For the 7 and 14 days candling eggs photos I show in this guide to remove non-viable eggs , and a successful hatch, we only really need to consider two high-risk periods for embryo death: At the beginning of incubation and just before the chicks hatch. We expect to see either fertile eggs or clear eggs, as shown in our first candling after seven days, but occasionally the embryo starts to develop in a fertile egg and then dies.
A thin ring around the inside of the egg indicates an early death. The embryo died at the start of incubation, usually within a couple of hours. These eggs are easy to identify and remove, and I have included a photo below. The second common type of early embryonic death occurs when the embryo starts to develop and dies within the first week. Eventually, the rest of the contents of the egg will become cloudy as the egg deteriorates.
You can see this in the second photo below. The contents may swish around when rotating the shell. There are more candling photos in the gallery at the end of this article. I have taken a photo of such an egg for day 14, candling photos below and a video clip of another. The most common cause for early embryonic deaths in eggs is rough handling, incorrect storage storing too long, or at the wrong temperature , adverse genetic traits, or ageing of the breeder flock.
Dirty eggs or an un-sterilised incubator are apparent sources of bacteria. There has been a lot of development after 14 days of incubation. The embryo is fully formed and starting to take up most of the space inside the shell. There are some photos below. We finish rotating chicken eggs at 18 days and duck eggs at 25 days. After this time, the chick is positioning itself, ready to emerge. The exception to this is if I have hatching problems that I suspect are caused by incorrect incubation humidity , then I will mark the size of the air sac onto the eggshell using a soft pencil and compare it with a known good egg.
More information is coming up below on air sac development , where I have included a handy chart. Dark shelled eggs Such as Marans or Welsummer Eggs are much harder to see through, so you will need the brightest light source you can get. One idea is to practice candling light eggs first or incubate with lighter coloured eggs, and then you have a comparison.
You will need to candle in a dark room to stand a chance. The image below should give you an idea of what is going on inside the egg by day 8. I have used black and white photography to highlight the contrast.
There are digits on the feet, the heart enclosed in the thoracic cavity, and the embryo starts to look more like a chick. Feathers begin to grow from day 8. There is a sack attached to the embryo that is called the allantois. This goes around the back and head of the embryo and holds the waste. The yolk sack is now very red and full of blood vessels that go out into the albumen egg white.
The air sack at the broad end of the egg has increased in size. Next time you crack open an egg, look carefully for a small white patch on the surface of the yolk about 3mm in size. This is called the blastodisc. This is where the sperm joins the egg. Once fertilised, the blastodisc changes its name to the blastoderm. Blood vessels start to appear, stretching into the yolk to carry nutrients back to the embryo.
Of course, it would be great to be able to sex eggs before they hatch to save the heartache of raising unwanted male chicks! Various old wives tales circulate that say you can tell by circling a key or piece of metal on a string above an egg or that male chicks hatch from pointed eggs, females from round ended eggs.
Unfortunately, there is no proven way to tell the sex of an embryo in the egg, well, almost. The only proven way has been inserting a needle and taking a sample from inside the shell to see whether there was estrogen hormone present. Hardly a suitable method for the backyard keeper. For autosexing breeds , or sex-linked crosses , you can determine the sex of day-old chicks, but for most pure breeds, you have to wait a while before you can sex them. Incubator temperature should be maintained between 36 and Too high a temperature is more damaging than too low a temperature.
Mortality will increase if the incubation temperature drops below Eventually, the chick will fill almost all of the space inside the egg, and the air sac will increase further in size see the diagrams below. When it finally hatches, it will break through the inner membrane into the air sac to take its first breaths of air. The eggshell hole allows further oxygen into the air sac so the chick can continue to breathe.
Over the final 24 hours, the chick absorbs the remainder of the yolk sack, and this will give it enough energy to turn inside the shell and slowly break from the shell as it goes. It will then use its feet to push itself out. The chick almost fills the shell. If you are on a budget, you could build an egg candler.
Place a desk lamp using a bright low energy light bulb inside a cardboard box. Cut a small, round hole in the top of the box, just big enough for the pointed end of your egg.
Alternatively, modern LED torches that do not give off much heat are also an excellent light source for candling eggs. I took this photo with a flashlight, using my hand to form the seal with the egg, and I could still see the embryo!
One way to confirm the humidity of your incubator is correct is to monitor the air-sac size. The images below show you the relative air sac sizes at different incubation stages for chicken and duck eggs. Humidity is tough to get right over the incubation period, and even incubators with automatic humidity control can fluctuate or run dry.
I use a Switchbot wireless sensor in my incubator and SwitchBot App on my phone. Most incubation problems are caused by incorrect humidity or by the health of the flock. Remove these from the incubator. Remove these from the incubator and throw them away not good for eating. Record your observations in a notebook, numbering each egg. If you are unsure whether an egg is a winner or not, place it back in the incubator, but make note of the number so you can check it again.
It's a good idea to candle your eggs before you even place them in the incubator. This will give you a baseline to compare to when you look later. You can also check at this time for cracks in the eggshells, which may allow bacteria inside that could contaminate the embryo and affect its development.
Don't discard eggs with cracks, but the record which ones they are so you can be sure to monitor them more closely. After the initial candling, you can wait until day seven to candle your eggs. Candling too often can create temperature shifts for the eggs that could impact their development. And before day seven there isn't much to see, anyway. After candling on day seven, you can wait another week and candle again on day fourteen. Avoid candling from day sixteen or seventeen up until the eggs hatch, as moving or shifting eggs this late in development could harm them.
Actively scan device characteristics for identification. Use precise geolocation data. Select personalised content. Create a personalised content profile.
Measure ad performance. Select basic ads. The white is thin. Most newly laid eggs are good quality. Eggs not over two or three days old, if held under good conditions, will meet the specifications for Grade A.
The only eggs to be removed by candling are those with bloody whites, blood or meat spots, and cracked shells. Incubated eggs are candled to determine whether they are fertile and, if fertile, to check the growth and development of the embryo. White eggs should be tested for fertility on the third day. Brown shelled eggs on the fifth or sixth day because it is difficult to see the embryo clearly before this time.
A small reddish area with blood vessels extending away from it will be visible in fertile eggs. This is the embryo floating around inside the egg, looking like a huge red spider.
If the embryo dies, the blood draws away from the embryo and forms what is called a blood ring.
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