Fine-Tuning Chicken Egg Incubation by Breed, Egg Size, and Shell Characteristics

Incubating eggs seems like a very straightforward process, but would you believe there can be differences between breeds, egg size, shell color, and individual breeding groups that show up during the incubation process?

Whether you're a seasoned professional or a beginner, hopefully this insight into the Fine Tuning process will make your next hatch even more successful!

The standard recommendations still give us our starting point. Mississippi State Extension recommends 100°F for chicken eggs in a forced-air incubator.¹ If you are still getting comfortable with the basics, Hatching Time's guide to temperature and humidity for hatching chicken eggs covers those starting settings in more detail.

REPLICATING MOTHER HEN

In the natural order of things, the mother hen gathers her clutch of eggs and spreads her body over them. A broody hen develops a bare patch on her chest that allows her body heat to reach the eggs more directly.²

She does get up and leave the clutch, and I like to remind people of this when they are nervous about candling. Mother Hen takes breaks to relieve herself, preen, or dust bathe, so a brief interruption is not automatically a disaster.

Illinois Extension recommends keeping eggs out of the incubator for no more than about 5 to 10 minutes at a time. If you have two dozen eggs in the incubator, they suggest candling about 5 to 7 eggs per session.³

So be organized, but you don't have to panic every time an egg is out for a few minutes. Hatching Time's egg candling guide can help you identify what you are seeing as development progresses.

Normally a mother hen incubates her own clutch, while we may have several different breeds together in our incubators. But Mother Hen is doing all her final preparations and Fine Tuning her process to get ready to sit for the next 21 days.

SET UP

When incubating multiple breeds and/or several different colors of eggs, the first setup for success is to separate them by breed and color when you can.

If you have more than one incubator, you can keep breeding groups separate and monitor the needs and results of each group. If you are working with several groups in the same incubator, there are different schools of thought about the best way to keep them organized.

When we have more breeds and colors than our Hatching Time trays can easily separate, we use our own tray modifications and mesh bags. The first photo shows one of our DIY separation setups; the following photo shows eggs organized in our Hatching Time CT120.

These are DIY modifications used in our own hatch room, not official Hatching Time tray accessories. Anything added inside an incubator must be positioned so it does not interfere with airflow, turning mechanisms, hatching operation, or chick safety.

Editor's note: Incubator conditions can also influence hatch timing. A published study found differences among incubators in incubation time, so the machine and tray position are useful details to record when comparing groups.⁵ Use the incubation settings recommended for your species and equipment; breed-specific setting changes should be supported by reliable evidence.

MAKE A RAINBOW

When choosing which trays to put which breeds in, we put the lightest-colored eggs at the bottom of our cabinet-style incubator, like the Hatching Time CT120, and the darkest eggs at the top.

We call it making a rainbow!

Our thinking has been about humidity. In our own hatch room, we place the darker eggs farther from the humidity tray and the lighter eggs closer to it. This is part of how we have managed different egg groups in our setup.

Editor's note: Kimberly's arrangement reflects what she has found useful with her own breeding groups. Eggshell permeability and the cuticle, often called bloom, can influence moisture loss during incubation.⁶ Shell darkness alone, however, does not establish a specific humidity requirement. A study of similar-weight commercial brown eggs found that pigment intensity did not affect incubation weight loss or hatch timing; it did not specifically examine very dark Black Copper Marans eggs.⁴ Hatching Time's CT120 is designed to maintain consistent conditions throughout the cabinet, so differences between tray positions should be measured rather than assumed. Follow the incubator's instructions and monitor egg weight loss or air-cell development when evaluating humidity.

HOSPITAL TIME ZONES

Hatching is similar to labor and due dates!

When you go to the hospital, time seems to stand still or just not happen according to our timing. The same is true for "Hatch Day."

Even though we talk about chickens hatching in 21 days, in our hatches we have seen some groups arrive earlier, some around day 21, and some keep us waiting into day 22 or 23.

Once you work with hatching a breed or breeding group long enough, you begin to notice things like:

"Oh look, the so-and-so's hatched first!"

Or:

"I don't even see any pipping on the so-and-so's, despite it being hatch day!"

You're ready for Fine Tuning!

