Dietary Zinc supplementation impact on relative frequency and innate function of peripheral bovine immune cells

Abstract

Abstract Zinc (Zn) is an essential micronutrient which is critical for optimum innate and adaptive immune function. While Zn deficiency leads to reduced growth and feed intake, the impact of Zn deficiency and supplementation on immune responses in beef cattle has not been properly addressed. To investigate to impact of dietary Zn supplementation on peripheral immune responses of growing cattle, 27 Angus crossbred steers were stratified by body weight and randomly assigned to three dietary treatments groups: 1) CON, no supplemental Zn, 2) Zn100, 100ppm of Zn or 3) Zn150, 150ppm of Zn delivered in premixes in total mixed rations. Whole blood obtained at 14 (D14) and 58 (D58) days after the start of the treatments was plated and stimulated with TLR agonists LPS (TLR4), PAM3CSK4 (TLR2/1), and Poly-I:C+Imiquimod (TLR3/7) for 48 h, then pro-inflammatory cytokine secretion was measured by ELISA on the supernatants. Additionally, whole blood was stained with surface antibodies to determine relative frequency of peripheral immune cell populations. We observed diminished IL-1ß secretion in response to Poly-I:C+Imiquimod in the CON group when compared to Zn150 (p=0.09) and Zn100 group (p=0.013) at D14 and D58, respectively. We observed no differences in IL-6 secretion upon TLR agonist stimulation between groups at any time point. Further, although no significant changes in CD4+, CD8+, TCRδ+ T cells, or CD21+MHCII+ B cells were observed, CD5+MHCII+ B cells had a higher relative frequency in the CON group when compared to Zn100 (p 0.03) and Zn150 (p 0.10) groups at D58. Future studies will address how Zn supplementation impacts the immune response to infection and disease susceptibility. This project was supported by Agriculture and Food Research Initiative Competitive Grant no. 2020-06540 from the USDA National Institute of Food and Agriculture