Recent advances in trace mineral deficiencies and their control

The study of trace element metabolism has intensified in the last 20 years due mainly to the availability of highly purified diets and to the development of sophisticated instrumentation capable of detecting minute amounts of elements in tissues and feeds. Since 1957, Se, Cr, Sn, V, F, Si and Ni have been isolated as essential nutrients for animal metabolism (Schwartz 1974). The recommended requirements for established trace elements have also changed. It is now recognised that the Zn requirements of Zn for chicks is greater than that originally proposed by ARC (1963). Preston and Willis (1974) have also suggested that the Zn requirements of cattle may be lower than initially proposed. It is also clear that precise requirement for many trace elements has not yet been determined, as shown by .the absence of recommendations for bin, I, Cu, Zn, MO and Se in laying poultry. (See ARC, 1963 and NRC).