Longitudinal dynamics of plasma bile acids and its associations with physiological parameters and fecal microbiome during the transition period in dairy cows.

Abstract

Objective: The aim of this study is to investigate the dynamic changes of plasma bile acids (BA) and their associations with physiological metabolisms and fecal microbiome in transitional dairy cows.

Methods: Twenty multiparous dairy cows were selected, the blood and fecal samples were collected at d -21, -7, +7, and +21 relative to calving. The targeted metabolome and 16s rDNA gene sequencing were applied to detect BA profiles and fecal microbial composition, respectively.

Results: Totally, 32 BA species including 9 primary BAs (PBA) and 23 secondary BAs (SBA) were identified. Most of the PBAs (7 out to 9) and SBAs (15 out to 23) exhibited significant increases postpartum compared to prepartum. Notably, ursodeoxycholic acid, taurocholic acid and 7-ketodeoxycholic acid showed higher importance. Correlation analysis showed the BAs concentrations positively correlated with the concentrations of aspartate aminotransferase, total antioxidant capacity, and glutathione peroxidase, but negatively correlated with the concentrations of triglyceride significantly. A decline in bacterial alpha diversity in postpartum and significantly different β-diversity were observed. Additionally, 30 significant different genera were identified over the transition period. Among these, six and eleven biomarkers such as Alistipes and Ruminococcaceae_UCG_014 were identified at +7d and +21d, respectively. Furthermore, the abundances of choloylglycine hydrolase and 7-alpha-hydroxysteroid dehydrogenase involved in SBA biosynthesis were significantly higher postpartum as determined by PICRUSt2 analysis over the transition period.

Conclusion: These findings underscore a significant surge in the demand for BAs for postpartum dairy cows and highlight the potential impact of BAs on bovine health. By shedding light on these metabolic dynamics, our study offers valuable insights into strategies for optimizing the nutrition and well-being of perinatal dairy cows.