Importance of Incubator Temperature and Humidity for Chicken Eggs
Believe it or not, incubation isn’t just an invention of the modern era. Historical records show that incubation of eggs was practiced in Ancient Egypt. Mud brick buildings, divided into chambers that were basically large ovens, were heated by burning straw, dung or charcoal. Temperature and ventilation were regulated by opening doors and vents to let smoke out and light in. Humidity was provided by moistened jute placed near and over the eggs. There must have been a lot of guesswork and trial and error involved in a successful hatch, and success rates were hopefully high enough to make the effort worthwhile.
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Effortless Modern Incubators
Fortunately, modern incubators take much of the guesswork out of incubation, maintaining consistent temperature and humidity pretty effortlessly, with a little good management. Even the simplest incubators have thermostats, and reservoirs for water. More complex incubator systems have sensors that can register humidity levels and add water accordingly.
We all know that temperature and humidity are critical for a successful incubation and hatch. But did you know that long before that egg you are about to put into your incubator becomes a fluffy, feathered chick, it is still a living, breathing organism?
Pores in the shell allow for the exchange of gases as the embryo develops, and also for the exchange of moisture between the embryo and the air in the incubator itself.
Evaporation is the process by which water changes from a liquid to a gas. Moisture will move from an area of higher concentration, such as the contents of the egg, to an area of lesser concentration, the air surrounding it. Higher temperatures increase the rate at which evaporation occurs. So the comparatively high temperatures in the incubator are a perfect place for evaporation to occur. This is why keeping humidity at the proper level during incubation is so critical, no matter what type of incubator you are using.
The volume of water lost in the egg via evaporation is replaced by air. When the humidity is too high, not enough water can leave the egg. This results in a small air cell (the pocket of air in the large end of the egg). When a chick begins to hatch, he breaks, or ‘internally pips’ through the membranes surrounding him into that air cell, and takes his first real breath there. If the air cell is too small the chick is often unable to pip internally and cannot complete the hatch process. If humidity is too low and too much moisture leaves the egg, this can result in an overly large air cell, and chicks that are weak and adhered to the shell. These chicks often do not survive hatching, and even if they do, they often die shortly after.
Keeping Eggs Clean
When the egg is laid, a protective cuticle is created around it. Immediately after being laid, the cuticle is moist, and if it comes in contact with dirt or other contaminants while still moist, those contaminants can be drawn into the egg. Therefore, keeping the nest box clean is of utmost importance when you know you are going to be incubating and hatching eggs. Gather eggs frequently to give fewer opportunities for damage to occur to the egg, and less exposure to bacteria and dirt.
Gently wipe off eggs if they are a little bit dirty. Don’t submerge them or soak them, but use a damp sponge or cloth. Remember that if you wash the eggs, you are also washing off their protective outer coating, making the shell more permeable. Use water that is warmer than the egg. If the egg is warmer, it will tend to contract as the water cools it which risks drawing contaminants in through the shell.
Use a solution that is specifically formulated for washing eggs, and then be sure to follow the directions exactly. Using too concentrated a solution can hurt the embryos if the solution is drawn into the egg.
Forced Air and Still Air Incubators
There are two basic types of incubator, forced air and still air. Either one can result in a successful hatch, as long as care is taken to make sure temperature and humidity are consistent. Both are very similar in function and design, with the exception that the forced air incubator has a fan that circulates air over the eggs. For best success, set the forced air incubator thermostat at 99 to 99.5 degrees Fahrenheit and 60% relative humidity. The fan will make sure temperature and humidity are consistent throughout the unit.
A still air incubator can be a little more challenging to manage temperature and humidity, but before the invention of the electronic circuitry and small fans available with a new incubator, countless eggs were successfully hatched in a still air incubator. Set the temperature of a still air incubator to 100-101 degrees F at the height of the eggs. Air will layer, or stratify in a still air incubator, so where the reading is taken is important. Set the humidity slightly higher, 60 to 65% relative humidity during incubation. Check the still air incubator often, eggs can overheat more easily in a still air incubator. Fortunately eggs can handle some variation from the ideal temperature, and tolerate slight underheating better than overheating for more than a few minutes, but the more constant environment you can provide, the better your hatch rate will be.
Hatching Begins in the Egg
The hatching process is one of the niftiest little miracles in the animal world. During the last days of incubation, the chick grows to fill up the entire egg, except for the air cell, the pocket of air at the large end of the egg. At this time, the chick begins to orient itself in the shell and prepare for hatching. Their head and beak are tucked under one wing, with their beak facing the air cell. At about day 19 of a 21-day incubation period, the chick’s head will thrust forward, breaking the membrane between them and the air cell, a process called the ‘internal pip’. The chick begins to take its first real breaths.
