ABSTRACT: The impact of mineral imbalances on livestock production has been and will continue to be reduced by addressing the three components of the question 'How much?': how much can the diet provide; how much does the animal need; how can we gauge from the animal the size of any deficit between supply and demand? Proper definition of supply and demand for Ca under steady state conditions (e.g. pre-partum) may facilitate control of the unsteady state (e.g. milk fever post-partum) and maximise the utilisation of other elements in non-ruminants (P, Mn and Zn). Better definition of ruminant needs for Mg in factorial models that allow for species and diet effects on the powerful antagonism of Mg absorption by K will lessen the incidence of Mg disorders. Wider use of marginal bands for biochemical indices of mineral status in animals may slow the speed of diagnosis but greatly improve its accuracy. The best indicator of imbalance is the presence or absence of individual responses in health or performance to specific mineral interventions. The best short-term preventive measure is mapping areas of maximal risk of deprivation. The best long-term preventive measure may reside in tapping the potential for genetic improvement in tolerance of mineral imbalance
