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The Effect of Dietary Fatty Acid Source on Gene Expression in the Rumen of Cattle

McConnell, H., A. Goldkamp, M. King, C. Salisbury, D. Montgomery, J. Moore, D. Hagen and A. Foote

The objective of this experiment was to ascertain how different fatty acid sources impacted gene expression in the rumen epithelium. The study utilized rumen cannulated Holstein steers (n = 8) in a crossover design with two 16-d periods with a 20-d washout between periods. The diets contained (DM-basis) dry-rolled corn (57%), Sweet Bran (25%), chopped prairie hay (8%), vitamin-mineral supplement (5%), and 5% of either high oleic soybean oil (Oleic) or 5% commodity soybean oil diet containing predominantly linoleic acid (Linoleic). The diets were provided ad libitum and refusals were collected and subsampled. Water access was unrestricted. Rumen papillae biopsies were taken on d-16 of each period and flash-frozen using dry ice and alcohol. RNA was extracted and sequenced using short-read sequencing. Differential gene expression (DEG) was analyzed using edgeR. Data were analyzed within periods to determine differences between treatments. In period 1, there were 25 DEG (False Discovery Rate (FDR) < 0.05) with 13 downregulated and 12 upregulated in the Oleic treatment. In period 2, there were 35 DEG (FDR < 0.05) with 12 downregulated and 23 upregulated in the Oleic treatment. The gene LILRA6, which is involved in immune function, was differentially expressed in both periods. Many of the KEGG pathways enriched were related to fatty acid metabolism, chemokine signaling, cytokine-cytokine receptor interactions, and immune function-related pathways.

Gene ontology enrichment analysis highlighted inflammatory response, chemokine-mediated signaling, and other immune-related processes. These data indicated that dietary fat composition may impact gut inflammatory and immune function.