May 27, 2015 / 0 Comment / in Animal and Pasture Nutrition / by Bryan McLeod

Dr Bob Scott was a great teacher

Although very technical it still gives a great understanding

LESSON 2

Calcium and Phosphorus

Introduction

Ca and P considered together

• -Major part of mineral content of bone.
• -Requirements related to each other.
• -Ca:P ratio in bone ~ 2:1.
• -Shortage in young animals results in rickets and osteomalacia in mature animals.

Ca and P - two most abundant elements in body.

• -Often insufficient in common feedstuffs.
• -P deficiency problem in grazing livestock.

Ca deficiency more for animals on concentrates

For humans, deficiency second only to Fe.

Chemical Properties and Distribution

Ca found in compounds, limestone (Ca carbonate), Ca fluoride, Ca sulfate.

• -99% Ca in bone and teeth, rest in extracellular fluid and within cells.
• -Ca low in grains (e.g., 0.02-0.10%), abundant in most forages.
• -Non legume, 0.31 - 0.36% Ca.
• -Legume, 1.2- 1.7% Ca.

P occurring as phosphates (orthophosphates).

• -Two major groups of sedimentary deposits important for feed phosphates are pellet phosphorite and guano.
• -Major P deposits (pellet phosphorite) in Florida, Morocco, Israel and the Carolinas.

Guano phosphate is excrement of birds and bats with limestone (Curacao, Christmas Island, Mexico).

Most phosphates occur as apatite Ca₁₀ (PO₄)₆(F, Cl, OH)₂ or 3Ca₃(PO₄)₂. Ca(F, CL, OH)₂.

• -High Floride limits effectiveness of P sources.
• -High F unimportant for fertilizer-grade phosphates.
• -P, 80-85% in bones and teeth.
• -Seeds and seed by-products high in P.
• -Milk and bone high in both P and Ca.

Metabolism

Absorption of Ca and P

• -A Ca:P ratio of 1:1 to 2:1, close ratio most critical if P intake is marginal.
• -Absorption of Ca and P throughout GI tract, but most in duodenum and jejunum.
• -For rat 10%, large intestine.
• -Contrary to other species, in horse for P absorption, colon major site (Frap, 1998).
• -In horse excessive Ca has little effect on P absorption as Ca and P are absorbed from different regions of GI tract (Briggs, 1999).
• -Only small amount of Ca absorbed from rumen.
• -Generally 30-50% feed Ca absorbed but 70-80% P (Ternouth and Coates, 1997).
• -Ca absorption 90% for milk, < 50% for dry feed.
• -Ca and P absorption, both active and passive
• -Major function for vitamin D to maintain blood Ca and P for normal mineralization and physiological functions (DeLuca and Zierold, 1998).
• -Ca absorption related to demand, higher in early lactation.
• -Indigestible carbohydrates also promote Ca absorption in rats (Mineo et. al. 2001).
• -Ca absorption favored by acid conditions (lactose promotes).
• -P absorption influenced by dietary level of P, source of P, intestine (pH), age, intestinal parasitism and intakes of Ca, Fe, Al, Mn, K and Mg.
• -In dairy cows, apparent P digestibility decreased with increasing dietary P (Knowlton and Herbein, 2002).
• -P combined with Fe, Al and Mg to form insoluble phosphates.
• -Phytates decrease absorption for both P and Ca.
• -Ca combined with oxalic acid, forms insoluble Ca oxalate (Weaver et al., 1997).
• -Fatty acids may form insoluble Ca soaps.
• -In humans, low estrogen (O'Loughlin and Morris, 1998) and dietary protein (Kenstetter et al., 1998) reduces Ca absorption.
• -In pigs, Ca digestion is 13.4% at 60 days of pregnancy but 30.6% during lactation.

Control of Ca and P Homeostasis

Blood Ca maintained within very narrow limits by three hormones

a. parathyroid (PTH)

b. 1, 25 dihydroxycholecalciferol [1,25 (OH₂)D]. (Vitamin D₃)

c. thyrocalcitonin (calcitonin)

Calcitonin depresses Ca gut absorption, halting bone demineralization and reducing re absorption by the kidney.

• -Vitamin D elevates plasma Ca and P by stimulating specific pump mechanisms in the intestine, bone and kidney.
• -Low blood Ca increased PTH causing 25 - OHD to be changed in kidney to 1,25(OH)₂D.
• -1,25(OH)₂D promotes synthesis of Ca-binding protein (calbindin).
• -No calbindin in intestine of rachitic chicks
• -Second protein is intestinal membrane Ca-binding protein (IMCal) translocation mechanism across luminal membrane.

