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  1. Trace Minerals Pages 36–39 in textbook

  2. Trace Elements (Minerals) • Needed in small amounts • Found in plants and animals • Content in plant foods depends on soil content (where plant was grown) • They are difficult to quantify biochemically • Bioavailability often influenced by other dietary factors (especially other minerals)

  3. Iron Sources • Plants • Leafy, green materials (especially legumes) • Seed coats • Animal sources • Meat and bone meal, meat meal, blood cells • Milk is a poor source of iron

  4. Iron • Iron exists in two oxidation states • Ferrous iron (+2 state) • Ferric iron (+3 state) • High affinity for oxygen, nitrogen and sulfur

  5. Iron Functions • Hemoglobin and myoglobin • Contain four and two iron molecules, respectively • 50% of iron in body is hemoglobin, 20% is myoglobin • Functions in oxygen transport • Only ferrous (+2) iron can reversibly bind oxygen • Redox processes • Fe2+, Fe3+ • Electron transfer chain • Component of many enzymes • Immune function • Brain function • Iron deficiency/toxicity thought to slow mental development in humans

  6. Iron Absorption • Primary regulator of iron homeostasis • Absorption varies between 1-50% • If body needs more iron, it increases amount of “transferrin” an iron-carrying protein (binds to ferric (+3) form of iron) • Iron can also be stored in another protein called “ferritin”

  7. Iron Absorption • Iron from animal sources (heme iron) much better absorbed than that from plant sources (non-heme iron) • Absorption of non-heme iron (plant sources) increased by: • Vitamin C • Meat in diet (MFP factor) • Citric acid and lactic acid from foods • HCl in the stomach • Sugars • Absorption is decreased by: • Phytates and fibers (grain products) • Polyphenols (tea, coffee) • Oxalates • Calcium and phosphorus in milk • Tannic acid • Other minerals (calcium, zinc)

  8. Iron Deficiency • Most common mineral deficiency worldwide • Anything that creates blood loss creates deficiency • Menstruation in primates • Gastrointestinal parasites or pathogens • Newborn and young animals easily deficient (piglets, veal calves, lambs) • Limited stores at birth (poor placental transfer) • Milk levels are very low, no soil contact (soil is iron source) • Rapid growth

  9. Iron Deficiency • Sow’s milk deficient in iron • Baby pigs injected with iron dextran • Symptoms • Anemia, poor growth • Pale skin, transparent ears • “Thumps” • Labored breathing • Enlarged heart • Diarrhea • Secondary symptom

  10. Iron Deficiency Anemia • Symptoms • Reduced number of red blood cells • Turnover of RBCs takes 60–90 days •  hemoglobin concentration of blood •  red blood cell size • Microcytic, hypochromic anemia • Cognitive problems, poor growth, decreased exercise tolerance • Iron deficiency and pica (geophagia) • Pica: craving for non-food substances (clay, paste, etc.) • Reduced resistance to infection; pale and itching skin; decreased cold tolerance

  11. Iron Toxicity • Iron overload known as hemochromotosis is caused by genetic disorder which increases iron absorption • Hemosiderosis: condition caused by long term over-consumption of iron resulting in large deposits of iron storage protein (hemosiderin) in liver and other tissues

  12. Copper (Cu) – Trace Mineral • Functions • Red blood cell formation • Required for iron absorption from small intestine • Required for transfer of iron from cells to plasma; oxidation of iron from ferrous to ferric state • Integral component of many enzymes (e.g., cytochrome oxidase) • Bone development • Structural integrity of collagen and elastin • Hair and wool pigmentation • Keratin formation in wool and hair • Stored in most tissues, especially liver

  13. Copper - Deficiency • Vitamin C interferes with absorption • Microcytic anemia • Cardiac and vascular disorders • Bone disorders (spontaneous fractures) • Depigmentation of hair or wool • Black sheep are sometimes kept as indicators of marginal Cu deficiency • Loss of wool crimp (“steely” wool) • Central nervous lesions with lack of muscular coordination

  14. Induced Copper Deficiency • Caused by relatively high levels of molybdenum and/or sulfur • Site of interaction is in the rumen • Formation of insoluble copper salts including sulfides and thiomolybdates • Net effect is decreased copper absorption

  15. Induced Copper Toxicity • Occurs with “normal” dietary levels of copper and “low” levels of molybdenum and sulfur • Copper accumulates in liver • Sheep are more susceptible than cattle or pigs

  16. Zinc (Zn) – Trace Mineral • Functions • Component of metalloenzymes • Includes DNA and RNA synthases • Synthesis of skin keratin and collagen

  17. Zinc (Zn) • Deficiency • Impaired reproduction, delayed puberty • Lesions of skin, disorders of hair, feathers, etc. • Parakeratosis • Growth retardation • Low insulin and high ammonia in blood • Low white blood cell count; susceptibility to infections • Anorexia • Night blindness

