RESUMO
Strategies to improve the onset of protective immunity induced by vaccination against respiratory pathogens may have a significant impact on health of newly received beef calves. The objective was to determine if the use of injectable trace minerals (ITM; Se, Zn, Cu, and Mn) concurrent with a modified-live virus (MLV) vaccine enhances the immune response and onset of protection in beef calves challenged with BVDV2 five days after vaccination. Forty-five calves were randomly assigned to one of three groups (15/group): VACâ¯+â¯ITM, received MLV-vaccine and ITM (Multimin®90) subcutaneously (SC); VACâ¯+â¯SAL, received the same vaccine and saline SC; or UNVAC, unvaccinated. Five days after vaccination (d.0), calves were challenged with BVDV2 strain 890. Health status was evaluated and blood samples were collected for leukocyte counts, BVDV1 and 2 serum neutralizing antibodies (SNA), BVDV-PCR, and percentage of CD4+, CD8+, WC1+ and CD25+ T-cells. VACâ¯+â¯ITM had lower health scores than UNVAC (d.8 and 9). VACâ¯+â¯ITM had higher BVDV1 & 2 SNA titers than VACâ¯+â¯SAL and UNVAC on d.21 and 28. Lymphocyte counts decreased in UNVAC but not in VACâ¯+â¯ITM or VACâ¯+â¯SAL (d.3 to 11). CD4+ T-cells significantly decreased in UNVAC and VACâ¯+â¯SAL (d.3). VACâ¯+â¯ITM had higher percentage of CD4+ T-cells than UNVAC (d.3 and 7). VACâ¯+â¯ITM had lower percentage of activated CD4+ and CD8+ T-cells than UNVAC (d.7). In summary, vaccination induced a rapid protection against BVDV2 infection. Administration of ITM was associated with increased SNA response to BVDV1 & 2, enhanced health status, mitigation of CD4+ T-cells decrease, and reduction of T-cell activation in calves challenged with BVDV2 five days after immunization. These results support the strategic use of ITM concurrent with vaccination, especially when a rapid protection is needed in newly received beef calves.