• -P is transported against an electrochemical potential gradient involving Na in response to 1,25(OH)₂D.
• -1,25(OH)₂D has roles in both mineralization of bone as well as mobilization of Ca from bone to extracellular fluid compartment.
• -Changes in plasma Ca relates to high and low affinity Ca-binding sites which is regulated by osteoclast and osteoblast (Bronner and Stein, 1995).
• -Placental and egg transfer of Ca and P.
• -Likely binding proteins in intestinal tract and mammary tissue (Mahan and Vallet, 1997).
• -Mineral reserves are diverted from maternal bone to meet fetal needs.
• -99% of filtered load of Ca reabsorbed (kidney) in absence of vitamin D and PTH. These hormones control the 1%.
• -For ruminants, saliva is the main contributor of P to the gut.
• -Salivary secretion of P is closely matched by net absorption in the small intestine.
• -In cattle, inadequate dietary P decreases P in saliva (Jain and Chopra, 1998).
• -Ruminants have a higher renal threshold for P excretion.
• -A clear advantage as diets often low in P.

Storage

Bone contains 98-99% Ca and 80-85% P

Excretion

Feces is the main pathway for Ca for most species, urine is however important for the horse and rabbit.

• -Some Ca lost in sweat; humans may lose 20 mg Ca per hour (350-500 mg Ca/hr in horse, Frape, 1998).
• -Feces primary path for P excretion in herbivores, but urine for carnivores and humans.
• -However, high concentrate diets in cattle increased urinary P.
• -During P deficiency, kidneys reduce loss to zero.

Physiological Functions

Structure of bone

• -Ca and P make up 70% of bone minerals.
• -Ca:P relation nearly constant, 2:1.

	Adult Bone		%
	HOH		45
	Ash		25
	Protein		20
	Fat		10

• -Mineral salts deposited in organic matrix, mixture of proteins (mostly ossein).
• -Bone ash 36% Ca, 17% P and 0.8% Mg.
• -Mammalian young born with poorly mineralized bones.
• -Ca and P in bone as Ca-phosphate [Ca₃(PO₄)₂] and hydroxy apatite [Ca₁₀(PO₄)₆(OH)₂].
• -Bone-length takes place at the junction of the epiphysis and diaphysis.
• -Cartilage (protein) in between is a temporary formation that is replaced by calcified bone.
• -Cortical bone is composed of densely packed layers of mineralized collagen, provides rigidity and major component of tubular bones.
• -Trabecular (cancellous) bone is spongy, provides strength and elasticity (major part of axial skeleton).
• -Bone undergoes a continuous process of resorption and formation

Osteoclast - bone resorption

Osteoblast - synthesis of matrix components

• -During pregnancy and lactation, minerals withdrawn from bone.
• -As animals and humans age, they loose peak bone mass, more of a problem for humans (longer life span)
• - of 70-79 year old and ½ of over 80 year old women have lost at least 25% of femoral bone mass.

risk of hip fracture by a factor of 6

Goal in life should be to building up bone mass

Physical activity will increase peak bone mass

Tennis players higher BMD in dominant arm

In poultry activity increased bone growth

Calcium and Phosphorus in Soft Tissue

Calcium - 1% in soft tissue needed for:

• -Blood clotting (for prothrombin to form thrombin).
• -Enzymatic reactions, activities ATPase.
• -Secretion of a number of hormones and hormone-releasing factors.
• -Muscle contraction.
• -Maintenance of normal blood pressure.
• -Immune responses of chickens.
• -Synaptic nerve transmission.
• -Low Ca, death from tetany.
• -Dietary Ca decreases Pb absorption, thereby reducing toxicity.
• -Needed for weight gains, feed utilization, milk production, egg production, and shell quality.
• -Egg shell CaCO₃ need 2 g Ca for every egg produced.
• -Phosphorus - 15-20% in soft tissue

• -P in organic combination as: phospholipids, phosphoproteins, nucleic acids, cyclic adenosine monophosphate, cyclic guanine monophosphate, inositol polyphosphates, coenzymes, and 2, 3-diphosphoglycerate (regulates O₂ released by hemoglobin) (Arnaud and Sanchez, 1996).
• -P is involved in almost all, if not all, metabolic reactions, and therefore, the most versatile of all mineral elements.
• -Involved with every aspect of feed metabolism and utilization of fat, carbohydrates, protein and nutrients.
• -Phosphorylation and dephosphorylation regulate cell activities, including functions of enzymes, hormones and transcription of genetic information.
• -High energy phosphate bonds (ATP) and nucleic acids (RNA, DNA)
• -Essential for buffer systems in blood and other fluids (e.g., rumen)
• -Rumen microorganisms need to digest plant cellulose

