The Effects of Copper Source and Concentration on Lipid Metabolism in Growing and Finishing Angus Steers

Forty-eight individually fed Angus steers (body weight 220 kg±9.1) were utilized to investigate the effects of copper (Cu) source and concentration on lipid metabolism and carcass quality. Steers were stratified by body weight and initial liver Cu concentration and randomly assigned to one of five groups. Groups were then randomly assigned to treatments. Treatments consisted of: 1) control (no supplemental Cu); 2) 10 mg Cu/kg DM from CuSO4; 3) 10 mg Cu/kg DM from a Cu amino acid complex (Availa Cu) 4) 20 mg Cu/kg DM from CuSO4; and 5) 20 mg Cu/kg DM from Availa Cu. Steers were fed a corn-alfalfa-based growing diet for 56 d. Steers were then switched to a high concentrate finishing diet for 145 d. On day 74 of the finishing phase subcutaneous adipose tissue biopsies were obtained from three steers/treatment to determine basal and stimulated lipolytic rates in vitro. Steers were then slaughtered after receiving the finishing diet for 145 d. Control steers tended (p<0.12) to have lower ceruloplasmin (Cp) activity than Cu supplemented steers. Steers receiving 20 mg Cu/kg DM from Availa Cu had higher (p<0.03) Cp activity than steers receiving 20 mg Cu/kg DM from CuSO4. Plasma non-esterified fatty acids were similar across treatments. Steers receiving 10 mg Cu/kg DM from Availa Cu had higher (p<0.02) total plasma cholesterol concentrations relative to steers receiving 10 mg Cu/kg DM from CuSO4. Steers receiving 20 mg Cu/kg DM from Availa Cu had lower (p<0.03) plasma triglyceride concentrations than steers supplemented with 20 mg Cu/kg DM from CuSO4. Fatty acid profile of longissimus muscle was similar across treatments. Backfat depth tended (p<0.18) to be lower in Cu supplemented steers relative to controls. Steers supplemented with 20 mg Cu/kg DM from Availa Cu had heavier (p<0.03) hot carcass weights and a greater (p<0.02) dressing percentage than steers supplemented with 20 mg Cu/kg DM from CuSO4. Furthermore, in vitro basal (p<0.06) and epinephrine stimulated (p<0.04) lipolytic rates of subcutaneous adipose tissue were higher in Cu supplemented steers relative to controls. The results of this study suggest that Cu supplementation has minimal effects on blood and lean tissue lipid profile. However, it appears that Cu may play a role in lipid metabolism in subcutaneous adipose tissue.