Altered rumen bacterial flora is associated with increased lipogenesis of adipose tissue in obese dairy cows before calving.

BACKGROUND: Prepartum obesity predisposes dairy cows to a higher risk of postpartum metabolic disorder. Volatile fatty acids (VFA) produced through ruminal microbial fermentation of feed substrates serve as a key form of energy for dairy cows. However, the precise mechanisms through which the rumen microbiota promote adipocyte lipid accumulation in obese dairy cows remain to be elucidated. Thus, the aim of this study was to investigate the mechanisms by which rumen microbiota regulates prepartum obesity in dairy cows. RESULTS: Plasma glucose, insulin, triglyceride, and free fatty acids were greater in obese dairy cows. In the adipose tissue, the triglyceride content and expression of genes involved in lipid synthesis were higher in obese dairy cows. In the liver, the expression of genes involved in gluconeogenesis and lipid synthesis was higher in obese dairy cows. The ruminal total VFA, acetate, and propionate were higher in obese dairy cows compared to normal cows. The 16S rRNA gene analysis revealed that rumen bacteria, including Tidjanibacter inops_A, Rikenella massiliensis, Papillibacter cinnamivorans, and Parabacteroides merdae, were enriched in the rumen of obese dairy cows. Enrichment of these bacteria promoted carbohydrate degradation and VFA production. The metabolome analysis showed that obese dairy cows had elevated citric acid level in the rumen, which was positively associated with body condition score, body weight, adipocyte diameter, ruminal VFA concentration, and the abundance of VFA-producing bacteria. CONCLUSIONS: Our results suggest that rumen bacterial flora in prepartum obese dairy cows supply more VFA to the host, which may induce lipid deposition in adipocytes. Video Abstract.