PS2-5. β-defensin, Cytokine, and C-reactive Protein Expression Within Blood in Calves diagnosed with Bovine Respiratory Disease Indicated by Elevated Body Temperature.

Abstract

Bovine respiratory disease (BRD) represents a complex disease that entails intricate interactions with the host immune system and is one of the largest sources of financial loss in the U.S cattle industry. An important component of the host immune system is a group of antimicrobial peptides with activity against bacteria and viruses, collectively known as β-defensins. These peptides function as the first line of defense against major infections and are likely expressed in association with BRD. Therefore, the objectives of this study were to1) characterize DEFB403 as a defensin gene marker and 2) determine if DEFB403 is related to pro-inflammatory marker expressions when calves were challenged with BRD. Rectal temperature and whole blood samples were collected on D 0, 1, 2, and 3 at 0800h from post-weaned crossbred beef calves (n = 9; average BW 278.1 ± 36 kg), for pro-inflammatory markers IL-6, IL1-β, TNFα, CRP, and β-defensin gene expression. Rectal temperatures were used to assign BRD status where sick calves had a rectal temperature ≥ 39.4 °C while healthy had a rectal temperature ≤ 39.4 °C. Gene expression was determined by qPCR using the 2-ΔΔCt method. Data were analyzed using the GLIMMIX procedures of SAS. Significance was declared at (P ≤ 0.05). Morbidity status did not significantly affect IL-6, IL1-β, TNFα, CRP, or DEFB403 expression (P = 0.45, 0.25, 0.14, 0.29, and 0.41, respectively), indicating no detectable univariate association between these gene markers and BRD. Results indicated individual markers had no significant association with health status. Ultimately, additional research is required to establish the conclusive relationship between pro-inflammatory cytokines and β-defensins when BRD is prevalent. Furthermore, additional β-defensins should be investigated for their relationship in the host immune response against BRD.