Requirements

• -Monogastric animals have higher Ca and P requirements than ruminants, highest requirements for egg production.
• -Requirement for maximum bone strength at least 0.1 percentage units higher then maximum rate and efficiency of gain.
• -Higher dietary Ca and P for prolonged reproduction periods.
• -Age is a factor, young dogs were unable to adjust the digestibility of Ca at either excessive or insufficient intakes (Dobenecker, 2002).
• -Different NRC and ARC requirements, e.g., for cattle, ARC concludes 68% of Ca available from feeds but NRC only 38%.
• -Additional error assuming total endogenous loss is constant (regardless of feed intake and age).
• -Different safety margins (NRC), but ARC minimum values.
• -Requirement dependent on Ca:P ratio, lowering Ca:P ratio from 1.5:1 to 1.3:1 or 1.0:1.0 increased P utilization (Corn-SBM) in pigs (Liu et al., 1998; 2000).
• -Higher vitamin D reduces the significance of adverse Ca:P ratios.
• -For most poultry diets 2 parts Ca to 1 part nonphytate P ratio is appropriate, 12:1 for egg shell formation.
• -When feeding high legumes Ca:P ratio of 6 to 10:1, or feeding overly mature forages (low in P).

-

Ruminants can tolerate wider Ca:P ratio (if vitamin D high),

but below 1:1 and over 7:1 adversely affected growth.

• -Low forage Ca will prevent responses to P supplementation because low dietary Ca will trigger 1,25(OH)₂D and mobilization of both Ca and P from bone.

e.g.,

greater responses to P supplementation from South Africa with cattle on Calcareous soils.

• -Some suggest that P requirements for beef cattle too high.

• -From Utah, no difference in gains for two years on diet containing 0.14 P (66% of NRC requirement).
• -However, studies from Florida demonstrated that 0.12-0.13% P was inadequate for growing Angus heifers in a 772 day experiment.
• -Lower gains with low P diet (205 vs 257 kg), pica, and bone demineralization.

• -Both Utah and Florida studies criticized because: done in dry lot feeding chopped or pelleted diets (not indicative of grazing conditions where animals walk).
• -Also Utah and Florida used beet pulp and citrus pulp, respectively, P availability from these feeds would seem higher than from tropical forages.
• -Other factors that influences Ca and P requirements:

1. High forage Fe and Al;

2. High fat diets (Ca soaps);

3. Parasitic infestations, demineralization of sheep bone;

4. High dietary energy and protein increased Ca and P retention in sheep (Rosero et al., 1983).

• -Phosphorus of plant origin is less available (e.g., phytates).
• -A large number of recent studies have shown that microbial phytases can improve P retention from 30 to over 45% in swine and poultry diets (BASF, 1997; Rodehutscord, 1998; Traylor et al. 2001).
• -Genetic effects; some breeds of cattle higher absorption of P, different strains of poultry different P requirements.

Production Effect		Ca, g		P, g
450 kg cow producing 4 kg milk		18.4		17.6
450 kg cow producing 10 kg milk		34		29
450 kg cow producing 30 kg milk		86		67

Human Requirements

DRI (2001) 700-900 mg for both sexes

• -Higher level to peak bone mass during early adulthood and bone mass can be maintained, 1300 mg/day is better (Carter and Whiting, 1997).

• -Do not need extra Ca during breast-feeding (Prentice, 1998).

Natural Sources

• -Ca greater in forages than grains.
• -Legumes high in Ca, cereal grain straws low.
• -Legume seeds and oil seed meals higher in Ca than grains.
• -Grass hays can be poor in Ca.
• -Milk and animal by-products containing bone, tankage, meat and bone scraps and fish meal high in both Ca and P.
• -Seeds (grains) and seed by-products, e.g., rice bran, oil-seed meals rich in P.
• -Ca and P in milk not affected by diet.

Milk Ca and P (Salih et al., 1987)
		Ca, %		P, %
Brahman colostrum		0.143		0.128
Brahman 3 mo postpartum		0.127		0.090

• -Phosphorus declines dramatically as forage matures.
• -Ca less affected by maturity, resulting in a wide Ca:P ratio.
• -Only of P in grains and oil seed meals is available to monogastrics, not true for all feedstuffs.
• -Availability of P in corn from seven experiment stations was low and varied from 9- 29%.
• -Phosphorus in fish meal and blood meal 100% available.
• -For ruminants, broiler litter and swine wastes good P sources.
• -Phytic acid is six phosphate molecules combined with myo-inositol.
• -Phytic acid reduced absorption of P, Ca, Fe, Mn and Zn.
• -In grains and plant protein supplements, ½ to P in phytin form.

