A Characterization of Inflammatory and Structural Markers within the Rumen Epithelium During Grain-Induced Ruminal Acidosis in Lactating Dairy Cattle

The objective of this study was to characterize the mRNA and protein expression of inflammatory and structural genes in the rumen epithelium during grain-induced ruminal acidosis in lactating dairy cattle. A total of 16 rumen-fistulated, lactating Holstein dairy cattle (618±35 kg of body weight, 221±32 days in milk) were used in a randomized complete block design study. All cattle were initially fed a high-forage diet (HF; 88.9% of dry matter) and after a baseline (wk 0) measurement, half of the cattle were randomly assigned and transitioned to a high-concentrate diet (HC; 62.2% of dry matter) which was fed for 3 weeks (weeks 1, 2 and 3). Continuous ruminal pH, ruminal LPS and plasma LPS-binding protein were measured each week followed by a rumen papillae biopsy used for mRNA and protein quantification. After the baseline period, ruminal LPS was higher in HC compared to HF cattle (28851±6905 vs. 5771±3042 EU mL^-1). There was no difference in mRNA expression of inflammatory and structure genes in rumen papillae between HF and HC cattle during all weeks. With regard to protein expression, there was an up regulation (p = 0.02) of nuclear factor of activated T-cells cytoplasmic 2 expression during weeks 1, 2 and 3; however, all other inflammatory markers within the rumen epithelium were unchanged by treatment. These results suggest that although grain-induced ruminal acidosis leads to characteristic whole-animal inflammatory response, only marginal changes in inflammatory and structural gene and protein expression in the rumen epithelium were detected.