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The number of mineral elements that have been shown to have essential functions in the body has been increasing steadily since the 1950s. Major or macrominerals are required in relatively larger quantities ( 50 mg=(kg DM)) and include calcium, phosphorus, potassium | 18 Mineral Metabolism E. Kebreab1 and D.M.S.S. Vitti2 Centre for Nutrition Modelling Department of Animal Poultry Science University of Guelph Guelph Ontario N1G 2W1 Canada 2Animal Nutrition Laboratory Centro de Energia Nuclear na Agricultura Caixa Postal 96 CEP 13400-970 Piracicaba SP Brazil Introduction The number of mineral elements that have been shown to have essential functions in the body has been increasing steadily since the 1950s. Major or macrominerals are required in relatively larger quantities 50 mg kg DM and include calcium phosphorus potassium sodium sulphur chlorine and magnesium. Trace or microminerals include iron zinc copper molybdenum selenium iodine manganese cobalt chromium fluorine arsenic boron lead lithium nickel silicon tin and vanadium. Due to lack of space all the minerals and their quantitative aspects of metabolism cannot be discussed in detail here. As in the previous edition of the book we chose to focus on quantitative aspects of two minerals. From the macro elements phosphorus is taken as an example mainly because it is the element which has been a subject of much research in recent years due to concerns of overfeeding phosphorus to ruminants and the contribution to environmental pollution. The principles outlined are also applicable to other macrominerals such as calcium. A model of magnesium metabolism in sheep was developed by Robson et al. 1997 and modified by Bell et al. 2005 which followed similar principles. Symonds and Forbes 1993 took copper as an example of trace elements and discussed its metabolism. Although research in trace elements has not had the progress of the 1970s and 1980s especially in terms of development of steady state kinetic models and dynamic modelling we have updated the information on copper metabolism. Phosphorus Phosphorus P is an essential nutrient involved not only with bone development growth and productivity but also with most metabolic processes of the body. Phosphorus and calcium Ca are the .
