Dietary copper effects on lipid metabolism, performance, and ruminal fermentation in finishing steers

Sixty Angus steers (391.1 +/- 6.1 kg) were used to determine the effects of dietary Cu concentration on lipid metabolism and ruminal fermentation. Ste ers were stratified by weight and randomly assigned to treatments. Treatmen ts consisted of 0 (control), 10, or 20 mg of supplemental Cu (as CuSO4)/kg diet DM. Steers were housed in pens equipped with individual electronic Cal an gate feeders. On d 86 and 92, ruminal fluid was collected from two steer s/treatment for IVDMD determination. Equal numbers of steers per treatment were slaughtered after receiving the finishing diets for 96 or 112 d. Gain, feed intake, feed efficiency, IVDMD, and ruminal VFA molar proportions wer e not affected by Cu supplementation. Copper supplementation increased (P < .05) Liver Cu concentrations, and steers supplemented with 20 mg Cu/kg DM had higher (P < .05) Liver Cu concentrations than steers supplemented with 10 mg Cu/kg DM. Serum total cholesterol concentrations were reduced by d 56 and at subsequent sampling dates in steers receiving supplemental Cu. Long issimus muscle cholesterol concentrations were lower (P < .10) in steers su pplemented with Cu. Backfat depth was less (P < .05) in steers receiving su pplemental Cu, but marbling scores were similar across treatments. Unsatura ted fatty acid composition of longissimus muscle was increased (P < .05) an d saturated fatty acid composition tended (P < .12) to be reduced in Cu-sup plemented steers. Polyunsaturated fatty acid concentrations were higher (P < .05) in steers receiving Cu. These results indicate that addition of 10 o r 20 mg Cu/kg to a high-concentrate diet containing 4.9 mg Cu/kg DM alters lipid and cholesterol metabolism in steers but does not affect ruminal ferm entation.