Candling During Incubation: The Fourth Week.
DAY 25
From Daily Changes in the Weight and Form of the Developing Chick Cornell Bulletin 205, by Dr. A. Romanoff (1931) duckling development image
What's Happening Now
can sleep; vocal apparatus functional
yolk begins to be pulled (ingested) into the body cavity
chorio-allantoic membrane (inner membrane lining shell) contains less blood (as the blood 'retracts' into the duckling) and is “sticky” in living embryo
NOTE: It is possible that the hatching process begins today. Our eggs are usually set come due to hatch on a Wednesday (day 28) and we often have eggs where the baby has broken into the air-cell and is breathing by Sunday (day 25). The best way to tell what stage they are at is to candle the eggs. While the timeline may change (i.e. be faster or slower), the order of events will not. Once you match up the stage at which your eggs are, you will know what is supposed to happen next and how long you can expect that to take. In ducklings, the hatch can take anywhere from 1 to 3 days if we start 'counting' from the time the aircell enlarges.
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What to Look For
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What to Watch Out For
The final 3 days are very difficult for the embryo and some losses can be expected as not all babies are strong enough to withstand the stress of hatching. If you loose a baby between now and the hatch, and if you decide to open the egg and examine it, you may see the following:

  • the yolk sac may not be fully ingested. Many people interpret this as the baby not being fully formed and think the yolk sac is part of the embryo's insides, but in fact it is simply because the embryo died before the sac was fully ingested.
  • the baby is likely to be fully formed

You are NOT likely to see any obvious reason for why the embryo died.
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If you are not sure whether the embryo is OK or not, wait another few days.
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