Days of Candling During Chicken Egg Incubation

Correct Answer: 7th & 18th day of incubation

Candling is performed twice using an electric candler in a dark room:

• 1st Candling: 7th day — to discard infertile eggs (clear/transparent appearance with no embryonic development visible).
• 2nd Candling: 18th day — to discard dead-in-shell eggs (dark, opaque mass with no movement).

What Each Candling Reveals

• Fertile egg (7th day): Spider-web appearance of blood vessels; embryo visible as a dark spot with radiating vessels.
• Infertile egg (7th day): Clear, no blood vessels — discarded to save incubator space and prevent contamination.
• Blood ring (7th–14th day): Ring of blood visible → indicates early embryonic death.
• Dead-in-shell (18th day): Dark, opaque mass filling the egg but embryo has died → discarded before transfer to hatcher.

Why Other Options Are Wrong

• 7th & 14th → second candling is not done on 14th; it is done on 18th (before transfer to hatcher).
• 14th & 21st → incorrect days for standard candling protocol.
• 10th & 18th → 10th day is not a standard candling time.