When we put eggs in the incubator or see mama hen settle down to brood, it’s so exciting looking
forward to seeing those adorable baby chicks. But sometimes it doesn’t quite happen, and eventually
mama hen gives up or we decide it’s long past time to abandon hope of those eggs ever hatching.
But you don’t just have to dump those failed eggs and write it off
as a disappointment. You can try to find out what went wrong, use it as a bit of a learning
experience, become a bit of an investigator. You’re going to have to be a bit brave, and open
up those eggs to see what went wrong. That can be very sad and maybe even a bit gruesome,
so if you’d rather not know about it or see anything like that,
then I suggest you stop watching this video and watch some of my other videos instead – I have
a really cute one about baby chicks sleeping. OK, you’re still here? Then let’s get started.
We’re going to work through a few of the possibilities that you might find when
you open an egg that has been incubated but is not developing or that failed to hatch.
And by the way, for the sake of simplicity, most of the time I’m using the term “incubate”
regardless of whether this is by a mechanical incubator or a mama hen.
One of the most common and obvious reasons for an egg failing to hatch is that it was never
fertilised in the first place. Of course if you don’t have a rooster and your hen just went broody
sitting on her own eggs then you know for sure they were never fertile and never going to hatch.
In that case I would not let the hen brood those infertile eggs – brooding is hard on a hen and it
doesn’t seem fair for her to go through all that when there’s no chance of anything coming of it.
I have a video about how to persuade your broody hen to give it up.
But assuming that you thought there was at least a chance of those eggs being fertile,
but no sign of any developing chick, then you can open it up and see whether or not the egg
had been fertilised. Last month I posted a video about how to tell the difference,
so you’re probably expert at that by now.
If the eggs were not fertilised, then that might be because:
- There was no rooster – maybe you had one but he died too long ago for
the hens’ eggs to still be fertilised. - The rooster wasn’t potent (perhaps
he is too old, or still too young, inadequate nutrition or water, or it’s just the wrong time
of year and he’s not in the mood, too fat to mate, or perhaps he’s sterile)
- The rooster wasn’t mating (too many hens/rooster, rooster too busy fighting to mate).
- The hen was rejecting the rooster and refusing to mate by running away instead of squatting for
him. Or she could be rejecting his sperm. Did you know the hen has to store the sperm and use
it to fertilise the eggs as they are coming down the oviduct, before their shells go on.
What might you see? If you open an egg that has
not been fertilised, even after days or weeks of incubation, it should look just like a fresh egg,
with an intact yolk and no change to the germinal disc. At worst, it will have a
lost some water by dehydration through the pores of the shell, so the air bubble will be bigger
and albumin might be a bit thicker than usual. The only exception to this is if the eggs got wet
and contaminated with bacteria – maybe they were sitting on muddy ground, or dirtied with chicken
poo from the hens’ feet before you collected them. But you always set clean eggs – right?
So let’s assume that the eggs were fertilised, but didn’t develop into a live chick.
A fertilised egg encounters several major challenges along its way to
developing into a live chick. - The first is before
incubation even starts. - The second is in the
first few day of incubation. - Chicks that make it past the
first five days usually continue to develop. Embryo deaths are uncommon
in the main incubation period but do occur. - The next danger period is when the chick needs
to start the hatching process by pipping a hole into the internal air cell and out to the world
- And the final challenge is to make it all the way out of the shell.
So let’s start from where you might candle an egg after the first few days of incubation
and not be able to see any embryo growing inside. Once you’re sure there is no developing chick,
you can open the egg to see where it went wrong. What might you see?
Even if the egg was fertilised, you might find that the germinal disc never developed at all.
The contents of the egg could still look exactly like a fresh egg, with even the yolk membrane
intact. You will be able to check the germinal disc to be sure it looks like it was fertilised.
Or the yolk membrane might break and you see an egg that looks like it’s full of yolk,
but with no evidence of any embryo.
What went wrong? If the eggs were fertilised but
failed to develop at all, then maybe the breeding flock didn’t get the proper nutrition required
for top breeding success, or they suffered some disease, or they have some genetic
abnormality that affects hatchability. The eggs might have been cracked or dirty,
or contaminated by muddy feet or in a poopy broody nest box.
