Subacute ruminal acidosis affects fermentation and endotoxin concentration in the rumen and relative expression of the CD14/TLR4/MD2 genes involved in lipopolysaccharide systemic immune response in dairy cows

Abstract

The first objective of this study was to investigate the effects of subacute ruminal acidosis (SARA) on fermentation, ruminal free lipopolysaccharides (LPS), and expression of the cluster of differentiation 14 (CD14), toll-like receptor 4 (TLR4), and myeloid differentiation protein 2 (MD2) complex in white blood cells involved in the systemic immune response in dairy cows. The second objective was a study of whether increased expression of the LPS receptor complex led to increases in the concentrations of plasma high-density lipoprotein (HDL) and serum Ca. Three hundred five dairy cows located in 13 Polish high-yielding dairy commercial farms were selected according to their days in milk (40-150 d; average = 75), 305-d milk yield (10,070-12,041 kg; average = 10,940), and number of lactations (primiparous, n = 139 and multiparous, n = 166). Next, the herds were segregated into 3 groups based on the percentages of cows with an assigned value of ruminal fluid pH: SARA-positive, SARA-risk, and SARA-negative herds. Moreover, 305 selected dairy cows were divided according to the classification based on ruminal fluid pH into 3 groups as healthy (pH >5.81), risk (pH 5.8-5.6) and acidotic cows (pH <5.6). Rumen fluid samples were collected via rumenocentesis. In the AC group, we recorded higher concentrations of ruminal free LPS [4.57 Log endotoxin units (EU)/mL; 42,206 EU/mL] compared with the healthy group (4.48 Log EU/mL; 34,179 EU/mL). Similarly, the concentration of ruminal free LPS was higher in SARA-positive herds (4.60 Log EU/mL; 43,000 EU/mL) compared with SARA-negative herds (4.47 Log EU/mL; 32,225 EU/mL). The relative mRNA abundance of genes associated with the function of LPS receptors, such as CD14, TLR4, and MD2, in white blood cells differed between all experimental groups on both cow and herd levels. In the acidotic group, we recorded higher concentrations of HDL (78.16 vs. 68.32 mg/dL) and serum amyloid A (10.80 vs. 9.16 µg/mL) and lower concentrations of Ca (8.26 vs. 10.16 mg/dL) and haptoglobin (470.19 vs. 516.85 ng/mL) compared with the healthy group. Similar results were obtained in the SARA herd status analysis, but the concentration of lipopolysaccharide-binding protein differed statistically. Moreover, the pH of ruminal fluid was negatively correlated with relative mRNA abundance of genes such as CD14, TLR4, MD2, and concentrations of serum HDL and serum amyloid A, although positively correlated with serum Ca. The results indicated that decreases in ruminal fluid pH increased the release of free LPS into the rumen and stimulated the expression of the LPS receptor complex and immune response. Moreover, an increase in the expression of the LPS receptor led to higher concentrations of plasma HDL and lower serum Ca, which may be a protective mechanism against endotoxemia. However, the biological significance of these results needs to be investigated further in larger field trials.

Effects of ruminal pH on gene expression in the rumen epithelium, peripheral blood mononuclear cell subpopulations, and blood metabolites from Holstein calves during weaning transition

“…Meanwhile, Stefanska et al . [26] reported that peripheral blood mRNA abundance of CD14 was higher ( P ≤0.01) in SARA-risk and -positive herds compared to SARA-negative herds, and was negatively correlated ( P ≤0.01) with ruminal pH. In the present study, however, decrease in the number of CD14 + cells was found in both groups, which is not consistent with the previous study [26].…”

Effect of high-concentrate corn grain diet-induced elevated ruminal lipopolysaccharide levels on dairy cow liver function

“…This result was likely due to the slight ruminal LPS level increase in the HC group. In a previous study, without feed treatment, the rumen LPS concentrations in the healthy and SARA groups in 13 farms were 34,179 and 42,206 EU/ml, respectively [35], which is consistent with the level recorded in our study. In contrast, the ruminal LPS level in grain-induced SARA cows was 12,589-168,391 EU/ml (3.4 to 16.2 times higher than that in the control) [10][11][12]33].…”

Dynamic ROS Production and Gene Expression of Heifers Blood Neutrophil in a Oligofructose Overload Model

“…TLR4 is important for the recognition of Gramnegative bacteria. In clinically SARA-positive cows, TLR4 had a higher relative mRNA level (22). Although plasma LPS was not measured in the current study, the upregulated TLR4 expression indicates the possibility that LPS was involved in the inflammatory response of OF-induced ARA.…”