The most important thing to remember about fertile eggs meant for hatching
is that they’re living things — they must be handled gently and kept at the
right temperature or they’ll die. Don’t shake them or toss them around — if
you do, you may kill the embryo.
Don’t wash fertile eggs intended for hatching!Washed eggs are far less likely
to hatch than unwashed eggs, and the unhatched, washed eggs may also affect
the hatching of eggs around them.
When you wash eggs, you remove the protective coating that the egg gets as
it leaves the hen, and the egg’s pores often draw in bacteria. The warmth of
incubation turns the contaminated egg into a factory for bacteria reproduction,
often killing the embryo and spreading to nearby eggs
The fertilized egg starts dividing to become an embryo as it travels down
the oviduct on its journey out of the hen. When it’s laid and cools below her
body temperature, it goes into a state of suspended growth until conditions
are right again. Eggs being stored for hatching should be stored at temperatures
between 45 and 65 degrees Fahrenheit. If the egg temperature drops
below 45 degrees for very long, the embryo will probably die; if it goes above
65 degrees, it may start to grow.
Growth at less than optimum temperatures makes weak chicks that seldom
survive the whole incubation period and can cause deformities in those
chicks that do survive. In cold or very warm weather, eggs should be collected
from your hens for hatching as soon after they’re laid as possible and
then moved to the right conditions. If you’re collecting your own eggs, you
may need to put them in a cool basement or even in the bottom vegetable
drawer of your refrigerator to suspend growth.
Store eggs for hatching with the small end down. An egg carton is good for
this purpose. Eggs can be stored for about a week without much drop in vitality,
but after a week of storage, the percentage of eggs that will hatch drops
sharply. After two weeks of storage, few eggs will hatch.
Eggs that are being stored for incubation should be rotated from side to side
twice a day. This keeps the early embryo from sticking to the shell in a bad
If you’re getting eggs from anywhere but your own hens, have your incubator
set up and ready to put them in as soon as you receive them. If you’re collecting
eggs from your hens, store eggs until you have about a week’s worth;
then set up the incubator and put them into the incubator all at once. Using
a pencil or nontoxic marker, mark the eggs with the date you set them. If
you’re going to be hand turning the eggs, put an x on one side so you know
which eggs have been turned.
It’s best not to have several different hatch dates in the same incubator unless
you have a cabinet incubator with multiple shelves or drawers. Eggs at different
stages of incubation require slightly different care.
Try to find a local source of fertile eggs if you can. Sending eggs through the
mail and getting a high percentage of them to hatch is very difficult — the
average rate of hatch under ideal conditions for fertile eggs sent by mail is
only 50 to 60 percent. Normally, you don’t get any guarantees when fertile
eggs are mailed to you because the seller can’t control the shipping temperatures
and the way the eggs are handled in transit.
If you’re saving your own eggs or you have the chance to pick and choose
which eggs you want, choose the cleanest ones. You can brush off dirt with
a dry cloth; some people even use fine sandpaper. If eggs are heavily soiled,
it’s best not to use them. Discard any cracked eggs and any eggs that have
very thin shells or are oddly shaped; oddly shaped eggs seldom produce good
Eggs you buy from the supermarket won’t hatch because those hens aren’t
kept with roosters. Even the eggs labeled organic are probably from hens
without roosters. We’ve heard of eggs that were bought at farmers’ markets
from free-range hens hatching, but don’t count on hatching eggs that were
meant for eating.
Candling eggs is a very exciting time. Candling a week after incubation allows you to find out if an egg is fertile and allows you to remove clear eggs. Candling again after another week allows you to remove any ‘dead in shell’ embryos, those that haven’t developed further and usually only show a blood ring inside.
A dark room and a bright torch is all you really need, even an old toilet-roll cut to fit the shape of the egg and held up towards the sun will work well.
With a freshly laid egg, you will see an almost clear egg. There is a feint shadow which is the egg yolk. This is called a ‘Clear Egg’ and is how the egg will remain during the first week of incubation if it is not fertile.
As the embryo develops, over the next few days, a very small darker patch will develop on the ‘shadow’ of the yolk. This is the germainal disc and takes an expert eye to spot this.
As time goes on, blood vessels begin to develop and become thicker and more visible and the embryo grows in size, until day 8 when the eye and the heart have developed and the embryo is starting to take the shape of a chick. If you are lucky, you may see the little peeps heart beating!
The air sack is easy to see. This grows as the egg develops and contains the first few breaths of air the chick will take when it pokes it little beak through on day 21.
The yolk sack itself I have shown in red (why? Because yellow didn’t show up too well and the yolk sack is so full of red blood vessels, it’s now pretty much all red).
The blood vessels emerge like spiders legs into the alubumen (egg white), the thicker of these can be seen when candling your eggs.
When eggs go into lockdown on day 18, they prepare to hatch by positioning their beaks towards the wide end of the egg where the air cell is. For much of the journey thus far, the embryo has been supplied with oxygen through the eggshell’s pores via a network of blood vessels called the allantois. Just prior to hatching, the chick pokes its beak through the membrane (pips) into the air cell and begins breathing with its lungs.
Chicken eggs are expected to hatch on or around day 21 into incubation and should generally hatch within 24 hours of the first pip in the batch. Various factors play into the process that can either advance or delay that schedule, primarily temperature fluctuations. Temperatures slightly higher than ideal can result in a premature hatch and physical challenges for the chick. Temperatures slightly lower than ideal can cause a delayed hatch and physical impairments.
It is reasonable to expect a chick to hatch within 12-24 hours of pipping.
If a pipped egg does not make progress by expanding the hole and chipping around the circumference of the shell within ~12 hours of the first pip, they may be unable to accomplish the job alone. Whether or not to assist in a hatch is a matter of personal preference. If the decision is made to help, the chick must have absorbed all of the blood in the membrane as well as the egg yolk in order to survive outside the shell. Helping risks severing a blood vessel in the membrane, hemorrhage and death. Any assistance rendered should proceed very slowly and cautiously, stopping at the first sign of bleeding.