The effect of replacing nonstructural carbohydrates with soybean oil on the digestibility of fibre in trotting horses.

The study investigates the effect of replacing nonstructural carbohydrates with soybean oil on the digestibility of fibre in horses, suggesting that a high-fat diet may reduce fibre utilisation and disrupt the function of fibre-breaking bacteria in the equine gut.

Research Approach

• The study was designed as a crossover trial, with feeding periods lasting 42 days each. This trial entailed feeding two alternative diets (a test diet and a control diet) to a group of six mature trotting horses aged between 4 and 12 years old.
• The test diet consisted of soybean oil, making up 37% of the net energy. Conversely, the control diet contained an equal energy portion of corn starch plus glucose. Their goal was to see if feeding extra fat instead of an equivalent energy amount of nonstructural carbohydrates would impact fibre digestion in the horses.
• Both diets were supplemented with identical amounts of hay, resulting in two diets with different fat levels but otherwise similar. Respective crude fat amounts were 25.13 g and 86.66 g per kilogram of dry matter.

Findings

• The results showed that the test diet led to a reduction in the apparent total tract digestibilities of crude fibre, neutral detergent fibre, and acid detergent fibre. These changes were significant with P-values suggesting a less than 5% chance that these results could have occurred by chance alone.
• These findings imply that a high fat intake in horses may increase the amount of fat reaching the large intestine to a degree which could potentially inhibit the fermentation process conducted by cellulolytic bacteria, microorganisms responsible for breaking down fibrous material in the equine digestive tract.

Implications

• This interaction between dietary fat content and fibre utilisation has potential consequences for practical horse feeding.
• The practice of calculating the energy content of trial diets based on feedstuff tables may lead to an overestimation of the energy provided by high-fibre ingredients within the diets.
• Therefore, a balance may need to be struck between fat intake and the requirements for an efficient fibre digestion when evaluating horse’s feeding regime.