Insight Into the Complex Dynamics of Diverse Endometrial Microbial Communities in Dairy Cows During the Transition Period: Normal Condition Versus Pathology

Background: Dysbacteriosis of the reproductive tract is a risk factor for the development of postpartum endometritis in cows. Understanding the complex dynamics of diverse endometrial microbial communities in dairy cows during the transition period, when healthy and compared to with a pathology, is crucial for developing the appropriate measures to control postpartum endometritis depending on the livestock farming system used. The aim of this study was to analyse the endometrial microbiome changes in cows during the transition period in two separate experiments on an industrial (IF) and an organic farm, or eco-farm (EF). Methods: Samples were taken on Days 20 (D−20) and 10 (D−10) before calving, at calving (D0), and on Days 3 (D+3), 5 (D+5) and 20 (D+20) postpartum. On IF, the samples were divided into three groups: healthy (IF1H), subclinical (IF2S) and purulent-catarrhal endometritis (IF3E) animals. To investigate the abundance of microbial operational taxonomic units (OTUs) and dynamics of endometrial microbiota composition, quantitative real–time PCR was used. The obtained macroecological time series data was additionally analyzed using the Hurst exponent approach. Results: In Group IF0, one of the total bacterial count peaks was observed on D0, reaching an average of 5.0 × 106 DNA copies/mL, which was 100-fold higher than on D–20 (p < 0.001) and 38.4-fold higher than on D–10 (p < 0.01). Abundance of Fusobacterium, Sneathia and Leptotrichia were 125 times higher in Group IF3E compared to Group IF1H. On IF, a high concentration of Aspergillus was also observed. On EF, these micromycetes were present only at the time of calving. Variability in the number of micromycetes Aspergillus and Fusarium spp. differed depending on the state of the reproductive system. The Hurst exponent-based analysis suggested a somewhat more persistent tendency in the short-time shifts observed in endometrial microbial communities in cows from EF. Conclusions: During the transition period, the endometrial microbiome on both farms underwent macroecological changes associated with the state of reproductive health and temporal fluctuations in microbiota abundances. The results of the study can be used to develop strategies for the prevention and treatment of postpartum endometritis in cows.