Dietary intervention in captive-bred hares fails to enrich gut microbiomes with wild-like functions

Abstract

Reintroducing captive-bred animals into the wild often faces limited success, with the underlying causes frequently unclear. One emerging hypothesis is that maladapted gut microbiota may play a significant role in these challenges. To investigate this possibility, we employed genome-resolved metagenomics to analyse the taxonomic and functional differences in the gut microbiota of wild and captive European hares (Lepus europaeus), as well as to assess the impact of a dietary switch to grass aimed at pre-adapting captive hares to wild conditions. Our analyses recovered 860 metagenome-assembled genomes, with 87% of them representing novel species. We found significant taxonomic and functional differences between the gut microbiota of wild and captive hares, notably the absence of Spirochaetota in captive animals and differences in amino acid and sugar degradation capacities. While the dietary switch to grass induced some minor changes in the gut microbiota, it did not result in a shift towards a more wild-like microbial community. The increased capacity for degrading amino acids and specific sugars observed in wild hares suggest that, instead of bulk grass, dietary interventions tailored to their specific dietary preferences might be necessary for pre-adapting hare gut microbiota to wild conditions.