Or maybe they were washed improperly. You should preferably not wash hatching eggs at all.
Perhaps the eggs got overheated or chilled briefly before setting,
or were kept too warm after laying past the point at which development can be paused.
Or the setting on the incubator might be incorrect, or the eggs might get too
cold too often if the broody hen keeps leaving the nest instead of sitting tight on the eggs,
or leaves some eggs on the edge of the clutch away from the warmth of her body.
Or maybe they were Stored too long before setting –
My video about storing fertile eggs before incubation
goes into more detail about these points. Trauma – Maybe the eggs got bumped by other
hens using the nest before you collected them, or by you when you were handling them. Or of course
eggs that have been shipped are at high risk of rough handling by couriers who don’t understand
the fragility of fertilised eggs – the hatch rate of shipped eggs is almost always reduced.
There might have been Insufficient ventilation in the incubator.
The embryo needs to take in oxygen through the shell membrane, so there needs to be a good flow
of fresh air across the shells of all the eggs. So if you open an egg and find no sign of any
growth at all, that doesn’t mean that it wasn’t fertilised - there are quite a few
possibilities that can stop the germinal disc from even beginning to develop. Think about
what you know about your egg has experienced and what might be the most likely cause.
Another possibility if you open an egg that doesn’t seem to be growing is to find that
the embryo did start to develop but then stopped after a day or two or three. Some
people call these “Early Quitters”. In this case you will almost certainly see
some sign of the embryo developing before it dies. If the embryo died in the first couple of days,
most likely what you will see is what’s called a blood ring, and it looks just like what it
sounds like – a circle of red blood vessels. The circle might collapse out of circular shape
but you can usually tell what it was. Or if the embryo got to about 5 days,
you will see the embryo itself looking like a small formless blob with a dark spot.
The dark spot is the chick’s eye. The rest of the body is unformed in comparison to the eye spot.
What went wrong? Many of the same reasons that stopped
the germinal disc from beginning to grow can also cause the embryo to die in the first few days.
Problems with the breeding flock’s nutrition or genetics. The egg got contaminated,
or was stored too long before setting, or experienced some Trauma during handling.
Remember to be very gentle with the eggs when you’re candling them. The temperature might
have got too high or too low early in incubation, either because of a problem with the incubator or
because the mother hen was away from the nest too long or left the egg outside the circle of warmth
generated by her body. Insufficient ventilation in incubator can stop an embryo from developing.
Also, if the eggs have not been turned properly during incubation, the embryonic membranes don’t
develop properly and the embryo can’t absorb nutrients from the yolk, and so it dies.
As I mentioned, if an embryo starts to develop at all and gets past those first critical few days,
it usually continues to grow for the next couple of weeks. Occasionally an
embryo will stop growing and die when it’s more than a week old. In that case, when you open the
egg you will see quite clearly the embryo as it would have been on the day it died.
What might you see? At Day 11, the embryo has
tiny limbs but still that big dark eye. At Day 13, eyelids cover the eye.
It will be quite obviously a fully-formed chick, although very small. Since death at this stage is
quite unusual, it’s worthwhile checking for any obvious physical deformities such as extra limbs.
At Day 15, tiny feathers are visible on the chick’s body.
What went wrong? One possibility is the
presence of a lethal gene in the parent flock. A well-known example of a lethal gene is the
gene that causes the characteristic ear tufts of Araucana chickens. Although these look like tufts
of feathers, they are actually protrusions of skin tissue, which happens to be covered in feathers.
Almost all the tufted Araucana chickens that you see have only one copy of the Et gene.
If the Et gene is passed on from both the rooster and the hen, so the embryo chick receives
two copies and is therefore homozygous, it almost always dies before hatching.
The Et gene is therefore called a lethal gene. And the hatch rate of chicks from
tufted parents is expected to be low – many of the chicks are likely to die before hatching.
Other possible reasons for mid-term chick death are:
If one or more eggs in the batch was contaminated with bacteria,
this contamination can spread to other eggs and kill off the other developing chicks
The Incubator Temperature being way too high Insufficient ventilation in the incubator
Inadequate turning of the eggs during the first week of incubation inhibits embryonic membrane
development and nutrient absorption If the Humidity is too low
this increases abnormalities of aortic arches in the embryo’s circulatory system.
