Microbiota in mild inflammatory bowel disease (IBD) can be modulated by beta-glucans and mannanoligosaccharides: A randomized, double-blinded study in dogs

Amaral, A. R., Rentas, M. F., Rosa, T. C. T., Pereira, T. A. E., Marchi, P. H., Teixeira, F. A., Filho, F. O. R., Putarov, T. C., Cogliati, B., Vendramini, T. H. A., Balieiro, J. C. C., & Brunetto, M. A. (2024). Microbiota in mild inflammatory bowel disease (IBD) can be modulated by beta-glucans and mannanoligosaccharides: A randomized, double-blinded study in dogs. Veterinary Sciences, 11(8), 349. https://doi.org/10.3390/vetsci11080349

Background

This study investigates prebiotics as a dietary approach for dogs with mild inflammatory bowel disease (IBD). The authors describe IBD as a chronic gastrointestinal condition in which the immune system reacts abnormally to food and resident gut bacteria, leading to intestinal inflammation and dysbiosis (an imbalanced gut microbiota). They aimed to test whether yeast-derived beta-glucans, alone or combined with mannanoligosaccharides (MOS), could change fecal microbiota and fermentation products under controlled feeding conditions.

Objective

The objective was to evaluate the effects of 60 days of oral beta-glucans, or beta-glucans plus MOS, on fecal microbiota composition and diversity, as well as on fecal fermentation products, in client-owned dogs with mild IBD maintained on the same hypoallergenic diet and without confounding medications.

Methods

This was a prospective, randomized, double-blinded clinical trial enrolling eighteen dogs with mild IBD (CCECAI 0–3) after screening to exclude other diseases and recent use of pre/probiotics, antibiotics, or corticosteroids.

All dogs consumed the same hypoallergenic diet for a 30-day run-in and throughout the 60-day intervention. Dogs received once-daily capsules for 60 days as follows: Group A received beta-glucan 0.1% (1,3/1,6-beta-glucan; 60% active), Group B received a beta-glucan + MOS blend 0.1% (25% beta-glucan; 20% MOS), and Group C received placebo (ground diet).

Outcomes included clinical status (body weight, body condition and muscle mass scores, fecal score, CCECAI), safety bloodwork, fecal microbiota by 16S rRNA sequencing (alpha and beta diversity; phyla/classes/families/genera), and fecal lactic acid, short-chain fatty acids (SCFAs), and branched-chain fatty acids (BCFAs).

Outcomes

• Clinical course and tolerance. Dogs remained clinically stable from baseline to day 60 across all groups, with no meaningful changes in body weight, fecal score, or CCECAI. Products were well tolerated, and blood values were generally within reference intervals; between-group differences (for example, cholesterol and platelets) were reported but were not linked to clinical problems in this cohort.
• Fecal metabolites. There were no treatment or time effects for lactic acid, SCFAs, or BCFAs. The authors note that fecal levels may not reflect colonic utilization of these compounds.
• Microbiota. Alpha diversity (Shannon index) increased over time only in the beta-glucan group (Group A), while observed OTUs did not differ. Firmicutes increased in Groups A and B. Bacteroidetes increased only in Group A and decreased in Group B. Changes in Proteobacteria were mixed and interpreted cautiously. The SCFA-associated genus Ruminococcus increased only in Group A. Beta-diversity analyses showed some group separations over time.

Authors’ Interpretation

The authors conclude that daily beta-glucan intake for 60 days favorably modulated the fecal microbiota of dogs with mild IBD by improving within-sample diversity and supporting taxa commonly reduced during dysbiosis. Adding MOS to beta-glucan did not provide clear additional benefit under the conditions tested. They suggest that unchanged fecal SCFAs/BCFAs may reflect absorption and use by colonocytes rather than an absence of biological activity.

Limitations

The sample size was small and limited to mild IBD, which restricts generalization to moderate or severe disease. The 60-day duration may be too short to capture broader metabolic effects. Fecal measurements may not fully reflect mucosal microbial communities, and some bacterial shifts, such as those in Proteobacteria, were not uniformly directional and should be interpreted with caution.

Conclusion

Under a uniform hypoallergenic diet and without confounding medications, beta-glucan supplementation modulated the fecal microbiota of dogs with mild IBD toward higher diversity and shifts consistent with partial improvement of dysbiosis, while the addition of MOS did not clearly enhance these effects in this trial. The authors recommend longer and larger studies, including dogs with greater disease severity, to clarify clinical outcomes and refine dosing.