Effects of copper source and concentration on copper status and immune function in growing and finishing steers

2002 Summer.Includes bibliographical referencesForty-eight, individually fed, purebred Angus steers (approximately 7 months of age, 218 + 9.1 kg) were used to determine the effects of copper (Cu) source and concentration on performance, Cu status, and immune function. Steers were stratified by weight and initial liver Cu concentration and randomly assigned to one of five treatments. Treatments consisted of: 1) control (no supplemental Cu), 2) 10 mg Cu/kg DM from Cu sulfate (CuS04), 3) 10 mg Cu/kg DM from a Cu-amino acid complex (Availa Cu), 4) 20 mg Cu/kg DM from CuS04, and 5) 20 mg Cu/kg DM from Availa Cu. Steers were housed in individual pens and fed an alfalfa-com based growing diet for 56 d then were fed a high concentrate diet for 144 d. On d 56 of the growing phase and d 112 of the finishing phase, liver Cu concentrations were higher (P < 0.01) in Cu supplemented steers. Steers receiving 20 mg Cu/kg DM had higher (P < 0.01) liver Cu concentrations than steers receiving 10 mg Cu/kg DM. On d 112 of the finishing phase, steers receiving 20 mg Cu/kg DM from Availa Cu had higher (P < 0.01) liver copper concentrations than steers supplemented 20 mg Cu/kg DM from CuS04. In the growing phase, steers supplemented with 20 mg Cu/kg DM had greater (P < 0.04) plasma Cu concentrations than steers supplemented with 10 mg Cu/kg DM. In the growing and finishing phases, plasma Cu concentrations were higher (P < 0.03) in steers supplemented with 20 mg Cu/kg DM from Availa Cu than steers receiving 20 mg Cu/kg DM from CuS04. Cell mediated immune response to phytohemagglutinin was higher (P < 0.01) in steers supplemented with 20 mg Cu/kg DM than 10 mg Cu/kg DM treatments. Total immunoglobulin (lg) and immunoglobulin G (IgG) concentrations specific to pig red blood cells (PRBC) were greater (P < 0.01) in steers supplemented with 10 mg Cu/kg DM from CuS04 than 10 mg Cu/kg DM from Availa Cu. During the finishing phase, IgG concentrations specific to PRBC were higher (P < 0.03) and antibody titers specific to ovalbumin (OVA) were lower (P < 0.05) in control steers relative to Cu supplemented steers. Steers receiving 20 mg Cu/kg DM had higher antibody titers specific to OVA (P < 0.02) than 10 mg Cu/kg DM steers. Steers receiving 20 mg Cu/kg DM from Availa Cu had higher (P < 0.01) antibody titers specific to OVA than steers supplemented with 20 mg Cu/kg DM from CuS04 . These results indicate that Cu source and concentration may have an effect on the immune system. Furthermore, it appears that the immune response to an antigen varies depending on the type of antigen administered as well as the concentration and source of Cu supplemented