Developmental Change of Yolk Microbiota and Its Role on Early Colonization of Intestinal Microbiota in Chicken Embryo

Simple Summary For nearly a century, genetic selection and improved management have led to significant progress in poultry's productive traits. The embryonic development of commercial broiler chickens, which has become a larger part of the production cycle of broiler chickens (approximately 33%), has attracted more and more attention. It has been shown in previous studies that microbes played an important role in animal growth and development. The yolk is an important source of nutrients for chicken embryonic development. At late embryonic development, the remaining yolk will enter the embryo intestine directly through the yolk stem and may contribute to the formation of intestinal microbiota. Therefore, we investigated the developmental change of yolk microbiota and its role on early colonization of intestinal microbiota in the chicken embryo. The results showed that the relative abundance of yolk microbiota was barely changed during embryogenesis. According to the KEGG analysis, the yolk microbiota were functionally related to amino acid, carbohydrate, and lipid metabolisms during chicken embryogenesis. The yolk microbiota influenced the embryonic intestinal microbiota by increasing the colonization of Proteobacteria, Firmicutes, and Bacteroidetes in the intestine. Although the fertilized eggs were found to contain microbes in early studies, the detailed composition of yolk microbiota and its influence on embryo intestinal microbiota have not been satisfactorily examined yet. In this study, the yolk microbiota was explored by using 16s rRNA sequencing at different developmental stages of the broiler embryo. The results showed that the relative abundance of yolk microbiota was barely changed during embryogenesis. According to the KEGG analysis, the yolk microbiota were functionally related to amino acid, carbohydrate, and lipid metabolisms during chicken embryogenesis. The yolk microbiota influences the embryonic intestinal microbiota through increasing the colonization of Proteobacteria, Firmicutes, and Bacteroidetes in the intestine, particularly. The intestinal microbes of neonatal chicks showed higher proportions of Faecalibacterium, Blautia, Coprococcus, Dorea, and Roseburia compared to the embryonic intestinal microbiota. Our findings might give a better understanding of the composition and developmental change of yolk microbiota and its roles in shaping the intestinal microbiota.