If the chick develops all the way through to day 20, it faces the challenge of breaking
into the air cell and taking its first breath into its lungs. In order to do this,
it must get into the correct position so its beak can puncture the inner shell membrane. The correct
position is with its head at the large end of the egg, where the air cell is, and with its head
tucked under its right wing ready to prod forward with its beak. This is called internal pipping.
Then, before that small amount of air in the air cell is used up,
the chick has to jab even harder and break a hole in the egg shell so it can breathe
the outside air. This is called external pipping. Some chicks just don’t manage to succeed in either
internal or external pipping. What might you see?
If you break open an egg with a fully mature chick that never pipped, you will certainly
find the shell is full of chick. There might be a bit of the yolk still left, or all the yolk might
have already been absorbed into the chick’s body. This is an egg that looked like it was developing
well right to the end but never pipped. I’m going to open it and we’ll see what’s inside.
Always be careful to open the egg from the large end where the air cell is. That way you’ll be
able to tell whether the chick has managed to make its internal pip. In this case we se
that the air cell is intact – this chick never took its first breath of air into its lungs.
As we carefully peel away the shell and the outer membrane,
we can see that the chick looks fully formed and is correctly positioned ready for hatching,
with its head under its right wing, near the air cell at the large end of the egg.
But as we peel away the rest of the shell and membrane covering the chick,
we can see that it dies before it had absorbed all its yolk. This means it died at about day 19 or 20
What went wrong? As we mentioned,
failure to pip is a common reason for a chick to fail to hatch.
And there are a lot of possible causes for the chicks inability to pip.
If the air cell itself was malpositioned or deformed
then probably the chick won’t be able to break into it, or to get enough air from it
to have the energy to break the egg shell. If the egg was stored or set to incubate
upside down, the air cell would probably form at the pointy end of the egg,
where there wouldn’t be enough room for the chick’s head to break into the air cell.
If the incubator didn’t have adequate ventilation, once the chick has made its internal pip,
there won’t be enough oxygen in the air cell for the chick to carry on to hatching.
Inadequate turning that affects embryonic membrane development results in an embryo
that is stuck to the shell and the chick can’t position itself inside the egg correctly. Or if
you continued turning the egg after day 18, or if other hens in the broody nest were disturbing the
eggs while the chicks were trying to pip, then the chick has a harder time breaking through.
If the egg cold chilled during incubation, because the broody hen wasn’t being quite as
diligent as she should be or the power to your incubator failed, then this can show
up at the end of incubation when the fully developed chick fails to pip.
Alternatively too high a temperature after day 18 can also overheat the
chick so it can’t manage to pip. And this is the time when humidity
problems show their damage. Humidity too low on average during incubation, increases
abnormalities of aortic arches, while if the humidity has been consistently high,
the air cell at day 20 is too small and the chick effectively drowns in the albumen.
And again we see the effect trying to hatch eggs that are too old – the chick manages to develop
all the way to maturity but just doesn’t pip. And that’s probably what happened to
this chick – the air cell and the chick were in the right position,
but it didn’t make the internal pip. I didn’t have any known problems with temperature, but
it was an egg that was shipped to me and I don’t know how old it was before I set it to incubate.
The final challenge for the baby chick is to peck right around the inside of the egg shell
and push itself out into the world.
But I think that’s a topic for a whole other video.
Meanwhile, if you have eggs that don’t hatch, I suggest you open them and see if you can tell
firstly at what stage the development stopped, and then maybe take a guess at what went wrong,
based on what you know about what’s happened to that egg – was it old when set to incubate? Was it
shipped or likely kicked around by other hens in the broody nest? Did you have a power
cut or an unreliable broody hen? What do you know about the genetics and nutrition of the parent
flock, or previous experience of hatchability from those parents?
You probably won’t be able to pinpoint the cause for every egg that fails to hatch, but you can
look for patterns. Remember that 100 percent hatch rate is not usual in nature – even if you do and
your broody do everything right, about 80% is a good hatch rate. But it’s still worth going
to the trouble to open and investigate every unhatched egg, because that can give you some
clues about how to improve the hatchability rate of future batches of eggs, so that every potential
chick gets its best chance of making its way from fertilised egg to a real live healthy baby chick.
Best of luck, And bye for now. See you next time.