Feeding modes shape the acquisition and structure of the initial gut microbiota in newborn lambs.

Early gut microbial colonization is important for postnatal metabolic and immune development. However, little is known about the effects of different feeding modes (suckling versus bottle-feeding) or microbial sources on this process in farm animals. We found that suckled and bottle-fed newborn lambs had their own distinct gut microbiota. Results from 16S rRNA gene sequencing and qPCR showed that, compared with suckling, bottle feeding significantly increased the abundances of Escherichia/Shigella, Butyricicoccus, and Clostridium XlVa, while significantly decreased the abundance of Clostridium XI. The higher levels of Escherichia/Shigella in bottle-fed lambs suggest that artificial feeding may increase the number of potential pathogens and delay the establishment of the anaerobic environment and anaerobic microbes. Feeding modes also affected the direct transmission of bacteria from the mother and the environment to newborns. The SourceTracker analysis estimated that the early gut microbes of suckled lambs were mainly derived from the mother's teats (43%) and ambient air (28%); whereas those of bottle-fed lambs were dominated by bacteria from the mother's vagina (46%), ambient air (31%), and the sheep pen floor (12%). These findings advance our understanding of gut microbiota in early life and may help design techniques to improve gut microbiota and health.