Introduction

Candling is the process of holding a strong light above or below the egg to observe the embryo. A candling lamp consists of a strong electric bulb covered by a plastic or aluminum container that has a handle and an aperture. The egg is placed against this aperture and illuminated by the light. If you do not have a candling lamp, improvise. Try using a torch.



Determining the viability of the embryo

Under the candling lamp, the embryo appears as a dark shadow with the head as a dark spot. Healthy embryos will respond to the light by moving. Sometimes the movement is very sluggish and it can take 30 to 40 seconds for the embryo to move when held under the candling lamp. This indicates the embryo is not healthy and the egg should be discarded.

Look carefully at the blood vessels. They are well defined in a healthy embryo. After an embryo has died, the blood vessels start to break down. They then appear as streaks under the shell when viewed under the candling lamp. Candling will also reveal cracks in the eggshells. Eggs with cracked shells should be discarded.

 Infertile eggs: These are easy to detect, as the egg is clear. Discard

 Early deaths: The embryo has developed for several days and then died. Candling will reveal a small dark area and disrupted blood vessels. Often deteriorating blood vessels will appear as a dark ring around the egg. Discard.

 Late Deaths: These are often difficult to tell apart from a viable embryo at the same stage of development. Look for the absence of movement and the breakdown of the blood vessels. Discard

 Viable Embryos: These move in response to the light and have well defined blood vessels. Mark the air sac and the inoculation site and then return the eggs to the incubator ready for inoculation.


 Procedure 

  • Procure six farm fresh and six market eggs (not fresh). 
  • Hold the eggs before a suitable light in the batch type or continuous egg Candler.
  • Put on the switch of the commercial Candler.
  • Pick up the eggs with defects of eggshell, yolk, albumen and abnormalities like dirty shell, cracks, leakers, misshaped, rough, thin shelled eggs. The defects in yolk and albumen are blood spots, meat spots and blood ring which render, the egg technology unsuitable for market channel.
  • Disposed them separately according to their merits.