July 1, 2021
DSM explains the relationship of vitamin D and estrogen in egg-laying hens
The sufficiency of vitamin D or a lack of it affects the reproductive functions of layer chickens. Studies indicated that feeding vitamin D, preferably in the form of 25(OH)D3, to egg-laying hens either maintain or increase the level of estrogens such as 17b-estradiol.
Vitamin D plays a key role in estrogen biosynthesis and regulates various gene expressions affecting many physiological functions. The vitamin D receptor is expressed in the ovary, that in complex with 25(OH)D3, regulates the gene expression of aromatase. Aromatase, a cytochrome P450 enzyme, helps in converting androgens (androstenedione, testosterone) into estrogens (estrone, estradiol).
In egg-laying hens, these conversions occur in thecal cells of the ovarian follicles, which are the main source of estrogen such as the 17b-estradiol, the main circulating form.
Estrogen, such as that of 17b-estradiol, induces the synthesis of vitellogenin in the liver. Vitellogenin, the egg yolk precursor protein (phospholipoglycoprotein), is secreted from the liver into the blood circulation, and travels to the oviduct, where they are deposited in the developing oocyte. While traveling in the blood, it picks up nutrients (vitamins, minerals, fats, proteins, carotenoids) and transfers these nutrients from blood circulation to the egg yolk. This is why vitellogenin is crucial in achieving consistency of deposited nutrient content in the yolk of functional eggs.
Vitamin D insufficiency, which results in lower estrogen levels, may compromise fertility in breeder hens. In essence, estrogen levels reflect the extent of ovary activity for functional reproduction.
Thus, ensuring adequate vitamin D — preferably in the form of 25(OH)D3 — is significant in maintaining estrogen levels for optimal reproductive function and vitellogenin synthesis in egg-laying hens.