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 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. The need for vitamin D depends to a large extent 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.
Chickens can get vitamin D3 in their bodies through two different routes---by ingestion of it in feed or by direct exposure to sunlight. Sunlight that comes through ordinary window glass is ineffective in producing vitamin D in skin since glass does not allow penetration of ultraviolet (UV) rays which need to reach the body.
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 Stage | IU/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 |
