Effects of Bacillus pumilus SG154 or Lacticaseibacillus paracasei 327 Postbiotic on the Fecal Characteristics and Microbiota of Healthy Adult Dogs Subjected to an Abrupt Diet Change

Background: Abrupt dietary changes may disrupt gut microbiota populations and lead to gastrointestinal issues. This study aimed to determine the effects of live Bacillus pumilus SG154 or Lacticaseibacillus paracasei 327 postbiotic on fecal characteristics and microbiota populations of dogs following an abrupt diet change. Methods: Twelve healthy adult English pointer dogs (6.38 ± 2.75 yr) were used in a replicated 3 × 3 Latin square design to test the following treatments: (1) placebo (control; 250 mg maltodextrin/d); (2) live B. pumilus [5 × 109 colony-forming units (CFU)/d]; and (3) L. paracasei postbiotic (100 mg; derived from 2 × 109 CFU/d). Each period lasted 42 days, with the diet change occurring on day 28. Fecal samples were scored and analyzed for pH, dry matter content, and microbiota before and 2, 6, 10, and 14 days after the diet change. Results: The abrupt diet change increased (p < 0.01) fecal pH, increased (p < 0.01) the dysbiosis index, decreased (p < 0.0001) fecal dry matter, and led to a large shift in the fecal microbiota community. Fecal scores were lower (p < 0.05) in the B. pumilus group. B. pumilus reduced (p < 0.05) the relative abundance of fecal Prevotella and Muribaculaceae, while both treatments (B. pumilus; L. paracasei) increased (p < 0.05) the relative abundance of fecal Holdemanella. Conclusions: These results suggest that an abrupt diet change leads to large shifts in fecal microbiota and modified fecal characteristics. The supplementation with a B. pumilus probiotic and a L. paracasei postbiotic slightly altered the relative abundance of a few microbial taxa but was unable to attenuate most responses.