Diet impacts the structure and function of the bacterial community in the gastrointestinal tract of a sloth bear

Abstract

Sloth bears Melursus ursinus are a threatened species that has a high incidence of hepatobiliary adenocarcinoma in human care. The diet of sloth bears under human care differs greatly from that consumed by wild sloth bears. Wild sloth bears consume a diet comprised predominantly of insects and wild fruits that is likely higher in fat and protein and lower in dietary starch compared to sloth bear diets in zoos. One male sloth bear was experimentally fed with a diet that was lower in dietary starch than its traditional diet. Overall, the faecal bacterial community of this sloth bear was dominated by 12 operational taxonomic units (OTUs) of bacteria (each having a greater than 1% relative abundance). The most predominant OTU was assigned to the genus Turicibacter within the class Erysipelotrichia. The relative abundances of some bacterial taxa changed when the lower carbohydrate diet was fed while bacterial OTU richness did not change. Of the 12 predominant OTUs, 8 shifted in relative abundance between the two diets. The lower carbohydrate diet also resulted in increased faecal branched-chain volatile fatty acids, which is indicative of increased protein digestion and amino acid fermentation, a decrease in faecal acetate to propionate ratio and an increase in pH. These results encourage further dietary changes to better mimic the wild sloth bear diet with the purpose of improving captive sloth bear health.