Maximum Weight Loss During Incubation of Chicken Egg

Correct Answer: 12.6%

During the entire 21-day incubation period, a chicken egg loses a maximum of 12.6% of its initial weight through evaporation of moisture via the pores of the eggshell.

Why Weight Loss Occurs

• The egg loses water vapour through its ~8,000 pores continuously during incubation.
• This weight loss is controlled by maintaining proper relative humidity in the incubator: 60% RH during days 1–18 and 70% RH during the last 3 days.
• Too much weight loss (>15%) → chick dehydration and failure to hatch.
• Too little weight loss (<10%) → excess fluid, drowned chick in shell.

Relationship to Air Cell

• As the egg loses moisture, the air cell (at the broad end) grows in size.
• The depth of the air cell in a freshly laid egg is only 1–3 mm.
• By day 18, the air cell should occupy approximately 1/3 of the egg — the chick will pip into the air cell before external pipping.