Evaluating the effect of liver copper concentration on vaccine response in lightweight dairy-beef steers

Dairy-beef crossbred calves often face greater copper exposure than native beef calves, which may affect their response to vaccines. To investigate this, 28 weaned dairy-beef steers (90.25 ± 1.28 kg; ∼8 wk old) were enrolled in a study to determine the effect of copper status on the antibody response to vaccine. Steers were blocked by BW into pens, and pens were randomly assigned to one of 2 dietary treatments: adequate liver Cu (ADE; fed no supplemental Cu) and excess liver Cu (HCU; supplemented with 20 mg Cu/kg DM). Steers were housed in pens of 6 to 8 animals for 82 d before d 0 of the vaccination period to create distinct liver Cu groupings. Seven days before initial vaccine dose, liver biopsies were collected, and steers were grouped into ADE (n = 13) and HCU (n = 15) treatments. Liver copper for ADE averaged 291 ± 24 mg/kg DM (range 240 to 376 mg/kg DM) and for HCU averaged 665 ± 23 mg Cu/kg DM (range 519 to 893 mg/kg DM). All calves were vaccinated on d 0 and boostered 21 d later with Bovilis Vista 5 SQ (Merck Animal Health, Madison, NJ) and an ovalbumin vaccine. Blood samples were collected on these days and again on d 49 to end the study. Serum antibody titers for bovine respiratory syncytial virus (BRSV), bovine herpesvirus 1 (BHV1), bovine viral diarrhea virus 1, and bovine viral diarrhea virus 2 (BVDV2) were analyzed by the Iowa State University Veterinary Diagnostic Laboratory (Ames, IA). Response to ovalbumin vaccination was determined using an ELISA. Plasma copper concentrations were determined on d 0, 21, and 49 via inductively coupled plasma-optical emissions spectrometry. Ovalbumin antibody production was determined by calculating the ratio of each sample to a positive control. Antibodies for BRSV, BHV1, and BVDV2 increased across days, but there were no differences by treatment, indicating that both treatments responded equally to the modified live vaccine. Ovalbumin antibodies were affected by treatment by day, where HCU had greater response to ovalbumin than ADE on d 21, but by d 49 ovalbumin antibodies were similar between treatments. These results suggest excessive liver copper concentrations may cause more rapid antibody production in response to certain antigens; however, more research is needed to determine the effects of increased liver Cu concentration on inflammation and immune system function.