Effect of copper and zinc on blood and milk parameters and performance of dairy cows

Thirty fives Holstein cows were chosen to study the blood biochemical indicators with a single-factor test design in three copper levels (21.5, 31.5 and 41.5 mg/kg) and three zinc levels (50.15, 90.15 and 130.15 mg/kg). The results showed that the supplement of 20 mg of Cu/kg DM and above 40 mg of Cu/kg DM may increase Cu-Zn-superoxide dismutase (Cu-Zn-SOD) in milk (P<0.05), but did not increase milk yield and improve chemical composition (P>0.05). Zinc concentration in milk could be higher as supplemented 80 mg of Zn/kg DM (P<0.05). The concentration of copper, serum ceruloplasmin, haemoglobin and the activity of Cu-Zn-SOD in blood may be increased (P<0.01) by 37, 60, 5.1 and 5.9%, respectively, as the supplement of dietary copper was above 31.5 mg/kg.