Dietary copper effects on lipid metabolism and circulating catecholamine concentrations in finishing steers.

Forty-eight Angus and Hereford x Angus steers were used to determine the effects of copper (Cu) on lipid and catecholamine metabolism. Steers were stratified by weight within breed and randomly assigned to treatments. Treatments consisted of 0 (control, no supplemental Cu), 10, or 40 mg of supplemental Cu (from Cu2(OH)3Cl)/kg DM. Steers were fed a corn silage-soybean meal-based growing diet for 42 d. Animals were then switched to a high-concentrate finishing diet and remained on the same dietary treatments. On d 70, indwelling jugular catheters were nonsurgically inserted into five steers per treatment. Blood samples were obtained from steers after a 24-h period of feed withdrawal, 1 h after feeding, and after i.v. administration of norepinephrine and were subsequently analyzed for nonesterified fatty acid (NEFA) and catecholamine concentrations. Average daily gain over the finishing period was higher (P < 0.06) in steers receiving supplemental Cu. Serum total cholesterol concentrations were reduced (P < 0.05) on d 84 and 112 in steers supplemented with Cu. Serum norepinephrine (P < 0.14) and NEFA concentrations following feed withdrawal tended (P < 0.12) to be higher in Cu-supplemented steers. Postfeeding norepinephrine concentrations tended to be higher (P < 0.14) in Cu-supplemented steers. Nonesterifled fatty acid concentrations were lower (P < 0.10) in Cu-supplemented steers after norepinephrine administration. Backfat depth was decreased (P < 0.10) and longissimus muscle polyunsaturated fatty acid percentages were increased (P < 0.10) in steers receiving supplemental Cu. These results indicate that Cu addition to a finishing diet containing 5 mg Cu/kg DM alters lipid metabolism. The reduction in backfat depth may be due to copper altering catecholamine metabolism in steers.