During egg laying, the yolk is released into the oviduct where it is surrounded by albumen (the “white” of the egg), and the shell is then produced in the uterus. The hen lays one egg per day or one every two days (100 to 300 eggs per year depending on species and age). Each year, the hen reduces her egg-laying by 20~30% until the oocytes are exhausted. Menopause occurs at around 7 or 9 years of age. Once 8 to 12 eggs are laid in the nest, the hen changes its behaviour and starts to brood.
Embryo development proceeds during an incubation period in which the egg is kept at a temperature of around 38-39°C. This incubation may also be carried out artificially using an artificial incubator. The brood is completed in a perfectly synchronous manner, and chicks communicate before the hatch. Brooding takes 19-21 days, depending on breed and size. The chicks are reared for 1.5 to 3 months depending on the breed.