Poultry Egg Incubation
While a broody bird hatches eggs simply by instinct, the budding poultryman (or poultry-woman) needs to carefully monitor and adjust 4 factors to guarantee a successful hatch in an incubator. Incubating poultry eggs requires control of temperature, humidity and ventilation and the eggs must be turned on the correct schedule.
In an incubator that has a circulation fan, the temperature needs to be maintained at 99-100 degrees Fahrenheit. In a still-air environment, add 2 to 3 degrees. In both styles, measure the temperature as close to the eggs as your equipment allows. A remote sensor thermometer is ideal for monitoring an incubator.
As a general guideline for all poultry species, the humidity in the incubator needs to be maintained between 55% and 60% relative humidity in the early stage of incubation. This varies marginally by species. The development of the embryo relies on liquid in the egg evaporating over the incubation period. Too much humidity and the albumen will not dry sufficiently and the developing chick will drown. Too little, and the egg will dry too quickly. Humidity can be monitored with either a wet bulb thermometer or a hygrometer. While the wet bulb thermometer method is more accurate, using it is somewhat complicated, and it is only accurate if done correctly. Shop carefully when buying a hygrometer and be sure that its accuracy is guaranteed by the manufacturer.
While it may not seem so, an eggshell is porous. The developing chick needs oxygen transfer through the shell. Once the chick "pips" (starts breaking through the shell), fresh air in the incubator is even more vital. Be sure that your incubator has adjustable ventilation, allowing fresh air in and expelling stale air. Ventilation control is a balancing act. Increasing ventilation will generally decrease humidity and temperature. You have to make sure your air exchange happens, but at a rate that allows you to maintain temperature and humidity.
Eggs need to be placed in the incubator with the large end slightly elevated. Then, the egg needs to be turned on its axis four to six times per day. Placing two different markings (an "X" and and "O" for example) on opposite sides of the egg makes it easy to make sure all eggs have been turned properly. Handle the eggs carefully in the very early days of the incubation. The embryos developing circulation system is very fragile in the early days. The eggs should not be turned the last three days of incubation. The incubation period is different for different poultry species. Mississippi State University has a renown poultry science department, and maintains a comprehensive chart on its website, indicating incubation periods along with temperature and humidity variables for a vast array of poultry species.
While your eggs are developing, you can check their progress. "Candling" an egg refers to holding the egg up to a strong light source in an otherwise dark room. This allows you to see the embryo's development. Eggs that are not developing properly should be disposed of to prevent contamination of the viable eggs.
In the final days, ventilation and humidity need to be increased. The day your chicks break out of their shell carries a lot of emotion. There's a strong urge to help, but that is generally a mistake. Humidity is crucial at this point, and when you open the incubator, humidity will plummet. If you help one chick break out of its shell, you're likely to cause several others to become bound in shells that have dried out too much at the critical moment. Chickens were breaking out of eggshells long before man was around, and likely will be long after we're gone. Leave them alone and just watch. If all goes according to plan, you'll have lots of happy, healthy peepers, ready to move to the brooder.