Effects of gut microbiota transfer on emotional reactivity in Japanese quails ().

The interaction between the gut microbiota (GM) and the brain has led to the concept of the microbiota-gut-brain axis but data for birds remain scarce. We tested the hypothesis that colonization of germ-free chicks from a quail line selected for a high emotional reactivity (E+) with GM from a line with low emotional reactivity (E-) would reduce their emotional behaviour in comparison with germ-free chicks from an E+ line colonized with GM from the same E+ line. The GM composition analysis of both groups revealed a shift in terms of microbial diversity and richness between day 21 and day 35 and the GM of the two groups of quails were closer to each other at day 35 than at day 21 at a phylum level. Quails that received GM from the E- line expressed a lower emotional reactivity than quails colonized by GM from the E+ line in tonic immobility and novel environment tests carried out during the second week of age. This result was reversed in a second tonic immobility test and an open-field run 2 weeks later. These behavioural and GM modifications over time could be the consequence of the resilience of the GM to recover the equilibrium present in the E+ host, which is in part driven by the host genotype. This study shows for the first time that a GM transfer can influence emotional reactivity in Japanese quails, supporting the existence of a microbiota-gut-brain axis in this species of bird.