Comparative Analysis of the Gut Microbiota of Wild Wintering Whooper Swans (Cygnus Cygnus) and Captive Black Swans (Cygnus Atratus) and Mute Swans (Cygnus Olor) in the Sanmenxia Swan National Wetland Park of China

The gut microbiota is a complex system that is involved in a variety of host physiological activities and plays a key role in the health of the host. Birds occupy a critical ecological niche in the ecosystem, performing a variety of ecological functions and possessing a complex gut microbiota composition. However, the gut microbiota of wild and captive birds in the same area has been less explored. Therefore, this study analysed the differences and potential microbial functions in the gut microbiota of wild wintering whooper swans (Cygnus Cygnus, Cyg group, n=25) and captive black swans (Cygnus Atratus, Atr group, n=20) and mute swans (Cygnus Olor, Olor group, n=30) using 16S rRNA sequencing to reveal differences in the physiological ecology of wild and captive birds. The results showed that Cyg group, Atr group and Olor group had significant differences in alpha diversity and beta diversity. Moreover, the microbiota exhibited similarities at the phylum level and genus level, consisting mainly of Proteobacteria and Firmicute. Furthermore, the association network analysis revealed a positive pattern of interactions between microorganisms. Based on linear discriminant analysis effect size (LEfSe) and random forest analysis, we found that Gottschalkia, Trichococcus, Enterococcus, and Kurthia differed significantly among the three groups. The area under curve (AUC) of Gottschalkia was 0.939 (CI = 0.879-0.999), suggesting that Gottschalkia may be a potential biomarker for wild and captive black swans. In addition, PICRUSt2 predictions indicated significant differences in gut microbiota functions between wild and captive trumpeter swans, with the gut microbiota functions of Cyg group focusing on carbohydrate metabolism, membrane transport, cofactor and vitamin metabolism pathways, and lipid metabolism in the Atr group, while the Olor group was enriched in cell motility, amino acid metabolism, and replication and repair pathways. These results indicated that the differences between gut microbiota in wild and captive swans, which is beneficial to understand the survival state of swans and improve local conservation strategies for wildlife.