Evaluation of the stress-reducing effect of trace mineral injection in beef calves

Background: Little is known about the effects of trace mineral supplementation on the stress response in beef calves. Objectives: To investigate the effect of injectable trace mineral supplementation (ITM) on the stress response in beef calves exposed to different types of stress. Animals: Thirty weaned Angus and Angus crossbred calves. Methods: The enrolled calves were randomly assigned to 2 groups: ITM, 15 calves received modified-live virus vaccine (MLV) and ITM SC and 15 calves received MLV and saline SC (CONT). The calves were exposed to 3 types of stress: the stress of MLV vaccination (d0), nasal aerosol with bovine viral diarrhea virus-2 (BVDV-2) challenge (d5), and liver biopsy (d26). The calves' body weights and health status were monitored. Leukocyte counts, serum cortisol concentration ([cort]), BVDV-2 serum neutralizing antibodies (SNA), and percentages of CD4(+), CD8(+), WC1(,)(+) and CD25(+) T-lymphocytes were measured. Results: Serum cortisol concentration ([cort]) showed strong associations with the percentage of CD8(+) (r(s) = .50), BVDV2-SNA (r(s) = -.43), and WC1CD25(+) (r(s) = .41) cells, and rectal temperature (r(s) = .40). The highest [cort] was reported 3 days after aerosol BVDV-2 challenge. Serum [cort] was decreased in ITM-treated calves 3 days post-BVDV-2 challenge, compared with CONT calves, with an average decrease of 18.5 ng/mu L (95% confidence interval [CI], -6.07 to -31.3). The ITM-treated calves were heavier and healthier (P < .01) than the CONT calves. Conclusions and Clinical Importance: Trace mineral supplementation appears to have stress mitigation effects in beef cattle that may reflect positively on growth and health performance. Viral exposure is associated with a high degree of stress, which is considered a major welfare concern.