Characterization of cecal microbiota of the emu (Dromaius novaehollandiae).

Emus (Dromaius novaehollandiae), large flightless ratites native to Australia, are farmed for their fat and meat. They are omnivorous and feed on a wide variety of plants and insects. Despite having a relatively simple gastrointestinal tract and a short digesta retention time, emus are able to digest a significant portion of the ingested dietary neutral detergent fibre. However, nothing is known about the microbial diversity in their gastrointestinal tract. In this study, we evaluated the phylogenetic diversity of the cecal microbiota of four emus (2 males, 2 females) that were fed a barley-alfalfa-canola based diet, using 454 pyrosequencing after amplification for V3-V5 region of bacterial 16S rRNA gene. Emus were slaughtered in early November, just prior to the onset of their breeding season, but after the seasonal decline in their feed intake had begun. A total of 822 operational taxonomic units (OTUs) (335.3 ± 70.5 OTUs/sample) belonging to 9 bacterial phyla were identified. The most predominant bacterial phyla were Bacteroidetes (≈ 57% of total classified diversity), Proteobacteria (≈ 24%), Fusobacteria (≈ 11.3%), and Firmicutes (≈ 7%). Our results indicate that the emus' ceca may have a higher microbial richness (Chao1: 624 ± 170 OTUs, and ACE: 586 ± 161 OTUs) than other species of birds, but they have a lower microbial diversity (Shannon diversity index: 3.4 ± 0.2, Simpson index: 0.79 ± 0.02), possibly reflecting their decrease feed intake. This is the first study to characterize the microbial community of the gastrointestinal tract of a ratite using pyrosequencing, providing a baseline for further study.