Dietary composition and yeast/microalgae combination supplementation modulate the microbial ecosystem in the caecum, colon and faeces of horses.

The study investigates how a diet high in fibre or starch, supplemented with yeast and microalgae, affects the gut microbiome of horses and their blood inflammatory parameters. It suggests that while a starchy diet can alter gut bacteria, the yeast and microalgae supplementation could potentially enhance fibre digestion and reduce disruptions in gut balance, regardless of dietary composition.

Study Design and Methodology

• The researchers utilized six geldings in a 2 × 2 Latin-square design in which they received alternating supplementation.
• For each cycle, the horses were fed entirely hay for four weeks, followed by a hay/barley diet (56/44 ratio) for three weeks.
• Caecal, colonic, and faecal samples were collected from the horses four hours after the morning meal, on three occasions per diet at five-day intervals. These samples were used to assess the bacterial composition and microbial end products.
• Simultaneously, blood samples were taken to measure inflammatory markers.

Findings

• The research found that the starchy diet did indeed alter the microbial ecosystem across all three digestive segments. It increased ‘amylolytic’ function (starch digestion) and decreased ‘fibrolytic’ function (fibre digestion).
• However, the diet did not affect the blood parameters.
• The yeast and microalgae supplementation did not significantly change concentrations of inflammation markers like lipopolysaccharides, PG-E2, serum amyloid A, or the count of cellulose, starch, and lactate-utilising bacteria. VFA (volatile fatty acids), lactate concentrations, and pH levels were similarly unaffected.
• The supplementation, however, led to an increase in the prevalence of certain bacteria in the caecum and faeces, irrespective of the diet, and in the colon and faeces during the hay/barley diet.

Conclusions

• Despite changes to the gut bacteria with the addition of diet supplementation, not all of these changes were observed in the hindgut.
• The data suggests that the yeast/microalgae supplementation might increase the fibrolytic function of the gut, regardless of the dietary starch or fibre levels, and could potentially minimise dysbiosis when horses transition from a high-fibre to a high-starch diet.