	Percentage of Total P as Phytin
	Cereal grains	59 - 70
	Legume seeds	20 - 46
	Oil seed meals	34 - 66
	(Eeckhout and DePaepe, 1994)

• -Utilization of phytate influenced by phytase in plant materials, vitamin D, Ca, Zn, GI tract pH, and ratio of Ca:P (Li et al., 1989).
• -Ca exaggerates inhibition of Zn by phytate.
• -Some grains (e.g., rye) contain enzyme phytase, but others, little (e.g., oats).
• -For broilers and turkeys, ratio of Ca:P above 1.4:1, adverse affect on P release.
• -A good rule, no more than ½ P in plant feeds is available.
• -Ruminants utilize phytin P well, phytase pro-duced by rumen microorganisms.
• -Much success for development of microbial phytase, Aspergillus niger (Um et al., 1999; Orbanet et al., 1999).
• -Coon and Leskey (1998) evaluated phytase on phytate degradation in eight feed ingredients: improved P retention 44.3-54.8% for barley, SBM, corn and wheat middings, and 30.7-34.4% for wheat, canola meal, sorghum and rice bran.
• -For Rainbow Trout phytase increased P digestion by 25-57% (BASF, 1999).
• -For grazing livestock Ca often adequate (particularly if legumes).
• -Sometime Ca in lucerne has low availability, may be oxalates (20-30% Ca oxalate).
• -Spinach for humans, enough oxalic acid to render all Ca unavailable.
• -Some tropical forages contain high levels of oxalate (Kiatoko et al., 1978).
• -1% oxalic acid in equine diets reduced Ca absorption by 66%.
• -Temperate forages higher in Ca.

a. From 9500 samples, mean of 0.84% (Adams, 1975).

b. Grasses 0.4% Ca, legumes 1.15% Ca.

• -Most feedstuffs used for swine and poultry very low Ca.

History

• -Rickets known since antiquity.
• -Not until 1800s was relationship among Ca, P and vitamin D studied.
• -1669 - Brandt isolated P from urine.
• -1736 - boiled dyes, mixed with bran and fed to pigs, showed dye deposited in bone.
• -1769 - Gahn recognized P as part of bone.
• -1808 - Sr. Humphrey Davey discovered Ca.
• -1817 - inorganic part of bone was Ca phosphate, with some Mg.
• -1841 - Boussingalt 1) noted phosphoric acid and lime should be part of diet and 2) related to depraved appetite of South American Indians.
• -1842 - Choussat - first experiment with Ca, CaCo₃ add to pigeon diets result in normal bones.
• -Late 1800s rickets produced in pigs with low Ca diet.
• -Late 1800s rickets prevented in calves with lucerne hay.
• -In early 1890's rickets produced by feeding low-P diets.

• -By 1900 need of Ca for nursing mothers, dentist knew gestation and lactation weakened the mother's teeth.
• -1785 - in South Africa disease of lamsiekte (lame sickness) and botulism, noted bone eating or osteophagia.
• -Theiler (1920, 1927) etiology of lamsiekte and botulism was P deficiency.
• -Related to subnormal growth, low reproduction and depraved appetite (pica).
• -1839 - Azara - osteophagia in cows of Paraguay, related to P deficiency.
• -1926 - Schmidt - in Texas fatal disease of cattle (creeps) prevented by bonemeal.
• -1933 - Becker et al. - "stiffs" or "sweeney" in Florida caused by deficiency of P.
• -In late 1960s, new phase of research on how vitamin D influences Ca and P metabolism.

Deficiency

Rickets - lack of Ca and P, decreased concen-trations in organic matrices of cartilage and bone.

Osteomalacia (adult), cartilage growth has ceased, decreased Ca and P in bone matrix.

Osteoporosis (an atrophy of bone), defective formation of protein matrix.

Same effect for vitamin D deficiency

• -In young, inhibition of growth, weight loss, reduced appetite before bone signs.

• -Decreased mineralization, results in lameness and fractures, also misshapen bones.
• -Demineralization first of spongy bones (ribs, vertebrae, sternum and cancellous end of long bones).
• -Compact shafts of long bones (Humerus, femur and tibia) later.
• -Tension of muscles pulls bones out of shape.
• -Signs of rickets depends on anatomy and severity.

a. Curving and bending of bones.

b. Enlarged hock and knee joints.

c. Tendency to drag hind legs.

d. Beaded ribs and deformed thorax.

