Dietary astaxanthin enhances egg yolk redness and carotenoid deposition in laying hens fed β-apo-8′-carotenoic acid ethyl ester and canthaxanthin

1. This study evaluated the effects of dietary astaxanthin supplementation on yolk pigmentation, carotenoid deposition and yolk quality in laying hens fed diets containing β-apo-8′-carotenoic acid ethyl ester (apo-ester) and canthaxanthin.2. A total of 168 NovoColor hens (71 weeks of age) were assigned to one of 14 dietary treatments. Treatments included a low-pigment control (CON), canthaxanthin-only (CAN), an apo-ester (AE) plus canthaxanthin treatment, with graded levels of astaxanthin (AX) supplementation (from 5 to 100 mg/kg). Each treatment consisted of six replicates of two individually housed hens. The study lasted for 4 weeks. Egg production performance, yolk colour, carotenoid deposition and yolk index were determined.3. Dietary treatments did not affect laying performance (p > 0.05). Increasing dietary AX supplementation increased yolk concentrations of AE, CAN and AX and improved yolk pigmentation (p < 0.05). Both CAN and AX deposition efficiencies showed both linear and quadratic responses to increasing AX inclusion, whereas AE deposition responded quadratically (p < 0.05), with AE and CAN deposition peaking at 50 mg/kg astaxanthin.4. Yolk pigmentation increased rapidly after dietary introduction and reached a plateau by d 8. Eggs from carotenoid-supplemented hens had higher yolk index values than eggs from CON hens (p < 0.05), while yolk index decreased with storage duration.5. In conclusion, dietary AX enhanced yolk pigmentation and carotenoid deposition without compromising laying performance, supporting its use as a complementary red pigment in layer diets. The higher egg yolk index from hens fed carotenoid-containing diets may contribute to maintaining yolk quality during ambient storage.