A Veterinary Gastrointestinal Diet Affects Fecal Characteristics, Metabolites, Bile Acids, and Microbiota Concentrations of Antibiotic-Treated Cats

Abstract Antibiotics are often used to treat animals with gastrointestinal diseases or infections, but their use is known to have negative effects on the intestinal microbiota community. Identifying dietary strategies that may aid in the recovery from antibiotic use is of interest. The objective of this study was to determine how a veterinary gastrointestinal diet affected the fecal characteristics and metabolite, bile acid (BA), and microbiota concentrations of cats recovering from metronidazole administration. Twenty-four healthy adult cats were used in an 8-wk completely randomized design study. The study began with a 2-wk baseline phase where all cats consumed a leading grocery brand dry diet (GBD; wk 0 to wk 2). Over the next 2 wk, cats continued to consume GBD and received metronidazole (20 mg/kg BW; wk 2 to wk 4). At wk 4, cats were randomly allotted to one of two treatments [GBD; Blue Buffalo Gastrointestinal Support (BB)] for the remaining 4 wk (wk 5 to wk 8). Fecal scores were recorded daily, and fresh fecal samples were collected at wk 2, 4, 5, 6, 7, and 8 for measurement of pH, dry matter, and metabolite and BA concentrations. Fecal microbiota were analyzed by 16S rRNA sequencing and qPCR, which was used to calculate dysbiosis index. All data were analyzed as repeated measures using the Mixed Models procedure of SAS 9.4, with treatment treated as a fixed effect, cat as a random effect, and significance set at P< 0.05 and trends at P < 0.10. Metronidazole administration had dramatic effects on the outcomes measured, including increased fecal scores (looser stools), reduced fecal pH and dry matter %, reduced fecal short-chain fatty acid (SCFA), branched-chain fatty acid, ammonia, phenol, and indole concentrations, and altered fecal BA concentrations (increased primary BA; reduced secondary BA). Furthermore, fecal bacterial alpha diversity was reduced, dysbiosis index was increased, and the abundance of several individual bacterial taxa were altered. Fecal outcome variables partially recovered over the next 4 wk, with some being impacted by diet. The change in fecal acetate concentrations were greater and the change in total SCFA concentrations tended to be greater in cats fed BB. Dysbiosis index and alpha diversity measures slowly recovered over 4 wk, without differences due to diet. Recovery of about 20 bacterial genera were impacted by diet. Primary and secondary BA concentrations and ratios demonstrated a prolonged impairment of primary to secondary BA conversion. Most of these changes were an effect of time, but the change of fecal cholic acid concentrations were less in cats fed BB. In conclusion, our data demonstrate that metronidazole is a powerful antibiotic that has long-lasting effects on the fecal microbiota and metabolites of cats. The veterinary gastrointestinal diet tested aided in the recovery of some variables measured.