Editor's note: A study involving commercial broiler breeder strains found average incubation-time differences of approximately 2 to 3 hours among strains, although the statistical findings varied between its two experiments. The study did not test Polish or Black Copper Marans chickens and does not establish a fixed hatch day for either breed.⁵ Consistently late hatches can also be a reason to check incubation conditions, particularly temperature.¹

For the standard hatch timeline, see Hatching Time's guide to how long chicken eggs take to hatch.

WATCH OUT FOR PITFALLS

Most advice available on the internet will suggest a standard in humidity and temperature, but some breeds and breeding groups can present different challenges. That is why it helps to research the eggs you are setting and pay attention to what happens from hatch to hatch.

A disappointing hatch can have more than one cause. Fertility, egg storage and handling, temperature, humidity, turning, and the condition of the breeding flock can all matter. A zero hatch doesn't automatically mean that a breed needed a different setting.

Do your research about the breed, learn what your equipment can do, and consider the whole incubation process before deciding what needs to change.

FINE TUNING EXPERIENCES

Chicken Math Professor specializes in Chicken Math and hatching. We run the Hatching Time CT120 and, in prime hatching season, we also run three Maticoopx incubators, a Kebonnixs, and a Brinsea incubator. These other brands are what we started with, and when we can invest in more incubators, we would love to replace them with Hatching Time tabletop models and more Hatching Time setter and hatcher systems.

We set eggs by incubator and by what we know about the needs of our breeding groups.

For example, our Black Copper Marans eggs, especially those scoring 7 to 9 on the Marans Color Chart, are a group we pay close attention to. In our hatch room, we try not to disturb them regularly and have used a lower-humidity approach for those batches. We believe the pigmentation and bloom on these eggs may be part of why they have needed extra consideration in our hatches.

Our Black Copper Marans can make us wait! We have seen eggs from this group begin pipping on day 22 or even day 23. We have been careful about how much we raise the humidity for these batches compared with others. Those are the methods and results we have experienced in our breeding program.

Editor's note: These are Kimberly's observations from her own breeding groups. Eggshell cuticle and permeability can influence water-vapor exchange,⁶ but research has not established a universal lower-humidity requirement or later hatch time for Black Copper Marans based on shell darkness alone.⁴ Monitor moisture loss or air-cell development and follow your incubator's guidance when evaluating adjustments.

In our hatching experience, the Polish are consistently some of our earliest chicks. Without fail in our breeding program, our Polish eggs begin hatching around day 20.5, and the strongest of the breed often arrive at that time. We may still be waiting for other eggs even to start pipping when the Polish are already hatching!

Then we started looking at egg size. Our Polish eggs are around 48 grams for a full-sized Polish hen's egg, compared with around 52 grams for our American Bresse, 55 grams for our Rhode Island Reds, and a range of about 50 to nearly 80 grams for our Black Copper Marans. These are examples from our own breeding groups, not official breed-wide egg-weight standards.

Could those differences in egg size play a part in incubation time or the ease of hatch? That's one of the things we have wondered about as we Fine Tune our process.

Editor's note: One study of commercial broiler breeder strains found a relationship between egg weight and incubation time, alongside effects involving breeder age, genotype, and incubator.⁵ That study cannot determine whether egg size contributed to the early Polish hatches described here. Kimberly's day-20.5 timing is her direct observation of her own breeding program, not a published standard for all Polish chickens.

ENJOY THE JOURNEY

Each hatching experience will bring victories, awe, and even possibly heartache, adding to your repertoire of what to expect for future hatches.

Enjoy the process and share your techniques that have been tried and true and enabled you to Fine Tune hatching by breeds.

References

1. Mississippi State University Extension Service. Hatching Quality Chicks.
2. University of Maryland Extension. Hatching Eggs at Home (FS-1114).
3. University of Illinois Extension. Incubation and Embryology Q & A.
4. Shafey, T. M., Al-Batshan, H. A., Ghannam, M. M., & Al-Ayed, M. S. Effect of Intensity of Eggshell Pigment and Illuminated Incubation on Hatchability of Brown Eggs. British Poultry Science, 2005.
5. Suarez, M. E., Wilson, H. R., Mather, F. B., Wilcox, C. J., & McPherson, B. N. Effect of Strain and Age of the Broiler Breeder Female on Incubation Time and Chick Weight. Poultry Science, 1997.
6. Properties, Genetics and Innate Immune Function of the Cuticle in Egg-Laying Species. Frontiers in Immunology, 2022.

Written by:

Kimberly Benjamin