egg 20140001   air sac2

figure 11.5 shows the size of the air sac in an incubating egg. The air sac increases in size as the embryo develops. If your air sac is not more or less in line with this diagram you need to adjust the humidity in the machine:

Too big an air sac means the humidity is too low. Too small an air sac means the humidity is too high.




egg 20140002


This is vital to any breeding operation.

You need to ensure your breeding eggs are clean, so the nesting boxes must be clean as well. Collect every day twice a day in breeding season. remove broken eggs at once or they will contaminate the others.


Never set broken or cracked, dirty or deformed eggs. Eggs must be of a good size, be uniform in shape, have a good strong shell, smooth in texture. Your eggs also need to be of more or less the same size though this is difficult if you are breeding different types of birds. Double yolks will not hatch and no, you will not get twins! Larger eggs take longer to hatch.

Don’t keep eggs for setting longer than seven days, ten at most.

Eggs collected for setting must be stored in a cardboard box, set on its side so the eggs are tilted, and tilt the eggs twice a day, that is tilt to the opposite side twice a day to keep the yolk centralised and stop it sticking to the side of the shell.

Wherever you store the eggs make sure it is cool, not cold and not in the fridge! The eggs must be well ventilated, hence the use of cardboard.  Polystyrene boxes make the eggs sweat and build up bacteria on the outside of the eggs.

Eggs are semi permeable, meaning anything can be absorbed by the egg but nothing can come out. This is why there can be a build up of gasses inside a maturing egg.

Candle all the eggs you want to set, and make sure there are no cracks or flaws.

Always store eggs with the rounded end upward, as this is where the air sac is.

Handle all eggs VERY GENTLY, there is already a dormant germ inside the egg and any rough handling may break the delicate membranes inside.

All eggs have a protective layer on the outside which is antibacterial, antimicrobial. This is why it is better never to wash eggs before setting but if there is an egg you need to set and it is dirty, wash with warm water warmer than the egg, with a litre of warm water to a teaspoon bleach. You should mark your eggs with the date of collection, pen number or ring number of the cock used. Never use anything but a pencil as ink will be absorbed inside the egg and may poison your chicks. Remember the eggs are semi permeable. Gently wash with a clean sponge and dry immediately with a clean towel. Infections are more likely if the egg is wet, and as it dries. So dry immediately and well.

If your eggs are clean, there is no need to wash.


Make sure your incubator has been running at the correct temperature for at least 24 hours before setting eggs. Also make sure you have DISINFECTED from the previous hatch!

aA good disinfectant to use is gluteraldehyde as it is anti fungal as well as anti bacterial.
At 18 days incubation candle again, and set eggs gently in the hatcher. You can now stop turning.
Check the humidity is set to 55% for the last few days and do not open your box again until removing dried chicks.
1. Try to set eggs that are the same size. Never set double yolks, they will not hatch, eggs that are too small or too large. If the eggs are too narrow at one end, discard, the chick will battle.
2.Handle very gently, I cannot stress this too much, from collection to hatching.
3. Make sure your incubator has sufficient air circulation. The exchange of C02 and oxygen is of primary importance. The exchange of C02 and oxygen takes place at two levels:

The first level is between the air sac and the egg itself and therefore the embryo. This is why your air sac is important and needs to be in line with the diagram provided on this page.

The second level is between the egg and the air inside your incubator. It is important to have good circulation in the box, and to open the  box occasionally to allow fresh air to circulate. You need a fan inside the box.
4. Do not fall into the trap of thinking you need to have more humidity if you are hatching ducks…you don’t!
5. When turning the eggs if your machine is not automatic, do so gently side to side, and always five or three times a day.
6.Mark eggs with a pencil, date of collection and pen number. Never use a coki pen.
7.Do not keep setting eggs longer than seven to ten days, and turn them twice a day before setting.
8.Candle eggs at ten days incubation not before as they are too fragile to handle. Remove and discard any clear eggs, but please make sure you are certain they are clear. If you are not sure, leave them in, and candle again at 18 days before setting in the hatcher.
9.If you can do so, have a separate hatcher. It is always a risk to hatch and incubate in the same machine but if this is not possible, make sure the incubator you have is kept pristine clean and disinfected, that any clear eggs are discarded immediately to avoid eggs exploding in the box, and that you remove any dead embryos after candling.
Disinfecting is best done between hatches with a quartenary ammonium compound such as VIRUKILL. This is very mild, is specifically designed for poultry and destroys all viruses without affecting the chicks in the hatching stage. You can also use gluteraldehyde, diluted 10ml to one litre.
Try to steer clear of harmful cleaners such as formalin. If you have nothing else, use plain bleach and hot water. Do NOT use Jeyes fluid. It smells clean but is harmful to young babies and is really useless as a poultry cleaning agent. Stick to any quartenary ammonium compound, not products derived from tar or cresylics like Jeyes. Jeyes fluid is a coal tar distillate, but is corrosive and toxic at high concentrations. It is not suited to proximity with young birds or eggs because it does give off noxious gasses.
Virukill is effective against viruses.  though it is not effective against spores or fungi.
You can also purchase gluteraldehyde which is relatively inexpensive and does destroy fungus, spores and is effective against ecoli and other bacteria. It is not a virucide.
If you work this in conjunction with Virukill, it should handle everything. See the section on disinfectants on this site.


Power failures. Eggs deprived of warmth for several hours, but of robust stock will hatch late but will hatch.

If your power goes off between day one and day five of incubation, you may lose the batch, and should remove the eggs and start again. If your power goes off between days seven and 18 of incubation, leave the incubator to reset itself, your eggs will hatch late but will hatch even if the power goes off for several days. The embryos at this stage will go dormant.

If your power goes off after day 18 of the incubation cycle, you have a problem. It will depend on the length of the power failure. If the eggs are still warm when the power returns you may be lucky. If the eggs are cold you may lose the lot. If birds are actually hatching when the power goes, you can wrap sealed glass bottles filled with boiling water in a towel and lay your eggs along the length of the bottles. They do not need turning, just warmth. I have hatched successfully like this.

Smaller eggs will hatch first.

Large eggs take up to 24 hours longer.

Large eggs from viable, young and robust stock and good breeding cocks will hatch first.

Eggs from older parent stock also take up to 24 hours longer.

Eggs from compromised parents, parents with MG or weak gene stock, will hatch later and chicks will be weak.  Some may die in the shell, being too weak to fight their way out of the egg. You may get deformed chicks, splayed legs, crossed beaks, bleeding navels, weeping eyes, closed eyes, sticky chicks, chicks that will not feed.

Soiled or dirty eggs will hatch with mushy chicks, see the section on incubation for OMPHALITIS.

Omphalitis is a bacterial infection that affects the embryo inside the egg, but it is also transferred from the hen to the egg to the chick, (called vertical transmission)  so be careful what parent stock you allow into your breed pens.







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