Copper deficiency in New Zealand is more evident in animals than in pasture or crops. In animals copper deficiency can be caused by an excessively high concentration of molybdenum in pastures with copper concentrations which are known to be adequate for stock health when molybdenum levels are lower. There is no evidence that very high, naturally occurring levels of available molybdenum can cause toxicity symptoms in pasture. The rather large amount of “copperised fertilisers” used by farmers are therefore mainly designed to improve stock health rather than pasture vigour. Nevertheless, there is evidence that on some soils of northern Hawke's Bay and north of Auckland, as well as on raw, acid peatland of the Waikato, copper deficiency of pastures may occur.