Safety and effectiveness of cupric oxide particles for increasing liver copper stores in sheep

Five groups of four, housed Cheviot ewes (mean live-weight 50 kg) were given single doses of 0, 2.5, 5, 10 or 20 g cupric oxide particles in gelatin capsules while receiving a diet of marginal copper content based on pelleted oats. After 65 days liver copper concentrations had increased curvilinearly in relation to dose and all ewes given 10 or 20 g cupric oxide particles showed increases of at least 13.4 mmol kg-1 dry matter (850 ppm). Liver copper concentrations had generally declined after 85 days but biochemical and histological evidence of copper toxicity was recorded in one ewe which had received 20 g cupric oxide particles. Despite marked variations between individual sheep a dose of 0.1 g kg-1 liveweight (5 g) was considered to be safe and did not induce clinical copper toxicity in five sheep of the susceptible North Ronaldsay breed given the same basal diet.