Relationship between intestinal and blood metabolome and fecal digestive efficiency in chicken

Digestive efficiency (DE) is an essential component of feed efficiency, especially in the context of increasing variety of feedstuffs with variable quality used in poultry diets. However, measuring fecal DE during balance trials is time-consuming nd constraining as birds are placed in individual cages. Moreover, all the mechanisms controlling DE are still not known. The aim of our study was thus to identify biomarkers of DE using intestinal and blood metabolomics.Our study used 60 chickens of an advanced intercross line (8th generation) between two broiler lines divergentlyselected for their fecal DE, based on metabolisable energy corrected to zero nitrogen retention (AMEn). At 3 weeks, fecal AMEn and coefficients of digestive use of lipids, nitrogen and starch were measured during a balance trial, ileal and caecal contents were sampled and blood collected. Metabolome was determinedby proton high resolution NMR. Correlation models (canonical partial least squares) were fitted to assess the links between efficiency and metabolites of the 3 compartments.Metabolites differences between animals with high or low levels of DE were mainly involved in amino-acids metabolism (lysine, isoleucine, methionine) and energetic metabolism (glutamate, glucose) in the 3 compartments. High positive correlations were especially found between glucose in caecal content and AMEnand coefficient of DE of nitrogen (Figure 1), which is consistent with the large divergence found in the divergent lines on these criteria. This result suggests an effect of microbial fermentation on DE.These metabolic profiles give us information on mechanisms implied in feed digestion in chickens. Further analyses will estimate if blood metabolome could be used as an indirect criterion of selection of feed and DE. This study has been supported by the EU H2020 Feeda--Gene project and by the INRA program GISA-GALMIDE.