摘要:SummaryMaternal parity can impact offspring growth, but the mechanisms driving this effect are unclear. Here, we test the hypothesis that vertically transmitted microbiota may be one potential mechanism. We analyzed 118 fecal and milk samples from mother-offspring vervet monkey dyads across the first 6 months of life. Despite poorer milk production, offspring born to low parity females grew larger than their counterparts. These offspring exhibited reduced alpha diversity in the first days of life, stronger seeding of maternal milk microbiota,Bacteroides fragilisdominance, and a greater abundance of glycan utilization pathways. Moreover, the attainment of greater body mass by 6 months of age was mediated by reduced early life alpha diversity andB. fragilisdominance. This work demonstrates that the establishment of a specialized, milk-oriented gut microbiota promotes infant growth and suggests an evolutionarily conserved developmental role ofB. fragilisin primates.Graphical abstractDisplay OmittedHighlights•Infants of low parity females grow fast despite poor maternal milk production•These infants have reduced gut microbiota diversity, moreBacteroides fragilisat 2–5 days old•The infant gut microbiota shares more ASVs with milk than with the maternal gut•A milk-oriented infant gut microbiota mediates faster growth to 6 months of ageMicrobiology; Microbiome