Ileal epithelial tissue transcript profiles of steers with experimentally induced liver abscesses

Objective: Liver abscesses in cattle negatively affect production and cause economic losses across the beef cattle industry. Recently, a nutritional model has been developed to induce liver abscesses that will provide a method to evaluate the underlying mechanisms driving their development. The objective of this study was to evaluate gene expression of ileal tissue from calves challenged using the new model. Materials and Methods: In the model, calves were fed a diet to induce ruminal acidosis and were then intraruminally inoculated with bacteria typically associated with liver abscesses. On d 21, following inoculation, calves were euthanized. Seven of the 13 calves had liver abscesses. Ileal tissues were collected and total RNA was isolated for RNA-sequencing. Results and Discussion: A total of 26 genes were differentially expressed in the calves with liver abscesses compared with those without. Two genes (COX2, COX3) are components of the cytochrome c oxidase enzyme in the electron chain transport pathway, and both were downregulated among the animals with liver abscesses. Other genes involved in cellular restructuring, transport of compounds across cell membranes, protection of RNA, and protection of protein products were also identified. These functions illustrate that there are changes in the ileal epithelium that correspond to the development of liver abscesses. Implications and Applications: We identified several genes that were differentially expressed in the ileal tissue of calves that developed liver abscesses using the combination of an acidosis-inducing diet and intraruminal inoculation of bacteria. Our results suggest that the ileum has a role in liver abscess development, and future studies to validate the involvement of the mucosal barrier of the ileum are warranted.