PSII-1 Beef steers divergent in average daily gain have differential expressions of immunity-related genes in whole blood

Abstract

Abstract We evaluated the whole-blood immune-related gene expression profiles in beef steers divergent in average daily gain (ADG). Forty-eight healthy Angus crossbred beef steers (21 d post-weaning; 210 ± 12 kg of BW) from a single source were housed in individual slatted floor pens and were fed similar corn silage-based total mixed ration ad libitum. After 42 days of feeding, the steers were assigned into two groups with lowest ADG (LF: n = 8) and highest (HF: n = 8) ADG. The average daily DM intake of the steers in LF and HF were 6.08 kg ± 0.57 and 6.04 kg ± 0.42, respectively, and was similar between the two groups (P = 0.72). Whole blood samples were taken from both LF and HF steers and were immediately processed for RNA extraction. Messenger RNA expressions of 84 genes related to innate and adaptive immune responses were analyzed using the RT2 Profiler cow innate and adaptive immune responses PCR Array (PABT-052ZA; Qiagen). Immune genes with FC ≥ 1.2 or ≤ 0.83 having P-value ≤ 0.05 were considered to be differentially expressed. A total number of 11 immune genes were differentially expressed between HF and LF steers. The mRNA expressions of 10 immune genes (IRF3, TLR3, CCR4, MAPK3, TYK2, STAT3, STAT4, STAT6, CCR8, and GATA3) were upregulated in HF steers; these genes were involved in viral pathogen recognition and eradication, defense against intracellular and extracellular pathogens and parasites, and immune response homeostasis. A pro-inflammatory cytokine, IL-2, was upregulated in LF steers. These findings demonstrate that beef steers with divergent ADG had differential expressions of immune-related genes in the blood and future studies are needed to evaluate the mechanisms that cause differences in the expression of these immune genes and how these mechanisms can be employed to drive improved animal performance.