Exploring fecal microbial activity in zoo felids of varying body mass on a similar diet.

Under human care, felids are typically fed similar diets, unlike wild counterparts whose diets vary by body mass and ecology. This study evaluated fecal microbiota and fermentation products in 18 zoo felids from Pairi Daiza Zoo, Belgium, grouped by body mass: under 100 kg ("small") and over 100 kg ("large"), with 9 animals in each group. Fresh feces were collected from the rectum under anesthesia. Microbial composition was assessed via 16S rRNA gene sequencing, while the fecal volatile fatty acids were quantified using gas chromatography. At the phylum level, regardless of body mass, the gut microbiota of zoo felids was predominantly composed of Firmicutes (61.7%), Actinobacteria (16.4%) and Bacteroidetes (12.5%). At the genus level, the most abundant genus was Clostridium sensu stricto 1 (15.9%), followed by Collinsella (15.7%). Although no significant differences in microbial composition or alpha diversity were found, beta diversity showed body mass influenced overall microbial structure. Smaller felids had significantly higher acetate levels than larger felids (p < 0.01). Additionally, acetate proportions were positively correlated with Clostridium sensu stricto 13 (r = 0.6, p < 0.01) and Peptoniphilus (r = 0.5, p < 0.05). These results show particular associations between body mass and the response of the intestinal microbiome to diet, suggesting that a uniform diet may not suit all felids under human care.