Beef steers with average dry matter intake and divergent average daily gain have altered gene expression in the jejunum

The objective of this study was to determine the association of differentially expressed genes (DEG) in the jejunum of steers with average DMI and high or low ADG. Feed intake and growth were measured in a cohort of 144 commercial Angus steers consuming a finishing diet containing (on a DM basis) 67.8% dry-rolled corn, 20% wet distillers grains with solubles, 8% alfalfa hay, and 4.2% vitamin/mineral supplement. From the cohort, a subset of steers with DMI within +/- 0.32 SD of the mean for DMI and the greatest (high) and least (low) ADG were chosen for slaughter and jejunum mucosa collection (n = 8 for each group). Dry matter intake (10.1 +/- 0.05 kg/d) was not different (P = 0.41) but ADG was greater in the high-gain group (2.17 and 1.72 +/- 0.02 kg/d for the high-and low-ADG groups, respectively; P < 0.01). A total of 13,747 genes were found to be expressed in the jejunum, of which 64 genes were differentially expressed between the 2 groups (corrected P < 0.05). Ten of the DEG were upregulated in the low-ADG group and 54 were upregulated in the high-ADG group. Gene ontology analysis determined that 24 biological process terms were overrepresented (P < 0.05), including digestion, drug and xenobiotic metabolism, and carbohydrate metabolism. Additionally, 89 molecular function terms were enriched (P < 0.05), including metallopeptidase activity, transporter activity, steroid hydrolase activity, glutathione transferase activity, and chemokine receptor binding. Metabolic pathways (28 pathways) impacted by the DEG (P < 0.05) included drug and xenobiotic metabolism by cytochrome P450, carbohydrate digestion and absorption, vitamin digestion and absorption, galactose metabolism, and linoleic acid metabolism. Results from this experiment indicate that cattle with average DMI and greater ADG likely have a greater capacity to handle foreign substances (xenobiotics). It is also possible that cattle with a greater ADG have a greater potential to digest and absorb nutrients in the small intestine.