Lactobacillus and Bacillus Improve Egg Production in Zhedong White Geese via Gut Microbiota-Metabolite-Endocrine Axis...

Enhancing egg production in geese without antibiotics remains a challenge in poultry science. This study compared the effects of Lactobacillus (LAB) and Bacillus (BAC) probiotics on laying performance, gut microbiota, and serum metabolism in Zhedong White geese. Birds were fed a control diet or diets supplemented with LAB or BAC. Egg production and quality were monitored throughout the trial. Serum metabolomics and fecal 16S rRNA sequencing were integrated with KEGG enrichment and correlation analyses to uncover functional mechanisms. Both probiotics improved laying performance and egg quality. Total egg production of the LAB group was 8.5% higher than that of the BAC group (p < 0.05). The LAB group's advantage in egg production was consistent with its stronger activation of the steroid hormone biosynthesis pathway (elevated serum corticosterone and tetrahydrocorticosterone indicated an overall enhancement of steroidogenic flux). Simultaneously, the LAB group exhibited a more efficient conversion of L-phenylalanine to catecholamine precursors, which drove activation of the neuroendocrine reproductive axis. The BAC group showed more significant changes in nitrogen and energy metabolism pathways and a more pronounced expansion of energy-harvesting Firmicutes. These findings reveal two strain-specific regulatory pathways: LAB functions through the "aromatic amino acid-neuroendocrine-steroid hormone axis," while BAC relies on the "gut microbiota-energy metabolism" pathway, with direct implications for the precise application of probiotics under antibiotic-free farming conditions.