The intestinal microbiome of animals is a complex ecosystem that is in constant interaction with the host as well as the external environment. A diverse range of factors, such as diet, influence the microbiome and its function, and consequently the effect that it has on the host. On the other side, the genetic and metabolic potential of the microbiome greatly impact the metabolites excreted by the animals, and the emission of gases in the poultry house. The objective of the present symposium is to provide insights outside of our current way of thinking when it comes to microbiome research, with focus on the genetic potential of the intestinal bacteria and its impact on sustainability.