Phylogenetic and functional alterations of bacterial community composition in the broiler caecum as a result of mannan oligosaccharide supplementation.

This study focused on identifying reproducible effects of dietary supplementation with a mannan oligosaccharide (MOS) on the broiler caecal bacterial community structure and function in a commercial production setting. Two separate trials each with a control and a supplemented group were carried out in the same commercial location and run concurrently. Approximately 10,000 birds from the same commercial hatchery were mirror imaged into each of four commercial broiler sheds and fed either a control or supplemented diet. Caecal contents were obtained from 12 randomly caught broilers on days 7, 21 and 35 posthatch from each group. Bacterial pyrosequencing was performed on all samples with approximately 250,000 sequences obtained. The predominant phyla identified at all three timepoints in both trials were Firmicutes, Bacteroidetes, Proteobacteria, Actinobacteria and Tenericutes, representing >99 % of all sequences. MOS supplementation altered the bacterial community composition from 7 days supplementation through to 35 days supplementation. Bacteroidetes appeared to be replacing Firmicutes as a result of supplementation with the most noticeable effects after 35 days. The effects of supplementation were reproducible across both trials. PICRUSt was used to identify differences between the functional potential of the bacterial community as a result of MOS supplementation. Using level 3 KEGG ortholog function predictions, differences between control and supplemented groups were observed with a very strong segregation noted on day 35 post hatch in both trials. This indicated that alterations of bacterial communities as a result of MOS are likely to alter the functional capability of the caecum.