• -Degree of resorption - vertebrae and bones of head, next scapula, sternum and ribs.
• -Phosphorus deficiency problems for grazing ruminant (especially cattle).
• -Ca deficiency, more for hand fed animals, pigs and poultry.
• -Ca deficiency inevitable for those receiving grain-based diets, e.g.,

corn - 0.02% Ca and 0.3% P

wheat - 0.04% Ca and 0.4% P

• -In P deficiency (vs Ca) anorexia, feed efficiency result in weight gain, production milk, eggs, fertility, pica

Swine

Deficiency of Ca, P, vitamin D results in poor growth, lameness, stilted gait, posterior paralysis, bone deformation, beading of ribs and enlarged joints.

• -Bone depletion from long lactation, rapid fetal bone development.

Ca:P ratio <1:1 result in excessive bone resorption.

• -Nutritional secondary hyperparathyroidism (excess P related to Ca).
• -Low levels of Ca and P can reduce litter size.

Poultry

• -Little difference exists among poultry species
• -Rickets, lower growth rate, egg production, hatchability.
• -Phosphorus deficiency results in death, particularly laying hens.
• -For ducks high mortality (65%), stunted growth, lack of appetite (Cui et al., 1997).
• -Ca and P most important minerals for commercial egg production to maintain egg shell quality and embryonic development.
• -If Ca deficiency in breeder diet, egg weight loss, increased contamination, embryos with stunted growth, increased mortality.
• -Breeders on litter floors can recycle some P by coprophagy.
• -Clinical signs for laying hens:

1. or cessation of egg production;

2. feed consumption and efficiency;

3. shell quality;

4. egg quality (blood spots, yolk mottling);

5. egg size and weight;

6. reproduction (less hatchability, mating activity).

• -Skeletal abnormalities

1. bone resorption;

2. cage-layer fatigue (osteoporosis);

3. rickets;

4. soft beak;

5. osteodystrophy fibrosa;

6. paralysis;

7. lameness;

8. beaded ribs;

9. enlarged and painful joints;

10. abnormal posture and misshapen bone.

• -Cage-layer fatigue (osteoporosis) - unable to stand, paralyzed, bones easily broken.
• -In broilers, bone condition tibial dyscondroplasia, a high blood P, increased Ca to prevent.

Ruminants

• -Lack of Ca, P or vitamin D, improper bone mineralization, swollen tender joints, enlargement of ends of bones, an arched back, stiffness of legs, beads on ribs.
• -For Caribou, P deficiency results in limited growth of antlers (Moen et al., 1998).
• -Chemical, physical and mechanical properties of bone illustrate extreme bone demineralization for cattle with inadequate P (Williams et al., 1990, 1991, a,b).

• -Calves develop bowed and deformed legs.
• -Cows develop osteomalacia, milk yields, muscle weakness and eventually tetany if prolonged and severe.
• -Grazing Ruminants, P deficiency
• -Those consuming high-concentrate diets, Ca deficiency.
• -Milk fever (parturient paresis) is a hypocalcemia near parturition and initiation of lactation.
• -It is a malfunction of 1,25(OH)₂D and PTH.
• -Older animals have a decreased response to dietary Ca stress due to decreased production of 1,25(OH)₂D.
• -Cows may have defective hormone receptors and the number of receptors declines with age.
• -Aging process also associated with reduced renal 1-hydroxylase (Goff et al., 1991)
• -Milk fever is associated with increased mastitis, ketosis, dystocia, displaced abomasum and retained placenta.
• -Each case of PP cost $334 (Horst et al., 1997).
• -PP also problem with pregnant and lactating ewes.
• -Deficient Ca and P influenced by availability of different sources and interrelationships with other nutrients.
• -In India, Ca deficient cattle fed straw with high oxalates.
• -Soils in humid tropics, often acid soils high in Fe and Al makes P unavailable to plants.

• -Direct soil consumption high intakes of Fe and Al.

• -Compared to P deficiency, Ca deficiency uncommon in grazing cattle.
• -For grazing beef cattle P vs Ca deficiency because:

1. Higher Ca in vegetative part of plant;

2. More P deficient soils than for Ca;

3. P declines with maturity of plant vs Ca.

• -For grazing livestock, the most prevalent mineral element deficiency throughout the world is lack of P.
• -Phosphorus deficiency reported in 46 tropical countries of Latin America, Southeast Asia and Africa.
• -Serve P deficiency causes pica, the chewing of wood, rocks, and bones.

