Calcium (Ca) is an essential mineral that is required for bone growth of chicks, egg shell formation in hens, muscle contraction, transmission of nerve impulses, and blood clotting. Calcium also acts as an important co-factor for several different enzymes and hormones.
There are many causes of calcium deficiency 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 range from 1:1 to 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).
In order for chickens to be able to absorb calcium, they require adequate amounts of phosphorus (P) and vitamin D3. However they must all be in balance, as if birds are receiving excess amounts of P, it can decrease the chicken's ability to properly absorb Ca.
Calcium and phosphorus sources
|Ingredient||% Ca||% P|
|Defluorinated rock phosphate||34||19|
|Phosphoric acid (75%)||-||25|
Too much phosphorus can result in a condition known as secondary nutritional hyperparathyroidism. The ideal calcium to phosphorus ratio for chickens is 2:1.