lNHlBlTlON OF TRACE MINERAL METABOLISM IN RUMINANTS

Trace minerals exist in cells and tissues of the animal body in a variety of chemical combinations, and in characteristic concentrations, depending on the trace mineral consumed and the tissue in which the trace mineral is metabolized (McDowell, 1992; Underwood and Suttle, 1999). Concentrations of trace minerals must be maintained within narrow limits in a cell (McDowell, 1989, 1992; Underwood and Suttle, 1999). Trace mineral deficiencies, toxicities, and imbalances require the animal to metabolically compensate for the nutrient deviation (McDowell, 1989, 1992; Underwood and Suttle, 1999). In doing so, certain metabolic diseases can be produced and overall animal performance can be depressed. The intent of this review is to: 1) give a general description of the function of certain trace minerals; 2) briefly discuss trace mineral absorption; and 3) discuss factors that affect trace mineral requirements in ruminants (Galyean et al., 1995; Galyean et al., 1999; Spears, 2000; Baker et al., 2003).