Submitted to: Animal Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2017
Publication Date: 7/13/2017
Publication URL: http://handle.nal.usda.gov/10113/5801841
Citation: Reynolds, J.G., Foote, A.P., Freetly, H.C., Oliver, W.T., Lindholm-Perry, A.K. 2017. Relationships between inflammation- and immunity-related transcript abundance in the rumen and jejunum of beef steers with divergent average daily gain. Animal Genetics. 48(4):447-449. doi:10.1111/age.12546.
Interpretive Summary: The health status of the rumen and small intestine is important for efficient nutrient absorption. Additionally, the gastrointestinal tract is a first-line defense in preventing infections. The inflammation and immune response that the rumen and small intestine have in response to microbes and foreign particles can require a large amount of energy and vital nutrients that could otherwise be used for growth. However, it is important that these tissues have an adequate response to prevent infections. This experiment was conducted to determine expression of genes related to immune function and inflammation are associated with greater or lesser average daily gain of feedlot steers. No genes were found to be differentially expressed in the jejunum of these steers. A total of 9 genes were found to be expressed at a lower level in the rumen of steers with greater average daily gain. These genes included chemokines, cytokines, and cytokine receptors. It appears that cattle with greater average daily gain have less inflammation in the rumen. A reduction in inflammation could lead to a more efficient rumen due to less energy and nutrients required to mount an inflammatory response.
Technical Abstract: The bovine rumen papillae are in contact with a wide array of microorganisms and the metabolites they produce, which may activate an inflammatory and/or immune response. Cytokines, chemokines and their receptor genes were tested for differential expression in the rumen and jejunum of beef steers with greater and lesser average daily body weight gain (ADG) near the average daily dry matter intake (DMI) for the population. Angus-sired steers (n = 16) were used to represent the greater (ADG = 2.2 +/- 0.07 kg/day; DMI = 10.1 +/- 0.05 kg/day) and lesser (ADG = 1.7 +/- 0.05 kg/day; DMI = 10.1 +/- 0.05 kg/day) ADG groups with eight steers each. Rumen epithelium and jejunum mucosal samples were collected at slaughter, and gene expression was evaluated using a commercially available qRT-PCR array containing 84 genes representing chemokines, cytokines and their receptors. None of the genes on the array were differentially expressed in the jejunum of the steers with greater vs. lesser ADG. However, in the rumen, two chemokine genes (CCL11, CXCL5) and one receptor gene (IL10RA) were detected as differentially expressed (P < 0.05). The genes IL1A, BMP2, CXCL12 and TNFSF13 also displayed trends for differential expression (P < 0.10). All of the genes identified were lower in transcript abundance in the greater ADG animals. Thus, greater ADG steers have a lesser inflammatory response in the rumen papillae, which may lead to a more efficient use of nutrients.