Role of diet-microbiota interactions in precision nutrition of the chicken: facts, gaps, and new concepts.

In the intestine, host-derived factors are genetically hardwired and difficult to modulate. However, the intestinal microbiome is more plastic and can be readily modulated by dietary factors. Further, it is becoming more apparent that the microbiome can potentially impact poultry physiology by participating in digestion, the absorption of nutrients, shaping of the mucosal immune response, energy homeostasis, and the synthesis or modulation of several potential bioactive metabolites. These activities are dependent on the quantity and quality of the microbiota alongside its metabolic potential, which are dictated in large part by diet. Thus, diet-induced microbiota alterations may be harnessed to induce changes in host physiology, including disease development and progression. In this regard, the gut microbiome is malleable and renders the gut microbiome a candidate 'organ' for the possibility of precision nutrition to induce precision microbiomics-the use of the gut microbiome as a biomarker to predict responsiveness to specific dietary constituents to generate precision diets and interventions for optimal poultry performance and health. However, it is vital to identify the causal relationships and mechanisms by which dietary components and additives affect the gut microbiome which then ultimately influence avian physiology. Further, an improved understanding of the spatial and functional relationships between the different sections of the avian gut and their regional microbiota will provide a better understanding of the role of the diet in regulating the intestinal microbiome.