Comparison of Bacterial Community in the Jejunum, Ileum and Cecum of Suckling Lambs During Different Growth Stages

Given that suckling lambs with immature rumen development rely on intestinal microbiota for nutrient utilization, investigating the composition and functional characteristics of their intestinal microbiota is therefore of paramount importance. In this study, 16S rRNA gene amplicon sequencing technology was adopted to characterize and analyze the diversity and composition of the jejunum, ileum and cecum bacterial communities of lambs at 0, 7 and 28 days of age, and to predict the functions of the bacterial communities. The α-diversity analysis results revealed that in the jejunum of lambs, the Chao1, PD, Simpson and Shannon indexes differed significantly among the three age groups (<i>p</i> < 0.05). In the ileum, Shannon and Simpson indexes of the 0-days-of-age group were slightly lower than those of the 7 (8.84% and 12.66% reductions, respectively) and 28-days-of-age groups (19.34% and 15.85% reductions, respectively) (0.05 < <i>p</i> < 0.10). In the cecum, Simpson and Shannon indexes differed significantly (<i>p</i> < 0.05) among the three age groups. At the phylum level, Firmicutes (64.68%) and Proteobacteria (21.76%) dominated the bacterial communities across all intestinal segments, with a total of 42 phyla detected. At the genus level, 19 dominant genera were identified in the jejunum. Except for <i>Bifidobacterium</i>, which showed no significant age-related variation (<i>p</i> > 0.05), the relative abundance of the remaining 18 genera changed significantly with age (<i>p</i> < 0.05). In the ileum, compared with the 0-days-of-age group, the <i>Lactobacillus</i> abundance was significantly higher in the 7- and 28-days-of-age groups (<i>p</i> < 0.05), while the <i>Escherichia-Shigella</i>, <i>Mannheimia</i> and <i>Enterobacter</i> abundances were significantly reduced (<i>p</i> < 0.05). In the cecum, the genera, including <i>Blautia</i>, <i>Sellimonas</i> and <i>Ruminococcaceae UCG-014</i>, exhibited significant age-related differences (<i>p</i> < 0.05), whereas other genera showed no significant variation (<i>p</i> > 0.05). Collectively, the bacterial community α-diversity, compositional structure and specific genus abundance in the jejunum, ileum and cecum of lambs demonstrated pronounced age-dependent variation and intestinal segment specificity patterns. This study provides a foundation for a deeper understanding of the succession patterns of the early digestive tract microbiota in lambs, and is conducive to the development of early nutrition strategies based on precise regulation of the microbiome.