• -Urge to eat bones lost by intravenous infusion of Na phosphate.
• -Major consequence of P deficiency is the decreased food intake.
• -DM intake in lambs reduced 40% with low P diet (Ternouth and Sevilla, 1990).
• -With low P, fiber digestibility, decreased microbial protein synthesis, P for intermediary metabolism.
• -Low feed intake for grazing animals with a P deficiency may relate to lameness.
• -"Peg-leg" - P deficiency in Australian cattle, hamper ability to secure food.
• -Phosphorus supplementation, in many world reports increased overall performance, increased weight gains, increased birth weights, increased milk production.
• -Most devastating result of P deficiency is reproductive failure.
• -Failure to reproduce associated with loss of body weight, result of decreased F.I.
• -Less F.I. caused by decreased appetite, impaired locomotion.
• -Two-year observation of South African cattle

Control 51% calf crop

Control + bone meal 80% calf crop

reproductive performance due to mineral supplementation in 17 different experiments in Latin America, Africa and Asia (McDowell, 1985).

Average of 17 Experiments for Calving Percent

Control 52.6% With P 75.6%

• -From Zimbabwe and Northern Australia, lactating cows did not calf two years in succession.
• -If Calf produced, cows not in regular estrus until body P levels restored, feed supplementary P or cessation of lactation.
• -Severe P deficiency - botulism (bone eating).
• -In Piauí, Brazil, 2-3% of 10,000 cattle die annually of botulism.
• -In Brazil, the three most important causes of adult cattle mortalities are botulism, rabies and plant poisoning.

Horses

• -Deficiency of Ca, P or vitamin D causes rickets.
• -Reduced bone calcification, stiff and swollen joint, stiffness of gait, bone deformities.
• -Rickets in Florida ponies (El Shorafa et al., 1979), bone ash, cortical area and bone density and delayed epiphyseal closure.
• -In mature horse, severe lameness.
• -Low Ca high P, a condition called nutritional secondary hyperparathyroidism (also called big head and bran disease), this causes Ca removal from facial bones, following fibrous connective tissue invading area.

• -A benefit of feeding a greater amount of Ca (more than NRC) to the young racehorse at the onset of training (Nielsen et al., 1998).

• -Phosphorus deficiency appetite, eating bones, wood, hair, rocks, clothing, etc.
• - weight, weakness, FE, milk production, failure to exhibit estrus and low conception rate.

Other Animal Species

Dogs - rickets with typical bone lesions.

• -Jaw bones earliest signs followed by skull bones, detachment of teeth.
• -May result in tetany and convulsions.
• -Under natural conditions no problem with P.

Cats - severe rickets results in enlarged costo-chondral junctions (rachitic rosary)

• -Nutritional secondary hyperparathyroidism, most common bone disease.

Results from feeding meat-rich diets, problem with felines in zoos.

• -Ca:P ratio of meat 1:20

Laboratory animals - rickets in rats, uncalcified cartilage, growth, F.I., rear-leg paralysis, reproduction, lactation.

Rabbits - bones demineralized, sometimes parturient paresis.

Fox - muzzles enlarge, gums swell, teeth loosen.

Fish - P deficiency causes growth, FE, bone mineralization.

Salmon - bone deformities.

Non-human primates - rickets, lack of vitamin D vs Ca and P.

Humans

Rickets - disordered cartilage cell growth.

• -Bowlegs, knock-knees, curvature of the spine, pelvic and thoracic deformities.

• -Beading of ribs, referred to as "rachitic rosary" (swollen cartilaginous end of ribs).

• -Narrow chest described as "pigeon" chest.
• -Osteomalacia (softening of bone) - rickets of adults.
• -Osteoporosis (defective formation of protein matrix) associated with endocrine disorders.
• -Both terms refer to demineralization of bone, sometimes terms used interchangeably.
• -Osteoporosis - absolute decrease in bone mass, susceptibility to fracture, bone deformity, localized pain (wrist, spine, hip).

• -Common in elderly of both sexes and post-menopausal women.
• -Bone loss general phenomenon, starting 4^th decade in females, 6^th in males.
• -The more bone mass available before these periods, the better.

Characterization of osteoporosis:

1. Less estrogen bone resorption;

2. Higher bone turnover;

3. Impaired Ca absorption, less conversion of 25 OH D to 1,25(OH)₂D; (Vitamin D₃)

4. Less able to conserve body Ca by urinary loss;

5. Less physical activity, rate of bone loss.

• -Estrogen + Ca bone loss (Bronner, 1997).
• -500 mg Ca + 700 I.U. vitamin D for 3 years bone loss (O'Brine, 1998).
• -Hip fracture (Yugoslavia), with high Ca, 50% lower than low-Ca diet.

Japanese women Ca intake 400 mg/d highest hip fracture.

Finnish women Ca intake 1300 mg/d lowest hip fracture.

