Soyasaponin and vertical microbial transmission: Maternal effect on the intestinal development and health of early chicks

Multiple factors, including genetics, nutrition, and health, influence the vertical transmission of microbiota from mothers to their offspring. Recent studies have shown that avian microbiota can be passed to the next generation via the eggshell and egg albumen. However, it remains unclear whether these microbial communities are regulated by nutrition and how they are associated with the host genotype. Chickens, with their controlled rearing conditions and stable genotypes, provide a promising model for investigating microbiome transmission in birds. This study aims to determine whether host genotype-associated bacteria are vertically transmitted between generations, and how maternal nutritional intervention with soyasaponin modulates this microbial transfer, thereby shaping chick intestinal development and informing effective nutritional strategies. We established a microbial vertical transmission model across various anatomical sites in breeder hens, chicken embryos, and chicks. Avian gut microbiota and reproductive tract microbiota can both be found in chicks at various developmental stages. Supplementing breeder hen diets with soyasaponin interacts with vertically transmitted <i>Bifidobacterium adolescentis</i> to produce γ-aminobutyric acid. This compound modulates offspring intestinal development through distinct mechanisms in chick epithelial cells, including the inhibition of LC3 and caspase3-associated autophagy and apoptosis pathways, as well as the promotion of proliferation and differentiation pathways mediated by LGR5 and Olfm4. Our study highlights that avian gut and reproductive tract microbiota are transmitted to chicks through the cloaca, with the yolk sac also being instrumental in this vertical transfer. The incorporation of soyasaponin in avian diets affects microbial transfer, providing a theoretical basis for studying maternal effects in poultry and formulating corresponding dietary strategies.