Obviously these follicles are very small at the time of hatching. At sexual maturity a broiler breeder hen will have both large and small follicles. Egg yolk is deposited in layers, with a layer of yolk being deposited every 24 hours. By providing the birds with feed containing red dye one day, and black dye the next day, and then hard boiling the ovary, the pattern of yolk deposition can be visualized. When a breeder hen lays her first egg, at about 24 to 27 weeks of age she will probably have 7 to 11 large follicles greater than 1 cm in diameter.
Follicular maturation is a very important concept in egg formation.
This property does not mean that it has to be a certain size. The small ovarian follicles are a major source of estrogens and androgens, and this steroid output is highly LH responsive. If the follicle is mature outside of this time period, it will ovulate the start of the following open period for LH release. This means that the eyes are not the primary messenger for perceiving that the days may be getting longer or shorter. The light energy stimulates the bird by impacting on the brain of the bird.