Vitamin D enrichment of eggs and its effects on performance and intestinal health in late-stage laying hens

Vitamin D deficiency remains a concern in both poultry production and human nutrition. This study evaluated the effects of dietary co-supplementation with vitamin D3 and 25-hydroxyvitamin D3 [25(OH)D3] on productivity, egg vitamin D enrichment, systemic inflammation, and intestinal health in late-stage laying hens. A total of 150 Rhode Thai hens (72 weeks old) were assigned in a completely randomized design to five diets containing varying levels of vitamin D3 (300 to 3,200 IU/kg) with or without 25(OH)D3 (69 µg/kg) for 12 weeks under non-challenged conditions. Co-supplementation significantly improved hen-day egg production, yolk proportion, and Haugh unit (P < 0.05). Vitamin D enrichment was substantial, with the highest concentration reaching 8.52 µg per whole egg, nearly 39-fold greater than unsupplemented controls and providing more than half of the human recommended dietary allowance (RDA). Serum 25(OH)D concentrations increased while C-reactive protein decreased, indicating improved vitamin D status and reduced systemic inflammation. Intestinal morphology and the expression of tight junction genes (ZO-1, Claudin-1) were also enhanced, suggesting strengthened barrier function. Collectively, these findings demonstrate that combining vitamin D3 with 25(OH)D3 sustains laying performance, improves gut health, and produces vitamin d-enriched functional eggs. Such eggs represent a sustainable and cost-effective innovation in precision poultry nutrition and may help support dietary vitamin D intake in humans.