Major trace elements limiting livestock performance in New Zealand.

Many New Zealand soils are naturally deficient in cobalt and/or selenium and/or copper, or are naturally high in molybdenum. Livestock grazing pasture grown on such soils may be deficient in one or more of these trace elements. In the 1940s and 1950s, New Zealand researchers were at the forefront of research to define the cause of trace-element related ill-thrift and clinical diseases like white muscle disease, peat scours and enzootic ataxia. New Zealanders have devised production-related reference ranges for blood and liver copper, vitamin B12 and selenium that are used for the diagnosis and prevention of deficiencies. A range of supplementation procedures has been devised, from topdressing or spraying pasture to direct animal supplementation, to suit the range of livestock management systems found in New Zealand. Trace-element monitoring programmes are now a routine procedure for farmers grazing cattle, sheep, and deer on trace-element deficient land. Copper deficiency is the main trace-element deficiency diagnosed in deer.