Question

The following body parts show depigmentation of skin in laying chickens:
(A) Beak
(B) Eye ring
(C) Vent
(D) Shank
Choose the correct order (first to last) from the options given below:

• A. (A), (B), (C), (D)
• B. (C), (B), (A), (D)
• C. (C), (D), (A), (B)
• D. (B), (A), (C), (D)

Hint:

Flock managers use this depigmentation order to evaluate a hen's past egg production performance.
A hen with completely bleached shanks has been in continuous, high-level egg production for several months, whereas a hen with bright yellow shanks is either a poor layer or has recently stopped laying.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
In yellow-skinned chicken breeds (such as the White Leghorn), carotenoid pigments (primarily xanthophyll) are deposited in the skin, beak, and shanks, giving them a yellow color.
When a hen begins to lay eggs, these dietary pigments are diverted from the body tissues to the egg yolk, causing the yellow color to fade (bleach/depigment) from various body parts in a highly predictable, chronological sequence.
Detailed Explanation:
The bleaching of pigment follows the rate of blood flow to each tissue as egg production progresses.
The sequential order of depigmentation, from first to last, is as follows:
1. Vent (C): The vent loses its yellow color very quickly once egg laying begins, typically bleaching within the first 1 to 2 weeks of production (or after laying about 3 to 8 eggs).
2. Eye ring (B): The thin skin around the eye ring loses pigment shortly after the vent, usually within 2 to 3 weeks of continuous laying.
3. Beak (A): Bleaching of the beak starts at the base (corner of the mouth) and progresses toward the tip. It takes about 6 to 8 weeks of continuous laying for the beak to bleach completely.
4. Shanks (D): The shanks have the thickest skin and the slowest blood flow, making them the last part of the body to lose pigment. Complete bleaching of the shanks requires about 4 to 6 months of continuous, high-rate egg production.
Therefore, the chronological order of depigmentation is: Vent \(\rightarrow\) Eye ring \(\rightarrow\) Beak \(\rightarrow\) Shank.
This corresponds to the sequence (C), (B), (A), (D).

Step 2: Final Answer:
The correct order of depigmentation is (C), (B), (A), (D).