Metabolic response to dietary fibre composition in horses.

The research article explores the metabolic response in horses to differing levels of soluble fibre in their diets. It finds that a diet high in soluble fibre promotes stable plasma metabolite and regulatory hormone levels, providing sufficient energy for horses engaged in medium levels of work.

Study Design

• The experiment was designed as a 4×4 Latin Square design, a balanced experimental design often used in animal feed research. The arrangement helps control the effect of two potentially confounding variables.
• Each stage of the design involved a 17-day adaptation period for each diet followed by a subsequent 8-day sampling period.
• The horse’s diets consisted of timothy hay only (H); hay plus molassed sugar beet pulp incorporated with either whole oats (OB) or barley (BB); and hay with a chaff-based concentrate (M).

Procedure

• Four horses fitted with permanent caecal cannulas, a tube inserted into a part of the horse’s intestine, allowed researchers to manually obtain liquid caecal content, which is partially digested food.
• Blood was drawn from the horse’s jugular vein at 0, 3, and 9 hours postprandial, or after eating.
• All horses underwent a daily medium level exercise period for approximately 1 hour.

Results

• Samples were evaluated for short-chain fatty acids (SCFA) and various metabolic markers.
• Increased dietary starch and soluble fiber led to elevated caecal SCFA and propionic acid concentrations. Propionic acid is a type of SCFA produced in the gut that provides energy to cells.
• The M diet, with the highest soluble fibre content, provoked the morning’s highest plasma glucose and insulin concentrations. However, these levels remained stable throughout the day.
• A significant interaction between time and diet was observed for plasma urea, glucose, insulin, and leptin, proteins that help regulate metabolism.
• Diets rich in cereal grain (the OB and BB groups) had the most considerable variations in plasma glycaemic and insulinaemic responses, which measure blood sugar levels and insulin response.
• There were signs of negative energy balance as shown by a significantly higher plasma β-hydroxybutyrate concentration, a marker of fat breakdown, and a numerically higher non-esterified fatty acid concentration, another indicator of lipid (fat) metabolism.

Conclusion

• The research concluded that a diet high in soluble fibre increased caecal SCFA and propionic acid concentrations, leading to stable and consistent plasma glycaemic and insulinaemic responses.
• Soluble fibre content was therefore enough to supply the necessary energy for horses engaged in medium levels of work.