Macrominerals

1. Macrominerals Pages 36–37 in textbook

2. Calcium Sources • Minerals • Limestone, dicalcium phosphate • Animal sources • Meat and bone meal, fish meal • Milk products • Roughages • But not cereal grains

3. Calcium • Most abundant mineral in animal tissues • Lots of functions • Bone structure • Nerve function • Blood clotting • Muscle contraction • Cellular metabolism

4. Calcium (Ca) • Functions • Bone/teeth formation and maintenance • 99% of body calcium • In 2:1 ratio with phosphorus in hydroxyapatite Ca5(PO4)3OH • Soft tissues • Enzyme activation • Blood clotting • Muscle contraction • Transmission of nerveimpulses to muscle • Calcium binds to troponin C

5. Calcium Absorption • From duodenum and jejunum • Active or passive • Dependent on vitamin D – stimulates calbindin in small intestinal cells and enhances absorption • Absorption depends on need • Particularly high during growth, pregnancy and lactation • Bioavailability decreased by • Phytates (grains) • Wheat bran • Low estrogen levels (postmenopausal women) • High fat diets (form soaps with fatty acids)

6. Calcium (Ca) • Dietary ratio of 1:1 to 2:1 ideal for most animals (except for laying hen, optimal ratio is 13:1; Ca:nonphytate phosphorous) • Never want P > Ca Grains tend to be low in calcium while forages are moderate to high

7. Calcium Regulation • Three hormones involved in regulation • Vitamin D3 • from kidney • Parathyroid hormone (PTH) • from parathyroid gland • Calcitonin • from thyroid gland • PTH and vitamin D3 act to increase plasma Ca, while calcitonin acts to decrease plasma Ca

8. GI Tract Dietary Ca Fecal Ca Endogenous Ca Absorbed Ca + 1,25(OH)2D3 from kidney Blood Ca Sweat Ca Urinary Ca - + Ca Apposition Ca Resorption PTH Calcitonin Plasma Ca Parathyroid Gland Bone Ca Plasma Ca

9. Calcium Deficiency - Causes • Low calcium intake or absorption • Soap formation (fatty acids) in rumen • Competition with divalent ions for absorption • Abnormal Ca:P ratio (2:1) • High calcium and low phosphorus leads to formation of insoluble CaPO4 in intestinal lumen • High phosphorus (and low calcium) also inhibits absorption • Vitamin D deficiency

10. Calcium Deficiency - Symptoms • Reduced growth or production rate • Egg-shell strength • Rickets • Young, fast-growing animals • Misshapen bones, enlarged joints, lameness • Osteoporosis • Decalcification of bone and loss of bone mass • Estrogen involved, bone mass decreases following menopause • Isoflavones (estrogen-like compounds) in soy help alleviate losses

11. Osteoporosis – Symptoms Wedged Upper Vertebrae and Crushed Lower Vertebrae

12. Osteoporosis • Decrease bone mass • Related to aging, poor diet, and estrogen loss • Leads to 1.5 million bone fractures per year • Slender, inactive women who smoke are at highest risk • Type I (postmenopausal) • Type II (senile)

13. Bone Strength • Depends on bone mass • Related to age, gender, activity level and genetics • Peak bone mass in women achieved by age 20-30 • Same in females of all mammalian species – peak mass achieved as animal reaches maturity and then decreases thereafter • Cannot increase bone density after this point, but can slow rate of bone density loss • By age 65, some women have lost 50% of bone mass

14. Calcium Deficiencies • Rickets • in growing animals • Osteomalacia and osteoporosis • in adult animals • Milk fever (parturient paresis) • in lactating animals

15. Calcium Deficiency – Milk Fever • High demand for milk calcium during early lactation – calcium pulled from blood • Cannot absorb enough calcium from gut or reorb from bone rapidly enough to keep up • Severe hypocalcemia (low blood calcium) results • Factors associated • Parturition • Onset of lactation • Breed • Age • Diet

16. Plasma calcium Hypocalcemiaat Parturition PTH 1,25(OH)2D3 Absorption from GI tract Plasma calcium increased Absorption from kidney Resorption from bone

17. Milk Fever • Symptoms • Listless • Staggers or weaves when walks • Lies down in characteristic pose • head retraction • Decreased plasma calcium

18. Milk Fever • Treatment • IV calcium solution • Oral calcium gels • Prevention options • Dietary acid–base balance, not calcium level • Alter dietary cation-anion balance • Feed anion salts or adjust dietary potassium • Increased calcium release from bones and increased calcium absorption from diet • Mediated through parathyroid hormone

19. Phosphorus Sources • Minerals • Dicalcium phosphate • Monocalcium phosphate • Deflourinated rock phosphate • Animal sources • Meat and bone meal • Fish meal • Cereals • Large portion of phosphorus unavailable for non-ruminants • Phytic acid (poorly absorbed)

20. Phosphorus (P) • Functions • Component of bones/teeth • 80% in bone (hydroxyapatite) • 20% in soft tissue • Membrane phospholipids, DNA, RNA • Similar to calcium • Vitally important in energy metabolism • ATP and creatine phosphate • Sugar phosphates • Acid-base balance (HPO4–) • Regulation of metabolism • Glucose-6-phosphate • Phosphorylation activates or inactivates enzymes

21. Phosphorus (P) • Absorption • Both active and passive mechanisms • High phosphorus limits calcium absorption • Plant phosphorus often unavailable to animal • Phytic acid • Released by phytase (enzyme often supplemented) • Blood levels controlled by vitamin D and parathyroid hormone

22. Phosphorus Deficiency • Deficiency • Symptoms similar to calcium deficiency • Reduced growth or production rate • Rickets or osteomalacia • Pica (depraved appetite) – chewing of wood fences, bones, soil • Low fertility and poor milk production or growth

