Comparative characterization of bacterial communities in geese fed all-grass or high-grain diets

Background: Gut microbial composition is dependent on diet. Geese are herbivores and can digest crude fibre, but the relationship between composition of the microbiota and a fibre-rich diet in geese is not well understood. Results: Here, caecal and faecal samples were collected simultaneously from all-grass-fed geese and high-grain-fed geese and the hypervariable V3–V4 regions of the bacterial 16S rRNA gene were sequenced. The results was identified that high-grass-fed geese possessed significantly higher alpha diversity both in caecum and faeces compared with that in all-grain-fed geese. In addition, the composition of dominant bacterium occurred remarkable shifting due to different diet patterns, Firmicutes were more abundant in all-grass-fed geese, whereas Bacteroidetes were abundant in high-grain-fed geese. Fusobacteria and Deferribacteres were obviously present in high-grain-fed geese and few in all-grass-fed geese. Most importantly, some specific microorgnisms such as Ruminococcaceae, Lachnospiraceae and Bacteroidaceae which may associated with cellulose-degrading that were characterized to show distinctly diverse between the two diet patterns. PICRUSt analysis revealed the metabolic pathways such as carbohydrate and amino acid metabolism were overrepresented in all-grass-fed geese. Conclusions: In conclusion, Firmicutes and Bacteroidetes were identified abundantly when the geese was fed with all-grass feed and high-grain feed, respectively. And Ruminococcaceae, Lachnospiraceae and Bacteroidaceae were recognized as main cellulose-degrading bacteria in the geese. The functional profiles of gut microbiota revealed the dominant microbiota communities were involved mainly in the carbohydrate metabolism in all-grass-fed geese.