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Hypocalcemia

Hypocalcemia

Hypocalcemia occurs when a chickens blood-calcium levels are dangerously low. It is mainly a problem in hens, especially ex-battery hens and breeds known for having excessive egg production traits. This is because egg-laying requires calcium to form the eggshell, resulting in depletion of it from her own body.

Causes of Hypocalcemia


There are many causes of hypocalcemia in chickens, even for birds that receive adequate amounts of dietary calcium in their daily diet. Dietary calcium can be reduced in chickens receiving:
  • Diets with too much phosphorus, such that it off balances the Ca:P ratio which should be 2:1.
  • Foods high in oxalic acid (cassava, spinach, carrots, beet leaves, lettuce, sweet potatoes, turnips) which form insoluble calcium oxalates and decreases calcium availability.
  • Excess vitamin C
Several different vitamins and minerals interact with calcium, some act with calcium, and are required in order for the body to absorb it, and others act against it (antagonists).
calcium nutrient interactions


Calcium Food Sources


Ingredient% Ca% P
Limestone38-
Oyster shell38-
Calcium carbonate40-
Bone meal2613
Monocalcium phosphate1725
Dicalcium phosphate2120
Tricalcium phosphate2319
Defluorinated rock phosphate3419
Curaco phosphate3516
Phosphoric acid (75%)-25


Calcium Nutritional Requirements for Chickens


Requirements for calcium in chickens at various life stages are:

Feed TypeBird AgeCaPVitamin D3
Chick StarterHatch to 6 weeks0.90%0.40%200 ICU
Grower6 to 20 weeks0.80%0.30%250 ICU
Layer20 weeks and older4%0.31%375 IU
Breeder20 weeks and older3.25%0.35%300 IU
In order for chickens to be able to absorb calcium, they require adequate amounts of phosphorus (P) and vitamin D3.

Clinical Signs

Decreased egg production
Small eggs
Thin-shelled eggs
Increased risk of bone fractures

Diagnosis

  • History
  • Clinical signs
  • Blood test
  • Diet analysis

Treatment

Calcium: Oral supplementation of calcium in the diet or providing free choice calcium-rich options such as crushed oyster shells or limestone.

Prevention

  • Feeding a balanced diet and providing additional calcium sources such as limestone or crushed oyster shells to laying hens.
  • Supplementing diet with psyllium may increase absorption of calcium

Scientific References

Risk Factors

  • Egg laying hens
  • Not receiving enough vitamin D and Phosphorus in diet
  • Diets heavy in grains (such as scratch), predisposes hens to inadequate calcium availability, and secondary reproductive disorders such as egg binding
  • Getting fed table scraps containing spinach or chard, which can potentially augment calcium availability issues in chicks and adult hens due to the presence of oxalates.