Copper, zinc and manganese concentrations in equine liver, kidney and plasma

Five groups of horses were fed different diets of known trace mineral concentration for a minimum of six months. Copper (Cu), zinc (Zn) and manganese (Mn) concentrations were measured in livers of 125 yearling horses and kidneys of 81 yearling horses as an assessment of trace mineral status. Plasma Cu and Zn determinations were made for all horses.

Mean hepatic Cu concentrations of horses fed diets containing 6.9 to 15.2 mg Cu/kg dry matter (DM) feed were 0.27 to 0.33 μmol/g DM tissue. Plasma Cu concentrations ranged between 22.8 to 28.3 μmol/L. There was no simple mathematical relationship between plasma and hepatic Cu concentrations. Mean hepatic Zn concentrations in horses fed diets containing 25.6 to 52.2 mg Zn/kg DM feed were determined to be between 2.75 to 2.91 μmol/g DM tissue. Mean plasma Zn concentrations in groups of horses were between 11.7 to 13.5 μmol/L. Plasma Zn concentrations were not indicative of hepatic Zn concentration. Hepatic Mn concentrations ranged between 0.13 and 0.14 μmol/g DM tissue.

Renal Zn concentrations ranged between 1.55 to 1.63 μmol/g DM tissue and did not differ with diet. Mean renal Mn concentrations were 0.09 μmol/g DM tissue for all groups of horses. Renal Cu concentrations ranged from 0.36 to 0.47 μmol/g DM tissue and differed with diet.