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Vitamin D Deficiency

Hypovitaminosis D

Vitamin D is a fat-soluble vitamin that regulates calcium homeostasis and is vital for bone health. The two most prominent forms of vitamin D are ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3).
Vitamin D3
Vitamin D3 can be destroyed by exposure to ultraviolet (UV) light and by peroxidation in the presence of rancidifying polyunsaturated fatty acids (PUFA). Like vitamins A and E, unless vitamin D3 is stabilized, it is destroyed by oxidation, which is increased by heat, moisture and trace minerals. Vitamin D3 is absorbed from the intestinal tract in association with fats, as are all the fat-soluble vitamins. Like the others, it requires the presence of bile salts for absorption.

Vitamin D Deficiency Effects on Chickens

Vitamin D3 is an important nutrient for chickens, especially for growing chicks and laying hens. In young chicks, a vitamin D deficiency can cause rickets, resulting in leg and beak deformities. In hens, a vitamin D deficiency adversely affects egg production and can cause calcium deficiency. In order for absorption of calcium (Ca) and phosphorus (P), adequate levels of vitamin D3 must be present. Chickens can get vitamin D3 in their bodies through two different routes---by ingestion of it in feed or by exposure to sunlight.

Vitamin D Interactions

When chickens receive too much vitamin D3 it can result in excess calcium in the blood which is referred to medically as hypercalcemia. This is a serious condition which can lead to gout, heart problems, and liver damage. A clinical sign of too much vitamin D3 in the diet of laying hens is the production of eggs with calcium pimples on the eggshells. When the pimples are scraped off they will leave tiny holes in the shell.

Nutritional Recommendations for Vitamin D in Chickens

A chickens need for vitamin D depends on the ratio of calcium to phosphorus. The vitamin D needs of poultry are increased several fold by inadequate levels of calcium and (or) phosphorus or by improper ratios of these minerals in the diet. For chickens, the optimum dietary ratio of calcium:inorganic phosphorus is approximately 2:1. Recent research studies have shown Vitamin D3 requirements for chickens at various ages include:

Vitamin D Recommendations for Chickens
Age/Life StageIU/kg
Newly Hatched Chicks (0 - 10 wks)3,000-4,000
Young & Growing (10 - 20 wks)2,000-3,000
Laying hens (Actively laying eggs)3,000-4,000
Breeders (20 wks & older)*3,000-4,500
Broiler/'Meat' Breed Chicks (0-18 wks)3,000-4,000
Broiler/'Meat' Breeds* (19 wks & older)3,000-5,000
*Includes roosters

Clinical Signs

Penguin-like (weak) stance prior to laying an egg
Decreased egg production
Thin or soft-shelled eggs
Small eggs
Calcium pimples on eggshells
Stunted growth
Softening of beak, feet, and keel
Poor hatchability
Bent or malformation of beak
Bowing of legs


  • History
  • Clinical signs
  • Diet analysis


Increase access to sunlight
Cod liver oilAdd to feed ration at a rate of 2 tablespoons per 5 pounds (65 mL per 5 kg)G Damerow, 2015
For young chicksProvide full-spectrum fluorescent lighting for part of the day



Feed a balanced diet with adequate levels of vitamin D

Scientific References

Risk Factors

  • Keeping chickens indoors, with little to minimal access to natural sunlight.
  • Keeping chickens in an outdoor enclosure that doesn't get much sunlight, and is mostly shaded.
  • Egg laying hens
  • Feeding chickens table scraps containing foods with high amounts of oxalates, which will interfere with absorption of calcium.