Trace elements in grazing domestic ruminants in Norway - present situation and long-term trends.

Deficiency of copper, selenium and cobalt, as well as chronic copper poisoning, are all known in Norwegian domestic ruminants. In the 70s and 80s several surveys of trace element levels were carried out, primarily in sheep and in pasture plants. These stu dies confirmed substantial regional differences, and are still used as a basis for advice on trace element supplementation in Norway. In the last decades, the amount of atmospherically transported pollution elements in Norway has changed. Preliminary o bservations may indicate that also the levels of copper and other essential elements are altered, in some regions. If this is true, it is important for ruminant feeding. In the same period, the amount of beef cattle in Norway has increased. The beef cattl e are generally fed more on roughage and pasture than the dairy cows. Selenium deficiency has been observed, but the status of other trace elements is less known. New analytical methods (ICP-MS) have made it possible to determine a range of elements simu ltaneously, and thus reduce the cost of systematic surveys. In this study, liver samples will be collected at slaughter from adult sheep and lambs, and from beef cows, from a representative selection of Norwegian flocks and herds, together with sample s of pasture plants from different areas. The concentrations of a set of essential and non-essential elements will be measured with ICP-MS, and selenium separately with AAS. Information about grazing areas and other feeding in the herds will be collected through questionnaires. The data will be analysed for geographical differences, correlations between concentrations in the animals and in pasture plants, as well as effects of kinds of pasture, age and other relevant factors. The results will also be compared to data from previous studies. The findings will be used to re-evaluate the current advice on trace element supplementation to domestic ruminants in Norway.