• -Kidney stones are associated with low dietary Ca intake (Martini and Heilberg, 2002)

Assessment of Ca and P Status

• -Compositional and mechanical criteria for bones.
• -Plasma P < 4.5 mg/100 ml for cattle and sheep.
• -OK, if stress factors, time of sampling and blood preparation controlled
• -Blood Ca controlled by 3 hormones (~10 mg/100 ml), laying hens (20-30 mg/100 ml), nonlaying (9-12 mg/100 ml).
• -Williams (1991) analyzed P of blood, milk, feces, bone, saliva, rumen fluid, etc.

Rib-bone P best reflected P intake

• -Incomplete calcification of skeleton easily detected with x-rays, bone density (BMD), bone mineral content (BMC), dual photon absorptiometry, ultrasound.
• -BMC or BMD are the best indicators for risk of fracture (Yates, 1998).
• -Dried fat-free ash when dietary Ca and P (Eklou-kaloni, 1999).
• -In pigs, femur breaking strength better than bone ash.

Williams et al 1991 for cattle

	Breaking Load		Breaking Strength
0.12% P	1179 kg		189.2 Mpa
0.20% P	1348 kg		202.5 Mpa

Supplementation

For most animal classes, the two most important minerals for supplementation are Ca and P.

Ca - swine, poultry, feedlot cattle, high producing dairy cattle

P - grazing livestock

- Laying hens, 3.25% Ca

Feed grains and oil seed meals are good P sources but in phytin form.

Two problems from phytate P

1. Need to add more inorganic P.

2. Excretion of large amounts P in manure.

• -Excess P in streams causes uncheck growth of algae
• -High levels of algae and cyanobacteria, leads to low O₂ and loss of aquatic life (Correll, 1999).
• -Governments have (or are) enacting legislation to reduce P pollution.
• -Providing phytases to monogastric diets make P more available and less inorganic P required.
• -Almost of P in grains and 34-66% in oil seed meals in phytin form.
• -Phytases may improve bioavailability by 20-45%, reduces P excretion by ~30%.
• -Phytases also a benefit for other minerals (e.g., Zn and Fe) and energy-protein.
• -High available P corn varieties have been developed (Sands et al., 2001)
• -Phosphorus is the most expensive mineral.
• -Studies from UK and the Netherlands, show no effect on milk production by use of 80% P requirements.

Factors that influence Ca and P requirements.

1. Variability of ingredient nutrients;

2. Nutrient availability;

3. Animal performance potential;

4. Energy level of the feed;

5. Ambient temperatures;

6. Stress of disease, overcrowding, poor ventilation, and inadequate temperature control;

7. Compensatory growth;

8. Interaction of ingredients;

9. Interaction of nutrients;

10. Variability in animal response;

11. Variability in management; and

12. Adequacy of vitamin D intake, and adequacy of liver and kidney integrity to convert it to the proper hormonal form of vitamin D.

• -Swine breeding herd needs more Ca and P than for maximum growth and F.E.

• -Sources of Ca: limestone (Ca carbonate), oyster shell, calcium sulfate, Ca chloride, Ca phosphates, bone meal.
• -Particle size, fineness of grind, more surface area.
• -For laying hens may replace part of limestone with oyster shell, large particles remain in gizzard longer.

Many P sources available including Ca phosphate (dicalcium phosphate, monocalcium phosphate, defluorinated rock phosphate, bone meal, guano-origin phosphates), ammonium polyphosphate, sodium phosphates (e.g., monosodium phosphate).

• -Considerable variation in biological availability.
• -Colloidal phosphate or soft phosphate is significantly less available.
• -Ground rock phosphate (continental deposits) is less palatable, less available and contains 3-4% F.

• -Fertilizer phosphates are sometimes used.
• -Triple superphosphate, 21% P and 2% F.
• -Fertilizer phosphates used for short periods or combined with safe sources.
• -Superjuices are fertilizers + water, CaF₂ precipitates out.

Methods of Supplementation

a. Concentrates;

b. Fertilizers e.g., 0.07-0.10 to 0.25-0.30 (Florida Study);

c. Individual dosing (drenching) or injections;

d. Water;

e. Free-choice.

• -Season of year for free-choice, wet or dry?
• -Supplementation to prevent parturient paresis.
• -Can often prevent by feeding a prepartum low-Ca and adequate diet (also low K).
• -Prepartal low-Ca diets associated with plasma PTH and 1,25-(OH)₂D, so a "prepared" and effective gut and bone Ca homeostatic mechanism at parturition.
• -However, it has been found that these two hormones were higher in cows with PP.
• -Most effective prevention is to provide an anionic diet prepartum e.g., CaCl₂,Al₂(SO₄)₃, MgSO₃, NH₄Cl or (NH₄)₂SO₄ etc
• -Cation-anion difference (CAD) Na⁺ and K⁺ relative to Cl + SO₄²

Diets high in cations (K and Na) induce milk fever, those high in anions (Cl, S) can prevent.

