Whole blood immune gene expression in Angus bulls with divergent residual feed intake expected progeny differences

Objective

Our objective was to examine the differ- ences in the whole blood mRNA expression profiles of im- mune-related genes in Angus bulls with either negative or positive residual feed intake expected progeny differences (RFI-EPD).

Materials and Methods

Twenty Angus bulls with the most negative (n = 10; RFI-EPD = −0.29) and most positive (n = 10; RFI-EPD = 0.26) RFI-EPD values were selected from a group of 106 Angus bulls (average BW = 376 ± 36 kg; 370 ± 1.3 d of age) after a 78-d feed ef- ficiency testing period. At the end of this testing period, blood samples were collected for RNA extraction followed by the mRNA expression analysis of 84 genes involved in innate and adaptive immunity using pathway-focused PCR-based arrays. Differentially expressed genes (DEG) were determined using false discovery rate (FDR) ≤0.10.

Results and Discussion

Results from the analysis revealed a total of 5 DEG (FDR ≤0.10) in bulls with divergent RFI-EPD values. We found IL23A to be up- regulated, whereas IL18, TRAF6, TLR2, and MX1 were downregulated in negative RFI-EPD bulls, compared with the positive group. Gene ontology analysis of the DEG indicated the enrichment of different biological pathways linked to innate immune response, NF-κB signaling, cy- tokine and T cell regulation, lipopolysaccharide-mediated signaling pathway, and cellular response to bacteria.

Implications and Applications

These findings re- vealed that negative RFI-EPD bulls exhibit mRNA ex- pression of genes directly related to immune cell function and biological pathways involved in the activation of anti- microbial mechanisms, pathogen recognition mechanisms, and inflammatory response.