An Overview of the Current Known and Unknown Roles of Vitamin D 3 in the Female Reproductive System: Lessons from Farm Animals, Birds, and Fish.

Recent studies have clearly shown that vitamin D is a crucial regulator of the female reproductive process in humans and animals. Knowledge of the expression of vitamin D receptors and related molecules in the female reproductive organs such as ovaries, uterus, oviduct, or placenta under physiological and pathological conditions highlights its contribution to the proper function of the reproductive system in females. Furthermore, vitamin D deficiency leads to serious reproductive disturbances and pathologies including ovarian cysts. Although the influence of vitamin D on the reproductive processes of humans and rodents has been extensively described, the association between vitamin D and female reproductive function in farm animals, birds, and fish has rarely been summarized. In this review, we provide an overview of the role of vitamin D in the reproductive system of those animals, with special attention paid to the expression of vitamin D receptors and its metabolic molecules. This updated information could be essential for better understanding animal physiology and overcoming the incidence of infertility, which is crucial for optimizing reproductive outcomes in female livestock.