Variations in gut microbiota and fecal metabolic phenotype associated with Fenbendazole and Ivermectin Tablets by 16S rRNA gene sequencing and LC/MS-based metabolomics in Amur tiger. 
The Amur tiger is one of the most endangered species in the world, and the healthy population of captive Amur tigers assists the recovery of the wild population.  Gut microbes have been shown to be important for human disease and health, but little research exists regarding the microbiome of Amur tigers in captivity.  In this study, we used an integrated approach of 16S rRNA gene sequencing combined with ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS)-based metabolomics to analyze the effects of Fenbendazole and Ivermectin Tablets on the gut microbiota and fecal metabolic phenotype of the Amur tiger.  The relative abundances of the bacterial genera Collinsella, Clostridium XI and Megamonas were decreased, whereas those of Escherichia and Clostridium sensu stricto were increased in experimental Amur tigers compared with those in normal controls.  Meanwhile, distinct changes in the fecal metabolic phenotype of the experimental Amur tigers were also found, including lower levels of acrylic acid, acetoacetate and catechol and higher amounts of 5,6-dihydrouracil, adenine hydrochloride hydrate and galactitol.  Moreover, the differentially abundant gut microbes were substantially associated with the altered fecal metabolites, especially the bacteria in the Firmicutes and Actinomycetes, which were involved in the metabolism of 5,6-dihydrouracil, 6-phospho-d-gluconate and 1-methylnicotinamide.  Our results indicate for the first time that Fenbendazole and Ivermectin Tablets not only disturb the gut microbiota at the abundance level but also alter the metabolic homeostasis of the Amur tiger.