Incubation, Hatchery and Chick Management
Incubation rules
Chicken eggs hatch in 21 days; duck and turkey eggs usually need 28 days. Artificial incubation uses a setter for the first 18 days and a hatcher for the last 3. Forced-air setter temperature is about 37.5-37.8°C with 50-60% relative humidity; the hatcher runs slightly cooler, about 37.2-37.5°C, with 65-75% humidity. Turn eggs 4-6 times daily, stopping at day 18. Candle at day 7 and day 14 to remove infertile eggs and early dead embryos.
Hatchery and chick management
Store hatching eggs at 13-18°C and 75-80% humidity for no more than about 7 days. Use clean, uncracked, normal-shaped eggs from healthy breeders. Disinfect the hatchery, equipment and eggs; formalin fumigation is traditional but must be controlled. At hatch, separate chicks, count and record, vaccinate for Marek's disease at the hatchery where practiced, and transport in ventilated boxes without delay.
Worked example. Set 1,000 eggs. Fertility is 85%, so 850 are fertile. Hatchability of fertile eggs is 90%, so expected chicks = 850 x 0.90 = 765. The remaining 85 fertile eggs are early, middle or late dead embryos or unhatched pips.
Traps. Do not keep turning eggs after day 18; do not confuse setter and hatcher humidity; do not store eggs for weeks; and do not judge hatchability on total eggs set when the exam asks for hatchability of fertile eggs.