cows and the saliva of corresponding calves at the time of weaning. On 15 organic dairy farms, milk samples from 269 cows and saliva samples from 403 calves were collected at weaning. Pathogen differentiation was performed via Matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF), and strain typing was additionally conducted via randomly amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR). Dominant pathogens in milk were Non-aureus-Staphylococci (NaS)/Mammaliicoccus spp. and Corynebacterium spp., and in calf saliva, NaS/Mammaliicoccus spp. (primarily M. sciuri, S. xylosus). There were a total of 12 strain concordances, exclusively in foster cow–calf pairs (Fisher’s exact test, p = 0.012). The highest observed/expected ratio was found for P. multocida (21.1). For S. aureus, strain matches were found in 3 foster cow–calf pairs across 2 farms. Direct strain concordance was generally observed rather rarely. The observed strain concordances suggest transmission between cows and calves, particularly for S. aureus and P. multocida. NaS and Mammaliicoccus spp. concordances are likely attributable to a common environmental source.