Bovine Udder Health: From Standard Diagnostic Methods to New Approaches-A Practical Investigation of Various Udder Health Parameters in Combination with 16S rRNA Sequencing.

Abstract

Bovine udder health is an important factor for animal wellbeing and the dairy farm economy. Thus, researchers aim to understand factors causing mastitis. The gold standard for diagnosing mastitis in cows is the conventional culturing of milk samples. However, during the last few years, the use of molecular methods has increased. These methods, especially sequencing, provide a deeper insight into the diversity of the bacterial community. Yet, inconsistent results regarding the mammary microbiome have been published. This study aimed to evaluate the udder health of eight dairy cows at seven days postpartum with the standard methods in veterinary practice. Additionally, swabs from the teat canal and milk samples were analyzed using 16S rRNA gene amplicon sequencing. The sensitive low-biomass milk samples displayed only a few contaminations even though they were sampled in a field environment. In healthy udders, no bacterial communities were detected by the bacterial culture nor the 16S rRNA gene amplicons. The results from the standard examination of the cows, the cell count, and the bacteriological examination were comparable with the results from 16S rRNA gene amplicon sequencing when cows displayed subclinical or latent mastitis. Besides the pathogen detected in bacterial culturing, a second bacterial strain with low but significant abundance was detected by sequencing, which might aid in the understanding of mastitis incidence. In general, molecular biological approaches might lead to promising insights into pathological events in the udder and might help to understand the pathomechanism and infection source via epidemiological analyses.