Major Elements

  • Rickets in the young
  • Osteomalacia in the adult
  • Hypophosphatemia in humans
    1. Causes
      1. Nutritional vitamin D deficiency
      2. Blocks in metabolism of vitamin D due to genetic abnormalities
      3. Liver disease
      4. Pharmacological agents (anticonvulsant, addiction to antacids)
      5. Abnormalities of renal tubular reabsorption of phosphate
    2. Effects
      1. Failure of bone mineralization
        1. Rickets in growing bone
        2. Osteomalacia in adult bone
      2. Severe hypophophatemia
        1. Pronounced muscle weakness, possibly due to reduction to organic phosphates in muscle cells
  • Phosphorus deficiency in ruminants
    1. Cause
      1. Most forages contain little more than adequate P
      2. Weathered, leached forage is nearly always borderline or deficient in P
      3. Phosphorus is usually one of the most limiting of the mineral nutrients for ruminants in many situations
    2. Effects
      1. A drop in plasma inorganic P below the normal levels (4 to 6 mg/dl in adults; 6 to 8 mg/dl for young animals)
      2. Increased plasma phosphatase
      3. Depletion of mineral content of bones
      4. Stiff joints, lameness, fractures may occur
      5. Anorexia is the first clinical symptom
      6. Depraved appetite (may eat rocks, dirt, wood, bones, or hair)
      7. Reduced gain or milk production
      8. Impaired reproductive performance
        1. Lower conception rates and smaller calf crops
        2. More calving difficulty
        3. Lowered milk yield and consequently lowered weaning weight of calf
  • Phosphorus deficiency in chickens
    1. High mortality
    2. Cage layer fatigue syndrome
      1. Affected birds appear paralyzed and cannot rise or stand
      2. They eventually die of starvation

    • VIII.  Phosphorus Excess

    1. Nutritional secondary hyperparathyroidism
      1. Increased concentration of serum P
      2. Secondary lowering of serum Ca
      3. Stimulation of PTH secretion
        1. Increased urinary excretion of phosphate
        2. Increased resorption of Ca from bone
        3. Pronounced skeletal demineralization
      4. Metastic calcification in soft tissues (especially kidney, stomach and aorta)
    2. Hyperphosphatemia in humans
      1. Renal insufficiency can result in failure of urinary excretion of absorbed phosphate
        1. Secondary hyperparathyroidism
        2. Demineralization of bone
        3. Resorption of matrix
      2. In some patients, hyperparathyroidism results in elevated serum P because of increased tubular reabsorption of phosphate
      3. Treatment of hyperphosphatemia
        1. Reduction of phosphate intake is difficult since even the minimum protein diet compatible with good nutrition supplies too much phosphate
        2. Absorption of phosphate can be reduced by aluminum hydroxide
    3. Hyperphosphatemia in ruminants
      1. Relative excess P in relation to Ca can cause urinary calculi (urolithiosis)(J. Anim. Sci. 21:995, 1962: 22:510, 1963; 23:1079, 1964)
        1. Formation of stones in the kidney or bladder with resultant obstruction of urine excretion
        2. Bladder rupture results in temporary relief, but this is followed by abdominal distention, depression, and death due to uremia
        3. Maximum dietary level of P tolerated by sheep without development of calculi lies between 0.37% and 0.69%
        4. Increased dietary Ca provides partial protection against occurrence of calculi in sheep receiving higher levels of P (J. Anim. Sci. 24:671)
      2. In contrast to d. above, see Schrier, C. J., and R. J. Emerick. 1986.  Diet calcium carbonate, phosphorus and acidifying and alkalizing salts as factors influencing silica urolithiasis in rats fed tetraethylorthosilicate. J. Nutri. 116:823-830, 1986
        1. Rats fed diets containing 2% tetraethylorthosilicate were used as a model to investigate uroliths primarily of silica in range cattle and sheep
        2. Supplementary dietary phosphorus offers partial protection against silica uroliths
          1. Not associated with increases in urine volume
          2. Only partial dependent on urine acidification
        3. Increase in urolith incidence of rats fed CaCO3 appear to result from an alkalization of urine and a reduction in urine
    4. P excess in chickens
      1. Reduced egg production and egg shell quality in hens
      2. Decreased weight gain and efficiency of feed utilization in broiler
      3. Increased mortality when dietary P is raised to 2% (approximately four times requirement)
    5. Maximum tolerable phosphorus levels (assuming dietary Ca is adequate)
      1. Cattle 1%
      2. Sheep 0.6%
      3. Swine 1.5%
      4. Poultry 1% (laying hens, 0.8%)
      5. Horse 1%

    Major Elements




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