Impact of an Injectable Trace Mineral Supplement on the Immune Response and Outcome of Mannheimia haemolytica Infection in Feedlot Cattle

Abstract The study aimed to assess the impact of injectable trace mineral (“ITM”; Multimin90; Fort Collins, CO) supplementation on bacterial infection in cattle. Angus-crossbred steers ( n = 32) were organized into two blocks by initial body weight. Steers were maintained on a ryelage and dry-rolled corn-based growing diet without supplementation of Zn, Cu, Mn, and Se for the duration of the study. The steers were transported 6 h, then randomized into three treatment groups: control received sterile saline (“CON”), ITM administered 1 day after transport (6 days before infection, “ITMPRE”), and ITM administered 2 days post infection (dpi) concurrent with antibiotic treatment (“ITMPOST”). Steers were infected with Mannheimia haemolytica on day 0, and all were treated with tulathromycin at 2 dpi. Plasma levels of Zn, Cu, and Se did not differ among treatments ( P ≥ 0.74). Liver Se was higher in ITMPRE at 2 dpi ( P 0.10) were observed for bacterial detection from bronchoalveolar lavage (BAL) or nasopharyngeal swabs. At 5 dpi, both ITMPRE and ITMPOST showed higher frequencies of γδ T cells and NK cells in BAL compared to CON ( P < 0.05). Before infection, leukocytes from ITMPRE steers produced more IL-6 ( P < 0.01) in response to stimulation with the TLR agonist, Pam3CSK4. Use of ITM may be an effective strategy for improving disease resistance in feedlot cattle facing health challenges.