Effect of copper deficiency on tissue, blood characteristics, and immune function of calves challenged with infectious bovine rhinotracheitis virus and Pasteurella hemolytica

Fourteen Holstein steers, averaging 30 d of age, were fed a semipurified diet (1.5 mg of Cu/kg) supplemented with 0 (-Cu) or 10 mg of Cu/kg of diet (+Cu) for 5 mo. Calves were then challenged by consecutive exposure to aerosol preparations of infectious bovine rhinotracheitis virus (IBRV) and Pasteurella hemolytica on d 0 and 7, respectively, of the 30-d study. Serum ceruloplasmin and plasma copper were higher in +Cu calves throughout the challenge period and increased in +Cu calves after microbial challenge. Heart weights were higher in -Cu calves, although weights of liver, spleen, and thymus were not different between treatments. Copper concentrations in all tissues as well as thymus zinc were higher in +Cu calves. Serum immunoglobulin M tended to be higher in +Cu calves and increased in both treatments after IBRV challenge. Serum IBRV antibody titers were higher in -Cu calves with detectable seroconversion by d 10 postinfection. In contrast, antigen-specific antibodies to P. hemolytica tended to be higher in +Cu calves on d 21. Copper status did not affect blastogenic response, but phytohemagglutinin (PHA)-stimulated blastogenesis was higher in both treatments after IBRV challenge. Repletion of lymphocyte cultures with copper chloride increased proliferative responses to PHA in both +Cu and -Cu calves, and greater responses at all levels of copper (1 to 16 micrograms/mL) were noted in -Cu calves. These results indicate that copper deficiency affects various physiological characteristics that may be important in immunological defense to pathogenic challenge.