The objective of this studywas to evaluate the effect of subcutaneous supplementation of 300mg of zinc,
50 mg of manganese, 25 mg of selenium, and 75 mg of copper on peripheral blood leukocyte activity and
serum β-hydroxybutyrate (BHBA) concentrations at 10 ± 2 days in milk (DIM), and on serum superoxide
dismutase (SOD) activity during the transition period and subsequent lactation of multiparous Holstein
cows. A total of 250 multiparous cows were randomly allocated into one of two treatments groups,
namely, trace mineral supplemented (TMS) or control. Cows in the TMS group were injected at 230 and
260 days of gestation, and 35 days postpartum. Serum SOD activity wasmeasured at enrollment, and 10,
60 and 100 DIM. Serum BHBA concentration and leukocyte function were assessed at 10 DIM. Overall
serum SOD activity for TMS and control was 16.01 and 12.71 U/mL, respectively. The interaction between
treatment and time of serum collection was significant. Additionally, overall serum SOD activity was
12.85 and 14.78 U/mL for cows diagnosed with mastitis and unaffected cows, respectively. Treatment did
not affect leukocyte function. For parity >2, TMS cows had lower serum BHBA concentrations than
control cows; BHBA concentrations were 0.41 and 0.27 mmol/L for control and TMS cows, respectively.
In conclusion, cows diagnosed with mastitis had decreased serum SOD activity, and trace mineral
supplementation increased serum SOD activity although leukocyte function was not affected by
supplementation.