Diversity and Succession of the Intestinal Bacterial Community of the Maturing Broiler Chicken

TLDR

The study examined the diversity of bacterial communities in the ileum and cecum of chickens fed a vegetarian corn‑soy diet without additives by sequencing 1,230 partial 16S rRNA genes. Statistical comparison of 16S rRNA libraries revealed population succession during sampling periods, indicating shifts in community composition over time. The ileum was dominated by Lactobacillus (~70%) with minor Clostridiaceae, Streptococcus, and Enterococcus, whereas the cecum was dominated by Clostridiaceae (65%) with Fusobacterium, Lactobacillus, and Bacteroides; after 14 days the ileum and cecum developed distinct, increasingly complex bacterial communities.

Abstract

ABSTRACT The diversity of bacterial floras in the ilea and ceca of chickens that were fed a vegetarian corn-soy broiler diet devoid of feed additives was examined by analysis of 1,230 partial 16S rRNA gene sequences. Nearly 70% of sequences from the ileum were related to those of Lactobacillus , with the majority of the rest being related to Clostridiaceae (11%), Streptococcus (6.5%), and Enterococcus (6.5%). In contrast, Clostridiaceae -related sequences (65%) were the most abundant group detected in the cecum, with the other most abundant sequences being related to Fusobacterium (14%), Lactobacillus (8%), and Bacteroides (5%). Statistical analysis comparing the compositions of the different 16S rRNA libraries revealed that population succession occurred during some sampling periods. The significant differences among cecal libraries at 3 and 7 days of age, at 14 to 28 days of age, and at 49 days of age indicated that successions occurred from a transient community to one of increasing complexity as the birds aged. Similarly, the ileum had a stable bacterial community structure for birds at 7 to 21 days of age and between 21 to 28 days of age, but there was a very unique community structure at 3 and 49 days of age. It was also revealed that the composition of the ileal and cecal libraries did not significantly differ when the birds were 3 days old, and in fact during the first 14 days of age, the cecal microflora was a subset of the ileal microflora. After this time, the ileum and cecum had significantly different library compositions, suggesting that each region developed its own unique bacterial community as the bird matured.