When a hen is sitting on a clutch of eggs, the last thing you want to have happen is for a rotten egg to explode under her and soil her and all the other eggs. Eggs can become rotten during a hatch either because they were never fertile to begin with and never developed, or because they were fertile and started to develop, but the embryo died for whatever reason. During the process, bacteria can get into the egg and start to form gasses that eventually cause the egg to rupture.
Exploding rotten egg=no fun.
They way that you can avoid this is to candle your eggs. This is sort of like an egg “ultrasound” to allow you to see if an egg is developing or not. It takes some practice, but at about day 15, it should be very obvious which eggs are developing and which aren’t and you should be confident enough at that time to discard any eggs with no development.
You will need a strong LED flashlight, and you will want to do this at night. It will probably make mama hen very nervous, so you will want to work swiftly, but carefully so that you don’t crack any eggs. To candle the eggs hold them horizontally in one hand and use the other hand to put the flashlight behind the egg. You will need to wrap your hand around the bulb area of the flashlight to seal any light from escaping out the sides and force all the light to shine into the egg.
This egg has a chick in it. The light part is the air sack and the darkness is the chick! I candled the night prior to taking this picture and I could see the chick moving and the heart beating. Tonight they’ve grown so much they can’t move!
This is another developing egg. If you were seeing it with your own eyes, you would see blood vessels and a bit of slow squirming. When they get this developed, just like a human baby, they have a hard time moving around.
By contrast, this is one of Coco’s eggs that isn’t developing. You can see through it completely because the embryo doesn’t block any light. You cannot see a pronounced air sack. If you were to candle an egg from your refrigerator, it would look similar to this.
Keep in mind, that I started candleing eggs at about day 15 of a 21 day gestation period and then candled periodically up to hatching. If you candle earlier, you won’t see as distinct a contrast between developing and undeveloped eggs. I waited until the differences were very obvious and I felt sure about discarding the undeveloped eggs.
This candleing was done just a few days before hatching, and in my next post, we will show a video and some photos of the hatch!