Different artificial feeding strategies shape the diverse gut microbial communities and functions with the potential risk of pathogen transmission to captive Asian small-clawed otters ().

Unlabelled: Captive otters raised in zoos are fed different artificial diets, which may shape gut microbiota. The objective is to evaluate the impacts of two different artificial diets on microbial communities and function capabilities and short-chain fatty acid (SCFA) profiles in healthy otters' feces. A total of 16 Asian small-clawed otters in two groups ( = 8) were selected. Group A otters were fed raw loaches supplemented with commercial cat food (LSCF) diet, and group B otters were fed raw crucian diet. The communities and functional capabilities of microbiota in feces were assessed with metagenomic sequencing. Captive otters fed two kinds of diets possessed different gut microbial communities and functional capabilities. Various pathogenic bacteria, like and , were enriched in the samples from the two groups, respectively. Most of the differential pathways of nutrient metabolism were significantly enriched in group A, and the distributions of carbohydrate enzymes in the two groups significantly differed from each other. Multiple resistance genes markedly accumulated in fecal samples of the group A otters with LSCF diet. Higher concentrations of SCFAs were also observed in group A otters. Two feeding strategies were both likely to facilitate the colonization and expansion of various pathogenic bacteria and the accumulation of resistance genes in the intestines of captive otters, suggesting that risk of pathogen transmission existed in the current feeding process. Commercial cat food could supplement various nutrients and provide a substrate for the production of SCFAs, which might be beneficial for the otters' intestinal fermentation and metabolism.

Importance: Captive otters fed with different diets possessed distinct gut microbial communities and functions, with the enrichment of several pathogens and multiple resistance genes in their gut microbiota. The current artificial feeding strategies had the possibility to accelerate the colonization and proliferation of various pathogenic bacteria in the intestines of otters and the spread of resistance genes, increasing the risk of diseases. In addition, supplementation with commercial cat food had benefits for otters' intestinal fermentation and the metabolism of gut microbiota.