Yeast Beta-Glucans (β-glucans) incorporated in a Dry Food Diet may Boost Healthy Dogs' Gut Health and Immune Response

Background

Beta-glucans (β-glucans) are a type of polysaccharide derived from sources such as yeasts, fungi, mushrooms, algae, bacteria, barley, and oats. β-glucans are investigated for use in animals to manage disorders associated with immune-mediated and inflammatory mechanisms, including the chronic diseases Atopic Dermatitis (AD), Osteoarthritis (OA), and Inflammatory Bowel Disease (IBD), in dogs and cats. In aquaculture, they are also used to reduce high, varying, and unpredictable mortality and morbidity in stressed marine life, such as shrimp larvae and trout. β-glucans are valuable as supplements because they are recognized as biological response modifiers possessing immunomodulatory and anti-inflammatory effects. Studies indicate that undenatured, unaltered biological structure, beta-glucans (UDBG) positively influence gene transcription related to overall health, modifying inflammatory responses, protecting from cellular stress, and enhancing immune function without causing immune system over-activity. Additionally, β-glucans function as prebiotics, being selectively fermented by gut bacteria to produce short-chain fatty acids (SCFAs), molceules produced by gut bacteria, that help regulate inflammation, repair mucosal damage, and modulate the intestinal microbiota. Due to its immune-modulating and positive  gut heath properties, β-glucan is becoming a supplement of interest to treat a variety of ailments in animals.

Study objective

Evaluate the effects of yeast β-glucans (BG) included in a dry food diet on the digestibility, immunity variables, and fecal microbiota of healthy adult dogs.

Methods

Study Design: Dogs were randomly split into four experimental groups that received diets with different percentages of β-glucan ( 0%, 0.07%,0.14%, and 0.28%). The study lasted a total of 140 days, and was divided into four periods.  Each period took 35 days: the first 28 days were were intended for diet acclimation, and the following 7 days were used for sample collection.

Researchers evaluated the following:

Results

No adverse reactions are observed in dogs fed a β-glucan diet

• No episodes of vomiting or diarrhea were reported, and all animals maintained health, body weight (BW), and body condition score (BCS), a visual and hands-on way to assess fat and muscle coverage, throughout the study. The inclusion of BG proved safe.

The β-glucan diet improved digestibility in dogs

• A significantly higher crude protein ADC was observed after 0.14% and 0.28% BG consumption (p<0.0001) compared to the 0.0% and 0.07% groups. 

 A β-glucan diet may influence gut microbiota composition

• Alpha diversity indices (measures the diversity within a single sample or habitat) showed no differences. However, beta diversity, which measures the difference in species composition between two or more communities or ecosystems, was different between the 0.0% and 0.14% BG groups (p=0.047), indicating taxonomic variability.
• The Firmicutes phylum (considered beneficial) was the most abundant in all groups and exhibited the highest relative abundance after 0.14% BG consumption.
• The potentially pathogenic Proteobacteria phylum displayed a lower abundance after the consumption of 0.14% BG.
• Favorable bacteria associated with butyrate production—specifically the Erysipelotrichaceae and Ruminococcaceae families, and the Faecalibacterium and Prevotella genera—showed increased abundance after 0.14% BG consumption.

A β-glucan diet may influence gut microbiota composition

• The group treated with a diet containing 0.14% BG treatment increased the ratio of CD4:CD8 cells, which is an important marker of immune system efficiency.

Takeaways

A diet including β-glucan may improve gut health and improve immune function in healthy, adult dogs.

1. A  0.14% of BG (10.60 mg/kg daily) resulted in the best overall responses for the variables evaluated, demonstrating the optimal dose among those tested.
2. Proposed Pathway for Benefits to Gut Health: BG acts as a prebiotic by stimulating the proliferation of beneficial bacteria→ increase in Firmicutes, Ruminococcaceae, and Faecalibacterium( bacteria known to participate in carbohydrate/fiber digestion) →  increase in  Short-Chain Fatty Acid (SCFA) production, particularly butyrate. 
3. Proposed Pathway for Benefits to Immunomodulation: Following ingestion, BG particles are captured in the small intestine by M cells ( specialized epithelial cells that line the GI tract) and macrophages, fragmented into nanoparticles(extremely small particles) →   BG particles transported to the bone marrow/reticuloendothelial system → fragments activate immune cells such as CD4 and CD8 cells.

The inclusion of b-glucan in dry food diets for healthy adult dogs increased the beneficial fecal microbiome and decreased potentially pathogenic bacteria and enhanced the cellular immune response important for fighting infections. 

Limitations

Small study size and design

• The study was conducted on a small population (n=8) using two specific breeds. 
• The observed variations in the chemical composition of the experimental diets, specifically the higher crude protein in the 0.14% and 0.28% diets, complicate the interpretation of the increase in crude protein ADC. 
• Furthermore, the lack of significant changes in several immunological variables (phagocytosis, oxidative burst, T cell populations, fecal IgA) may reflect the fact that the animals were healthy and not subjected to immunological challenges during the experiment.