A comparative view on trace elements and growth.

The term 'essentiality' of trace elements is interpreted. The major human diseases due to trace element deficience (Fe, Cu, Zn, Cr) are briefly considered. In growing animals the first clinical deficiency symptom most often is a growth retardation. In order to diagnose a deficient situation before the manifestation of clinical symptoms, model studies with growing animals are presented to show criteria that respond sensitively even to suboptimum intake of trace elements (Zn, Cu, Fe, Ni). Activity measurements of enzymes and hormones are found suitable. During the phase of reproduction, which is closely associated with growth, the trace element concentration in milk may provide an additional diagnostic means. In conclusion, the problems of diagnosing the supply status are discussed. A possibility for determination of the trace element requirement is indicated.