Teat skin microbiota of dairy cows: a study of seasonal-, farm-, and cleaning-related differences with emphasis on Clostridium spp.

The quality and microbial composition of raw milk critically influence cheese quality. Ensuring high-quality raw milk with minimal bacterial contamination requires adequate teat skin hygiene. The teat skin microbiota of dairy cows is highly diverse, especially the presence of endospore-forming Clostridium spp., which is a major concern for cheesemakers, as these bacteria primarily cause the late blowing defect in hard and semi-hard cheeses. This study aimed to assess seasonal-, farm- and cleaning-related differences in the teat skin microbiota and clostridial numbers via culture-independent methods and to discuss the potential relevance for raw milk quality. In total, 192 teat skin swabs from 382 cows on eight Austrian dairy farms, before and after routine cleaning during summer, winter and spring were investigated via 16 S rRNA gene amplicon sequencing and quantitative PCR. Seasonal differences and variations in farm management significantly affected the diversity of the microbiota and the presence of Clostridium spp. Bacterial diversity before and after cleaning was not significantly different. However, teat cleaning resulted in a mean clostridial pta -gene copy number reduction of 83.3%. This culture-independent quantification of C. tyrobutyricum strongly correlated with culture-dependent results, although the mean counts obtained by culture-dependent analyses were higher. Further correlation analysis revealed the co-occurrence of other bacterial genera, e.g. Acinetobacter and Facklamia , with C. tyrobutyricum . This study provides a comprehensive analysis of the teat skin microbiota of Austrian dairy cows, revealing pronounced differences among farms, seasons and cleaning practices.