EFFECT OF COPPER DEFICIENCY ON TISSUE, BLOOD CHARACTERISTICS, AND IMMUNE FUNCTION OF CALVES CHALLENGED WITH INFECTIOUS BOVINE-RHINOTRACHEITIS VIRUS AND PASTEURELLA-HAEMOLYTICA

Fourteen Holstein steers, averaging 30 d of age, were fed a semipurifi ed 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 exp osure to aerosol preparations of infectious bovine rhinotracheitis vir us (IBRV) and Pasteurella hemolytica on d 0 and 7, respectively, of th e 30-d study. Serum ceruloplasmin and plasma copper were higher in +Cu calves throughout the challenge period and increased in +Cu calves af ter microbial challenge. Heart weights were higher in -Cu calves, alth ough weights of liver, spleen, and thymus were not different between t reatments. 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 EBRV challenge. Serum IBRV antibody titers were higher in -Cu calves with detectable s eroconversion by d 10 postinfection. In contrast, antigen-specific ant ibodies to P. hemolytica tended to be higher in +Cu calves on d 21. Co pper status did not affect blastogenic response, but phytohemagglutini n (PHA)-stimulated blastogenesis was higher in both treatments after I BRV challenge. Repletion of lymphocyte cultures with copper chloride i ncreased proliferative responses to PHA in both +Cu and -Cu calves, an d greater responses at all levels of copper (1 to 16 mug/mL) were note d in -Cu calves. These results indicate that copper. deficiency affect s various physiological characteristics that may be important in immun ological defense to pathogenic challenge.