The effectiveness of using supplementary zinc and molybdenum to reduce the copper content in the liver of hypercuprotic sheep.

Two trials were conducted to evaluate the effectiveness of different methods of reducing the liver copper (Cu) concentration of sheep whose livers had been loaded with Cu, in order to protect the sheep from Cu toxicity, after dietary Cu had been withdrawn. In the first trial 0, 75, 150 and 300 mg zinc (Zn) kg-1 feed were added to a basic diet low in Cu and fed to hypercuprotic sheep (n = 32) for 88 d. At the end of the trial, liver Cu concentrations (c 800 mg Cu kg-1 DM) in all 4 treatments did not differ significantly from the Cu concentrations of the liver biopsy samples taken at the onset of the trial. From other measurements taken, none of the sheep appeared to be close to the haemolytic phase of chronic Cu toxicity. In the second trial, lasting 79 d, 40 hypercuprotic sheep were allocated to 4 treatments, viz. a control, a group receiving a parenteral treatment of Zn, amounting to approximately 7 mg Zn d-1 and 2 further groups receiving molybdenum (Mo) (15 and 30 mg Mo sheep-1 d-1), added to the basic diet high in sulphur (4,06 g kg-1 DM). The parenteral Zn treatment did not change liver Cu concentrations. The 15 mg and 30 mg Mo treatments reduced the Cu in the livers significantly by 24% and 42% respectively. It is suggested that both oral and parenteral Zn supplementation are ineffective in reducing liver Cu concentration once dietary Cu has been withdrawn from the diet.(ABSTRACT TRUNCATED AT 250 WORDS)