Metronidazole-sulfadimethoxine combination affects diet digestibility, immunity indicators, fermentation metabolites, and intestinal microbiome of puppies.

Objective: This study aimed to evaluate the effects of a commercial metronidazole-sulfadimethoxine formulation on the apparent digestibility coefficients and metabolizable energy of the diet and immunity, gut permeability, fermentation metabolites, and intestinal microbiome of puppies.

Methods: 12 growing Beagles (65 ± 14 days old) were divided into a control group (n = 6), without administration of antimicrobials, and an antimicrobials group (6), with oral administration (q 24 h) of 15 mg of metronidazole and 15 mg of sulfadimethoxine/kg of body weight for 5 days. Both groups were fed the same dry extruded diet for growing dogs for 80 days. Diet digestibility and fecal characteristic analyses were performed between days 20 and 25. Feces were collected for ammonia, pH, short-chain fatty acids, branched-chain fatty acids, phenols, indoles, biogenic amines, immunoglobulin A, and fecal microbiome analysis. In addition, blood samples were collected to analyze intestinal permeability and inflammatory and oxidative indicators.

Results: The use of antimicrobials reduced the diet apparent digestibility coefficients of dry matter, organic matter, and crude protein and resulted in lower butyrate and higher branched-chain fatty acid concentrations in feces. The antimicrobials group had higher serum concentrations of nuclear factor κB and higher intestinal permeability. The use of antimicrobials reduced fecal immunoglobulin A (days 50 and 80), bacterial diversity, and genera such as Blautia and Turicibacter.

Conclusions: Metronidazole combined with sulfadimethoxine may negatively affect markers of intestinal functionality, increasing inflammation, and compromising the intestinal barrier function in puppies.

Clinical relevance: Antimicrobials may negatively affect intestinal health indicators in puppies, and veterinarians should consider their use carefully.