Topics:
Animal Refresher, Poultry Science
Purpose of Second Candling (Day 18) in Incubation
During incubation of chicken eggs, the 2nd candling is done on the 18th day to discard:
- Dead-in-shell — Correct Answer
- Piped eggs
- Infertile eggs
- Double-yolk eggs
Explanation:
Correct Answer: Dead-in-shell
The second candling on the 18th day of incubation is done to discard dead-in-shell eggs before the eggs are transferred from the setter tray to the hatcher tray. At this stage, dead-in-shell eggs appear as a dark, opaque mass with no embryo movement.
Dead-in-Shell Condition
- Cause: Poor ventilation (low O₂ / high CO₂) and/or faulty turning of eggs.
- Appearance at candling: Completely dark/opaque without any movement or blood vessel pulsation.
- Why remove before hatcher? If left in the hatcher, dead-in-shell eggs can burst or rot and contaminate live, healthy eggs.
Comparison of Two Candlings
| Candling | Day | Purpose |
|---|---|---|
| 1st | 7th day | Discard infertile eggs |
| 2nd | 18th day | Discard dead-in-shell eggs |
Why Other Options Are Wrong
- Piped eggs → these are hatching eggs found on day 21; not discarded during incubation.
- Infertile eggs → already removed at 1st candling on day 7.
📚 About this Topic — Animal Refresher
This multiple choice question is from Animal Refresher, Poultry Science. It has 4 options with a detailed explanation of the correct answer. Practice more MCQs from Animal Refresher to strengthen your preparation.