  18. Zinc (Zn) • Toxicity • Relatively non-toxic in excess • Anemia • Higher LDL and lower HDL levels • High white blood cell count • Renal failure

  19. Manganese (Mn) • Functions • Cofactor for enzyme systems • Synthesis of chondroitin sulfate in bone matrix • Deficiency • Defective bone formation • Perosis – slipped tendon • Poultry • Diet is adequate for most species

  20. Cobalt (Co) – Trace Mineral • Functions • Required only as a component of vitamin B12 • Ruminant animals require for microbes • Vitamin B12 is an essential cofactor for enzymes involved in: • Propionate metabolism • methylmalonyl CoA to succinyl CoA • DNA synthesis • Bacterial synthesis of methionine • Deficiency • Mimics B12 deficiency in ruminants • Anemia • Emaciation

  21. Cobalt • In 1930s, a wasting disease was first associated with cobalt deficiency in plants and soils • Vitamin B12 was found to contain cobalt

  22. Cobalt and Vitamin B12 • Injection of cobalt-deficient sheep and cattle with vitamin B12 was as effective as feeding cobalt in curing the disease • Injection of cobalt has no effect • Microbial synthesis of vitamin B12 was the key!

  23. Cobalt Deficient Areas of the US

  24. Chromium • Involved in carbohydrate, lipid, and protein metabolism • Component of “glucose tolerance factor” when chelated with niacin and several amino acids • Increased insulin binding to receptor • Increased numbers of insulin receptors • Alleviates gestational diabetes in some cases • Established as an essential mineral in swine • However, requirement is not known • In the ppb range • Hard to show a deficiency

  25. Dietary Sources of Iodine • Seafoods • Milk/dairy products • Iodized salt

  26. Iodine • Iodine from foods is converted to iodide (ionic form) in the GI tract • Function • Essential component of thyroid hormones • Important for regulation of body temperature, basal metabolic rate, reproduction and growth • Regulation in body • Almost all is absorbed • Excess removed in urine

  27. Iodine Deficiency • The hypothalamus controls the production of thyroid hormones • Monitors thyroid stimulating hormone produced by the pituitary • When iodine deficiency occurs, thyroid hormone production decreases • Body responds to this by secreting more thyroid stimulating hormone • Eventually leads to the enlargement of the thyroid gland - simple goiter

  28. Iodine Deficiency • Decreased growth • Goiter (less severe) • Enlarged thyroid gland due to body’s attempt to increase thyroid hormone production • Cretinism (more severe) • Severe iodine deficiency during pregnancyserious problems in fetal development • Increased incidence of stillbirths & abortions • Stunted growth, deaf, mute, mentally retarded

  29. Iodine Deficiency • Certain foods from the cabbage family contain antithyroid substances, called goitrogens • Over-consumption of these foods also may cause hypothyroidism • Excessive intakes of iodine also may cause the enlargement of the thyroid gland

  30. Functions of Selenium • Component of glutathione peroxidase • Free radical scavenger that catalyzes removal of hydrogen peroxide from cell membranes • Interrelated with vitamin E • Can partially spare vitamin E (makes up for slight deficiencies) • Improves killing ability of neutrophils • Reduces the prevalence and severity of mastitis • Conversion of T4 (thyroxine) to T3 (4x more active) GSH + H2O2 GSSG + H2O GSH = reduced glutathione GSSG = oxidized glutathione

  31. Selenium - Deficiencies • Keshan disease is characterized by heart enlargement replacing the muscle tissue with fibrous tissues • White muscle disease in lambs and calves • Skeletal and cardiac myopathies • Exudative diathesis (hemorrhagic disease) in chicks • Liver necrosis • Concentration in feeds is soil dependent • Toxicity/deficiency related to geographic area

  32. White Muscle Disease • Results from a deficiency of selenium or vitamin E • Characterized by white streaks in striated muscle • Prevented by injection of vitamin E and selenium

  33. Selenium • Toxicity causes blind staggers or alkali disease • Range between minimum requirement and maximum tolerable level is narrow • Supplementation must be done with care • FDA regulations allow only two forms of inorganic selenium (sodium selenite and sodium selenate) to be used • 0.3 mg of supplemental selenium/kg of dietary DM is maximum

  34. Selenium Content of Soils

  35. Molybdenum (Mo) – Trace Mineral • Sources • Legumes, cereals, organ meats • Functions • Component of many metalloenzymes • Component of xanthine oxidase • Nucleic acid (purine) metabolism • Deficiency • Toxicity more common than deficiency • Induces copper deficiency

  36. Sources of Fluoride • Water • Natural • Fluoridated • The practice of fluoridation is questioned now because of risk of fluorosis (mottling) of teeth

  37. Fluoride • 99% of ingested fluoride is found in bones and teeth • Function • To promote mineralization of calcium and phosphate • Inhibits bacterial growth in mouthdecreases cavity formation • More toxin than dietary essential for animals • Not commonly supplemented • Cumulative poison