Acute ruminal acidosis (ARA) is a detrimental metabolic digestive disorder in ruminants, triggered by sudden intake of high-concentrate diets such as corn and wheat flour. This condition leads to a sharp drop in rumen pH and excessive accumulation of fermentation products like L-lactic acid, D-lactic acid, and lipopolysaccharides (LPS), which can enter the bloodstream. Using a sheep model, we investigated the link between ARA and systemic inflammation. Acidotic sheep exhibited significantly greater concentrations of LPS and D-lactic acid in both rumen fluid and plasma, which were associated with elevated levels of acute phase proteins and pro-inflammatory cytokines in blood and liver tissues, confirming systemic inflammation. In vitro studies further revealed that LPS and D-lactic acid stimulated strong inflammatory responses in peripheral blood mononuclear cells (PBMC), while only LPS had a similar effect on primary hepatocytes. L-lactic acid showed no inflammatory activity in either cell type. These findings are important because they show for the first time that besides LPS, blood D-lactic acid is also responsible for systemic inflammation during ARA. This new understanding of the pathophysiology of ARA could lead to novel strategies to manage it, for example, by monitoring or reducing D-lactic acid buildup during ARA.

Read the full article in the Journal of Animal Science.