Dietary marigold-derived lutein produces dose- and time-dependent egg yolk enrichment and coordinated hepatic-ovarian responses in laying hens.

Marigold-derived lutein is widely used to enhance egg yolk pigmentation, but its dose-dependent deposition efficiency, temporal accumulation, post-withdrawal clearance, and associated hepatic-ovarian responses remain incompletely defined. This study evaluated these responses in 450 23-wk-old Jingfen No. 6 laying hens assigned to diets containing 0, 40, 80, 120, or 160 mg/kg marigold-derived lutein for 12 wk, with 6 replicates of 15 hens per treatment. Dietary lutein did not affect overall laying performance or conventional egg-quality traits (P > 0.05). Yolk color increased rapidly in a dose-responsive manner from D3 of supplementation and remained elevated through D28 (P < 0.001). At D21, egg lutein content increased with supplementation level (P < 0.001), whereas incremental apparent deposition efficiency declined from 8.42% at 40 mg/kg to 5.28% at 160 mg/kg (P = 0.016). After withdrawal, egg lutein content remained relatively stable during the first 3 d, declined sharply between WD3 and WD7, and no longer differed among groups by WD10. Exploratory analyses comparing the 0 and 120 mg/kg groups showed that hens fed 120 mg/kg lutein had lower serum total cholesterol, LDL-C, VLDL, and MTTP and higher vitellogenin, estradiol, luteinizing hormone, and follicle-stimulating hormone (P < 0.05). It also decreased hepatic BCO2, PPARγ, and apoVLDL-II expression, while increasing hepatic ERα and ApoA1 and ovarian VLDLR, ApoA1, and ERα expression (P < 0.05). Serum estradiol was positively correlated with ovarian ERα and ApoA1, and serum vitellogenin was positively correlated with ovarian VLDLR. These findings show that marigold-derived lutein rapidly enriches egg yolk, but incremental apparent deposition efficiency declines at higher dietary inclusion levels. Continuous supplementation was required to maintain enrichment, and the serum and transcriptional responses observed at 120 mg/kg were consistent with reduced hepatic carotenoid cleavage, altered circulating endocrine and lipid-related status, and greater ovarian yolk-precursor uptake capacity, which may jointly favor lutein deposition in egg yolk.