Comparative efficacy of selenium nanoparticles vs. sodium selenite in mitigating summer stress: Enhancing egg biofortification, antioxidant defense, and hatchability in aged laying breeder hens.

This study investigated the effects of different levels of selenium nanoparticles (Nano-Se) and sodium selenite (SS) on the production performance, egg quality, hatchability, yolk selenium (Se) deposition, serum antioxidant enzyme of aged laying breeder hens in summer, as well as to evaluate the relative biological potency of Nano-Se relative to SS. A total of 756 healthy 60-week-old Hy-Line Grey laying hens were randomly divided into 9 groups, with 6 replicates in each group (13 hens and 1 roosters), After 4 weeks of Se depletion, all groups were provided with the same basal diet (no Se supplementation) fortified with SS or Nano-Se at concentration of 0.0 mg/kg, 0.1 mg/kg, 0.2 mg/kg, 0.3 mg/kg, or 0.4 mg/kg, for 8 weeks. Egg performance, egg quality, Se content in egg yolk, hatchability, and eggs antioxidant indices were evaluated. The results indicated the following: (1) production performance: the dietary supplementation of different Se sources had no significant effects on production performance (P > 0.05); (2) egg biofortification: Nano-Se supplementation significantly enhanced Haugh units compared with SS supplementation (P < 0.05), and 0.4 mg/kg Nano-Se or SS exhibited a marginally higher yolk Se deposition (P < 0.05); (3) reproductive efficiency: 0.4 mg/kg Nano-Se or SS increased significantly fertilization, hatching of incubated eggs, and hatching of fertilized eggs, and the Nano-Se supplementation decreased early embryo mortality compared with SS supplementation(P < 0.05); and (4) antioxidant defense: 0.4 mg/kg Nano-Se or SS exhibited superior serum GSH-Px and T-SOD activities with concurrent MDA reduction (P < 0.05). Notably, relative biological potency analysis revealed that Nano-Se achieved 118 %-151 % efficacy compared to SS in key parameters, including fertilization rate enhancement and oxidative stress mitigation. These findings establish Nano-Se as a thermal stress adaptive Se source, providing dual benefits of nutrition enrichment and physiological resilience enhancement in aged poultry under seasonal challenges.