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 three cows similar in parity, days in milk, and milk yield were assigned randomly 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 cows at the end of the 61-d study. Cows receiving 40 mg of Cu/kg of DM had higher liver Cu concentrations than cows receiving 10 mg of Cu. Plasma Cu concentrations were similar across treatments. Total serum cholesterol concentrations were higher in cows receiving supplemental Cu. Cows receiving 40 mg of Cu/kg of DM had higher serum cholesterol concentrations than cows receiving 10 mg of Cu. Dry matter intake, average daily milk production, and milk lipid, protein, and somatic cell numbers were similar across treatments. On d 61, milk fatty acids C18:1 trans and C18-conjugated dienes were lower in cows receiving supplemental Cu relative to the nonsupplemented controls. Cows receiving 40 mg of Cu/kg of DM had higher C12:0 and lower C18:2 and total polyunsaturated fatty acids in milk than cows receiving 10 mg of Cu/kg of DM. These results indicate that Cu supplementation alters lipid metabolism in high producing dairy cows and that Cu supplementation at 40 mg/kg of DM for 61 d can elevate liver Cu concentrations to levels considered to be marginally toxic in dairy cattle.