Abstract: High-throughput sequencing technology was used to analyze the difference in the intestinal flora of infants of different age groups (I: 0–6 months old, II: 6–12 months old, III: 12–36 months old) subjected to different feeding methods (breast milk, goat milk, and cow milk) and different delivery modes (vaginal delivery and cesarean section). A total of 54 fecal samples were collected and used to determine the composition of intestinal flora with a special focus on the influence of goat milk infant formula on the intestinal flora. Meanwhile, the abundance and diversity of intestinal flora were analyzed and the abundance of dominant bacteria was compared. By doing so, this study aimed to provide technical support for the development of new infant formulas and scientific feeding of infants. The results showed that different delivery modes had different effects on the intestinal microbiota of infants of the same age with the same feeding pattern. At the phylum level, the relative abundance of Actinobacteria, Firmicutes, Bacteroidets and Proteobacteria were 43.74%, 25.48%, 17.93% and 9.71%, respectively in breasted infants vaginally delivered, and 40.83%, 44.31%, 3.81% and 11.01%, respectively in those born by caesarean section in the 0 to 6 month age group; 41.44%, 43.84%, 8.38% and 6.27%, respectively in goat milk infant formula-fed infants vaginally delivered, and 60.76%, 24.85%, 8.66% and 5.70%, respectively in those born by cesarean section in the 6 to 12 month age group; 26.58%, 47.73%, 24.07% and 1.58%, respectively in infant formula-fed infants vaginally delivered, and 34.77%, 51.94%, 11.10% and 2.16% in those born by cesarean section in the 12 to 36 month age group. For the same delivery mode and the same age, the composition of intestinal flora in infants fed on goat milk infant formula was more diverse and the abundance of dominant bacteria was higher, Actinobacteria accounting for 62.98% and 43.74% of the total abundance in vaginally delivered infants fed on goat milk infant formula and breastmilk in the 0 to 6 month age group, respectively, and Bacteroidets accounting for 43.84% and 35.71% for those in the 6 to 12 month age group, respectively. For infants delivered by the same route and fed by the same method, the composition of intestinal flora changed significantly with age (P < 0.05). The intestinal flora in the 6 to 12 month age group was more diverse than in the other age groups and Lactobacillales had the highest relative abundance in this age group and was the dominant bacteria, with significant differences being observed compared with other bacteria detected. This study provides a rationale to protect infant health and defend against metabolic diseases.

Key words: feeding and delivery modes, high-throughput sequencing, infants, gut microbiota