Effects of Selenium-Enriched Yeast on Laying Performance, Egg Quality, Selenium Deposition, and Serum Biochemical Parameters in Laying Hens

Selenium (Se) is essential for livestock, and selenium-enriched yeast (SY) is widely used to produce Se-enriched eggs. However, the optimal dosage for late-peak laying hens remains unclear. This 8-week trial evaluated graded SY (0, 0.1, 0.3, and 0.5 mg/kg Se) in 28-week-old Hy-Line Brown laying hens to explore the comprehensive effects. SY did not affect laying performance or egg quality (p > 0.05), whereas egg Se content increased dose-dependently from 0.211 to 0.521 mg/kg (p < 0.001). SY enhanced antioxidant capacity, with glutathione peroxidase and catalase activities rising from 90.67 and 7.91 U/mL to 493.33 and 21.43 U/mL (p < 0.001), and malondialdehyde decreasing from 0.46 to 0.13 nmol/L (p < 0.001). Serum lipid parameters were markedly improved, with total cholesterol and triglycerides declining from 8.82 and 17.60 mmol/L to 2.86 and 13.73 mmol/L (p < 0.001). Humoral immunity was also positively modulated, as immunoglobulin G and A increased from 401.68 and 73.06 μg/mL to 756.30 and 115.80 μg/mL (p < 0.001). Integrating egg enrichment efficiency, laying hen physiological health, and economic benefits, 0.3 mg/kg Se was identified as optimal, achieving 0.358 mg/kg egg Se. This study provides a novel paradigm for standardized and cost-effective commercial production of Se-enriched eggs.