LAUSR

ABSTRACT Previous studies reported heightened innate and humoral immune responses among cattle administered injectable trace minerals (ITM) concurrent to immunogen challenge, thus suggesting a potential adjuvant-like activity of ITM. To pursue this concept further, a two-year study was conducted at the Mountain Research Station (North Carolina State University, Waynesville) to evaluate immunological responses of Angus heifers (n = 22, 235 ± 18 kg of BW and 225 ± 4 d of age in yr 1; n = 36, 237 ± 6 kg of BW and 247 ± 5 d of age in yr 2). On d 0 (30 days after weaning), heifers were administered two 5-mL i.m. injections of porcine red blood cells (PRBC; Lampire Biological Laboratories, Pipersville, PA) solution (25% PRBC and 75% sterile PBS; Amresco, Solon, OH), concurrent to either a single 2.5-mL s.c. injection of sterile saline (SAL; 0.9% NaCl), a squalene-based oil-in-water adjuvant (ADJ; AddaVax; InvivoGen, Inc. San Diego, CA) that specifically induces a humoral immune response, or injectable trace minerals (ITM; MultiMin 90; MultiMin USA, Inc. Fort Collins, CO; 60, 10, 15 and 5 mg/mL of Zn, Mn, Cu and Se). During the 28-d study, heifers were offered tall fescue hay (Lolium arundinacea) and concentrate at 1.2 and 1.0% of BW (DM basis), respectively, blended with 114 g daily of a complete mineral mix. Shrunk BW was recorded on d 0 and 28 following 12 h of feed and water withdrawal. Blood samples were collected on d 0, 2, 7, 15, and 21 for determination of antibody titers against PRBC and plasma concentrations of ceruloplasmin and haptoglobin. Liver biopsy samples were collected 1 mo prior to weaning and on d 15 after weaning for determination of trace mineral status. No differences were detected (P ≥ 0.13) for BW change, ADG, G:F, or DMI. Liver Se concentrations on d 15 were greater (P ≤ 0.01) for heifers receiving ITM compared to SAL and ADJ treatments. Plasma haptoglobin concentrations on d 2 were greatest for ADJ (P