Pipping and Zipping
By day 20, their lungs are functioning and the chick will begin the serious part of the hatching process. Using the egg tooth, a tiny projection on the end of their beaks, they will begin to peck at the shell thousands of times. The shell has become thinner by this stage, as the chick absorbs some of the calcium from the shell in making its skeleton, and this ‘external pipping’ happens fairly quickly.
Once the chick has pecked through the shell, they will rest for several hours, as their lungs adjust to breathing outside air. Proper humidity in the hatcher is critical at this point; if the membranes dry out and adhere to the chick’s body, it will be more difficult for the tiny bird to leave their shell. During the second stage of pipping, the chick will move inside the egg, turning clockwise in a circle, pecking away at the shell until a circumferential break in the shell is created, known as “zipping”. After this, the chick will push out of the shell, to lay squirming and exhausted on the floor of the hatcher.
You will see the newly born chicks fall deeply asleep for several minutes, then move a bit, then sleep more as they gain strength and flexibility. But it doesn’t take long for them to begin moving around more as their muscles gain strength and coordination. In a successful hatch, 95% of the eggs will hatch within 24 hours. Wait to move the chicks to the brooder until they are dried and fluffy, otherwise they can get chilled during the move.
Watch and Wait
If you have several chicks that do not hatch, the culprit is likely a humidity issue, either during incubation or hatching. Humidity should be around 50% during incubation and closer to 65-75 percent during the hatch process. Keep in mind that too much humidity isn’t good either. Pay attention to the manufacturer’s recommendations for their unit, and realize that you may have to do a couple of hatches to get a real feel for your incubator.
While it’s tempting to try to help out a chick that seems to be struggling during the hatching process, you can often do much more harm than good. The entire process can take up to 24 hours. Trying to speed things up by removing the shell and tearing the membranes can speed up the drying of the membranes, making it more difficult for the chick or damage the chick’s delicate feathers and skin. Depending on the stage of hatching, the membranes might still be filled with blood that has not been drawn into the chick with the yolk. Tearing the membrane and rupturing the blood vessels will almost always result in a dead, or seriously weakened chick.
Non-Slip Incubator Flooring
The floor of your hatcher is also important. Many of the new incubators have bases that are hard plastic. These are wonderful for being able to clean and disinfect thoroughly between hatches, but they are often too slippery for the chicks to be able to get good footing. If chicks have to struggle too much to be able to get to their feet, there is a good chance they can become spraddle-legged. This means that their legs spread out beneath them, and if left like this too long it can permanently damage their legs. Cut a piece of inexpensive rubber shelf liner to fit the floor of your hatcher. This material is readily available and it can be washed and reused for many hatches. Some Styrofoam incubators have fine wire mesh floors, which will also work for giving new chicks much needed traction.
Once the chicks are dried and fluffed out, it’s time to move them into a brooder. A good brooder should provide protection from drafts and be small enough that the chicks do not wander too far from a heat source and become chilled, but not so small to prevent them from getting away from the heat source if they choose.
Non-slip flooring is also important in the brooder. Many people use shavings with good results, but depending on the size of the brooder, a rubber liner can work well too. Whatever you choose, make sure it’s easy to clean. After the first three or four days, once the chicks start eating well, it’s amazing how much poop they can produce.
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Moving to the Brooder
The brooder temperature should be near 95 degrees Fahrenheit for the first week, and can be reduced about five degrees every week after that, until the chicks are accustomed to room temperature, or are fully feathered enough to handle the outdoors.
Traditionally, the heat source for a brooder was limited to a heat lamp. These do well as a heat source, and can be raised or lowered to adjust the temperature in the brooder, but take care to keep it from getting too hot for the chicks. It may take some trial and error to get the temperature just right. And, the longer the heat lamp shines on the floor of the brooder, the more heat can build up. And, an important downside to heat lamp bulbs is the risk of fire. If the holder breaks and the bulb falls into the brooder, it won’t take long for things to melt or catch fire.
A great alternative to heat lamps are chick brooder heating plates. These radiate heat down to the chicks and can be height adjusted to tweak the temperature. Chicks will huddle underneath much like they would if brooded by a hen. They can cost a bit more than a heat lamp, but properly cared for can last for years, and will be unlikely to overheat or set something on fire. These small brooders are available from many poultry supply companies, and come in a variety of sizes.
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