Dietary supplementation with grape seed extract improves energy metabolism by enhancing the production of inosine in the rumen of dairy cows

Abstract

Background The ruminal microbiota plays a key role in the supply of nutrients and energy-generating compounds to the animal. However, during the transition into lactation dairy cows experience dysbiosis of the microbial community and negative energy balance, both of which render animals prone to metabolic disorders and decreased milk production. Grape seed extract (GSE) can modulate the ruminal microbiota in vitro, but whether it could improve energy metabolism and inflammation during the transition period is unclear. Results Feeding GSE during the transition period led to greater milk yield and lower milk somatic cell count. In addition, GSE led to greater concentrations of glucose and lower concentrations of non-esterified fatty acids, β-hydroxybutyric acid, acute-phase proteins (haptoglobin and serum amyloid A), and the activity of alanine aminotransferase and aspartate aminotransferase in serum. The ruminal microbiota composition and their metabolites were altered, with the concentration of microbiota-derived inosine being greater both in serum and rumen due to feeding GSE. There was a positive correlation in cows fed GSE between inosine and abundance of differentially enriched genera, better milk performance and improved metabolic and inflammation-related markers. In vitro studies showed that inosine acted through adenosine receptors to reduce lipid accumulation, and increase insulin sensitivity and gluconeogenesis in hepatocytes, and inhibit lipolysis and inflammation in adipocytes. In dairy cows with ketosis, inosine treatment alleviated negative energy balance, liver injury, and hepatic lipid accumulation, enhanced insulin sensitivity, and decreased lipolysis and inflammatory response in adipose tissue. Conclusions GSE improves energy metabolism and inflammatory state around parturition by promoting the production of ruminal microbiota-derived inosine. Thus, feeding GSE and inosine can be a potential strategy to alleviate metabolic disorders and inflammation in dairy cows during the transition period.