Eggs may be candled after 5 days of incubation and every few days thereafter. For best results you should candle eggs in a darkened room or in dimly lit conditions. The candler should be held right against the shell at the larger end of the egg where the air sac is located.
* During the last 3 days of a hatch, it is best to avoid candling the eggs unless you have a specific reason to. * A vague ring inside the egg and little or no veins. * After 10 days the egg is still clear.
Day 1-18: Turning the eggs
Eggs must be physically turned to prevent the developing chick from sticking to the shell. More scientifically, the embryo should be resting on top of the yolk. The yolk tends to float upward, on top of the albumen (egg white) towards the shell if the egg is not turned.
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.
The presence of branch-like structures indicates you likely have a partially incubated egg. If you can't see any defined shapes, it appears solid, or all you can see is an air cell, discard that egg because it's likely gone bad. Likewise, if cracks in the shell are visible when candling, trash it.
You'll see blood pumping through the heart of a tiny, developing embryo if you candle a fertile egg on Day 4. If the embryo dies at this point, you may still see a faint network of blood vessels inside the egg's contents. An embryo dying at this point will show a large, black eye.
Wet or Dry Hatch? Humidity can be a bigger problem. Many experts believe that 'dry hatching' is the best way to go. The theory is that many chicks drown in the shell because the air cell is not big enough.
The optimum time is three days before the eggs are due to hatch. For normal sized chicken eggs this is at Day 18 of incubation. Bantam eggs tend to hatch earlier, at around 19 days into incubation. So they should be locked down at day 16.
If you see a blood ring inside the egg with no embryo, or a tiny embryo with no visible eye, this indicates that the embryo stopped developing in the first three days.
You will see that supermarket eggs are infertile. Did you know you can determine if an egg is fertile or not by looking at the germ spot? The germ spot is the white spot on the yolk. The non-fertile germ spot contains only the female's cells and looks like a solid white spot.
Hatching chicken eggs: days 1, 2 and 3.
There's really not much to see at this point. Initially the egg will look clear, apart from the air cell which you may be able see at the 'fat' end of the egg – but probably not before day 4 or 5. As time goes by you'll notice this air sack become larger.
Your broody hen will usually be able to tell if an egg is rotten, and she is likely to push it out of the nest; however, it's an idea to candle the eggs. Candling is where we shine a bright light through the eggshell in a darkened room to see whether the embryo is developing as expected.
Starting on day 10, the eggs will benefit from daily misting and cooling. Once a day, remove the lid of the incubator and leave it off for 30-60 minutes.
During hatching the humidity should be at least 60% RH, and in order to keep the humidity stable it is recommended to keep the lid on the incubator at all times.
Too little moisture results in excessive evaporation, causing chicks to stick to the shell sometimes and hatch crippled at hatching time. Table 3 (Relative Humidity) will enable you to calculate relative humidity using readings from a wet-bulb thermometer and the incubator thermometer.
The results indicated that incubation of eggs under 12 and 24 h of lighting significantly improved (P ≤ 0.05) hatch window, hatchability % (0.0002), a hatch of fertile % (0.001), and carcass yield % (0.0454). Embryonic mortality, dead germs, and dead in shell embryos were lower in eggs incubated under 12 h light.
The incubation period for chicken eggs is 20 to 21 days, and increases up to 30 days for other poultry. After sitting for some days, a broody hen can be given some newly hatched chicks and, if they are accepted, the original eggs can be removed and replaced with more chicks.
The developing embryos have delicate blood vessels that rupture easily when severely jarred or shaken, thus killing the embryo.
Do fertile eggs sink or float? Eggs sinking or floating is nothing to do with fertility – it's to do with freshness. The older an egg is, the more it will float. So a fresh egg will sink; the more it tilts upwards or even floats, the older it is.
Storage time
It is best to incubate eggs within 7 to 10 days of their being laid. Hatchability decreases rapidly when eggs are stored for more than 10 days. After 7 days, hatchability decreases 0.5 to 1.5 percent per day. Each day in storage adds one hour to the incubation time.
If chick embryos develop to the pipping stage, or at first shell cracking at hatching, they are normally healthy enough to hatch unless some incubator adjustment prevents it from happening. The problem is usually caused by either 1) poor ventilation or 2) improper humidity.