Copper fertiliser increases pasture copper concentration and improves the copper status of grazing sheep

Abstract

Application of copper-amended fertiliser ("topdressing") increases pasture herbage Cu concentration and can increase dietary Cu intake of grazing ruminants. Animal responses to dietary Cu, in terms of changing blood and liver Cu concentrations monitored throughout the season, have not been well documented. In this study 10 experimental paddocks were topdressed with 0 (Control), 0.4 (Low) or 4.0 (High) kg Cu/ha as CuSO4.5H2O, resulting in mean herbage Cu concentrations of 8, 13 and 41 mg Cu/kg DM, respectively. The treated pastures were significantly greater than controls for at least 100 days. Romney lambs of low but not deficient initial Cu status grazing the Cu-treated paddocks for 176 days had increased Cu intake compared with controls, resulting in substantial accumulation of Cu in liver. Maximum liver Cu concentration occurred after 99 days, when the levels in low- and high-treated sheep were 3 to 12 times greater than controls (900 to 3270 vs 270 mg Cu/kg fresh tissue). No changes in blood plasma Cu concentration were observed. A predictive relationship between pasture Cu and liver Cu concentrations of grazing lambs was determined, and recommendations for sheep Cu supplementation via Cu topdressing are made. Keywords: copper status, copper supplementation, liver biopsy, Romney lambs, topdressing