Copper supplementation of grazing cattle using pasture topdressing and individual animal treatment

Three methods of copper supplementation were compared in 9to 15-month-old Friesian bulls on a farm with a history of copper deficiency. A group of 60 bulls grazed 19 ha which had been topdressed in May with 120 kg copper sulphate (6.3 kg/ha). Five of the bulls were identified for repeated sample collection. A second group of 60 bulls grazed an untreated area and five of these were each given a 20 g copper capsule (Cuprax), five were injected with 100 mg calcium copper edetate (Coprin) and five were not supplemented with copper and served as controls. The response to supplementation was assessed by monitoring liver copper concentrations of the designated five bulls in each treatment plus the five control bulls at 34, 78, 121, 197 and 314 days after treatment. Pasture copper concentrations increased on the topdressed area from 12 to 25 ppm DM for 6 weeks and subsequently remained at 10 ppm for the remainder of the trial. Pasture molybdenum concentrations were low (0.3–0.5 ppm DM) initially and rose to 1.0–1.2 ppm DM during spring on both grazing areas. Despite the elevation of pasture copper, liver copper concentrations of the bulls grazing the topdressed pasture declined in a similar way to the controls. However, at slaughter, day 314, the bulls grazing the copper topdressed area had higher liver copper concentrations than the controls (P = 0.099). Copper capsules resulted in a significant elevation of liver copper concentration throughout the trial. Copper calcium edetate injection did not significantly increase liver copper concentrations. More information on the factors affecting copper uptake by grazing ruminants is required.