**3.6 Differences of microbial communities among samples from different intestinal segments of broiler chickens**

**Table 7** shows the p value distribution of 16S rDNA gene sequence libraries used to compare relative abundance differences of microbial communities between


#### **Table 7.**

*P-value distribution of 16S rDNA gene sequence libraries compared the abundance differences of microbial communities among samples from the different segments for cobb 500 broiler chicken.*

*Microbial Diversity and Community Dynamics in the Intestines of Broiler Chicken Raised… DOI: http://dx.doi.org/10.5772/intechopen.103815*

samples from different intestinal regions of broiler chickens. The composition of the bacterial microbiota in the duodenum-jejunum, duodenum-ileum, cecum-duodenum, cecum-ileum, and cecum-jejunum differed considerably (p0.05) in statistical comparisons of the libraries, implying that each region established its own bacterial community. The relative abundance of Actinomycetales at different intestinal segment differed significantly (p<0.05). In the duodenum, jejunum, and ileum libraries, Lactobacillales were the most common 16S rDNA sequences, while Clostridiales were the most common 16S rDNA sequences in the cecum libraries.

### *3.6.1 Differences of microbial communities among samples of different age groups*

**Table 8** presents the p value distribution of 16S rDNA gene sequence libraries used to compare quantitative differences in microbial communities between samples from broiler chickens of various age groups. Statistical analyses of the libraries revealed that the microbial composition at different age groups—day 5-day 15, day 5-day 25, day 5-day 35, day 15-day 25, day 15-day 35, and day 25-day 35 had no significant changes (p > 0.05).

### **3.7 The taxonomic composition distribution of the bacterial Community in Intestinal Segments at the order-level**

The diversity of the bacterial population in the intestinal segments of broiler chickens shifted from one age period to the next, as shown in **Figure 2**. Species with an abundance of less than 0.5% across all samples were labeled "Unclassified." The duodenum, jejunum, and ileum had a larger abundance of Lactobacillales, and the


#### **Table 8.**

*P-value distribution of 16S rDNA gene sequence libraries compared the abundance differences of microbial communities among samples at different age period for cobb 500 broiler chicken.*

#### **Figure 2.**

*Percentage of relative abundance of the bacterial community of cobb 500 broiler chicken determined from different intestinal segments at different age periods from 16S rDNA libraries. These results emanate from our own experiment.*

percentage of Lactobacillales declined as the birds aged, but the cecum had a higher abundance and the percentage of Clostridiales increased as the birds aged.

## **4. Discussion**

The luminal content samples obtained from the duodenum, jejunum, ileum, and cecum of broiler chicks at four-time points from day 5 to day 35 of age were compared in this study. Understanding how the microbiota evolves over time at specific places in the small intestine could lead to a better understanding of the chicken gut's microbial succession and dynamics. In this study, the dynamic of microbiota in the duodenum, jejunum, ileum, and cecum of broiler chickens raised in an open-sided house and supplied with a commercial diet was examined through 16S rDNA gene sequencing. The most significant finding in this work is that statistical comparisons of the compositions of distinct 16S rDNA libraries of microbial communities indicated that each region from separate intestine segments generated its own bacterial community, with very diverse relative abundances.

Our data showed that Lactobacillales were the dominant Order of bacteria in the duodenum, jejunum, and ileum through all age periods. In contrast, Clostridiales were the most abundant Order detected in the cecum at different ages. Our results agree with the previous studies [19, 20] who reported that nearly 70% of sequences from ileum were related to those of lactobacillus, whereas Clostridiaceae related sequences 65% were the most abundant group detected in the cecum. An interesting observation is that we found changes in community composition, diversity, and richness across all intestinal segments over time. More specifically, we observed an increase in the richness of microbial communities in all gut sections and a general increase in diversity.

However, the microbial community structure was moderately transient at an early age (day 5) and was replaced by a rather stable bacterial community during *Microbial Diversity and Community Dynamics in the Intestines of Broiler Chicken Raised… DOI: http://dx.doi.org/10.5772/intechopen.103815*

the period of rapid growth, according to our findings (15–35 days of age). Other research [7, 11, 19, 20] showed similar findings, indicating that different regions of the chicken gut harbor different microorganisms and that the microbial community structure varies with age.

The microbiome is known to be affected by developmental changes in the chicken GIT as the distinct segments of the GIT become differentiated [21]. The current study discovered that the microbial composition and abundance in the four intestinal segments vary, implying that diverse intestinal microbial compositions may influence intestinal function. The alpha-diversity indices (ACE index, Chao1 index, Simpson index, and Shannon index) revealed considerable differences in microbial abundance between different intestinal portions. Gut functional variations could be caused or exacerbated by changes in microbial makeup between the four intestinal segments/locations [9, 22, 23].
