Assessing Fecal Microbial Diversity and Hormone Levels as Indicators of Gastrointestinal Health in Reintroduced Przewalski’s Horses (Equus ferus przewalskii)

Diarrhea serves as a vital health indicator for assessing wildlife populations post-reintroduction. Upon release into the wild, wild animals undergo adaptation to diverse habitats and dietary patterns. While such changes prompt adaptive responses in the fecal microbiota, they also render these animals susceptible to gastrointestinal diseases, particularly diarrhea. This study investigates variations in fecal microorganisms and hormone levels between diarrhea-afflicted and healthy Przewalski's horses. The results demonstrate a significant reduction in the alpha diversity of the fecal bacterial community among diarrheal Przewalski's horses, accompanied by notable alterations in taxonomic composition. Firmicutes, Proteobacteria, and Bacteroidetes emerge as dominant phyla across all fecal samples, irrespective of health status. However, discernible differences in fecal bacterial abundance are observed between healthy and diarrhea-stricken individuals at the genus level, specifically, a diminished relative abundance of Pseudobutyrivibrio is observed. The majority of the bacteria that facilitate the synthesis of short-chain fatty acids, <i>Christensenellaceae_R_7_group</i> (<i>Christensenellaceae</i>), <i>NK4A214_group</i> (<i>Ruminococcus</i>), <i>Lachnospiraceae_XPB1014_group</i> (<i>Lachnospiraceae</i>), [<i>Eubacterium</i>]_<i>coprostanoligenes_group</i> (<i>Eubacterium</i>), <i>Rikenellaceae_RC9_gut_group</i>, <i>Lachnospiraceae_AC2044_group</i> (<i>Lachnospiraceae</i>), and <i>Prevotellaceae_UcG</i>_001 (<i>Prevotella</i>) are noted in diarrhea-affected Przewalski's horses, while Erysipelotrichaceae, Phoenicibacter, Candidatus_Saccharimonas (<i>Salmonella</i>), and Mogibacterium are present in significantly increased amounts. Moreover, levels of immunoglobulin IgA and cortisol are significantly elevated in the diarrhea group compared with the non-diarrhea group. Overall, this study underscores substantial shifts in fecal bacterial diversity, abundance, and hormone levels in Przewalski's horses during episodes of diarrhea.