Dietary Silicon Supplementation Improves Egg Production Performance in Late-Phase Laying Hens: Roles of Antioxidant...

Silicon (Si) is an essential trace element involved in multiple physiological processes of animals. This study aimed to investigate the dose-dependent effects of dietary silica (SiO₂) supplementation on production performance and key blood parameters in laying hens. A total of 360 hens were randomly assigned to five groups (6 replicates/group, 12 hens/replicate) and fed basal diets supplemented with 0% (control), 0.1%, 0.2%, 0.4%, or 0.8% SiO₂ for 8 weeks. Laying performance, egg quality, serum immune indices, reproductive hormone levels, antioxidant status, and serum trace element concentrations were determined. The results showed that dietary SiO₂ supplementation significantly affected egg production rate (p < 0.05), with the 0.2% group achieving the highest rate compared to the control. For egg quality, yolk weight and yolk thickness were significantly reduced only in the 0.8% group (p < 0.05), while other parameters were unaffected (p > 0.05). Dietary supplementation with 0.2%, 0.4%, and 0.8% silica significantly increased serum levels of IL-2 and IL-4 (p < 0.05), whereas the 0.8% supplementation decreased IL-1 levels (p < 0.05). Compared with the control group, serum IgA and IgG levels were elevated in the 0.2%, 0.4%, 0.8% silica-supplemented groups (p < 0.05), and serum IgM levels were higher in the 0.4% and 0.8% groups (p < 0.05). Regarding reproductive hormones, dietary SiO₂ significantly increased serum concentrations of β-endorphin, estradiol, growth hormone, luteinizing hormone, and progesterone (p < 0.05), with follicle-stimulating hormone elevated in the 0.4% and 0.8% groups (p < 0.05). Dietary silica supplementation did not affect serum activities of SOD, GSH-Px, CAT, or T-AOC. Serum POD activity decreased gradually and was significantly lower in the 0.2%, 0.4%, and 0.8% groups than in the control group (p < 0.05). Furthermore, SiO₂ supplementation significantly altered serum Cu and Zn levels (p < 0.05), with the 0.8% group having the highest Ca concentration and the 0.1-0.8% groups showing increased Zn levels compared to the control; no effects on Fe and Mn were observed (p > 0.05). In conclusion, dietary supplementation with 0.2-0.4% SiO₂ effectively improves egg production rate, along with enhancing immune function, modulating reproductive hormone secretion, and regulating serum Cu/Zn homeostasis in late-phase laying hens.