23. Phosphorous • Impact on environment has scientists revisiting nutritional requirements • Requirements are being lowered without any negative effects on reproduction or milk production • Bioavailability could be improved if phytate phosphorus can be reduced • Increasing availability would reduce dietary requirements and fecal excretion • Feeding phytase

24. Magnesium Sources • Mineral sources • MgCO3, MgCl2, MgO (“mag-ox”) • MgSO4 • a.k.a. Epsom salts, milk of magnesia

25. Magnesium (Mg) • Functions • Bone formation • ~60% in bone • Enzyme activation • Carbohydrate, lipid metabolism • 7 enzymes in glycolysis require magnesium as a cofactor • Urea cycle • Binds mRNA to ribosomes • Associated with ATP metabolism • ATP–Mg2+ complex

26. Magnesium and Muscle Function • Magnesium required for energy releasing enzyme activity in skeletal muscle • ATP needed for detachment and calcium uptake • Calcium is the link between excitation and contraction • Lack of ATP to return calcium to storage results in tetany

27. Magnesium • Deficiency • Vasodilation • Results in reduced blood pressure • Hyperirritability, convulsions • Anorexia, reduced weight gain • Hyperemia • Hypomagnesemic tetany (grass tetany) • Early lactating cows on grass • Poor nervous and muscular control • Usually not an issue, adequate levels present in most diets

28. Magnesium Deficiency – Grass Tetany • Also called grass staggers, hypomagnesemia • Low blood magnesium • Symptoms • Nervousness • Tremors, twitching of face muscles • Staggering gait or convulsions • Etiology not completely understood

29. Grass Tetany • Spring pastures, lush grasses • Low magnesium content • Some magnesium absorption in rumen • Requires relatively low pH • High potassium forages raise rumen pH and impedes Mg absorption • Potassium alters acid-base balance (cation induces alkaline environment) • Pasture contains organic acids that bind magnesium • Solution • Dust pasture with MgO • Feed 1:1:1 magnesium oxide:TM salt:grain starting 2 weeks before turning ruminants out on pasture

30. Sodium and Chloride Sources • Minerals • Salt (iodized, 0.007% iodine added) • Add at 0.25–0.50% of diet • Free-choice salt blocks • May be combined with other minerals • Animal sources • Meat and bone meal, meat meal • Fish meals may have a (very) high salt content • Cereal grains • Low sodium and choride content

31. Sodium (Na) and Chloride (Cl) • Functions • Electrolytes • Absorption of glucose and amino acids • Transmission of nerve impulses • Action potential • Osmotic pressure balance • 10% sodium and chloride intracellular, 90% extracellular • Sodium is main extracellular cation • Maintained by Na/K ATPase • Chloride is main extracellular anion • HCl and chloride salts in gastric secretions

32. Sodium and Chloride • Blood concentrations highly regulated • Excess intake = increased excretion • Little danger of toxicity if water available • NaCl added to diets to increase palatability • Causes of deficiencies: • Lactation • Sodium and chloride secreted in milk • Rapid growth • On a diet of cereals or forages • High temperatures or hard work • Sweat

33. Symptoms of Sodium and Chloride Deficiency • Decreased osmotic pressure • Leads to weakness • Circulatory failure • Metabolic alkalosis (decreased chloride) or acidosis (decreased sodium) • Poor growth • Reduced appetite and feed consumption • Reduced carbohydrate and amino acid absorption • Diminished HCl secretion from parietal cells • Reduced bacterial defense and protein digestion • Pica or salt craving • Animals will seek out salt sources • Soil, urine, sweat of other animals, etc.

34. Pica • Animals do not necessarily seek out sources of the mineral that is deficient in diet – just consume “non-feed” items • Coprophagia (consumption of excrement) • Geophagy (consumption of soil, clay, or chalk) • Consumption of dust or sand in iron deficient patients. • Vampirism (ingestion of blood) • Hyalophagia (consumption of glass) • Pagophagia (pathological consumption of ice) • Self-cannibalism (rare condition where body parts may be consumed; sometimes called Lesch-Nyhan syndrome) • Trichophagia (consumption of hair or wool) • Urophagia (consumption of urine) • Xylophagia (consumption of wood) • Cautopyreiophagia (consumption of burnt matches)

35. Sodium and Health • High blood sodium is associated with high blood pressure and risk of heart disease • However, high blood sodium rarely due to dietary excesses • Genetics is primary factor, although other factors are involved • 10%-15% of adults are “salt-sensitive” and should limit salt intake

36. Potassium Sources • Plants generally have a high potassium content • Grains 0.3–0.8% • Vegetable proteins 1.0–2.5% • Alfalfa ≈ 2% or more • Implications for dairy in developing anionic diets for preventing milk fever!! • Animal products vary

37. Potassium • Functions: • Third-most abundant mineral in the body • 2/3 of whole-body potassium content in skin and muscles • >95% of potassium intracellular (major intracellular cation) • Maintained by Na/K ATPase • Regulation of osmotic and acid-base balance • Transmission of nerve impulses • Potassium is the major determinant of the resting membrane potential of all cells • Cofactor for several reactions in carbohydrate metabolism

38. Potassium Deficiency • Rare • Has to be induced • Major salt in ruminant sweat • Increases requirement in heat stress • Reduced appetite and growth • Other symptoms • Tetany, nervous disorders • Degeneration of organs • Abnormal heart function

39. Sulfur (S) • Located in organic compounds • Thiamin & biotin; methionine, cystine and cysteine • Chondroitin sulfate matrix of cartilage • Feathers, wool, etc. • Wool contains about 4% sulfur • Minimal involvement in acid-base balance • Ideal N:S ratio of 10:1 in ruminant diets • Potential for toxicity