Increasing condensed corn distillers solubles affects gene expression in rumen epithelial tissue
Five ruminally-fistulated steers were used in a 5 × 5 Latin square design to determine the effects of increasing dietary fat from corn distillers solubles (CDS) on the gene expression within rumen epithelial tissue. Treatments included a corn-based control (CON), and four levels of CDS (0, 10, 19, and 27%) in a coproduct-based (corn gluten feed and soybean hulls) diet. Fat concentrations were formulated to 3, 5, 7, and 9%, respectively, for diets containing CDS, and all steers were fed to ad libitum intake once daily. After 18 d of adaptation to the diet, ruminal epithelium tissue was collected and frozen in liquid N. Real-time quantitative PCR was used to determine dietary effects on expression of genes related to fatty acid oxidation, ketogenesis, transcriptional regulation, and monocarboxylic transporters. Data were analyzed using the MIXED procedure of SAS with treatment and period as fixed effects and steer as the random effect. Pairwise comparisons were implemented to separate means. Genes associated with long chain fatty oxidation (CPTIA, ACADS, and ACADS) were affected by treatment (P ≤ 0.01). Steers fed 10% CDS diet had the least epithelial mRNA expression of CPTIA and ACADSB compared with all other treatments (P < 0.01). ACADS epithelial mRNA expression was decreased in epithelial tissues of steers fed 0 and 10% CDS diets. Among genes related to ketogenesis, HMGCS2 was affected by treatment (P = 0.02); epithelial mRNA expression remained similar for CON, 0%, 19%, and 27% CDS, but HMGCS2 was downregulated for steers fed 10% CDS diet. Although ACAT1 was affected by treatment (P = 0.04), CON and 10% CDS had less expression compared to 19% CDS treatment (P ≤ 0.01). Expression of transcriptional regulation-associated genes (PPARA and RXRA) in rumen epithelium was not consistent. PPARA mRNA expression was the greatest for 27% CDS treatment and alternatively the least for 10% CDS. However, RXRA was affected by treatment (P = 0.04); epithelial mRNA expression was decreased at 10, 19, and 27% inclusion of CDS compared with the greatest expression for steers fed CON diet. SLC16A1, a monocarboxylic transporter-related gene, expression was increased for steers fed 0% CDS compared with 10 and 27% CDS treatments. Results indicate different concentrations of CDS alter the rumen epithelium transcriptome.
Keywords: rumen, epithelium, gene expression