If you’re considering hatching your own flock of backyard chickens here’s a few things you need to know to successfully hatch eggs in an incubator.
For embryos to develop correctly eggs need to be kept at the right temperature, turned often and correctly positioned. Eggs breathe and loose water through the pores in their shell so they need fresh air and the right humidity level. Eggs can catch infections and need a clean environment. But they also need time and an incubator will not hatch eggs faster than a hen!
Let's look at each of these key requirements
Accurate incubation temperature is by far the most important factor for successful hatching of chicks. Small differences will make embryos develop too fast or too slow causing deaths or deformities.
37.5°C is usually the correct temperature for most species when incubating in a forced draft incubator (an incubator with a fan which offers good, even temperature). But you can still find incubators without fans (still air incubators) so if using one of those remember that hot air rises and measure temperature right at the top of the eggs. 39.0°C is usually the correct temperature for these basic incubators but follows the manufacturer’s recommendations.
Whatever the type of incubator you will get best results if the room temperature is between 20 and 25°C, the incubator is kept away from drafts and not in direct sunlight. Let the temperature stabilize for an hour or so before adjusting or setting your eggs. Let eggs warm up to room temperature before setting them and do not make any further adjustments for 24 hours to allow the eggs to reach incubation temperature.
Tip: Eggs can be stored up to a week provided they are kept cool (around 15-18°C with 75% humidity) and turned once a day.
Positioning and turning of eggs
As the embryo develops on the yolk, it causes the yolk to become lighter and float upwards. As the egg is turned the embryo is swept downwards into fresh nutrients in the white of the egg allowing the embryo to develop. This is particularly important for the first week of incubation when the embryo has no circulation system.
Turning can be done manually, but bearing in mind eggs need to be turned at least thrice a day and preferably every hour you may want to consider automatic turning. Some fully digital models like the 352 and 1056.
When turning eggs manually mark each egg with an X on one side and O on the other with a pencil and turn them from one side to the other.
Automatic incubators have different types of turning mechanisms such as tilting shelves or egg carriers, rotating discs and moving floors; some are fully programmable. Whatever the system, eggs should be placed on their side or pointed end down but never large end down as this causes inverted hatches (when chicks pip at the small end of the egg and usually die). A 90° angle (1/4 turn) every hour is recommended for most poultry, game or waterfowl.
Turning should be stopped 2 days before the chicks are due to hatch and the incubator or tilting shelves should be level. Best to remove all dividers, egg turning discs or egg carriers to avoid any possible injuries to the chicks.
Humidity and Ventilation
Incorrect humidity is the no. 1 cause of poor hatching success. Of the four primary factors which must be controlled during incubation (temperature, turning, humidity and ventilation), humidity is the most difficult to measure and control accurately.
Humidity does not directly affect embryo development unless the egg is seriously dehydrated. Only temperature and turning affect growth of the embryo directly. Humidity is important only to achieve the right balance between excessive dehydration and space within the egg to allow the chick to maneuver into hatching position.
Ideally, eggs need to lose 13-15% of their weight between the time of laying and pipping. Variations in humidity are less critical than temperature as long as the chicks end up losing the correct amount of weight by the time of hatching. Corrections can be made later for earlier errors.
Humidity is affected by evaporation from the eggs themselves and the incubator water reservoirs, the amount of fresh air entering the incubator and the ambient humidity. All incubators have water reservoirs and ventilation holes, some have ventilation controls and digital humidity displays.
Humidity is usually measured in % Relative Humidity (%RH) but sometimes in older books and reference manuals you will see it quoted in Wet Bulb Temperature and those should not be confused as the effects could be devastating.
Ideal humidity during incubation is 40-50%RH for poultry and gamebirds (25-28°C wet bulb temperature) and 45-55% for waterfowl (26-29°C wet bulb temperature).
If humidity is too high you will need to increase ventilation or if the incubator does not have ventilation control remove some water. In very humid ambient conditions the incubator may be run dry for a few days. Conversely if humidity is too low you will need to reduce ventilation and/or add water. In very dry ambient conditions you may need to use evaporating pads or blotting paper to increase the surface area of the water reservoirs.
Humidity at hatching time needs to be higher than during incubation - at least 60% (above 30°C wet bulb temperature) to prevent the membranes of the egg drying too fast as the chick hatches and becoming tough and difficult to tear. It is tempting but do not open the incubator – humidity needs to remain high!
Direct measurement of RH is not easy and therefore expensive. Cheap hygrometers are available but you get what you pay for! So if the incubator does not have digital humidity readout, you should candle the eggs to monitor the air cell and ideally weigh them.
The air cell increases as incubation progresses
If the air cell is larger than expected too much water is being lost and humidity should be raised. Conversely, if the air cell is smaller than expected humidity should be reduced.
If you weigh eggs before setting them and again periodically during incubation, the weight loss can be plotted on a graph to check that the average weight loss is on track.
If the eggs are losing too much weight humidity should be increased and vice-versa.
Don’t forget to check the water reservoirs regularly following the manufacturer’s recommendations to achieve the correct humidity.
Incubators are warm and wet and the ideal breeding ground for bacteria. If left with debris from the last hatch they will harbor germs which are highly likely to damage future hatches.
Use antimicrobial additives to help reduce batceria and achieve higher hatch rates. Incubators should always be cleaned immediately after each hatch and totally dry before storing or setting the next batch.
If possible cracked or very dirty eggs should not be set. All cleaning procedures will remove the outer protective cuticle from the eggshell as well as the dirt leaving the eggs at greater risk of bacterial contamination. If you must wash eggs use a solution significantly warmer than the egg so that expansion in the egg causes flow out through the pores rather than dirty water flowing inwards. Always use a proprietary solution and follow the manufacturer’s instructions.
Even the most advanced incubator will not hatch eggs faster than a bird.
It usually takes 21 days for chickens, 28 days for ducks, guineas and turkeys, 30 days for geese, 24 days for partridge and pheasants and 18 days for quails.
Eggs can be candled starting at day 5 to monitor the size of the air space and observe embryo development. For best results you should candle eggs in a darkened room holding the candler right against the shell at the larger end. Modern candlers are usually LEDs because they are very bright, very efficient and do not emit heat that could damage embryos.
Initially, you will be able to see a small embryo and a web of blood vessels radiating from it. As the chick grows it will be hard to make out detail but you should still be able to see movement.
Eggs that are infertile or have died should be removed to avoid contaminating the developing eggs. Finally birth also takes time! It can take 24 hours or more for a chick to come out after it has first piped. So be patient; don’t be tempted to help and don’t transfer the chicks under a brooder until they are fully fluffed up or they could chill. Your patience will be rewarded with little bundles of fuzzy cuteness nobody can resist. Beware: Hatching can be addictive!