Step 1: Understanding the Concept:
Consumer preference for egg quality is highly influenced by the intensity of the yellow-to-orange color of the egg yolk.
Since laying hens cannot synthesize carotenoid pigments de novo, the pigment profile of the egg yolk is directly determined by the pigments present in their diet.
Step 2: Detailed Explanation:
Let us analyze the chemical properties of the listed pigments:
1. Zeaxanthin (C): This is a natural xanthophyll carotenoid pigment widely distributed in yellow maize and marigold flowers. It is highly lipophilic (fat-soluble).
When added to poultry feeds, zeaxanthin is absorbed in the gut, transported in the bloodstream bound to lipoproteins, and deposited directly into the lipid-rich egg yolk, giving it a deep, highly desirable golden-yellow to orange color. Thus, (C) is correct.
2. Anthocyanins (A): These are water-soluble vacuolar pigments that give red, purple, or blue colors to plants. Because they are hydrophilic, they are not deposited in the lipid-rich egg yolk.
3. Carmoisine (B) & Indigo Carmine (D): These are synthetic, coal-tar-derived food dyes (red and blue, respectively) that are not used as standard feed additives for natural yolk pigment deposition due to toxicity regulations and metabolic clearing.
Step 3: Final Answer:
Therefore, Zeaxanthin is the pigment used as a feed additive to strengthen the yolk color.