Whisky production generates fermentation and distillation residues of considerable nutritive value for livestock but when processing takes place in copper (Cu) vessels, by-products become so enriched with Cu that poisoning can occur in recipient animals. However, absence of Cu toxicity in studies with sheep given pot ale syrup, a distillation by-product, have inferred a low availability of the Cu contained. Since no quantitative estimates of Cu availability in distillery by-products have been published, these were sought and compared with those of cupric sulphate (CuSO45H2O).