Dietary supplementation with Enterococcus faecium Ef026 elicits a systemic improvement in Hy-Line Brown laying hens during the mid-to-late laying phase

This study investigated the effects of dietary Enterococcus faecium Ef026 supplementation on mitigating the systemic decline in Hy-Line Brown laying hens during the mid-to-late laying phase. A total of 560 hens (48-week-old) were allocated to five groups supplemented with 0, 10 7 , 10 8 , 10 9 , and 10 10 CFU/d of Ef026 for 12 weeks. Supplementation significantly increased laying rate and improved egg quality (albumen height, Haugh unit, eggshell thickness), while reducing broken and soft-shelled egg rates. Systemic enhancements were evidenced by elevated serum antioxidant capacity (total antioxidant capacity, superoxide dismutase, glutathione peroxidase), immunoglobulins (IgA, IgG, IgM), and reproductive hormones (gonadotropin-releasing hormone, follicle-stimulating hormone, luteinizing hormone). Gut microbiota analysis revealed an increased Firmicutes/Bacteroidota ( F/B ) ratio and beneficial shifts in bacterial composition. The most consistent and pronounced improvements across all parameters were observed at the supplementation level of 10 8 CFU/d. These findings demonstrate that E. faecium Ef026 effectively promotes systemic health and productivity in aging laying hens, with 10 8 CFU/d recommended as the optimal dosage.