Candling eggs, why candling, candling equipment, time and methods, making judgment

What is eggs Candling?

Candling is a way of checking whether they are fertile and, if fertile, to check the growth and development of the embryo., with the use of a light source in a darkened room. In a darkened room, carefully hold the egg up to the light to observe the contents of the egg. The light penetrates the egg and makes it possible to observe the inside of the egg. Candling detects bloody whites, blood spots, or meat spots, and enables observation of germ development.

Why Candling?

• To remove infertile eggs or eggs with a dead embryo so that the egg incubator does not become contaminated.

• To adjust the incubation environment, including humidity and temperature, or ventilation, according the candling result compared with the standard candling map

Candling Equipment:

1. A torch with a lense the size of a small coin may be used.
2. A commercial candler may be purchased.
3. A homemade candler which uses a bulb or torch placed in a container with a small hole to let the light pass through.

Requirements for candling torch

1. The Candling Torch should throw out a strong, focused beam of light

2. The Candling Torch should also put out a cool light rather than a lot of heat that might damage your embryos.

When To Candle

White eggs should be tested for fertility on the third day. Brown shelled eggs on the fifth or sixth day because it is difficult to see the embryo clearly before this time.

Day 8 onwards is usually when the embryo is more easily identified.

1. Day 3 of incubation (usually pale shelled eggs).
2. Day 5/6 of incubation (usually dark shelled eggs).
3. Between day 8 - 12 of incubation (embryo more easily identified).
4. 3 days prior to hatching.

How to Candle?

In candling, the egg is held in a slanting position with the large end against the hole in the candler. The egg is grasped by the small end and, while held between the thumb and tips of the first two fingers, is turned quickly to the right or left. This moves the contents of the egg and throws the yolk nearer the shell.

Any eggs you are not sure of, pencil a question mark onto. Have another look at them later. Comparing them to your good eggs will help you decide.

How to make a judgment

The embryo is located at the large end of the egg, where blood vessels will be present under the surface if the egg is fertile. The embryo appears as a dark spot which becomes larger as the incubation period continues.

Negative results:

1) Clear when candled – may be infertile or had a very early death.
2) Embryo with red blood “ring” – early death.
3) Red or black staining – early death.
4) Fertile with red blood vessels.

Neutral or Positive results:

1) Dark outline with ill defined detail – possible late death (10 – 16 days) Give them a little more time though.
2) Live embryo with bill in air sack – due to hatch in 24 – 48 hours.
3) Normal development of air pocket according to number of days.

Note that dark or brown shelled eggs are more difficult to candle than white or pale shelled eggs.

 Egg Candling and Air Sac Development

During incubation the air sac size should increase as moisture evaporates from the egg. If your humidity levels are about right, the air sac should increase at different days of incubation according to the diagram shown here.

If the incubation humidity is too high, the air sac will be smaller than it should be. If humidity is too low (i.e. very dry conditions) the egg will lose more moisture than it should and the air sac will be larger than normal.

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