Teat skin microbiome of dairy cows: Seasonal, farm-specific, and cleaning-related influence with emphasis on Clostridium spp.

Raw milk quality and its microbial composition critically influence cheese quality. The production of high-quality raw milk with minimal bacterial contamination requires proper teat skin hygiene. The teat skin microbiome of dairy cows is highly diverse and especially the presence of endospore-forming Clostridium spp. creates a major concern for cheesemakers, as these bacteria are primarily causing the late blowing defect in hard and semi-hard cheeses. This study aimed to assess seasonal-, farm- and cleaning-related variations of the teat skin microbiome and clostridial numbers using culture independent methods and to evaluate implications for raw milk quality. To this end, 192 teat skin swabs of eight Austrian dairy farms, before and after routine cleaning during summer, winter and spring were investigated by 16S rDNA amplicon sequencing and quantitative PCR. The quality and microbial composition of raw milk critically influence cheese quality. The production of high-quality raw milk with minimal bacterial contamination requires proper teat skin hygiene. The teat skin microbiome 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 variations in the teat skin microbiome and clostridial numbers via culture independent methods and to evaluate the implications 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 16S rDNA amplicon sequencing and quantitative PCR. Seasonal differences and variations in farm management significantly affected the diversity of the microbiome 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, with higher clostridial numbers. 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 microbiome of Austrian dairy cows, revealing pronounced differences among farms, seasons and cleaning practices.