Abstract
Despite the importance of gut microbiota for broiler performance and health little is known about the composition of this ecosystem, its development and response towards bacterial infections. Therefore, the current study was conducted to address the composition and structure of the microbial community in broiler chickens in a longitudinal study from day 1 to day 28 of age in the gut content and on the mucosa. Additionally, the consequences of a Campylobacter (C.) jejuni infection on the microbial community were assessed. The composition of the gut microbiota was analyzed with 16S rRNA gene targeted Illumina MiSeq sequencing. Sequencing of 130 samples yielded 51,825,306 quality-controlled sequences, which clustered into 8285 operational taxonomic units (OTUs; 0.03 distance level) representing 24 phyla. Firmicutes, Proteobacteria, Bacteroidetes, Actinobacteria, and Tenericutes were the main components of the gut microbiota, with Proteobacteria and Firmicutes being the most abundant phyla (between 95.0 and 99.7% of all sequences) at all gut sites. Microbial communities changed in an age-dependent manner. Whereas, young birds had more Proteobacteria, Firmicutes, and Tenericutes dominated in older birds (>14 days old). In addition, 28 day old birds had more diverse bacterial communities than young birds. Furthermore, numerous significant differences in microbial profiles between the mucosa and luminal content of the small and large intestine were detected, with some species being strongly associated with the mucosa whereas others remained within the luminal content of the gut. Following oral infection of 14 day old broiler chickens with 1 × 108 CFU of C. jejuni NCTC 12744, it was found that C. jejuni heavily colonized throughout the small and large intestine. Moreover, C. jejuni colonization was associated with an alteration of the gut microbiota with infected birds having a significantly lower abundance of Escherichia (E.) coli at different gut sites. On the contrary, the level of Clostridium spp. was higher in infected birds compared with birds from the negative controls. In conclusion, the obtained results demonstrate how the bacterial microbiome composition changed within the early life of broiler chickens in the gut lumen and on the mucosal surface. Furthermore, our findings confirmed that the Campylobacter carrier state in chicken is characterized by multiple changes in the intestinal ecology within the host.
Highlights
A diverse microbiota is found throughout the gastrointestinal tract (GIT) of chickens, most predominant in the cecum (Mead, 1997; Videnska et al, 2014)
At the first day of life Proteobacteria were significantly higher in the jejunal (P = 0.0000, q = 0.0000) and cecal (P = 0.016; q = 0.059) mucosa of the birds and decreased thereafter, as no significant differences were found between samples from day 14 to day 28 of age (P = 0.140; q = 0.438 and P = 0.519; q = 0.955)
The current results revealed that E. coli, E. faecalis, C. paraputrificum, and C. sartagoforme were more predominant in the mucosa than in the lumen, suggesting significant implications for birds’ health, considering that the mucosa-associated bacteria are of great importance in the host mucosal responses with consequences for the mucosal barrier (Ott et al, 2004)
Summary
A diverse microbiota is found throughout the gastrointestinal tract (GIT) of chickens, most predominant in the cecum (Mead, 1997; Videnska et al, 2014). There is little information about the diversity and function of the gut microbiota in chickens, its impact on the host and the impact of certain pathogens. Gong et al (2002) demonstrated that the cecal microbiota protects chickens against bacterial infections, while microbiota in the small intestine contributes significantly to its function, including digestion and nutrient absorption, which significantly determines the growth rate of the bird. Studies on gut microbiota have mostly been performed with chickens older than 1 week of age due to the various influences in day-old birds. The composition of gut microbiota at the first day of life in newly hatched chickens is a matter of interest within a longitudinal study. The focus of the actual study was to determine the diversity and community structures of the microbiota within the small and large intestine from hatch until 4 weeks of age. Differences among the mucosaassociated and luminal content microbiota were determined for the first time
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