In this experiment sodium bentonite was evaluated for its effect on egg yolk pigmentation and performance when synthetic pigment was added to the diet of laying hens. About 256 Hy-Line W-36 laying hens 35-weeks old were allocated to 8 experimental diets with 4 replicates each. Four levels of sodium bentonite (0.0, 1.0, 2.0 and 3.0%) and 2 levels of synthetic pigment (0.0 and 0.04%) were used for the 12-week experiment with a 4 × 2 factorial arrangement and a completely randomized design. Pigment was supplied by 20 g of lucantin and 20 g of xanthin that were diluted with 9960 g wheat bran. About 1 week before the experiment, the birds fed dietary treatments for adaptation. The measured records were feed intake, feed conversion ratio, egg production, egg weight, specific gravity, shell percent, shell thickness and yolk color index. The addition of sodium bentonite decreased (P < 0.05) the specific gravity and yolk color index compared to the control diet. The addition of pigment significantly increased specific gravity and as expected, increased the yolk color index compared to the control diet.

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