Geographical and botanical variation in concentrations of copper, molybdenum, sulphur and iron in sheep pasture plants in Norway

To obtain a better knowledge basis for the correct supply of Cu to sheep in Norway, a systematic, countrywide investigation of element composition of pasture plants was conducted, with emphasis on natural pastures. Samples of pasture grass, herbs, willow shrub leaves and bilberry (N = 575) from 142 locations were analysed for Cu, Mo, S and Fe. A large geographical variation was observed for Mo concentration and Cu:Mo ratio, a somewhat smaller variation for Fe, while Cu and S concentrations showed limited geographical variation. The Mo variation led to a Cu:Mo ratio 20 in 62% of samples, confirming that the trace element composition of Norwegian sheep pastures may represent a risk of Cu deficiency as well as Cu overload, depending on location. A considerable botanical variation was also observed, in particular for Cu and Mo.