Trace Minerals and Vitamins in Preventative Nutrition

摘要

Trace minerals and vitamins exist in cells and tissues of the animal body in a variety of functional, chemical combinations, and in characteristic concentrations, which vary with the mineral and/or vitamin and tissue (McDowell, 1989, 1992; Underwood and Suttle, 1999). The concentrations of trace minerals and vitamins must usually be maintained within quite narrow limits if the functional and structural integrity of the tissue is to be maintained and the growth, health, and productivity of the animalare to remain unimpaired (McDowell, 1989, 1992; Underwood and Suttle, 1999). Ingestion of diets that are deficient, imbalanced, or excessively high in trace minerals or vitamins induce changes in the form or concentration of that trace mineral or vitaminin the body tissues and fluids, so that it falls below or rises above the tolerable limits. In such cases, biochemical lesions develop, physiological functions are affected adversely and structural disorders may arise, in ways which vary with the mineral or vitamin, the degree and duration of the dietary deficiency or toxicity and the age, sex, or species of animal involved (McDowell, 1989, 1992; Underwood and Suttle, 1999). Certain homeostatic mechanisms in the body can be activated which delay or minimize the onset of such diet-induced changes. Ultimate prevention of the changes requires that the animal be supplied with a diet that is palatable and non-toxic and which contains the required minerals and vitamins, as well as other nutrients, in adequate amounts, proper proportions, and available forms (Underwood, 1971; Combs, 1998; Underwood and Suttle, 1999).