Effects of dietary copper source and level on performance, carcass characteristics and lipid metabolism in lambs

An experiment was conducted to determine the effect of dietary copper (Cu) on performance, carcass characteristics and lipid metabolism in lambs. Fifty DorperxMongolia wether lambs (approximately 3 month of age; 23.8 +/- 0.6 kg of body weight) were housed in individual pens and were assigned randomly to one of five treatments. Treatments consisted of 1) control (no supplemental Cu), 2) 10 mg Cu/kg DM from Cu-lysine, 3) 20 mg Cu/kg DM from Cu-lysine, 4) 10 mg Cu/kg DM from tribasic copper chloride (Cu-2(OH)(3)Cl; TBCC), 5) 20 mg Cu/kg DM from tribasic copper chloride. The Cu concentration was 6.74 mg/kg DM in the basal diet. Body weight was measured on two consecutive days at the start and the end of the 60-day experimental period. Blood samples were collected and then the lambs were slaughtered on d 60. Performance was not affected (p > 0.05) by dietary Cu treatment. Cu-supplemented and control lambs had similar hot carcass weight, dressing percentage and longissimus muscle area, but Cu supplementation, regardless of source and level, reduced (p < 0.01) 12th rib backfat and kidney fat in lambs. Plasma tumor necrosis factor-alpha (TNF-alpha) and serum triglyceride concentrations were increased (p < 0.05), total cholesterol concentrations were decreased (p < 0.05) and nonesterified fatty acids (NEFA) concentrations tended to be increased (p < 0.07) by Cu supplementation. However, Serum concentrations of HDL-cholesterol and LDL-cholesterol were not affected (p > 0.05) by dietary treatment. Fatty acid profile of longissimus muscle was similar across treatments. These results indicate that Cu-lysine and TBCC are of similar availability in lambs. Cu supplementation given to DorperxMongolia wether lambs altered lipid metabolism. The reduction in backfat depth may be due to copper altering TNF-alpha metabolism in lambs. Supplementation of 10 or 20 mg Cu/kg DM showed similar effects on lipid metabolism in lambs.