Copper status, serum cholesterol, and milk fatty acid profile in Holstein cows fed varying concentrations of copper

An experiment was conducted to determine the effects of dietary copper (Cu) on Cu status and lipid metabolism in Holstein cows. Three primiparous and 21 multiparous Holstein cows were utilized in this experiment. Groups of th ree cows similar in parity, days in milk, and milk yield were assigned rand omly to one of the following three treatments: 1) control (no supplemental Cu), 2) 10 mg of Cu/kg of DM from Cu sulfate (CUSO4), and 3) 40 mg of Cu/kg of DM from CUSO4 Liver Cu concentrations were higher in Cu supplemented co ws at the end of the 61-d study. Cows receiving 40 mg of Cu/kg of DM had hi gher liver Cu concentrations than cows receiving 10 mg of Cu. Plasma Cu con centrations were similar across treatments. Total serum cholesterol concent rations were higher in cows receiving supplemental Cu. Cows receiving 40 mg of Cu/kg of DM had higher serum cholesterol concentrations than cows recei ving 10 mg of Cu. Dry matter intake, average daily milk production, and mil k lipid, protein, and somatic cell numbers were similar across treatments. On d 61, milk fatty acids C-18:1 trans and C-18-conjugated dienes were lowe r in cows receiving supplemental Cu relative to the nonsupplemented control s. Cows receiving 40 mg of Cu/kg of DM had higher C-12:0 and lower C-18:2 a nd total polyunsaturated fatty acids in milk than cows receiving 10 mg of C u/kg of DM. These results indicate that Cu supplementation alters lipid met abolism in high producing dairy cows and that Cu supplementation at 40 mg/k g of DM for 61 d can elevate liver Cu concentrations to levels considered t o be marginally toxic in dairy cattle.