In fowls, vitamin D is responsible for normal growth, egg production, shell quality, and reproduction. Alpha vitamin D3 (1,25 dihydroxycholecalciferol) is involved in Ca and P absorption in the gut, bone mineralization (bone formation) and demineralization (bone mobilization); Ca and phosphate reabsorption by the kidneys.
Commercial layers are usually maintained indoors, and do not receive enough sunlight to convert 7-dihydrocholesterolin sufficient levels to supply their vitamin D3 requirements. This is why vitamin D is routinely added to layer feeds, which is essential for the maintenance of egg production, eggshell formation, and calcium homeostasis.
The two most prominent forms of vitamin D are ergocalciferol (D2) and cholecalciferol (D3). Vitamin D3 is an important nutrient for chickens, especially for growing chicks and laying hens.
The inadequacy of vitamin D in birds results in rickets, retarded growth, soft and rubbery beak, hypocalcemia, parathyroid hyperplasia, elevated serum alkaline phosphatase, a marked expansion of epiphyseal growth plates including cartilage hypertrophy, failure of calcification of cartilage and osteoid, and fibrous osteodystrophy.
In hens, a vitamin D deficiency adversely affects egg production and causes 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 folds by inadequate levels of calcium and (or) phosphorus or by improper ratios of these minerals in the diet.
Cholecalciferol is the most common form of vitamin D added to feeds. After absorption by the intestinal mucosa, it is transported to the liver, where it is hydroxylated in the position 25, resulting in 25-hydroxycholecalciferol (25(OH)D3). This metabolite is directed to the kidneys and hydroxylated at carbon 1, originating the active metabolite of vitamin D, 1,25-dihydroxycholecalciferol (1,25(OH)2 α-D3). Vitamin D has been shown to stimulate the synthesis of a calcium binding protein in the intestine.
It is a blend of Phytoconstituents (Natural absorbance enhancers) and contains plant origin metabolites of Vitamin D3. It increases the absorption efficiency of liposoluble vitamin D3 present in the feed of birds. It maintains homeostasis of Ca:P in body, improves bone density, increases egg shell thickness and vitamin D levels of eggs.