Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/31/2017
Publication Date: 10/13/2017
Publication URL: https://handle.nal.usda.gov/10113/5852193
Citation: Foote, A.P., Keel, B.N., Zarek, C.M., Lindholm-Perry, A.K. 2017. Beef steers with average dry matter intake and divergent average daily gain have altered gene expression in the jejunum. Journal of Animal Science. 95(10):4430-4439. https://doi.org/10.2527/jas2017.1804.
Interpretive Summary: The influence and role of the small intestine of beef cattle in feed efficiency and growth has not been well defined. The majority of research on the influence of the gastrointestinal tract on growth and feed efficiency has focused on the rumen. However, the small intestine could be equally as important in grain fed cattle as there is less reliance on fiber digestion in the rumen for energy. The goal of this study was to use next generation RNA sequencing technology to explore physiological differences in the mid-small intestine (jejunum) of cattle with average feed intake and relatively fast or slow growth rates. A total of 64 genes was found to be expressed at different levels between these 2 groups of cattle. The genes that were up-regulated in the faster growing cattle (54 genes) are largely related to digestion, absorption, and metabolizing foreign substances. If the differences in gene expression translate into real functional changes, it could indicate that the faster growing cattle are better at digesting starch into glucose, absorbing glucose, digesting protein, and protecting against oxidative stress and microbial infection. Results from this experiment indicate that it may be possible to select animals that have an improved ability to digest dietary components to achieve a greater growth rate with no additional inputs.
Technical Abstract: 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.