Clinical effect of probiotics in prevention or treatment of gastrointestinal disease in dogs: A systematic review

Systematic review of 17 studies in dogs, including 12 acute and 5 chronic gastrointestinal disease studies. Populations ranged from healthy kennel or shelter dogs at risk for GI signs to dogs with acute diarrhea, parvoviral or bacterial enteritis, and chronic conditions such as idiopathic inflammatory bowel disease, food-responsive diarrhea, tylosin-responsive diarrhea, and dietary sensitivity.

Probiotic regimens varied widely across the included dog studies, most commonly involving Enterococcus faecium, Lactobacillus spp., Bifidobacterium animalis, Saccharomyces boulardii, or multistrain probiotic/synbiotic products. Doses ranged from short courses of 3 to 7 days in acute diarrhea to 4 to 6 weeks, and several chronic GI studies used probiotics alongside controlled or hydrolyzed diets or standard symptomatic therapy.

Overall, probiotic supplementation showed at most a small benefit for acute gastrointestinal disease in dogs and did not provide meaningful additional benefit for chronic disease. Several acute studies favored probiotics, such as shorter time to last abnormal feces (1.3 vs 2.2 days), fewer total diarrhea days (6 vs 17), and lower diarrhea-day percentages (2.0% vs 3.2%), but other outcomes were nonsignificant. In chronic disease, diet remained the main effective therapy; for example, one IBD study found no between-group difference at day 90, and another chronic study reported no significant difference in CIBDAI change. The review authors judged the effect to be limited and possibly clinically unimportant overall.

The evidence base was small, heterogeneous, and frequently at high risk of bias, with many underpowered studies. Probiotic strains, doses, durations, background diets, and disease types varied substantially, limiting pooling and generalizability. Several reports also lacked detailed baseline reporting and had incomplete or inconsistent outcome assessment.