• -Anions in prepartal diet induces metabolic acidosis, facilitates bone Ca resorption and intestinal Ca absorption (Horst et al., 1997).
• -Anions increase osteoclastic bone resorption and syntheses of 1,25(OH)D. (Vitamin D₃)
• -Underlying cause of milk fever is metabolic alkalosis, inability to respond to PTH (which affects active form of vitamin D).
• -Vitamin D activity in tissues (intestine, kidney and bone) is mediated by vitamin D receptors (Uhland-Smith and DeLuca, 1992).
• -1,25(OH)₂D receptor identified as a Zn binding structure of amino acid loops around a Zn atom (Reid, 1993).
• -Goff et al. (1991) proposed that target tissues of 1,25(OH)₂D in cows with PP may have defective receptors.
• -Number of receptors with age and with

pregnancy and lactation (Goff et al., 1991).

• -CAD concept suggest milk fever managed best if K reduced.
• -Ca chloride or Ca propionate used to induce metabolic acidosis.
• -"Downer cows" with PP use Ca borogluconate intravenously.
• -Another Ca supplementation consideration is minerals as buffers.
• -Buffers (e.g., Na bicarbonate, dolomitic limestone (MgO), ground limestone, control low rumen pH.
• -Limestone not as affective.

For humans, Ca and P supplementation not needed for children that consume milk (and milk products) and sunlight.

• -Using vitamin D fortified milk, rickets has disappeared from more developed countries.

For adults, Ca is most limiting mineral.

• -Lack of Ca not realized until later in life.
• -Phosphorus deficiency rare (defects of renal tubular reabsorption).
• -Human milk 1/7 of cow's milk in P.
• -Cow's milk better for premature infant.
• -Diets rich in protein, low Ca:P ratios promote hypercalciuria and PTH (reducing bone mass).
• -However, 70-90 years old with the highest protein consumption had less bone loss than those consuming ½ as much protein (Tucker and Mayer, 2001).
• -Exercise important to slow down loss of bone mass.
• -Bone mass achieved at 25-30 years of age.
• -Ten years before menopause bone loss 2-5% per year.
• -Estrogen replacement therapy and Ca bone loss.
• -Treatment with 1,25(OH)₂D benefit (O'Brien, 1998).
• -Ca and vitamin D also good.
• -Older individuals need longer sunlight to get effect.

• -Ca intake of 1300 mg/d for children 9-18 yr will maximize peak bone mass (Carter and Whiting, 1997; Rourk et al., 1998).
• -Ca supplementation reduces risk of hypertension by lowering high blood pressure (Osborne et al., 1996) and risk of colon cancer (Mobarhan, 1999)

Toxicity

• -Maximum tolerance for Ca 2% (cattle, sheep, horses, and rabbits), 1% (swine), 1.2% for most poultry and 4% for laying hens.
• -Maximum tolerance for P is 0.6 - 1.5%.
• -Excess Ca may cause deficiency of P, Mg, Fe, I, Zn, Mn.
• -Parakeratosis in swine (Zn deficiency) caused by excess Ca.
• -Excess Ca antagonistic to vitamin K.
• -2.5% Ca in pullets, Ca deposits in ureters, 10-20% death.
• -High Ca (4.4%) depressed protein and energy digestion in steers.
• -Main pathological effect of massive amounts of vitamin D is calcification of soft tissues.
• -Grazing animals in several parts of the world develop calcinosis, a disease characterized by deposition of Ca salts in soft tissues.
• -Ingestion of the leaves of shrub Solanum malacoxylon.
• -Local diseases in Argentina (enteque seco) and Brazil (espichamento).
• -Other world regions Alpine (Europe), New Guinea, Australia, Jamaica, and some ornamental plants in Florida (Cestrum diurnum).

Toxic factor - glycoside of 1,25(OH)₂D₃. (Vitamin D₃)

Result - soft tissue calcification, destruction of connective tissue.

Signs - stiffened and painful gait, progressive loss of weight, joints cannot be extended, walking with arched back.

• -Calcification of the vascular system, lungs, kidney.
• -Some fields in Argentina, between 10-30% of cattle show signs of enteque seco.
• -Solanum malacoxylon the most important poisonous plant in Argentina.

• -Excess P (in relation to Ca) nutritional secondary hyperparathyroidism.
• -In a number of species, low production and loss of bone with excess P.
• -Excess P in human diets.
• -Diets high in protein and P inhibit development of peak bone mass.